15th Varenna Conference on Nuclear Reaction Mechanisms

Villa Monastero

Villa Monastero

Varenna (Italy)
Varenna 2018
    • 1
    • Nuclear structure
      Convener: Horst Lenske
      • 2
        Microscopic calculations of nuclear level densities with the Lanczos method

        see the attached pdf

        Speaker: Prof. Alex Brown (NSCL, Michigan State UNiversity)
      • 3
        Inverse kinematics and reaction mechanism at the drip line: probing virtual states and the nuclear vacuum

        see attached pdf

        Speaker: Prof. Ricardo A. Broglia (Department of Physics,University of Milan,Milan,Italy)
      • 4
        The deformation dependence of level densities in the configuration-interaction shell model

        The dependence of statistical nuclear properties such as level densities on intrinsic deformation is an important input to models of fission. The auxiliary-field quantum Monte Carlo (AFMC) method has enabled the microscopic calculation of nuclear level densities from the underlying Hamiltonian. However, AFMC is applied within the rotationally invariant framework of the configuration-interaction (CI) shell model, while deformation arises in the framework of a mean-field approximation that breaks rotational invariance. We have introduced a novel method to study deformation in the CI shell model without invoking an intrinsic frame or a mean-field approximation. We have calculated the axial quadrupole distribution in the laboratory frame using AFMC, and showed that this distribution carries a model-independent signature of deformation [1,2]. Using a Landau-like expansion of the logarithm of the distribution of the quadrupole tensor in the so-called quadrupole invariants, we can determine the dependence of this distribution on intrinsic deformation [3,4]. The temperature-dependent expansion coefficients are determined by the expectation values of the quadrupole invariants, which in turn are calculated from moments of the axial quadrupole in the laboratory frame. We can then calculate the dependence of nuclear level densities on intrinsic deformation [4]. The method is demonstrated for an isotope chain of samarium nuclei.

        [1] Y. Alhassid, C.N. Gilbreth, and G.F. Bertsch, Phys. Rev. Lett. 113, 262503 (2014).
        [2] C.N. Gilbreth, Y. Alhassid, and G.F. Bertsch, Phys. Rev. C 97, 014315 (2018).
        [3] Y. Alhassid, G.F. Bertsch, C.N. Gilbreth and M.T. Mustonen, arXiv:1801.06175 (2018).
        [4] M.T. Mustonen, C.N. Gilbreth, Y. Alhassid, and G.F. Bertsch, in preparation (2018).

        Speaker: Prof. Yoram Alhassid (Yale University)
      • 5
        Probing nuclear structure with neutron transfer reactions

        One of the essential questions in nuclear structure is how the nucleus reacts to the addition or removal of a nucleon. In standard quantum many-body theory, this single-nucleon response can be described by the single-particle Green's function, which is non local in space, as well as energy dependent. This quantity provides access to a wealth of structure information, such as the spectral function (for each spin and parity), level densities, non-local density matrix, etc. The Green's function is linked to the effective nucleon-nucleus interaction (self-energy) through the Dyson equation, and this interaction can be either calculated microscopically or fitted from experimental data. In order to respect causality and particle conservation, the effective interaction is both non-local and energy dependent. Arguably, the experimental tools of choice to probe the nuclear response to the addition and removal of neutrons are (d,p) and (p,d) reactions, we thus present recent developments towards a unified structure and reactions framework that links cleanly the observed cross sections with the single-particle Green's functions, dealing with the technical difficulty introduced by non-local, energy dependent neutron-nucleus interactions.

        Speaker: Gregory Potel Aguilar (Michigan State University FRIB/NSCL)
    • 11:00 AM
    • Nuclear structure/reactions
      Convener: Jose Manuel Quesada Molina (Universidad de Sevilla (ES))
      • 6
        Geometric shapes describing nuclear reaction mechanisms such as fusion, alpha emission and capture, binary and ternary fission, planar fragmentation and n-alpha nuclei


        {\bf Geometric shapes describing nuclear reaction mechanisms such as fusion, alpha emission and capture, binary and ternary fission, planar fragmentation and n-alpha nuclei}

        \author{G. Royer, J. Jahan, N. Mokus}

        {Laboratoire Subatech, UMR : IN2P3/CNRS-Universit\'e-IMT, 44307 Nantes Cedex 03, France}

        %*** USE \ TO END A PARAGRAPH

        To describe macroscopically nuclear reaction mechanisms such as fusion [1], alpha emission and capture [2], binary and ternary fission [3], planar fragmentation [4] and n-alpha nuclei [5] it is necessary to simulate the distributions of matter or charge by geometric shapes and to know their main macroscopic characteristics such as volume, surface, curvature, center of inertia, moments of inertia, quadrupole moment, ...\
        The purpose of this presentation is to provide such geometric shape sequences and to give their main mathematical properties in order to determine the energy and the dynamics of the reactions. After recalling general definitions, the following shapes will be successively investigated: ellipsoids, symmetric and asymmetric elliptic and hyperbolic lemniscatoids, prolate symmetric and asymmetric compact ternary shapes, toroids and bubbles [6,7].\
        Other planar and three-dimensional multibody shapes such as linear chain, triangle, square, tetrahedron, pentagon, trigonal bipyramid, square pyramid, hexagon, octahedron, octagon and cube used to describe some light nuclei as alpha molecules will be also shown as the associated potentials [5].


        [1] G. Royer and B. Remaud, Nucl. Phys. A 444, 477 (1985).\
        [2] G. Royer, J. Phys. G: Nucl. Part. Phys. 26, 1149 (2000).\
        [3] G. Royer, M. Jaffr\'e, and D. Moreau, Phys. Rev. C 86, 044326 (2012).\
        [4] C. Fauchard and G. Royer, Nucl. Phys. A 598, 125 (1996).\
        [5] G. Royer, G. Ramasamy, and P. Eudes, Phys. Rev. C 92, 054308 (2015).\
        [6] G. Royer, N. Mokus, and J. Jahan, Phys. Rev. C 95, 054610 (2017).\
        [7] R. W. Hasse and W. D. Myers, 1988, Geometrical Relationships of Macroscopic Nuclear Physics, (Springer verlag, Berlin, 1988).\

        Speaker: Guy ROYER (IN2P3/CNRS)
      • 7
        Oscillation symmetry applied to: 1) hadronic and nuclei masses and widths, and used to suggest unknown spins, 2) astrophysic

        Like in classical physics (pendulum, spring, ...), opposite interactions (potential and kinetic) generate oscillating behaviours in quantum physics. This is observed for masses resulting from Schr\"{o}dinger equations but also for widths of hadronic families and excited state nuclei masses.

        The masses are ordered by increasing values, and the successive mass differences are plotted versus their corresponding mean masses. The widths are plotted versus the corresponding masses. The data are fitted using a simple cosine function.

        The results will be shown, and used in some cases to suggest the spin of unknown spin particles. The variation of oscillating periods of meson and baryon families, exhibit regular behaviours between unflavoured mesons and N$^{*}$ baryons in one side, between strange mesons and $\Lambda$ baryons in the other side.

        The same approach is performed to study the oscillation properties of the nuclei energy levels, and used to suggest the spin of some unknown level spins.

        The astrophysical bodies are bound by two opposite forces, kinetic and gravitational. An oscillating symmetry is again observed between several properties. It will be illustrated by:
        - solar planet moon diameters versus their distance from planets,
        - milky way satellite galaxy brightnesses, masses, and diameters versus their distance fron earth,
        - etc .....
        This symmetry is used to tentatively predict the mass of the seventh's TRAPPIST-1 terrestrial planet, and also different properties of the hypothetical ninth and tenth solar planets, which masses are predicted to be close to ten times and half the earth mass.

        Speaker: Boris Tatischeff (CNRS IN2P3)
      • 8
        Symmetry energy in the liquid–gas mixture

        Results from classical molecular dynamics simulations of infinite nuclear systems with varying density, temperature and isospin content are used to calculate the symmetry energy at low nuclear densities at several temperatures. The results show an excellent agreement with the experimental data (from Texas A&M Cyclotron Institute) and corroborate the claim that the formation of clusters has a strong influence on the symmetry energy in the liquid–gas coexistence region.

        Speaker: Prof. Jorge Lopez (University of Texas at El Paso)
    • Fission
      Convener: Patrick Talou (Los Alamos National Laboratory)
      • 9
        Microscopic Description of Nuclear Fission: Progress and Perspectives

        Since its discovery in the late nineteen thirties, nuclear fission has remained one of the most complex and elusive problems in physics and gaps in our understanding of this phenomena can impact progress in other areas. For example, in basic science accurate knowledge of spontaneous fission half-lives is key to predicting the stability of superheavy elements, and fission fragment charge and mass distributions are also important ingredients in simulations of the formation of elements in nuclear capture processes (fission recycling). In applications of nuclear science for energy production, fuel cycle optimization is also strongly dependent on the characteristics of the fission process in actinides. In all these examples, measurements are sometimes difficult, for technological, financial or safety reasons. Therefore, most information comes from theoretical predictions. These predictions are often based on powerful semi-phenomenological models that have been developed several decades ago and have been finely tuned on existing data, which limits their predictive power. In an ideal world, a predictive theory of fission should instead be based solely on quantum many-body methods and our best knowledge of nuclear forces. Today, there is a consensus that the nuclear energy density functional theory (DFT) is currently the best framework to achieve a microscopic description of fission. Unfortunately, the proper implementation of nuclear DFT comes at a tremendous computational cost, which explains why progress had been relatively slow in the past. The recent development of leadership computing facilities in the USA, Europe and Asia has, however, introduced a paradigm shift: Calculations that were simply unfeasible only 5 or 10 years ago can now be completed in just a few hours. Such a massive increase in computing power has opened entirely new perspectives and triggered a spectacular renaissance of fission studies. After a very brief historical introduction to fission theory and models, I will give an overview of the DFT approach to nuclear fission and highlight a few recent results.

        Speaker: Dr Schunck Nicolas (Lawrence Livermore National Laboratory)
      • 10
        A basis for scission dynamics

        We propose a framework to calculate the dynamics at the scission
        point of nuclear fission based as far as possible on a discrete
        representation of orthogonal many-body configurations. Assuming
        axially symmetric scission shapes we use the $K$ orbital quantum number
        to build a basis of wave functions. In this first exploratory
        study, we examine how close to the scission point co
        exist that are eigenstates of self-consistent mean-field
        Hamiltonians, and thus stable against decay. These configurations,
        which we call cliff states, connect to configurations which we call
        gliders, that fission into fragments purely by mean-field dynamics.

        Speaker: Dr Walid Younes (Lawrence Livermore National Laboratory)
      • 11
        Hauser-Feshbach Statistical Decay and Beta Decay Calculation for Primary Fission Fragments

        We develop a Hauser-Feshbach Fission Fragment Decay model code, HF$^3$D and demonstrate its application to more than 1,000 primary fission fragments formed in the low-energy neutron-induced fission of $^{235}$U. The HF$^3$D code allows us to calculate the de-excitation of highly excited primary fission fragment by emitting prompt neutrons and $\gamma$ rays, and the sequential $\beta$ decay. The model calculation is extended to higher incident neutron energies up to the second chance fission threshold.

        In the past, fission product yield (FPY) data evaluations relied on some models such as the $Z_p$ model by Wahl [1] and isomeric ratios by Madland and England [2] to provide a complete set of FPY. There still remains a need for developing a more sophisticated method to improve the quality of FPY data. The Monte Carlo simulation is the most widely used technique to obtain stochastically distributed fission observables such as FPY. However, the Monte Carlo technique is sometimes time-consuming especially when it samples the fission fragment with very small probability in the tails of the yields.

        Instead of performing the Monte Carlo sampling, we generate the distribution of primary fission fragments $Y_p(Z, A, TKE)$ and integrate over the distributions of yield, spin, parity, and excitation energy in a deterministic way. Two important model parameters that define an initial configuration of a fission fragment; (1) the anisothermal parameter of energy split into two complementary fission fragments and (2) the spin distribution of the populated states, are adjusted to reproduce the experimental data. The HF$^3$D code calculates the neutron multiplicity $\overline\nu(A)$, prompt neutron and $\gamma$ spectra, independent fission product yield $Y_I(Z, A)$, and isomeric ratio. We also demonstrate for the first time the energy dependency of the $Y_I(Z, A)$ and the isomeric ratios. The calculated $Y_I(Z, A)$ is further tested in the $\beta$ decay chain to obtain the cumulative fission product yield $Y_C(Z, A)$.

        We will present and discuss our results calculated with the HF$^3$D model by comparison with available experimental data. This model aims at improving the evaluation of the FPY and isomeric ratios by using the Hauser-Feshbach and $\beta$ decay treatments for the fission fragment de-excitation process.

        [1] A. C. Wahl. Systematics of fission-product yields. Technical Report LA-13928, Los Alamos National Laboratory, 2002.
        [2] D.G.MadlandandT.R.England.The influence of isomeric states on independent fission product yields. Nuclear Science and Engineering, 64(4):859–865, 1977.

        Speaker: Dr Shin Okumura (Tokyo Institute of Technology)
      • 12
        Dependence of the prompt fission gamma-ray spectrum on the entrance channel of compound nucleus: spontaneous vs neutron-induced fission

        Prompt gamma-ray spectra were measured for the spontaneous fission of 240,242Pu and the neutron-induced fission of 239,241Pu with incident neutron energies ranging from thermal to about 100 keV. Measurements were made using the Detector for Advanced Neutron Capture Experiments (DANCE) array in coincidence with the detection of fission fragments using a parallel-plate avalanche counter. Comparison of the unfolded prompt fission gamma-ray spectrum (PFGS) between spontaneous and neutron-induced fission reactions is shown in the figure below. The PFGS can be reproduced reasonably well by a Monte Carlo Hauser-Feshbach statistical model for the neutron-induced fission channel but not for the spontaneous fission channel. However, this entrance-channel dependence of the prompt fission gamma-ray emission can be described qualitatively by the model due to the very different fission-fragment mass distributions and a lower average fragment spin for spontaneous fission. The description of measurements and the discussion of results are presented.

        This work benefitted from the use of the LANSCE accelerator facility and was performed under the auspices of the US Department of Energy by Lawrence Livermore National Security, LLC, under contract No. DE-AC52-07NA27344 and by Los Alamos National Security, LLC, under Contract No. DE-AC52-06NA25396. Funding is acknowledged from the US DOE/NNSA Office of Defense Nuclear Nonproliferation R&D and US DOE/SC Office of Nuclear Physics.

        Speaker: Ching-Yen Wu (Lawrence Livermore Nat. Laboratory (US))
      • 13
        Correlations between the fission fragment yields and the prompt fission gamma-ray spectrum

        The fission fragment yields are intimately connected to the resulting prompt fission γ-ray spectrum (PFGS). In combination with the prompt neutron emission, the fragment yields determine the fission products that are produced, which ultimately emit the majority of the prompt γ rays in fission. We use a Monte Carlo Hauser-Feshbach model to calculate the de-excitation of the fission fragments through the emission of prompt neutrons and γ rays. We vary generic aspects of the fragment yields, such as the location of the peaks and the widths of those peaks, and note the resulting impact on the PFGS. In particular, a measurably softer PFGS results when the fragment yields peak near the N=82 neutron shell closure. We study this effect for multiple fission reactions involving the same compound nucleus, finding that it is more dramatic for some plutonium isotopes where the spontaneous fission reaction results in significantly larger yields near the neutron shell closure. In addition to the spectral changes, we find that the fission fragment yields will directly impact the intensities of low-energy discrete γ-ray transitions. Inferring yields from the intensities of these γ-ray transitions has been studied in the past, but generally relies on certain assumptions about the existence of other contaminating γ rays or the impact of side-feeding transitions. We determine the validity of these assumptions for a selected range of isotopes and calculate the necessary corrections to obtain the true fission product yields.

        Speaker: Patrick Jaffke (Los Alamos National Lab)
    • 5:00 PM
    • Fission
      Convener: Andreyev Andreev (University of York (GB))
      • 14
        Systematic TDDFT data for nuclear fission analysis

        Nuclear fission is an important process that is not well understood microscopically. The nuclear Time-Dependent Density Functional Theory (TDDFT), which is a microscopic theory accounting for the nucleon degrees of freedom, describes dynamics of atomic nuclei [1]. Recent computational developments enable us to obtain physical quantities systematically from the TDDFT calculations. Those results are now utilized to astrophysics, nuclear engineering, and so on. In this paper, with respect to the utility for the fission analysis (for our previous results of fission and the related fundamental mechanism, see [2-6]), we focus on the systematics of fission barrier heights and the friction coefficients (cf. Figure). As a result the possibility of making (TD)DFT-based nuclear database is discussed.

        [1] Y. Iwata, T. Otsuka, J. A. Maruhn, and N. Itagaki, Phys. Rev. Lett. 104 (2010) 252501.

        [2] Y. Iwata and S. Heinz, EXON-2012, World Scientific (2012) 153-162.

        [3] Y. Iwata and S. Heinz, CERN Proceedings 2012 – 002 (2013) 241

        [4] Y. Iwata and S. Heinz, J. Phys. Conf. Ser. 420 (2013) 012012.

        [5] Y. Iwata, Mod. Phys. Lett. A 30 (2015) 155008.

        [6] J. R. Stone, P. Danielewicz, Y. Iwata, Phys. Rev. C 96 (2017) 014612.

        This work is based on the collaboration with Kean Kunratha (JAEA, Tokyo Institute of Technology), Takashi Nishikawa (Tokyo Institute of Technology).

        Speaker: Dr Yoritaka Iwata (Tokyo Institute of Technology)
      • 15
        Real-time description of fission

        Two major recent developments in theory and computational resources created the favorable conditions for achieving a microscopic description of nuclear fission almost eighty years after its discovery in 1939 by Hahn and Strassmann. The density functional theory (DFT) provides the only microscopic framework suitable for description of heavy nuclei and feasible on today’s computers. Instead of computing the full many-body wave function, one can determine only the one-body density within the DFT, the highly successful approach pioneered by Kohn (Nobel prize, 1998), Hohenberg, and Sham (1964-1965) for many-electron systems in chemistry and condensed matter physics. Within the extension to time-dependent DFT, fission dynamics becomes computationally manageable and, hence, a microscopic description feasible. To study quantum dynamics we developed a real-time DFT extension, explicitly including the dynamics of the crucial pairing correlations, used existing reasonably accurate energy density functionals (EDF), and implemented it on leadership class computers. The current implementation allows us to obtain information about important aspects of the fission process, such us the particle emission during the fragment acceleration, or the excitation energy sharing between fragments, before neutron emission. For such observables, only indirect experimental information exists, but they are crucial in obtaining a good description of the emission of neutrons and gamma-rays from de-exciting fragments. Thus, even if no complete process description can be achieved yet (e.g. no neutron and gamma-ray emissions from fission fragments, which require very long evolution times), the information provided by the dynamics can be used as input into phenomenological Hauser-Feshbach codes that treat the de-excitation of fission fragments.

        Speaker: Ionel Stetcu (Los Alamos National Laboratory)
      • 16
        First comparison between microscopic and macroscopic-microscopic potential energy surfaces for the description of fission

        Until now, the theoretical description of fission through the effective calculation of potential energy surfaces (PES) has been made in two different approaches: the microscopic approach on the one hand and the macroscopic-microscopic approach on the other hand.

        1. In the microscopic ones, we assume an effective two-body interaction between the nucleons (e.g. Skyrme or Gogny interaction). The microscopic state of the nucleus is then obtained with a self-consistent mean-field method (e.g. HF, HFB). These approaches allow us to connect fission properties to the basic constituents of the nucleus and their interaction using a few parameters (< 15) but are time-consuming.
        2. In the macroscopic-microscopic ones, we calculate in a first step the macroscopic part of the energy by describing the nucleus as a classical system (e.g. Liquid Drop Model). In a second step, we add microscopic correlations using, for example, the Strutinsky method and the Lipkin-Nogami pairing model. These approaches are very fast and in good agreement with experimental data, but cannot take into account all microscopic correlations.

        The aim of this work is to couple both kind of approaches. As a first step in this work, potential energy surfaces for the same nucleus have been generated with both approaches. In this presentation, the first part will detail each approaches, and the second part will show a first comparison between potential energy surfaces obtained with each of them.

        Speaker: Marc Verriere (Los Alamos National Laboratory)
      • 17
        Effects of the temperature on nuclear deformation energy and the predictions of fission observables calculated within the Langevin approach

        Predictions of fission observables by solving the Langevin equations are highly dependent on the potential energy surface along which the shape configuration of the nucleus evolves. This potential energy surface is calculated by adding together the liquid drop deformation energy and the shell correction energy. In our recent four-dimension (4-D) Langevin approach 1, the shell corrections [2,3] are calculated using the single particle energies derived from the deformed Wood-Saxon potential of Pashkevich [4]. Usually, the shell correction is calculated for zero temperature and the dependence on the excitation energy is taken into account by Ignatyuk prescription [5], $\delta E(E^*)=\delta E(0)e^{-E^*/E_d}$. In the present work we have calculated the temperature dependence of the shell correction to the macroscopic nuclear energy directly starting from their formal definitions without any approximation. We have found out that below critical temperature when the pairing effects are important, both shell correction to energy and the shell correction to the free energy differ substantially from the approximation of [5]. We propose the approximations for the shell corrections to the energy $\delta E$ and free energy $\delta F$ that reproduce rather accurately the average dependence of $\delta E$ and $\delta F$ on the temperature (excitation energy). These approximations rely on the quantities calculated at zero temperature like $\delta E_{shell}(0)$ and $\delta E_{pair}(0)$ and few fitted constants. The accuracy of approximation for $\delta F$ is demonstrated in Fig. 1. In the current work, we will employ this temperature dependent potential energy surface on our 4-D Langevin calculation.

        Fig. 1 The temperature dependence of average shell correction to the free energy for $^{236}$U (black) and few approximations: that of present work (red), Ignatyuk [5] (dash), and Randrup-Moller [6] (dash-dot).

        [1] C. Ishizuka, M. D. Usang, F. A. Ivanyuk, J. A. Maruhn, K. Nishio, and S. Chiba, Phys. Rev. C 96, 064616 (2017).
        [2] V. Strutinsky, Nucl. Phys. A 95, 420 (1967).
        [3] V. Strutinsky, Nucl. Phys. A 122, 1 (1968).
        [4] V. Pashkevich, Nucl. Phys. A 169, 275 (1971).
        [5] A. Ignatyuk, K. Istekov, and G. Smirenkin, Sov. J. Nucl. Phys. 29, 450 (1979).
        [6] J. Randrup and P. Möller, Phys. Rev. C 88, 064606 (2013).

        Speaker: Mr Mark Dennis Usang (Tokyo Institute of Technology, Tokyo, Japan)
    • Fission
      Convener: Nicolas Schunck (Universidad Autonoma de Madrid)
      • 18
        An Unexpected Energy Evolution of the Fission-Product Yields from Neutron-Induced Fission of 235U, 238U, and 239Pu

        High-precision measurements of the fission product yields of 235U, 238U, and 239Pu using monoenergetic neutrons between 0.5 and 14.8 MeV have been performed to study the energy dependence. The results confirm the progression towards symmetric fission at higher incident neutron energy, i.e., 14.8 MeV. However, at lower energies (En < ~4 MeV) the experimental data reveal a peculiar energy dependence of some of the fission-product yields from neutron-induced fission of 239Pu: a positive slope up to about 4-5 MeV which then turns negative as the incident neutron energy increases. This latter finding at low-energy is in conflict with present theoretical predictions. New experimental cumulative and short-lived fission-product yield data will be presented at fast neutron induced fission.

        Speaker: Dr Anton Tonchev (Lawrence Livermore National Laboratory )
      • 19
        Correlated Prompt Fission Data in Transport Simulations

        Recent advances in the modeling of the decay of fission fragments have led to the integration of fission event generators in transport simulations. Event-by-event generators follow the decay of each fragment through the successive emissions of neutrons and gamma rays. Natural correlations in energy, multiplicity, angle of those prompt particles with themselves and with their parent nucleus are ignored in simplified models of the post-scission process, and therefore in most transport simulation codes such as GEANT or MCNP. Integrating those generators into transport codes translates into much more realistic transport and detector response simulations. Neutron-neutron angular distributions, neutron-gamma multiplicity correlations and specific neutron-gamma-fragment correlations are of particular interest to provide answers to fundamental questions about the fission process, e.g., energy sharing at scission, as well as to improve simulations for specific applications, e.g., active interrogation of special nuclear material.

        Through specific examples, I will discuss the meaning of these correlations in prompt fission data, and how they can help answer fundamental as well as applied physics questions. I will also provide an overview of the current experimental, theoretical and modeling efforts devoted to these studies.

        Speaker: Patrick Talou (Los Alamos National Laboratory)
      • 20
        Gamma-ray cascade study in abundant fission fragments with the EXILL experiment and FIFRELIN simulation

        The poor accuracy of microscopic models in the prediction of fission observables constrains nuclear industry to rely on semi-empirical models, which in turns need systematic and accurate experimental data on a significant number of observables. In the last decade, large efforts were made in the fission community to improve models of the fission process and of the de-excitation of fission fragments. This is performed through reliable Monte Carlo simulations that take into account prompt neutrons and gamma-ray emission. An ultimate aim of such a simulation is to predict e.g. gamma-heating in nuclear reactor. The code developed by CEA Cadarache, FIFRELIN, samples the characteristics of primary fission fragments (before neutron emission). These pre-neutron characteristics are: the mass, nuclear charge, excitation energy, spin, and parity. The code includes the RIPL3 database of nuclear level schemes and nuclear model parameters. The full nuclear level scheme is completed at higher energies by using level density, neutron transmission coefficient, and photon strength function models. In a recent update, conversion electron coefficients are also available at any energy from BrIcc tabulated values. It makes it able to estimate the intensities of gamma-ray transitions in all the fission fragments.

        In the EXILL experiment conducted in 2012 and 2013 at the Institut Laue Langevin in Grenoble, a target made of 235U was surrounded by an array of high-resolution gamma-ray detectors and irradiated by an intense cold neutron beam. We have extracted the intensities of the main discrete gamma-ray transitions in a set of fission fragments, using a triple gamma-ray coincidence technique, and we have compared our results to FIFRELIN simulation outputs. Extracted experimental data allows testing the accuracy of the FIFRELIN simulations and choosing the best implemented models (and their parameters) for level densities, photon strength functions and spin distributions. Result of our study on the gamma-ray cascades in the most abundant fission fragment pairs will be presented.

        Speaker: Michal Rapala (CEA Saclay)
      • 21
        Phenomenological study of fission yield for U233 induced by neutrons below 20 MeV

        The fission fragment mass distribution and the yield - energy dependence for U233 fission induced by neutron are of importance in the study of the Th/U fuel cycle. In this work, a semi-empirical method which includes the excitation energy dependent influence of nuclear shell effects, was adopted to study the yield mass distribution in the incident neutron energy below 20 MeV. This model was based on the multi channel fission and introduced 10 parameters which were determined by adjusting to the measured cumulative yields. The results showed it could well describe the fission fragment yield and yield-energy dependence for parts of fragments.

        Speaker: Ms Lile Liu
      • 22
        Fission properties of nuclei in the 180Hg region

        Nuclei in the neutron-deficient region of $^{180}$Hg$_{100}$ are different from the actinides traditionally used for fission studies, from the viewpoint of their fission barriers, separation energies and proton-to-neutron ratios. Fission properties of these nuclei were expected to be similar to those of their heavier isotopes around the stability line, known to fission symmetrically. The picture changed drastically in 2010, when the asymmetric-fission mass distribution of the $^{180}$Hg nucleus was discovered in a beta-delayed fission of $^{180}$Tl in a dedicated experiment at ISOLDE (CERN) [1]. This much unexpected observation promptly attracted extensive attention from both theory and experimental sides, leading to several important conclusions, first of all regarding the importance of the microscopic (shell) effects and their dependence on the excitation energy. Moreover, existence of a new and extended region of asymmetric fission was predicted for neutron-deficient Re-Pb nuclei [2].
        In order to investigate fission properties of nuclei in, and the extension of, this predicted region, a dedicated experimental campaign of prompt fusion-fission studies was initiated at the JAEA [3]. In the framework of this program, we investigated fission properties of $^{178}$Pt obtained from a complete fusion-fission reaction $^{36}$Ar+$^{142}$Nd $\rightarrow$ $^{178}$Pt* at the JAEA (Japan), studied at different beam energies. In order to improve on the precision of the fragment mass distributions, the JAEA experimental setup was upgraded with two time-of-flight sections allowing for independent velocity determination for coincident fission fragments. The made improvement has permitted for correlated fission-fragment mass and kinetic energy measurements, for the first time in the region of the interest.
        The obtained final mass distributions are found to be dominated by the asymmetric mass splits, in accordance with the prediction [2]. The contribution of the symmetric-fission events to the measured mass distributions, never done before in the $^{180}$Hg region, is on the level of ~30% and does not change with the beam energy, which is explained by taking into account the rotational energy of the compound nucleus. In the presentation, fission modes’ properties of 178Pt are also compared to those of actinides, which allows for better understanding of the modes’ dependence on the isospin.

        [1] A.N. Andreev et al., Phys. Rev. Lett. 105, 252502 (2010).
        [2] P. Moller et al., Phys. Rev. C 85, 024306 (2012).
        [3] K. Nishio et al., Phys. Lett. B 748, 89 (2015).

        Speaker: Prof. Igor Tsekhanovich (CENBG/Bordeaux University)
    • 11:00 AM
    • Fission
      Convener: Yukinobu Watanabe (Kyushu University)
      • 23
        Fission studies using multi-nucleon transfer reactions at the JAEA tandem

        In this talk we will discuss the use of multi-nucleon transfer (MNT) reactions to study fission properties of a series of exotic nuclei in the neutron-rich actinide region. Most of these nuclei cannot be accessed by the traditional method of complete-fusion reactions. The MNT transfer channels of the $^{18}$O+$^{232}$Th reaction were used to study fission of fourteen nuclei $^{231,232,233,234}$Th, $^{232,233,234,235,236}$Pa, and $^{234,235,236,237,238}$U [1]. Identification of fissioning nuclei and of their excitation energy is performed on an event-by-event basis, through the measurement of outgoing ejectile particle in coincidence with fission fragments. Fission fragment mass distributions (FFMDs) are measured for each transfer channel. In particular, the FFMDs of $^{234}$Th and $^{234,235,236}$Pa were measured for the first time. Predominantly asymmetric fission is observed at low excitation energies for all studied cases, with a gradual increase of the symmetric mode towards higher excitation energy. By using the same method, the measurements with $^{238}$U [2], $^{237}$Np, $^{248}$Cm, and $^{249}$Cf targets were recently performed.
        The obtained FFMDs are compared with a calculation based on the fluctuation-dissipation model [2,3], where effect of multi-chance fission (neutron evaporation prior to fission) was considered. It was found that multi-chance fission has significant role on the shape of FFMD, particularly at the high-excitation energies.

        [1] R. Leguillon et al., Phys. Lett. B 761, 125 (2016)
        [2] K.Hirose et al., Phys. Rev. Letters, 119, 222501 (2017)
        [3] Y. Aritomo and S. Chiba, Phys. Rev. C 88, 044614 (2013)

        Speaker: Prof. Andrei Andreyev (University of York (UK), JAEA (Tokai, Japan))
      • 24
        Isoscaling study of binary fission yields

        The isoscaling, which represents the exponential relationship exhibited in the isotopic yields of fragments between two systems with different neutron to proton ratios, can provide a direct link to the symmetry energy coefficient. In our work, the isoscaling relationships were investigated in the binary fission fragment yield of 236,234U targets induced by the thermal neutrons. With the experimental and evaluated fission yield data away from stronger shell effects region, we extracted information of symmetry energy coefficients and its temperature dependence. Based on the isoscaling relationship and the values of extracted isoscaling parameters, one could make predictions for fission yield for unmeasured U isotopes.

        Speaker: Ms Yongjing CHEN
      • 25
        Aggregate Decay Behavior of Fission Products in Nuclear Reactors -Decay Heat, Reactor Antineutrino and the Pandemonium Problem-

        The decisive importance of fission-product (FP) decay heat (DH) was far and widely recognized after the core-melt accident at the TMI nuclear power station in 1979. Even before this, in the late 1970s, a lot of experimental and theoretical studies on FPDH were motivated and initiated in Japan, the US and Europe. In these countries, extensive FP decay data libraries to be used in DH summation calculations were elaborated from the up-to-date FP decay data which had been taken from the high-resolution $\gamma$-ray measurements. Optimistic expectation for good agreement between the experimental and the theoretical results, however, were not materialized with one exception. That is the JNDC (Japanese Nuclear Data Committee) Library where the gross theory of $\beta$-decay was employed for supplementing the insufficiency of the experimental decay data which was not yet perceived clearly then. In due course beyond the TMI accident, the origin of the disagreement was identified as the Pandemonium problem which had been warned of by Hardy et al. based on computer simulation. The best experimental way to overcome to this difficulty, which is intrinsic to high $Q_\beta$-value decay, is now recognized as the total absorption $\gamma$-ray spectroscopy (TAGS). After the extensive effort at Idaho in the 1990s, TAGS was further motivated by series of the IAEA meetings on this subject since 2006 up to the present from the view points both of nuclear science and technology. Another important aspect of the aggregate FP in reactor cores is as the emitter of antineutrinos ($\bar{\nu}_e$). It is stressed that the gross theory of $\beta$-decay still have potential to play an important role in investigating the reactor $\bar{\nu}_e$ flux and its energy spectrum along with the steadily accumulating TAGS experimental data at present.

        Speaker: Dr Tadashi Yoshida (Tokyo Institute of Technology)
    • Nuclear reactions
      Convener: Roberto Capote (International Atomic Energy Agency)
      • 26
        Probing Nuclear Beta-Decay by Heavy Ion Charge Exchange Reactions

        Heavy ion charge exchange reactions are of manyfold interest for nuclear reaction and structure physics. A new theoretical approach is presented, emphasizing the role of single and double charge exchange reactions for probing nuclear response functions as encountered in single and double beta decay. In particular, a special class of nuclear double charge exchange (DCE) reactions proceeding as a one-step reaction through a two-body process are shown to involve nuclear matrix elements of the same diagrammatic structure as in $0\nu 2\beta$ decay. These correlated Majorana-DCE reactions are distinct from second order DCE reactions which are characterized the best as sequential double single charge exchange (dSCE) carrying a close resemblance to $0\nu 2\beta$ decay. The results suggest that ion-ion DCE reactions are the ideal testing grounds under well-defined dynamical conditions for investigations of double-beta decay nuclear matrix elements. Comparisons to recent single an double charge exchange data measured by the NUMEN collaboration at the LNS Catania are discussed.

        Speaker: Prof. Horst Lenske (U. Giessen)
      • 27
        Advances in microscopic modeling of (n,$x$n$\gamma$) reactions for actinides

        Recent developments in nuclear structure approaches offer a great
        mean to improve various aspects of nuclear reaction modeling and to
        further understand reaction mechanisms from a microscopic point of
        view. Recently, direct and pre-compound nucleon emission, for nucleon
        induced reaction on spherical and axially deformed nuclei, have been
        successfully modeled [1] using a description of target states provided
        by fully consistent axially-symmetric deformed quasi-particle
        random-phase approximation (QRPA) calculations [2]. Direct inelastic
        scattering to target excitations built from one-phonon QRPA states
        accounted simultaneously for direct inelastic scattering to discrete
        states, and pre-equilibrium emission as far as second order processes,
        that involve more complex excitations such as two-phonon states, and
        multiple emission remain negligible. The QRPA nuclear structure
        approach has also been applied recently to determine, for a large pannel of even-even nuclei,
        E1 and M1 photon strength functions [3],
        that play a key-role in the modeling of statistical reactions.\

        We will first review the status on the ongoing work on
        direct/pre-compound neutron emission for neutron induced reaction
        below 20~MeV for even-even actinides.
        Target states are described as rotational bands built from each state in the
        target intrinsic frame, described as QRPA one-phonon excitation of the
        intrinsic correlated ground state. QRPA excitations which display a
        collective character can thus be viewed as vibrational band heads.
        Couplings between states of the GS band and states belonging to an
        excited band are accounted for within a coupled channel framework.
        Relative strengths of these couplings, for various neutron
        incident energies, transfer angular momenta, and intrinsic states
        properties, are analyzed in order to define the relevent coupled channel
        scheme that is needed in the determination of direct/pre-compound cross-sections.\

        Our approach in then applied to the modeling of (n,n'$\gamma$)
        reactions for various even-even actinides and for both intra- and
        inter-band gamma transitions [4]. For these reactions, the role played by the present
        microscopic approach for direct/pre-equilibrium emission is discussed. Thus, we finally
        focus on the impact on the determination of (n,n'$\gamma$) cross
        sections of newly calculated QRPA E1- and M1-photon strength
        functions, that enter the description of statistical decay from compound nucleus states
        in the continuum.\[1cm]

        [1] M. Dupuis, E. Bauge, S. Hilaire, F. Lechaftois, S. P\'eru, N. Pillet and C. Robin, Eur. Phys. J. A, 51 12 (2015) 168.\[.1cm]
        [2] S. P\'eru,G. Gosselin, M. Martini, M. Dupuis, S. Hilaire, and J.-C. Devaux, Phys. Rev. C 014314 (2011).\[.1cm]
        [3] S. Goriely, S. Hilaire, S. P\'eru, M. Martini, I. Deloncle, and F. Lechaftois
        Phys. Rev. C 94, 044306 (2016); M. Martini, S. P\'eru, S. Hilaire, S. Goriely, and F. Lechaftois, Phys. Rev. C 94, 014304 (2016).\[.1cm]
        [4] M. Dupuis, S. Hilaire, S. P\'eru, E. Bauge, M. Kerveno, P. Dessagne and G. Henning EPJ Web Conf., 146 (2017) 12002.}

        Speaker: Dr Marc Dupuis (CEA, DAM, DIF)
      • 28
        Heavy Ion charge exchange reactions and the link with beta decay processes

        There is recently renewed interest in the study of single and double charge exchange reactions with heavy ions. We report here a preliminary theoretical study of double charge exchange (DCE) reactions in terms of two successive charge exchanges (SCE) in second order Distorted Wave Born approximation.
        We look in particular at the conditions where the corresponding cross section can be factorized into nuclear reaction and structure terms, showing that in this case one can establish a connection with two neutrino double beta decay. The possibility of a correlated DCE process, that should exhibit a closer analogy with netrinoless double beta decay, is also discussed.
        The role of competing transfer mechanisms is investigated. Theoretical estimates indicate that the charge exchange process is dominant.

        Speaker: Maria Colonna (INFN - National Institute for Nuclear Physics)
      • 29
        Coulomb-nuclear interference and isospin characterization of the first 2+ and 3- transitions by inelastic scattering of alpha particles on 90,92Zr

        The Zirconium isotopic chain, where rather abrupt changes in nuclear properties are experimentally observed, in special along the N=50 to 60 region, has attracted renewed interest in recent years. In particular, a group of authors of the University of Tokyo (1) after performing large-scale Monte Carlo shell-model calculations claims that a “Quantum Phase Transition” is observed in the systematics of the excitation energies of low-lying states in Zr isotopes. Shape coexistence has consistently been invoked as a cause of some of the experimentally observed aspects and the work of Heyde and Wood (2) may be taken as an example. However, from an experimental point of view, several unexpected results continue to intrigue researchers, resulting in an effort to find causes for differences in the outcomes of inelastic scattering by different probes, either in the data themselves or in their analyses. Some years ago, a great investment was made in the attempt of reconciling results of a (6Li,6Li') work by the Yale group (3) with other data, particularly with findings of a former (α,α') experiment on 90-96Zr, performed in Heidelberg by Rychel et al. (4). With this purpose, a very careful reproduction of the Heidelberg alpha results was undertaken by Lund et al. (5), at the Yale facility, with the same incident energy of 35.4 MeV. No disagreement with the german data or their analysis was found. In fact, a clear explanation of the observed differences of the results between different probes is still lacking. In this scenario, the present contribution aims at putting forward some interesting aspects of experimental studies which examine differences between 90Zr and its neighbors. The unpublished data for 90,92Zr(α,α') (6), taken with the São Paulo Pelletron-Enge-Spectrograph system, are being analyzed in more detail, in view of recent interpretations. Coulomb-nuclear interference effects are much enhanced at the lower incident energy (21 MeV) of this experiment, favoring thus the isospin characterization of the transitions to the first 2+ and 3- states. The experimental angular distributions demonstrate a clear difference in the excitation of the first quadrupole states of 90Zr and 92Zr . In fact, in 92Zr the excitation is preferentially driven by neutrons, to an extent that had not been formerly observed in other nuclei. On the other hand, the semi-magic 90Zr reveals the usual collective contribution of protons and neutrons. It is to be noted that no such difference is detected for the octupole excitations, for which data, taken simultaneously with those for first 2+ levels, are well reproduced by homogeneous collective contributions.
        (1) T. Togashi, Y. Tsunoda, T. Otsuka and N. Shimizu, Phys. Rev. Lett. 117, 172502 (2016)
        (2) K. Heyde and J.L. Wood, Rev. Mod. Phys. 83, 1467 (2011)
        (3) D.J. Horen et al., Phys. Rev. C 47, 629 (1993)
        (4) D. Rychel et al. Z. Phys. A 326, 455 (1987)
        (5) B.J. Lund et al, Phys. Rev. C 51, 635 (1995)
        (6) L.B. Horodynski-Matsushigue, T. Borello-Lewin and J.L.M. Duarte, Int. Nucl. Phys. Conference, São Paulo Brasil 1989, Proceedings I, 307

        Speaker: Prof. Thereza Borello-Lewin (Instituto de Fisica, Universidade de São Paulo)
      • 30
        Towards a non-local microscopic description of scattering observables of nucleons on deformed nuclei

        A good understanding of neutron scattering mechanisms and prediction capacity of associated
        cross sections is crucial to many nuclear technologies, among which all kinds of reactors based on
        fission process. For deformed nuclei, the computation of scattering observables for the elastic
        channel and the first, low-lying excited states requires coupled channel calculations. Local,
        phenomenological optical and macroscopic transition potentials are the most commonly used in
        coupled channel analyses, and various microscopic approaches are being developed in order to
        improve prediction power and theoretical understanding, like the Nuclear Structure Method [1] or
        nuclear matter approaches [2]. Potentials obtained microscopically are nonlocal, and while there
        exists methods to localize a potential that yield good results for elastic scattering [3] recent studies
        [4] [5] [6] have emphasized the importance of treating explicitly this nonlocality, especially for
        inelastic channels.
        We have developed a code that can solve coupled channel equations with nonlocal microscopic
        optical potentials, while treating the nonlocality with no approximation. We lead our study on 208Pb, with potentials derived from the Melbourne G-matrix and ground state and transition densities stemming from the Random Phase Approximation nuclear structure model. We consider 1 and 2- phonons excitations within the coupled channel framework. Extensive experimental data for both elastic and inelastic scattering of neutrons is available on 208Pb, and we use this target to validate our approach and investigate effects of nonlocality in the coupled channel framework before focusing on deformed nuclei.

        [1] G. Blanchon, M. Dupuis, H. F. Arellano and N. Vinh Mau, "Microscopic positive-energy
        potential based on the Gogny interaction," Physical Review C, vol. 91, no. 014612, 2015.
        [2] H. F. Arellano et W. G. Love, «In-medium full-folding model approach to quasielastic (p,n)
        charge-exchange reactions,» Phys. Rev. C, vol. 76, p. 014617, 2007.
        [3] F. G. Perey et B. Buck, «A non-local potential model for the scattering of neutrons by nuclei,»
        Nuclear Physics, vol. 32, pp. 353-380, 1962.
        [4] A. Ross, L. J. Titus, F. M. Nunes, M. H. Mahzoon, W. H. Dickhoff et R. J. Charity, «Effects of
        nonlocal potentials on (p,d) transfer reactions,» Phys. Rev. C, vol. 92, p. 044607, 2015.
        [5] N. Keeley et R. S. Mackintosh, «Dynamic polarization potential and dynamical nonlocality in
        nuclear potentials : Nucleon-nucleus potential,» Phys. Rev. C, vol. 90, p. 044602, 2014.
        [6] L. Titus, F. Nunes and G. Potel, "Explicit inclusion of nonlocality in (d,p) transfer reactions,"
        Physical Review C, vol. 93, no. 014604, 2016.

        Speaker: Mr Amine Nasri (CEA)
    • 4:45 PM
    • Facilities
      Convener: Lawrence Pinsky (University of Houston (US))
      • 31
        Novel Results from ALICE

        Abstract contained in the attached document.
        Talk presented on behalf of the ALICE collaboration

        Speaker: Siegfried Foertsch (iThemba LABS, National Research Foundation (ZA))
      • 32

        Asian Nuclear Physics Association (ANPhA) is the central organization representing nuclear physics in Asia Pacific. ANPhA is now preparing a list of accelerator facilities applicable for nuclear physics experiments in Asia Pacific. Among them, characteristics of world class “Major” accelerator facilities will briefly be summarized in my talk in Varenna Conference in comparing to similar facilities in Europe and North America.
        Major facilities in Asia Pacific are mainly locating in China (Heavy Ion Research Facility in Lanzhou (HIRFL), Beijing Tandem Accelerator National Laboratory (BTANL)), India (K500 Superconducting Cyclotron at Variable Energy Cyclotron Centre (VECC)), Korea (RISP/RAON), and Japan (RIBF at Riken, J-PARC, and ELPH/LIPS). Most of them (HIRFL, BTANL, VECC, RISP/RAON and RIBF) are medium energy heavy-ion accelerator facilities and are competing to European and American Facilities such as SPIRAL2, HIE-ISOLDE, ARIEL-II and FRIB. In addition future extension plans of these Asian facilities are really aiming far beyond the wave front of the research of this field of nuclear physics. In this meaning, Asian research facilities are keeping world best positions in medium energy heavy-ion physics. Hadron physics facility in Asia (J-PARC) is also world leading facility in the world. ELPH/LIPS facilities can provide world competitive photon beams.
        However, there are no high energy heavy-ion accelerators and colliders (such as ALICE in LHC, RHIC in USA, and NICA in Russia) in Asia Pacific region. In other word, we concentrated our research resources to medium energy heavy ion physics and chosen to promote high energy heavy-ion physics at abroad (outside Asia). This strategy seems successful at present. However we have to check our strategy of this field of Nuclear Physics for our future research collaborations in Asia Pacific. For example, too much concentration may be happening in medium energy heavy-ion accelerator facilities in Asia Pacific.

        Speaker: Prof. Kazuhiro Tanaka (KEK, High Energy Accelerator Research Organization)
      • 33
        Neutrinos, wine and fraudulent business practices

        The Neutrino Ettore Majorana Observatory (NEMO) experiment, located in the Modane Underground Laboratory, between Italy and France, is looking for the very rare neutrinoless double beta decay. The detector is built out of materials containing no measurable radioactive isotopes such as U, Th, Ra and their progeny. To ensure the best radiopurity for the materials, we had to develop ultra-low background γ-ray spectrometers on the basis of HPGe crystals.

        Four such spectrometers are hosted in the low-background environment PRISNA platform at our Institute in Bordeaux. We use them also for inter-disciplinary research, notably for dating wine by measuring its 137Cs content without opening the bottle. 137Cs, with a half-life of 30 years is a man-made isotope. Its origin comes mainly from the numerous atmospheric atom bomb tests during the 1950's and 1960's. The released activities were spread worldwide, then deposited on earth and on grapevines. Each year harvest is a “record” of that year's fallouts, which leads to a reference curve “137Cs activity vs vintage”. If there is no 137Cs radioactivity in a given wine, this means it dates back from preatomic era. This foolproof method is used to demonstrate that some alleged old vintage wines are counterfeits.

        Starting in 2010, a technical unit for service-delivery activities at PRISNA is now in charge of such measurements for a wide panel of public and private clients and it helped to clean up the market.

        Speaker: Dr Michael Pravikoff (CNRS/IN2P3)
    • 34
      Ettore Gadioli wine party
    • Medical radioisotopes
      Convener: Luciano Canton (INFN - National Institute for Nuclear Physics)
      • 35
        Future production of medical radioisotopes

        A large fraction of the radioisotopes used for diagnostics and therapy in healthcare are currently produced in research reactors build in the heydays of the development of nuclear power. These reactors will be decommissioned in the coming decade. For various reasons significantly less new reactors for research and isotope production are coming on-line. At the same time the use of radioisotopes in medicine is continuously growing. It is therefore important to investigate the possibilities of alternative, accelerator-based production routes for the isotopes currently used as well as for alternative isotopes that allow the same functionality to be realized. In addition new diagnostic and therapeutic radiolabelled compounds call for the development of production routes for new isotopes. To meet these objectives extensive R&D on high power accelerators and targetry as well as a significant experimental effort to collect the nuclear data required to assess the fundamental feasibility of proposed production routes are needed.
        The challenges associated with these ambitions will be discussed using a few specific cases, among which the most used radioisotope 99Mo.

        Speaker: Sytze Brandenburg (University of Groningen)
      • 36
        Nuclear data for production of novel medical radionuclides

        Syed M. Qaim
        Institut für Neurowissenschaften und Medizin, INM-5: Nuklearchemie
        Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
        E-mail: s.m.qaim@fz-juelich.de

        Nuclear data play an important role in optimisation of production routes of medical radionuclides. In general, the production data of all the commonly used diagnostic and therapeutic radionuclides are well known, except for some special applications, where improvements in data may be desired. Regarding research oriented radionuclides, great demands exist for non-standard positron emitters to study slow biological processes and to quantify dose distribution in internal radiotherapy. Some recent studies related to the development of the positron emitters 64Cu (T½ = 12.7 h) and 86Y (T½ = 14.7 h) will be described as typical examples. In general, the low-energy (p,n) reaction on a highly enriched target isotope is successfully utilized. However, for production of several other positron emitters, e.g. 73Se (T½ = 7.1 h), intermediate energy reactions are needed. Another area of increasing interest is internal radiotherapy and the choice lies on low-energy highly ionising radiation emitters, i.e. β-, α and Auger electron emitters. Cross section measurements to develop those novel therapeutic radionuclides are challenging, and interdisciplinary techniques are employed. This will be exemplified by studies on 67Cu (T½ = 2.6 d; Eß- = 577 keV), 193mPt (T½ = 4.3 d; Auger electrons) and 225Ac (T½ = 10.0 d; Eα = 5830 keV). The novel radionuclides are finding increasing applications in theranostics which involves the combination of a positron emitter and a therapeutic radionuclide of the same element. A few examples of such systems will be given.
        Regarding future perspectives of medical radionuclide production, the potential of high energy protons and heavier mass projectiles will be discussed and the increasing efforts to utilize fast neutrons and high-energy photons will be briefly outlined. Furthermore, the prospects of combining PET with MRI for enhanced quality imaging, and of radioactivity with nanotechnology for effective internal radiotherapy, will be discussed. The relevant nuclear data needs will be considered.

        Speaker: Syed M. Qaim (Forschungszentrum Jülich)
      • 37
        Diagnostic (99Mo/99mTc) and Therapeutic (67Cu) Radioisotopes Produced by Neutrons from C,Be(d,n)

        Radiopharmaceuticals containing gamma-ray and beta(-)(alpha, Auger electron)-ray emitting radioisotopes are used to diagnose the dynamics of a medicine in the living body and kill targeted cancer cells, respectively. Using 99mTc (T1/2 = 6 h), the daughter nuclide of 99Mo (T1/2 = 66 h), about 0.9 million and 6 million diagnostic procedures per year are carried out in Japan and in EU, respectively.1,2) Japan imports all of its required 99Mo. Most 99Mo is produced by the fission reaction of enriched 235U in nine research reactors around the world.3) The supply chain of 99Mo is fragile owing to the unscheduled shutdown of some of the research reactors and natural disasters such as Iceland volcano eruptions. 90Y (T1/2 = 64 h, pure beta-ray emitter with E(max) = 2.3 MeV) radiopharmaceuticals is used for cancer therapy.4) 67Cu (T1/2 = 64 h, E(max) = 0.58 MeV) is believed to be a promising radionuclide to treat small distant metastases in radioimmunotherapy.5) 67Cu emits low-energygamma-rays, and therefore it can be used simultaneously for diagnostics and therapy. Establishing a proper production method of high quality 67Cu is a longstanding problem.5)
        New routes were proposed to produce 99Mo and 67Cu via the 100Mo(n,2n)99Mo6) and 68Zn(n,np+d)67Cu7) reactions, respectively, using accelerator neutrons provided by the C(d,n) reaction at a deuteron energy of 40 – 50 MeV. In order to separate 99mTc from the 99Mo with a low specific-activity, a thermochromatography apparatus was developed.8) The quality control tests of the 99mTc-radiopharmaceuticals were shown to fulfill the United States Pharmacopeia regulatory requirements.9) We claim that about 30 – 50% of the demand for 99mTc in Japan would be met using a single accelerator of 40 MeV, 2 mA deuteron beams.10) The radionuclide purity, labeling efficiency, and specific activity of 67Cu, eluted from the 68ZnO sample irradiated with accelerator neutrons by using several ion exchange columns were measured.11) 67Cu chloride of 35 – 50 kBq dissolved in saline was injected into the colorectal tumor-bearing mice to determine the biodistribution, and a high uptake of 67Cu in the tumor was found.12) The result suggests that 67CuCl2 can be a potential radionuclide agent for cancer radiotherapy. Characteristic points of accelerator neutrons to produce a wide variety of medical radioisotopes of high quality will be discussed together with the results described above.

        [1] Report by Japan Radiation Association, Isotope News 54, 723 (2016) [in Japanese].
        [2] NuPECC Report “Nuclear Physics for Medicine”, 2014.
        [3] The Supply of Medical Radioisotopes: Report by Nuclear Energy Agency (March 2016).
        [4] Biogen Idec Inc. Zevalin (ibritumomab tiuxetan) (Biogen Idec Inc., San Deiego, CA, 2005).
        [5] I. Novak-Hofer and P. A. Schubiger, Eur. J. Nucl. Med. 29, 821 (2002).
        [6] Y. Nagai and Y. Hatsukawa, J. Phys. Soc. Jpn. 78, 2009, 033201-1
        [7] T. Kin, Y. Nagai et al., J. Phys. Soc. Jp. 82, 2013, 034201-1
        [8] Y. Nagai, M. Kawabata et al., J. Phys. Soc. Jpn. 83, 2014, 083201-1
        [9] Y. Nagai, Y. Nakahara et al., J. Phys. Soc. Jpn. 86, 2017, 053202-1
        [10] F. Minato, K. Tsukada et al., J. Phys. Soc. Jpn. 86, 2017, 114803-1
        [11] M. Kawabata, K. Hashimoto et al., J.Radioanal. Nucl. Chem, 303, 2015, 1205
        [12] Y. Sugo, K. Hashimoto et al., J. Phys. Soc. Jpn. 86, 2017, 023201-1

        Speaker: Prof. Yasuki Nagai ( National Institutes for Quantum and Radiological Science and Technology)
      • 38
        Cyclotron-based production of the theranostic radionuclides 67Cu and 47Sc

        The aim of this work is the analysis of 67Cu and 47Sc production by using high-energy and high-intensity cyclotrons, as the one operating at Arronax facility (Nantes, France) and the one recently installed at Legnaro National Laboratories (INFN-LNL, Padova, Italy), in the framework of SPES project. The aim of the SPES project is focused both on the use of Radioactive Ion Beams (RIB) in nuclear physics experiments and applied research in the field of nuclear medicine, through the LARAMED project – acronym of LAboratory of RAdionuclides for MEDicine. Among the radionuclides of major interest for LARAMED project there are 67Cu and 47Sc, thanks to their great potential in theranostics. This innovative medical approach is based on the use of the same radiopharmaceutical labelled with isotopes emitting radiation useful for both diagnosis and therapy. The use of theranostic radionuclides or theranostic mixture of isotopes of the same chemical element (as 64Cu/67Cu or 44Sc/47Sc) allows the selection of patients with higher chance to respond to specific treatments and the application of individually customized dosimetry.
        The interest on 67Cu and 47Sc production stands on their physical characteristics: they both emit β- particles of low-medium energy (mean Eβ- = 141 keV and Eβ- = 162.0 keV respectively) and γ-rays suitable for SPECT or SPECT/CT cameras (67Cu: Eγ = 184.58 keV, Iγ = 48.6%; 47Sc: Eγ = 159.381 keV, Iγ = 68.3%); moreover, their relatively long half-life (61.83 h and 3.3492 d) permit to follow the slow biodistribution of monoclonal antibodies and specific molecular vectors, such as peptides, allowing their use in radioimmunotherapy.
        In this work the production of 67Cu and 47Sc for medical use is analysed, taking into account the yield of different nuclear reactions induced by proton beams. Relevant production cross sections have been measured in collaboration with the ARRONAX facility. In view of an optimized production, considerations on the co-production of contaminant radionuclides, especially the isotopic impurities that can not be chemically separated from the desired product, are also given.

        Speaker: Gaia Pupillo (INFN - National Institute for Nuclear Physics)
    • 11:00 AM
    • Medical radioisotopes
      Convener: Arjan Plompen
      • 39
        Challenges in the modeling of nuclear reactions for theranostic applications

        The production of innovative radionuclides in the context of theranostics (i.e. the combined therapy and diagnostics) is currently a topic of great interest and the new generation of proton cyclotrons is offering many new routes for their production with charged particle beams, as an alternative to the more traditional neutron reactions at reactors. Many candidates have been identified by international committees, as for instance the IAEA recommended 67Cu, 47Sc or 186Re: they can be produced at cyclotrons with different nuclear reactions and together with other contaminants, as for example 64Cu in case of copper or 46Sc in case of scandium. Other promising isotopes are currently being proposed, as 52Mn for example. Other techniques, like for example the isotope separation online method, could also be investigated for the potentially higher purity of the reaction products.

        The optimal conditions for the production of a given isotope depend on various factors, like the irradiation conditions, the target properties, the beam type and energy and the nuclear reaction cross section: preliminary studies are required to identify the best reaction channels and the optimal energy windows that maximize the desired isotope yield, minimizing at the same time the contaminants. Often experimental data are missing or uncertain and nuclear models and codes have to be exploited for this purpose, in particular when the reaction products are stable or difficult to measure.

        In this talk we review the most recent activities in the context of the new LNL SPES/Laramed facility and we present the results obtained for a selection of nuclear reactions of interest (see Figure for an example) with state-of-art nuclear codes (Talys, Empire, Fluka and others).

        Speaker: Andrea Fontana
      • 40

        Cancer management is a major medical and economic issue because of the increasing incidence of the disease in the world. The need for radioisotopes in both cancer diagnosis and therapy is very well established. These needs have been addressed through a series of IAEA Coordinated Research Projects running for the last 20 years.

        Experimental data compilations, theoretical calculations and evaluations were carried out for many of the reactions of interest for isotope production and beam monitoring. The recommendations for both established and emerging radionuclides, monitor reactions, and validation/testing of the cross-section production library are discussed.

        Recommended data for charged-particle reactions have been also used to constrain nuclear reaction models for protons and cluster projectiles with neutron emission. Status and current issues in theoretical description of charged-particle induced reactions up to 100 MeV are reviewed.

        Speaker: Roberto Capote (International Atomic Energy Agency)
      • 41
        Production of innovative radionuclides for therapy or diagnostic: nuclear data measurements and comparisons with the TALYS code

        Nuclear medicine is a specialty that uses radioactive nuclei for therapy or diagnostic of diseases such as different types of cancer. These radionuclides are most of the time coupled with carrier molecules to target cells of interest. Currently, only few radionuclides are deployed in clinical practice. However, many others may be of medical interest due to their emitted radiation, their half-life and/or their chemical properties that can be adapted to the transit time of carrier molecule and to the pathology.
        Since nuclear data measurements are essential for the optimization of the radionuclide production, the PRISMA group of the SUBATECH laboratory carried-out experiments in collaboration with the GIP ARRONAX (Nantes, France), which possesses a multi-particle high-energy cyclotron (70 MeV for protons, 68 MeV for alpha particles and 35 MeV for deuterons). The cross section associated to a given nuclear reaction is the fundamental physical parameter needed to infer the production rate of a radionuclide. Using the stacked foils technique and the gamma-spectroscopy, we measured experimental data for a selection of radionuclides of medical interest: photon emitters (Hg-197m, Ru-97) and positron emitter (Sc-44g) for diagnostic as well as electron emitters (Re-186, Tb-155, Sn-117m) and α emitters (Th-226, Ra-233, Bi-213) for therapeutic applications.
        The aim of this presentation is to give the status of nuclear data collected for medical isotopes production and to present the large set of experimental data collected by our group using the protons, deuterons and alpha particles delivered by the ARRONAX cyclotron from few MeV up to 70 MeV and covering a wide range of target masses. Using these data, we will also show that constrains can be put on simulation tools such as the TALYS code and compare with TENDL-2015, the TALYS-based evaluated nuclear data library.
        The TALYS code, developed by NRG Petten (Netherlands) and CEA Bruyères-le-Châtel (France), provides a complete description of all reaction channels and observables based on many state-of-the-art nuclear models. It includes a combination of models, defined by the authors of the code and put as default, that best describe the whole set of data available for all projectiles. The last release of the code, TALYS-1.9, has been first used with these default models. Then, three main phenomena have been found to have a great influence on the calculated production cross section values in the energy range of the experiments: the optical model, the pre-equilibrium model and the level density model. Finally, a better overall agreement with our experimental data could be obtained with a different combination of models already included in the code.

        Speaker: Arnaud Guertin (Laboratoire SUBATECH, CNRS/IN2P3, IMT Atlantique, Université de Nantes)
      • 42
        Production of medically interesting $^{97}$Ru via $^{nat}$Mo($\alpha$,x) above 40 MeV at ARRONAX

        Recently there has been growing interest in the medical application of $^{97}$Ru isotope. It is intended to be useful for both diagnostic and therapeutic purposes due to its convenient physical properties ($T_{1/2}$ = 2.9 d, gamma lines 215.7 keV, 85.8% and 324.5 keV, 10.2%, decay 100% EC with no $\beta$+ to contribute to the dose). Its chemical properties are also favourable, as it has several degrees of oxidation (II, III, IV, VIII) and forms more stable compounds compared to the conventional $^{99m}$Tc [Zaitseva, 1996]. Therefore, there are already many $^{97}$Ru-labeled radiopharmaceuticals successfully used for different prolonged examinations [Mukhopadhyay, 2011].

        Materials and methods
        Presently, there are different identified routes to produce $^{97}$Ru, with the use of neutron and charge particle induced reactions [Lahiri, 2016]. In this work, we focus on the $\alpha$-induced nuclear reactions on $^{nat}$Mo target in order to extend the available data above 40 MeV, in coherence with $\alpha$ beam available at our facility. The irradiation of $^{nat}$Mo stack foils was performed at ARRONAX, with the $\alpha$-beam of 67.4 MeV. The energy straggling in the last foil was calculated to be 0.75 MeV. The irradiated foils were measured via $\gamma$-ray spectroscopy techniques.

        Results and discussion
        We have measured the cross-section for the α-induced reactions on $^{nat}$Mo in the energy range 67 – 42 MeV. Our results indicate that for example the irradiation of 250 µm $^{nat}$Mo with 65 MeV $\alpha$-beam will yield around 10 MBq/$\mu$Ah (0.27 mCi/$\mu$Ah) of $^{97}$Ru. Most importantly, the use of such high energy prevents the formation of long-lived contaminant $^{103}$Ru ($T_{1/2}$ = 39.35 d). Although the yield of 0.27 mCi/$\mu$Ah is lower compared to the $^{103}$Rh(p,x)$^{97}$Ru reaction with around 1.3 mCi/$\mu$Ah [Lagunas-Solar, 1982], it allows to use the cheaper target with better thermal properties. Therefore the method to produce $^{97}$Ru via $^{nat}$Mo($\alpha$,x) might be considered in certain cases.


        • Lagunas-Solar, M., Avalia, M., Navarro, N., Johnson, P., 1982. Cyclotron Production of No-carrier-added $^{97}$Ru by Proton Bombardment of $^{103}$Rh Targets. Int. J. Appl. Radiat. Isot., vol. 34, No. 6, p. 915
        • Lahiri, S., 2016. Across the energy scale: from eV to GeV. J. Radioanal. Nucl. Chem., vol. 307, p. 1571.
        • Mukhopadhyay, B., Mukhopadhyay, K., 2011. Applications of the Carrier Free Radioisotopes of Second Transitions Series Elements in the Field of Nuclear Medicine. J. Nucl. Med. Radiat. Ther., vol. 2:2
        • Zaitseva, N. G, Stegailov, V. I., Khalkin, V. A., Shakun, N. G., Shishlyannikov, P. T., Bukov, K. G., 1996. Metal Technetium Target and Target Chemistry for the Production of $^{97}$Ru via the $^{99}$Tc(p,3n)$^{97}$Ru Reaction. Appl. Radiat. Isot., vol. 47, No. 2., p. 145
        Speaker: Mateusz Sitarz (GIP ARRONAX; Srodowiskowe Laboratorium Ciezkich Jonow Uniwersytetu Warszawskiego; Wydzial Fizyki Uniwersytetu Warszawskiego)
      • 43
        General discussion
    • 44
    • Honorary session
      Convener: Carlos Dasso (University of Seville)
      • 45
        Speaker: Egle Tomasi (CEA saclay)
      • 46
        Speaker: Anton Antonov
      • 47
        Speaker: Todor Antonov
      • 48
        Speaker: Syed M. Qaim (Forschungszentrum Jülich)
      • 49
        Speaker: Dr Mike Herman (Brookhaven National Laboratory)
      • 50
        Speaker: Mark Chadwick
      • 51
        Speaker: Pavel Oblozinsky (Retired)
    • Hadrontherapy
      Convener: Lembit Sihver
      • 52
        Perspectives in Neutron Capture Therapy of Cancer

        The features of this experimental form of radiotherapy, its status and some research lines in direct relation to nuclear reactions and mechanisms will be discussed.

        Speaker: Ignacio Porras (University of Granada, Spain)
      • 53
        A radiobiological database produced by the BIANCA model to predict the biological effectiveness of hadrontherapy beams

        The BIANCA (BIophysical ANalysis of Cell death and chromosome Aberrations) biophysical model [1,2] was extended and systematically applied to a wide range of particle types and energies used in cancer hadrontherapy, and the simulation outcomes were analyzed and shaped in a form suitable for an interface with a radiation transport code like FLUKA. This allowed obtaining a tool capable of predicting cell death (and possibly chromosome damage) along hadrontherapy dose profiles.
        The BIANCA model, which is implemented as a Monte-Carlo code and assumes a pivotal role for DNA cluster damage, is based on the following assumptions: i) ionizing radiation can induce DNA “Cluster Lesions” (CLs), where a CL is defined as a critical DNA damage that produces two independent chromosome fragments; ii) chromosome fragment un-rejoining, or distance-dependent mis-rejoining, gives rise to chromosome aberrations; iii) certain aberrations (dicentrics, rings and large deletions) lead to cell death. The yield of CLs is the first adjustable parameter, and its value is tuned for each radiation quality following comparison with experimental data taken from the literature; in the model version applied in this work, the second, and last, model parameter is the chromosome-fragment unrejoining probability.
        The simulation outcomes were systematically tested against experimental data on cell lines of different radiosensitivity exposed to different particles over a wide energy range. Good agreement was obtained, which allowed producing a database of CL yields for different particle types and LET (Linear Energy Transfer) values. Before the so-called “overkilling region” (the high-LET region where the biological effectiveness stops increasing), for each ion type the CL yield showed a LET-dependence of the form a·L+b·L$^2$, thus allowing to establish a one-to-one correspondence between LET value and CL yield; in the overkilling region, a tendency to saturation was observed and other functions were tested. Thanks to these fits, the CL input parameter can now be derived a priori for every LET value, including those not investigated experimentally.
        It was therefore possible to perform many simulations of cell survival for protons, He- and C-ions over a wide LET range (at steps of few keV/µm) and for several doses, using as input the CL yields provided by the fits. Each simulated survival curve was then fitted by a linear-quadratic exponential function of the form S(D)=exp(-αD-βD$^2$). This allowed to produce an almost continuous set of α and β values as a function of LET for each ion type.
        In the context of hadrontherapy, the tables of α and β values provided by BIANCA can be read by FLUKA, which provides all the necessary information (particle type, LET and absorbed dose), thus allowing fast computing of biological outputs in every position of a therapeutic dose profile.

        1. M.P. Carante and F. Ballarini (2016), Calculating Variations in Biological Effectiveness for a 62 MeV Proton Beam. Front. Oncol. 6:76.
        2. F. Ballarini and M.P. Carante (2016), Chromosome aberrations and cell death by ionizing radiation: evolution of a biophysical model. Radiat. Phys. Chem. 128C, 18-25.

        Acknowledgements: this work was partially supported by INFN (projects “ETHICS” and “MC-INFN/FLUKA”)

        Speaker: Mario Pietro Carante (INFN - National Institute for Nuclear Physics)
      • 54
        MONET code: evaluation of the dose in Hadrontherapy

        The accurate evaluation of the dose distribution is an open issue in Hadrontherapy.
        MONET (Model of ioN dosE for Therapy) is a code for the computation of the 3D dose distribution for protons and Helium beam in water. MONET accounts for all the physical interactions and is divided in two part: the lateral and longitudinal distribution.
        For the lateral profile, MONET is based on the Molière theory of multiple Coulomb scattering (Embriaco et al, Phys. Med. Biol. 62 (2017) 6290–6303). To take into account also the nuclear interactions, we add the Cauchy-Lorentz function, where the two parameters are obtained by a fit to a FLUKA simulation (Bellinzona et al., Phys. Med. Biol. 61 (2016) N102–N117) (Embriaco et al., Physica Medica 40 (2017) 51–58). We have implemented the Papoulis algorithm for the passage from the projected to a 2D lateral distribution (Embriaco et al, Physica Medica 38 (2017) 66–75).
        For the longitudinal profile, we have implemented a new calculation of the average energy loss that is in good agreement with simulations and other formulas. The inclusion of the straggling is based on the convolution of energy loss with a Gaussian function. In order to complete the longitudinal profile, also the nuclear contributions are included in the model using a linear parametrization with only two parameters (Embriaco et al, Physica Medica 38 (2017) 66–75).
        The total dose profile is calculated in a 3D mesh by evaluating at each depth the 2D lateral distributions and by scaling them at the value of the energy deposition.
        We have compared MONET results with the FLUKA simulation in two cases: a single Gaussian beam and a lateral scan as a sum of many beams in order to estimate the accuracy of the model focusing on the tails of the distribution that give rise to the low-dose envelope. In both cases, we have obtained a good agreement for different energy of protons and Helium beam in water.
        The advantages are the physical foundation, the fast calculation time and the accuracy. A possible development is the creation of a dose database of clinical interest and an online fast dose evaluation tool.

        Speaker: Alessia Embriaco (INFN - National Institute for Nuclear Physics)
      • 55
        Development of the nuclear reaction and fragmentation models for heavy ion collisions in the therapeutic energy range

        Ionizing radiation is exploited in radiotherapy to damage malignant cells' DNA and therefore to cause tumor death. Proton and carbon ion beams are already used since decades in many institutes worldwide, while helium ions are planned to be used in the next future at the Heidelberg Ion-Beam Therapy center in Germany [1, 2].
        With increasing mass and charge of the primary beam particles, a more conformed dose to the tumor, less lateral scattering and a higher biological effects can be achieved. However, ions heavier than protons may undergo fragmentation in the patient tissues. The resulting fragments have broader lateral distributions and longer paths than the primary particles, and therefore they can reach and damage healthy tissues surrounding the tumor. For this reason, nuclear reaction and fragmentation processes need to be carefully considered for accurate treatment plannings and dose calculations.

        The FLUKA [3, 4] Monte Carlo code is used for medical purposes at HIT (Heidelberg), MIT (Marburg) and CNAO (Pavia). It provides all the basic inputs to the treatment planning systems (TPS), and it is also used to validate the TPS dose calculations, especially in complex scenarios [5]. Our work aims to improve the precision of the physics models embedded in FLUKA, in order to predict more accurately the dose delivered during radiotherapy treatments.

        Method and Results:
        For different primary particles (He, C and heavier ions) and various target materials (e.g. C, O, Al, Ti, water), we investigated the nuclear reaction cross sections as well as the angular and energy distributions of the secondary radiation produced by fragmentation of the primary ions. By comparison with experimental data available in literature, we identified the factors which need to be refined in the FLUKA physics models. Significant improvements were achieved, especially concerning i) the nuclear reaction cross sections of helium ions and ii) the angular and energy distributions of secondary protons originated from carbon ion beams in graphite.

        Conclusions and Outlook:
        Analysis of the nuclear reaction cross sections for helium ions is required prior to the clinical use of FLUKA for helium ion therapy. Initial studies have been carried out and new measurements, planned for February 2018, will provide the information required in order to finalize this study.
        Improvements in the FLUKA ion fragmentation modeling for C-C collisions (symmetric system) have been obtained. The results achieved will improve the FLUKA-based-TPSs used in the clinics.
        Asymmetric systems with heavy primary particles (e.g. O, Ne, Ar) and high-Z target materials (e.g. Al, Ti, Au) are currently under investigation. This work is of interest for radiotherapy and also for astrophysics and heavy ion research in general.

        1 Mairani A et al 2016 Biologically optimized helium ion plans: calculation approach and its in vitro validation, Phys. Med. Biol. 61 4283-4299
        2 Tessonnier T et al 2017 Helium ions at the heidelberg ion beam therapy center: comparison between FLUKA Monte Carlo code predictions and dosimetric measurements, Phys. Med. Biol. 62 6784-6803
        3 Bohlen T T et al 2014 The FLUKA Code: Developments and Challenges for High Energy and Medical Applocations, Nuclear Data Sheets 120, 211-214
        4 Ferrari A et al 2005 FLUKA: a multi-particle transport code, CERN-2005-10, INFN/TC_05/11, SLAC-R-773
        5 Battistoni G et al 2016 The FLUKA Code: An Accurate Simulation Tool for Particle Therapy, Front. Oncol. 6: 116

        Speaker: Dr Giulia Arico' (CERN)
      • 56
        The FOOT (FragmentatiOn Of Target) experiment

        Particle Therapy uses protons and light ions beams for the treatment of deep-seated solid tumors. Due to the features of energy deposition of charged particles a small amount of dose is released to the healthy tissue in the beam entrance region, while the maximum of the dose is released to the tumor at the end of the beam range, in the Bragg peak region. However, nuclear interactions between beam and patient tissues induce fragmentation both of projectile and target and must be carefully taken into account.
        In protontherapy clinical practice a constant RBE equal to $1.1$ is adopted, regardless of the demonstrated RBE variations, which depends on physical and biological parameters. Among other mechanisms, nuclear interactions might influence the proton RBE due to secondary heavier particles produced by target fragmentation that can significantly contribute to the total dose: an unwanted and undetermined increase of normal tissues complications probability (NTCP) may occur. The FOOT experiment (FragmentatiOn Of Target) is designed to study these processes. Target ($16O$,$12C$) fragmentation induced by $150-250\ MeV$ proton beam will be studied via inverse kinematic approach, where $16O$ and $12C$ therapeutic beams, with the quoted kinetic energy, collide on graphite and hydrocarbons target to provide the cross section on Hydrogen. This configuration explores also the projectile fragmentation of these beams. The detector includes a magnetic spectrometer based on silicon pixel detectors and drift chambers, a scintillating crystal calorimeter with ToF capabilities, able to stop the heavier fragments produced, and a $\Delta E$ detector to achieve the needed energy resolution and particle identification. The experiment is being planned as a ‘table-top’ experiment in order to cope with the small dimensions of the experimental halls of the CNAO and HIT treatment centers and GSI, where the data taking is foreseen in the next years. The detector, the physical program and the timetable of the experiment will be presented as well as the results of a Monte Carlo study, based on the FLUKA code, which aims to evaluate the detector performance and the expected resolution on fragment identification and on the nuclear cross sections relevant for charged particle therapy.

        Speaker: Michela Marafini (INFN Roma1 - Centro Fermi)
    • 11:00 AM
    • Radioactive waste, neutrino
      Convener: Tadashi Yoshida (Tokyo Institute of Technology)
      • 57
        Nuclear reaction study for high-level radioactive waste: Cross section measurements for proton- and deuteron-induced spallation reactions of long-lived fission products

        The disposal of high-level radioactive waste from nuclear power plants is one of the major issues in worldwide. As a promising solution, research and development has been devoted to the partitioning and transmutation technology where long-lived nuclides are converted to stable or short-lived ones. In particular, the transmutation on the long-lived fission products (LLFPs) has received much attention because the LLFP nuclei have large radiotoxicities and they can be produced continuously in the accelerator driven systems and next-generation nuclear reactors. However, experimental reaction data for LLFP nuclei are very limited.

        Aiming at bringing a new invention to the nuclear transmutation on LLFP, we have performed a series of systematic studies on the proton- and deuteron-induced spallation for the long-lived fission products ($^{90}$Sr,$^{93}$Zr,$^{107}$Pd,$^{126}$Sn,$^{137}$Cs) at reaction energies ranging from 50 to 200 MeV/nucleon at RIKEN Radioactive Isotope Beam Factory. The inverse kinematics technique was adopted. Namely, LLFP beams were used and proton/deuteron targets were conducted to induce the reactions. Our study on $^{137}$Cs and $^{90}$Sr [1] is the first attempt in the history of nuclear physics to solve the problem of the LLFP transmutation and has triggered the reaction studies for other long-lived fission products.

        The present work focuses on $^{137}$Cs, $^{90}$Sr and $^{107}$Pd. Cross sections on proton/deuteron were successfully obtained for these three nuclei and both target and energy dependence of reactions were investigated. In addition, the newly obtained data were compared with the nuclear interaction model including both intra-nuclear cascade and evaporation processes in the frame work of the Particle and Heavy Ion Transport code System (PHITS). In the presentation, the results for LLFP nuclei $^{137}$Cs, $^{90}$Sr [1] and $^{107}$Pd [2] as well as the potential of spallation reaction on the LLFP transmutation will be discussed.

        This work was supported and funded by the ImPACT program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).

        [1] H. Wang, H. Otsu, H. Sakurai et al., Phys. Lett. B 754, 104(2016).
        [2] H. Wang, H. Otsu, H. Sakurai et al., Phys. Theor. Exp. Phys. 2017, 021D01 (2017).

        Speaker: He Wang
      • 58
        The demand for TRU nuclide cross-sections from the view point of TRU production and radiotoxicity

        The environmental load reduction of nuclear energy is required in Japan, from the view point of public acceptance due to the increasing of safety demand to the nuclear energy utilization. This environmental load consists of the mass and radiotoxicity of radioactive wastes. The long-term radiotoxicity of the radioactive wastes is dominated by trans-uranium (TRU) nuclides. Additionally, most of the TRU nuclides, which are large part of environmental loads, are generated from light water reactor. Therefore, the evaluation of TRU nuclide production in the light water reactor is important to estimate the environmental load of nuclear energy.
        As well known, the amount of TRU nuclide is evaluated through burn-up calculations. Additionally, these burn-up calculations rely on the cross section data of a nuclear data library. However, these cross section data have a different value between libraries due to its uncertainty.
        We evaluated the effects of heavy-metal-nuclide cross-section between libraries on the TRU production and radiotoxicity based on the light water reactor. In this study, MVP-BURN and JENDL-4.0u were used as a burn-up calculation code and a reference nuclear data library, moreover, each heavy metal cross section was independently changed to JEFF-3.2 or ENDF/B-VII.1 to evaluate the cross section effect in each nuclide between libraries.
        The calculation results revealed that the productions of Pu-238, Am-241 and Cm-244 with JEFF-3.2 were different from more than 8% those with JENDL-4.0u and ENDF/B-VII.1 as shown in Fig.1~Fig.3. The thermal energy capture reaction of Pu-238 and 1.356eV resonance capture reaction of Am-243 have a large impact on the radiotoxicity of Pu-238 and Cm-244. These nuclides don’t have a large impact on the criticality of nuclear reactor core; hence, the precision of these nuclide cross sections is not a significant problem for core design. However, Pu-238 and Cm-244 contribute to the decay heat and radiotoxicity of TRU within 100 years after spent fuel discharge, therefore, the precision of these nuclide cross sections should be improved from the view point of TRU production and radiotoxicity.
        For present results, we extracted TRU nuclides which capture cross sections should be improved. In the future work, more accurate evaluation of the TRU production and radiotoxicity will be examined quantitatively.

        Speaker: Mr Rei Kimura (Toshiba Energy Systems & Solutions)
      • 59
        Charged-current quasielastic (anti)neutrino cross sections on $^{12}$C with realistic spectral functions including meson-exchange contributions

        We present a detailed study of charged-current quasielastic (anti)neutrino scattering cross sections on a $^{12}$C target obtained using a spectral function $S(p,{\cal E})$ that gives a scaling function in accordance with the electron scattering data. The spectral function accounts for the nucleon-nucleon (NN) correlations, it has a realistic energy dependence and natural orbitals (NO's) from the Jastrow correlation method are used in its construction [1-3]. The results are compared with those when NN correlations are not included, namely harmonic-oscillator single-particle wave functions are used instead of NO's. A comparison of the results with recent experiments spanning an energy range from hundreds of MeV up to 100 GeV, as well as to results from the superscaling approach, which is based on the analysis of electron-nucleus scattering data and has been recently improved with the inclusion of relativistic mean field theory effects. The contribution of two-particle two-hole meson-exchange currents on neutrino-nucleus interactions is also considered within a fully relativistic Fermi gas. The results show a good agreement with the experimental data over the whole range of neutrino energies.

        [1] A.N. Antonov, M.V. Ivanov, J.A. Caballero, M.B. Barbaro, J.M. Udias, E. Moya de Guerra, and T.W. Donnelly, Phys. Rev. C 83 045504 (2011).
        [2] M.V. Ivanov, A.N. Antonov, J.A. Caballero, G.D. Megias, M.B. Barbaro, E.M. de Guerra, and J.M. Udias, Phys. Rev. C 89 014607 (2014).
        [3] M.V. Ivanov, A.N. Antonov, M.B. Barbaro, C. Giusti, A. Meucci, J.A. Caballero, R. Gonzalez-Jimenez, E.M. de Guerra, and J. M. Udias, Phys. Rev. C 91 034607 (2015).

        Speaker: Martin Ivanov (Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences)
      • 60
        Double charge exchange reactions for neutrino physics: recent results and future perspectives

        The neutrinoless double beta (0νββ) decay, if observed, has important impli-
        cations on particle physics, cosmology and fundamental physics. In particular it
        can give access to the effective neutrino mass. In order to extract such informa-
        tion from the 0νββ-decay half-life measurement, the knowledge of the Nuclear
        Matrix Elements (NME) is of utmost importance. In this context the NUMEN
        and the NURE projects aim to extract information on the NME by measuring
        the Double Charge Exchange (DCE) reaction cross section in selected systems
        of interest for the 0νββ-decay.
        Early studies with heavy-ions DCE reactions performed in the 80’s and 90’s
        were not conclusive because of the experimental difficulties that have to be faced
        in such kind of measurements, like to obtain very forward-angle data, the very
        low cross section of the process to be measured, the requirement of a high energy
        resolution and, eventually, the unambiguous identification of the DCE reaction
        from other competing processes.
        All these requirements can be met by the large-acceptance spectrometer
        MAGNEX, present at INFN-LNS, Catania. Its high energy and angular res-
        olution and its large acceptance make MAGNEX a tool that can achieve the
        measurements of the DCE cross-sections in the zero-degree region.
        An experimental campaign focused on DCE reactions involving the nuclei
        of interest for 0νββ-decay has already begun. Recent results concerning the
        (20Ne, 20O) DCE reaction at 15 AMeV, on 116Cd and 130Te targets will be
        shown and discussed.

        Speaker: Domenico Torresi (INFN - LNS, Catania (IT))
    • Facilities
      Convener: Francesco Cerutti (CERN)
      • 61
        Recent results of n_TOF facility at CERN

        Astrophysics is approaching a stage where a number of long-standing central questions about our Universe can finally be addressed within a consistent and quantitative way. The so called Standard Model, based on the General theory of Relativity, the Nuclear and the Particle Physics, describes satisfactorily the hot Big Bang cosmology. The currently observed ratio of neutrons and protons (about 13% n and 87% p) was established, when the weak interactions froze out (after 1 s). In this context, the quest for the origin of the chemical elements plays a prominent role: The production of 2H, 3He, 4He and 7Li (after 200 s) in the Big Bang bears important consequences for cosmology and particle physics, whereas the heavy elements beyond Fe witness ongoing neutron capture nucleosynthesis in evolved stars and supernova explosions with immediate constraints for Galactic chemical evolution.
        The difficult task is to understand the formation of these heavy elements, where not only the nuclear physics is complicated but also the mechanisms and thermodynamics are not completely understood yet. Advances in our understanding of these processes and of the astrophysical sites where they occur, require advances in laboratory measurements of neutron cross sections.
        In this framework the n_TOF collaboration has started a vast program of nuclear capture measurements with the aim of reducing the respective cross section uncertainties below 3%, in order to improve the reliability of astrophysical models.
        The innovative feature of the n_TOF facility at CERN, in the two experimental areas, (20 m and 200 m flight paths), i.e. the high instantaneous flux, the high energy resolution and low background, allow for an accurate determination of the neutron capture cross section for radioactive samples or for isotopes with small neutron capture cross section, which are of interest for Nuclear Astrophysics
        The n_TOF facility itself, the main results obtained so far, and the implication of the astrophysical program of the n_TOF collaboration will be presented in this talk

        Speaker: Dr Giuseppe Tagliente (INFN)
      • 62
        Nuclear astrophysics at Gran Sasso Laboratory: the LUNA400 experiment

        Nuclear fusion reactions are the heart of nuclear astrophysics: they sensitively influence the nucleosynthesis of the elements in the earliest stages of the universe and in all the objects formed thereafter, and control the associated energy generation, neutrino luminosity, and evolution of stars. LUNA (Laboratory for Underground Nuclear Astrophysics) is an experimental approach for the study of nuclear fusion reactions based on an underground accelerator laboratory.
        Since 1991 the LUNA Collaboration has been directly measuring cross sections of nuclear processes belonging to Hydrogen burning and Big Bang nucleosynthesis relevant in several astrophysical scenarios, in the underground laboratories of Laboratori Nazionali del Gran Sasso (LNGS) with unprecedented sensitivity, due to the huge background suppression available in the underground location. In this talk, after a general introduction, the latest LUNA results and ongoing measurements will be presented.

        Speaker: Francesca Cavanna
      • 63
        (n,cp) reactions study at the n_TOF facility at CERN: results for the Cosmological Lithium problem

        see attached .doc

        Speaker: Massimo Barbagallo (Universita e INFN, Bari (IT))
      • 64
        The Study of the $^{22}$Ne($\alpha$,$\gamma$)$^{26}$Mg at LUNA

        The $^{22}$Ne($\alpha$,$\gamma$)$^{26}$Mg has an important role in nucleosynthesis of massive stars and AGB stars. As a matter of fact it competes with the $^{22}$Ne($\alpha$, n)$^{25}$Mg which is an efficient source of neutrons for s-process. In addition a recent study shows that the production of all isotopes from $^{26}$Mg to $^{31}$P is affected by the uncertainty of $^{22}$Ne($\alpha$,$\gamma$)$^{26}$Mg reaction rate.
        The main source of the high uncertainty on the $^{22}$Ne($\alpha$,$\gamma$)$^{26}$Mg reaction rate is the poorly costrained strenght of the 395 keV resonance. Due to the low cross section involved most of the studies of the $^{22}$Ne($\alpha$,$\gamma$)$^{26}$Mg reaction used indirect methods. As a result a wide range of strenghts values ($8.7\cdot10^{-15} - 3.1\cdot10^{-9}$ [eV]) are attributed to the 395 keV resonance.
        The direct measurement performed at LUNA (Laboratory for Underground Nuclear Astrophysics) is fundamental to improve the current state of art of
        $^{22}$Ne($\alpha$,$\gamma$)$^{26}$Mg. As a matter of fact, thank to the shield of 1400 m of rocks of Gran Sasso, the background in the region of interest is reduced of a factor 1000 at LUNA laboratory. This allowed LUNA to fix the contribute of the 395 keV resonance on the $^{22}$Ne($\alpha$,$\gamma$)$^{26}$Mg reaction rate.
        The experiment was performed at LUNA400kV accelerator, delivering a 400keV alpha beam to $^{22}$Ne gas target. In order to investigate such a low cross section a high efficiency 4$\pi$ BGO summing crystal was used. Details on the setup will be described during the talk.
        The first campaign was concluded in July 2016 and new upper limits for the 395keV resonance were found. Results and their impact on the efficiency of the $^{22}$Ne($\alpha$, n)$^{25}$Mg will be shown during the talk. A second campaign is planned in March and will cover three months. During the second phase of the experiment the residual background is further reduced surrounding the detector by a shield. An update on the status of the experiment will be presented during the talk.

        Speaker: Ms Denise Piatti (University of Padova and INFN of Padova)
    • 4:40 PM
    • Potential, strangeness, pion
      Convener: Jutta Escher (Lawrence Livermore National Laboratory)
      • 65
        Microscopic Optical Potential Derived from $NN$ Chiral Potentials.

        A microscopic optical potential for elastic proton-nucleus scattering has been derived at the first-order term within the spectator expansion of the non-relativistic multiple-scattering theory and adopting the impulse approximation.

        Two-basic ingredients are required to build the optical potential: a model for nuclear densities and the $NN$ interaction. For the $NN$ interaction we have used for the first time chiral potentials. Different versions of chiral potentials at fourth (N$^3$LO) and fifth (N$^4$LO) order have been used with the purpose to check the convergence and to assess the theoretical errors associated with the truncation of the chiral expansion in the construction of an optical potential.
        Results for the cross section, analysing power, and spin rotation of elastic proton scattering from different nuclei at different proton energy, in the range between 100 and 300 MeV, are presented and compared with the available experimental data and also with the results of a phenomenological optical potential.

        Speaker: Prof. Carlotta Giusti (Università degli Studi di Pavia and INFN, Sezione di Pavia)
      • 66
        Production of strange particles and hypernuclei in spallation reactions from the coupling of intranuclear cascade and de-excitation models.

        Motivated by a renewed interest of hypernucleus studies, strangeness degree of freedom was implemented in the intranuclear cascade model INCL.

        INCL takes care of the first stage of reactions between a nucleon (or a light cluster) and a nucleus at energies from a few tens of MeV up to a few GeV. After emission of fast particles, a hot remnant nucleus is produced and then another model, combined to INCL, treats its de-excitation (the Abla model in our case).

        INCL was known as a reliable model in the non-strange sector for energies up to 2-3 GeV [1] and, after 2010 with implementation of the multiple pion emission, up to ~15 GeV [2,3]. Since at those energies other particles can play a (smaller) role, on the one hand, and, on the other hand, new experiments on hypernuclei in several facilities are in progress or planned, K’s, $\Lambda$‘s and $\Sigma$‘s have been added as participant particles in INCL. Most important reactions involving these particles are also included. Concerning hypernucleus production, the de-excitation code Abla was also upgraded with evaporation of $\Lambda$'s and fission of hypernuclei (hyper-fission).

        Main ingredients will be discussed and results compared to experimental data will be shown. Kaon spectra obtained from experiments with several targets and at different energies show good agreements most of the time. Role of the Delta-induced Kaon production will be discussed and other specific channels mentioned. Much less data exist on $\Lambda$ spectra, however data from the HADES collaboration were used and here also the results are very encouraging, especially compared to other models. The main remaining discrepancy was analysed and will be explained. Finally, hypernucleus production rates will be compared to the very rare existing data. In addition, we put constraints on the $\Lambda$-nucleus potential by combining those experimental data to our calculation results.

        [1] S. Leray et al., J. Korean Phys. Soc. 59 791-796 (2011).
        [2] S. Pedoux and J. Cugnon, Nucl. Phys. A 866, 16-36 (2011).
        [3] D. Mancusi et al., Eur. Phys. J. A 53, 80 (2017).

        Speaker: Jason Hirtz
      • 67
        Isospin of pions - what do they tell us about the neutron skin of nuclei?

        The isospin of pions has long time been discussed as signal of the equation of state of asymetric matter. Especially in collisions of heavy ions (like Au+Au) at energies of several hundred MeV, the ratio of negative and positive pions has been proposed to be sensitive to isospin dependent potentials. However, the conclusions from comparison to experimental FOPI data have been rather controverse. We use the Isospin Quantum Molecular Dynamics Model (IQMD) to study the production and rescattering of pions in such reactions. We found the influence of different effects but however a very significant contribution from the definition of the radii of proton and neutron distributions, i.e. the neutron skin. We will analyse the effects of the neutron skin as function of energy, mass and centrality and discuss how to obtain information on the neutron skin from pion measurements.

        Speaker: Christoph Hartnack (SUBATECH)
    • Deuteron induced reactions
      Convener: Alfredo Ferrari (CERN)
      • 68
        Comparative analysis of empirical parametrizations and microscopical studies of deuteron-induced reactions



        \title{Comparative analysis of empirical parametrizations and microscopical studies of deuteron-induced reactions}

        \affiliation{Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 077125 Bucharest-Magurele, Romania}


        An extended analysis of the key role of direct interactions, i.e., breakup, stripping and pick-up processes, is carried out for deuteron-induced reactions. Particular comments concern the deuteron breakup and corresponding parametrizations \cite{ck2010,ma}, involved in actual model calculations \cite{talys}, as well as comparable microscopical analysis \cite{neoh}. Since the parametrized predictions have already been involved within successful analysis of all available data for deuteron interaction with various nuclei (e.g., \cite{BU2}), eventual similarities of these results represent an additional validation of the microscopic models, while the cross-section differences should be considered within the objectives of further measurements.

        \bibitem{ck2010} C Kalbach Walker, in {\it FENDL-3 Library}, Report INDC(NDS)-0645 (IAEA, Vienna, 2013), p. 11; https://www-nds.iaea.org/fendl/about/kalbach.pdf
        \bibitem{ma} M.~Avrigeanu, W.~von Oertzen, R.~A. Forrest, A.~C. Obreja, F.~L. Roman, and V.~Avrigeanu, Fusion Eng. Design {\bf 84}, 418 (2009); M. Avrigeanu and V. Avrigeanu, Phys. Rev. C {\bf 95}, 024607 (2017).
        \bibitem{talys} A.J. Koning, S. Hilaire, and S. Goriely, v. TALYS-1.9, 2017, http://www.talys.eu
        \bibitem{neoh} Yuen Sim Neoh, K. Yoshida, K. Minomo, and K. Ogata, Phys. Rev. C {\bf 94}, 044619 (2016).
        \bibitem{BU2} M.~Avrigeanu {\it et al.}, Phys. Rev. C {\bf 88}, 014612 (2013); {\it ibid.} {\bf 89}, 044613 (2014); {\it ibid.} {\bf 92}, 021601(R) (2015); {\it ibid.} {\bf 94}, 014606 (2016).



        Speaker: Prof. Marilena Avrigeanu (Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH))
      • 69
        Towards inclusion of low-energy deuteron interactions with target nuclei in FLUKA

        Deuteron interactions with nuclei at energies below $\sim$100 MeV/n remain a topic of ongoing research, with eminent practical interest (among other) as sources of mostly forward-scattered neutrons and protons. The inclusion of these interaction mechanisms in a general-purpose Monte-Carlo code for the simulation of radiation transport is not straightforward due to the idiosyncrasies of the deuteron: its low binding energy and the predominantly direct nature of its interactions with target nuclei in the considered energy domain. In this contribution, an account will be given of recent efforts undertaken towards the inclusion of deuteron interactions in the FLUKA transport model, relying on distorted-wave Born approximation (DWBA) calculations.

        Elastic deuteron break-up has been described within the zero-range post-form DWBA, accounting both for Coulomb and nuclear terms in the interaction potential, while disregarding spin-orbit coupling effects. The neutron, proton, and deuteron wavefunctions and phase shifts have been obtained using the RADIAL subroutine package to numerically solve the Schroeodinger equation for effective nucleon-nucleus and deuteron-nucleus optical-potential models. Integrals of the highly oscillatory product of three unbound radial functions have been evaluated with Vincent et al.'s contour-integral approach. Reasonable overall agreement with earlier deuteron elastic break-up cross section calculations in the literature has been obtained. With minor changes and simplifications, the DWBA scheme for elastic break-up can be prospectively used to account for the contribution of (d,p) or (d,n) nucleon-transfer reactions to bound states.

        State-of-the-art inclusive approaches to account for stripping to the continuum have been recently developed. However, it is not always easy to keep track of the final state of the target, as needed in a Monte Carlo simulation in view of phenomena like material activation. Effective modelling of the stripping to the continuum in a non-inclusive fashion is currently underway.

        Speaker: Francesc Salvat Pujol (CERN)
      • 70
        Production cross section of $^{197m}$Hg induced by deuterons on natural gold target

        Theranostics uses information coming from diagnostic to define specific targeted therapy on patient. The acquired image allows to identify the patient response and to estimate, for responder, the dose of the therapeutic agent to be injected. With this strategy, it is possible to give the right treatment, for the right patient, at the right time, with the right dose. Mercury-197 ($^{197(m)}$Hg) can be used for that purpose since their decay properties have convenient half-life, low energy gamma radiations for imaging and Auger electrons conversion for therapy. In addition, the starting target material is Gold which is monoisotopic easing the target preparation and the control of impurities. Moreover, the mercury extraction from the gold can be easily made by dry distillation.

        The main purpose is the study of the production of the $^{197m}$Hg (T$_{1/2}$ = 23.8h) which emits only low energies gammas emissions, 70-410 keV with main emissions at 134 keV 33% and 279.01 keV 6%. These features make the $^{197m}$Hg a great candidate for the SPECT imaging. Data exist on proton-induced reactions. Our work focuses on the use of deuterons as projectiles. The goal is to help selecting the right data in all the available ones in the literature and compare these data with existing one obtained using protons to determine the best production route for that radionuclide.

        The cross section values were obtained at the ARRONAX cyclotron in Nantes, France using the stacked foils technique in a vacuum enclosure. The particle flux of the beam crossing the stack, made of Gold, Titanium and Aluminum foils, was evaluated with a Faraday cup placed inside the enclosure to get a precise measurement of the current. These new set-up devoted to cross section measurements has been set-up and tested in well-known conditions. The Titanium foils serve as monitor and allow the monitoring of the particle flux along the stack. The monitor cross section values used are those recommended by the International Atomic Energy Agency (IAEA). The produced activities were assessed by gamma spectrometry using an HPGe detector coupled with the analysis software Fitzpeaks.

        The results obtained for the monitor reaction show that the new experimental set-up works well. Our results are in good agreement with the IAEA recommended cross section values and other available data in the literature. The cross sections obtained for the reactions $^{197}$Au(d,x)$^{197(m),195(m)}$Hg,$^{198(m),196(m2)}$Au with a deuteron beam up to 33 MeV will be shown. Our data are in agreement with those of Tarkanyi et al (2015). Our new set of data will also help extending the accuracy of databases and can be used to constrain theoretical calculations.

        Speaker: Etienne Nigron (Laboratoire SUBATECH, CNRS/IN2P3, IMT Atlantique, Université de Nantes, 4 rue Alfred Kastler)
      • 71
        Isotopic production cross sections of residual nuclei in proton- and deuteron-induced reactions on $^{91,92}$Y, $^{92,93}$Zr, and $^{93,94}$Nb around 100 MeV/nucleon

        In recent years, a new research project has been started for cross-section measurement of residues produced in proton- and deuteron-induced spallation reactions on long-lived fission products (LLFPs) (e.g., $^{79}$Se, $^{93}$Zr[1], $^{107}$Pd[2], $^{126}$Sn, $^{135}$Cs) using the inverse kinematics technique at RIKEN RI Beam Factory (RIBF) in order to provide basic data necessary for nuclear waste transmutation. In the measured isotopic-production cross sections for $^{93}$Zr, remarkable jumps originating from the neutron magic number N = 50 were observed in Zr and Y isotopes[1]. In the present work, we have derived isotopic-production cross sections for five nuclei adjacent to $^{93}$Zr (i.e., $^{91,92}$Y, $^{92}$Zr, and $^{93,94}$Nb) from further data analysis of the $^{93}$Zr experiment. Based on the systematic data, the behavior of isotopic production was investigated with particular attention to the effect of neutron shell closure with N=50.

        The experiment was performed at RIBF. The detail of the experimental procedure is described in Refs. [1,2]. The cocktail beam containing $^{91,92}$Y, $^{92,93}$Zr, and $^{93,94}$Nb at kinetic energies around 100 MeV/nucleon was produced by in-flight fission of $^{238}$U at 345 MeV/nucleon. Next, the cocktail beam was separated and identified by using the BigRIPS in-flight separator. Particle was separated by using energy degraders and slits placed at focal planes. Particle identification was performed by the TOF-$\Delta$E-B$\rho$ method. Then, the beam particles irradiated secondary targets (CH$_2$, CD$_2$, and C) placed at the entrance of ZeroDegree Spectrometer (ZDS). The residual nuclei produced by nuclear reactions in the second targets were identified event-by-event using ZDS.

        As in the case of $^{93}$Zr, characteristic jump structure near N=50 was observed in the isotopic distribution for the elements corresponding to charge-unchanging ($\Delta$Z = 0) and/or one-proton-removal ($\Delta$Z = -1) for $^{91,92}$Y, $^{92}$Zr, and $^{93,94}$Nb. The measured isotopic production cross sections were compared to PHITS calculation with INCL 4.6 for intra-nuclear cascade process and GEM for evaporation process. The overall behavior of isotopic-production cross sections was generally well reproduced by the calculation; however there were some differences: e.g., overestimation of the measured production yields corresponding to few-nucleon-removal reactions. The details of the experimental result and model analysis will be discussed in the presentation.

        This work was funded by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).

        [1] S. Kawase, K. Nakano, Y. Watanabe, et al., Prog. Theor. Exp. Phys. 2017, 093D03 (2017).
        [2] H. Wang, H. Otsu, H. Sakurai, et al, Prog. Theor. Exp. Phys. 2017, 021D01 (2017).

        Speaker: Prof. Yukinobu Watanabe (Kyushu University)
      • 72
        Cross-section measurements in the reactions of $^{136}$Xe on proton, deuteron and carbon at 168 $A$MeV

        Spallation reaction plays an important role in both fundamental research field and application field. For the fundamental research, spallation reaction is used as one of the mechanisms to produce unstable nuclei [1]. In application field, it is applied as neutron source in the accelerator-driven system [2] or for the transmutation of long-lived fission products (LLFP) [3]. In particular, $^{136}$Xe ($N$=80, $Z$=54) is a good candidate as a projectile to study both of the two fields. $^{136}$Xe is used as a primary beam in worldwide for radioactive beam generation. For transmutation, $^{136}$Xe is a stable isotope, neighboring with LLFP $^{137}$Cs. The comparison between $^{136}$Xe and $^{137}$Cs is critical to clarify the reaction mechanism and check the validity of the theoretical calculation used for $^{137}$Cs [3].

        In the present work, the isotopic cross sections of $^{136}$Xe on proton, deuteron and carbon at 168 $A$MeV were measured by using the inverse kinematics method. The experiment was performed at the RIKEN Radioactive Isotope Beam Factory. The secondary beams were produced by in-flight fission of $^{238}$U beam at 345 $A$MeV incident on a $^9$Be target. The particles in the secondary beams were identified event by event in the BigRIPS separator. CH$_2$, CD$_2$ and C targets were used to induce secondary reactions. The proton- and deuteron- induced cross sections were deduced from the CH$_2$ and CD$_2$ targets after subtracting contributions from carbon (using data from the C target run) and beam-line materials (using data from the empty- target run). The reaction products were analyzed by the ZeroDegree spectrometer.

        The cross sections for the reactions of $^{136}$Xe on proton, deuteron and carbon will be reported as well as the target dependence. The energy dependence could also be investigated by the comparison of these experimental results to previous studies for $^{136}$Xe at higher energies [5,6]. In addition, the measured cross sections will be compared with $^{137}$Cs, and with the theoretical model calculation for spallation reaction.

        This work was supported by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).

        [1] H. Suzuki et al., Nucl. Inst. and Methods B 317 (2013) 756.
        [2] C.D. Bowman et al., Nucl. Inst. And Methods A 320 (1992) 336.
        [3] H. Wang et al., Phys. Lett. B. 754 (2016) 104.
        [4] J. Alcántara-Núñez et al., Phys. Rev. C. 92, (2015) 024607
        [5] P. Napolitani et al., Phys. Rev. C. 76, (2007) 064609

        Speaker: X. Sun (RIKEN Nishina Center)
    • 11:00 AM
    • Nuclear reactions
      Convener: Mr Marc Dupuis (CEA)
      • 73
        Statistical-model description of gamma decay from compound-nucleus resonances

        see the attached pdf

        Speaker: Hans Weidenmueller (Max-Planck-Institut fur Kernphysik)
      • 74
        Statistical multi-step direct reaction models and the RPA

        Nucleon-induced pre-equilibrium reactions are now recognized as consisting almost exclusively of direct reactions in which incident nucleons induce excitations over a wide range of energy in the target nuclei. At low energies, one step reactions dominate. As the incident energy increases, multi-step reactions become important too. Tamura, Udagawa and Lenske pioneered the use of the RPA response function to describe the nuclear excitation in calculations of one-plus-two-step reactions of this type [1]. Modern calculations can describe both the excitation of low-energy collective states and the more uniform higher energy part of the spectrum, but are limited to a single direct interaction step [2]. However, it has been argued that the time scale of the two-step reaction is too short to permit the residual interaction to modify the response function to the RPA one [3]. Explicit calculations corroborate this conclusion [4]. The response function in this case would then be better approximated by the bare particle-hole one [5, 6]. Our objective here is to analyze the properties of the RPA response function and compare these to those of the bare particle-hole one.
        We used the Skyrme RPA code of G. Colò and collaborators [7] to study the collective and non collective excited states within the RPA for several nuclei and spin/parity from 1+ to 5-. By our definition, collective states show larger (or smaller) than average transition strengths, spread over a large number of particle-hole states and tend to be shifted in energy. We find them to be interspersed with non-collective state up to an energy of about 20 MeV in our calculations, although we could define no clear separation point between the states we considered collective and those we did not. At higher energies, the RPA excited states are predominantly well-localized particle-hole states of an average width that grows roughly with the square of the excitation energy. The non-collective states satisfy the statistical assumption of Tamura, Udagawa and Lenske in the sense that an average over the RPA modes in an energy range of a few times the average width of the modes reduces to an incoherent sum over the underlying particle-hole modes. The average RPA transition strengths and widths of the states were found to be independent of the spin and parity .

        [1] T. Tamura, T. Udagawa, and H. Lenske, Phys. Rev. C 26, 379 (1982).
        [2] M. Dupuis, Eur. Phys. J. A 53, 111 (2017).
        [3] H. Nishioka, H. A. Weidenmüller, and S. Yoshida, Ann. Phys. (N.Y.) 183, 166 (1988).
        [4] C. A. Pompeia, B. V. Carlson, Phys. Rev. C 74, 054609 (2006)
        [5] A. J. Koning, M. B. Chadwick, Phys. Rev. C 56, 970 (1997).
        [6] T. Kawano, S. Yoshida, Phys. Rev. C 64, 024603 (2001).
        [7] G. Colò, L. Cao, N. Van Giai, L. Capelli, Comp. Phys. Comm. 184, 142 (2013).

        Speaker: Mr Emanuel V. Chimanski (Instituto Tecnológico de Aeronáutica,NAPC-Nuclear Data Section, International Atomic Energy Agency)
      • 75
        The role of nucleon knockout in pre-equilibrium reactions

        Nucleon-induced pre-equilibrium reactions are predominantly direct reactions. At low incident energies, excitation of all but the lowest energy collective states can be well described in terms of one-step reactions that produce particle-hole pairs. As the incident energy is increased, more complex excitations involving two or more particle-hole pairs become accessible through multi-step reactions. Quantum mechanical models of such multi-step direct reactions were developed many
        years ago [1,2,3] and have been studied and improved many times over since then [4,5,6,7]. In these models, a leading continuum particle initiates the reaction and remains in the continuum as it scatters repeatedly from the nucleus to produce successive particle-hole pairs. However, as the incident energy increases, the probability of exciting a nucleon to the continuum rather than to a bound particle state also increases. [8] These knockout nucleons can escape the nucleus or induce
        secondary collisions that create still other continuum or bound particle-hole pairs. Calculations using Blann and Chadwick’s DDHMS pre-equilibrium simulation model [9,10] reveal that a 20 MeV neutron incident on 56Fe produces an additional continuum particle in 10% of its scatterings with nucleons in the nucleus and yields a knockout cross section of approximately 4% of the reaction cross section. At 200 Mev, knockout of at least one nucleon, that is, emission of two or more pre-equilibrium nucleons, corresponds to almost 80% of the pre-equilibrium reaction cross section. Here we discuss these calculations in more detail. We also analyze and compare the typical energy and angular distributions obtained from one-step quantum mechanical calculations of inelastic excitation and knockout reactions.

        [1] H. Feshbach, A. Kerman, S. Koonin, Ann. Phys (N.Y.). 125 (1980) 429.
        [2] T. Tamura, T. Udagawa, H. Lenske, Phys. Rev. C 26 (1982) 379.
        [3] H. Nishioka, H. A. Weidenmüller, S. Yoshida, Ann. Phys. (N.Y.) 183 (1988) 166.
        [4] A. Koning, M. Chadwick, Phys. Rev. C 56 (1997) 970.
        [5] T. Kawano, S. Yoshida, Phys. Rev. C 64 (2001) 024603.
        [6] M. Dupuis, T. Kawano, J. P Delaroche, E. Bauge, Phys. Rev. C 83 (2011) 014602.
        [7] M. Dupuis, E. Bauge, S. Hilaire, S. F. Lechaftois, S. Péru, N. Pillet, C. Robin, Eur. Phys. J. A 51 (2015) 168.
        [8] B. V. Carlson, J. E. Escher, M. S. Hussein, 41 (2014) 094003.
        [9] M. Blann, Phys. Rev. C 54 (1996) 1341.
        [10] M. Blann, M. Chadwick, Phys. Rev. C 57 (1998) 233.

        Speaker: Brett Carlson (Instituto Tecnológico de Aeronáutica)
      • 76
        Proton induced pre-equilibrium reactions to the continuum as a test to the reaction mechanism

        The pre-equilibrium proton induced emission of light complex nuclei with energies in the continuum has been studied comprehensively for many years. Double-differential cross sections and especially analyzing power distributions are typical of an intranuclear nucleon-nucleon multistep statistical re-
        action mechanism. The final stage of the reaction may be a result of a direct
        pickup or knockout of the ejectile. The discussion on this subject continues to
        be a hot topic for theoretical and experimental investigations. In the talk will be discussed the interplay between the knockout and pickup mechanisms as final step of the pre-equilibrium reaction and its dependence on the energy in the incident channel.

        Speaker: Sevdalina Dimitrova
    • Nuclear reactions
      Convener: Toshihiko Kawano (Los Alamos National Laboratory)
      • 77
        Capture Cross Sections for Unstable Isotopes from Surrogate Reaction Data and Theory

        Obtaining reliable data for nuclear reactions on unstable isotopes remains an extremely important task and a formidable challenge. Neutron capture cross sections -- crucial ingredients for models of astrophysical processes, national security applications and simulations of nuclear energy generation -- are particularly elusive, as both projectile and target in the reaction are unstable. Various methods have been proposed for determining capture cross sections from indirect measurements. The 'surrogate reaction method' [1] uses inelastic scattering or transfer ('surrogate') reactions to produce the compound nucleus of interest and measure its subsequent decay. In principle, this data provides constraints for the models describing the decay of the compound nucleus, which dominate the uncertainties of the cross section calculations. Past applications of the surrogate approach assumed the decay to be independent of the mechanism that formed the compound nucleus. This approximation, which neglects the need to describe the surrogate reaction, works reasonably well for (n,f) cross sections [2], but has long been known to break down for capture reactions [3].

        This contribution demonstrates that a proper theoretical description of the surrogate reaction mechanisms is key to overcoming the limitations encountered previously. Specifically, theoretical descriptions of the (p,d) and (d,p) transfer reaction have been developed to complement recent measurements in the Zr-Y-Mo region. The procedure for obtaining constraints for unknown capture cross sections is illustrated and indirectly extracted cross sections for both known (benchmark) and unknown capture reactions are presented. The method makes no use of auxiliary constraining quantities, such as neutron resonance data, or average radiative widths, which are not available for short-lived isotopes; thus it can be applied to isotopes away from stability.

        [1] Escher et al, RMP 84, 353 (2012).
        [2] Escher and Dietrich, PRC 74, 054601 (2006).
        [3] Forssen et al, PRC 75, 055807 (2007); Escher and Dietrich, PRC 81, 024612 (2010); Scielzo et al, PRC 81, 034608 (2010); Chiba and O. Iwamoto, PRC 81, 044604 (2010); Boutoux et al, PLB 712, 319 (2012); Ducasse et al, PRC 94, 024614 (2016).

        *This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Partial support from the Laboratory Directed Research and Development Program at LLNL, Project No. 16-ERD-022, is acknowledged.

        Speaker: Jutta Escher (Lawrence Livermore National Laboratory)
      • 78
        Neutron Capture Cross Sections and Strength Functions on 147Sm Nucleus

        Capture processes of neutrons, starting from thermal region up to 14 MeV, on 147Sm, with emission of charged particles, were analyzed. Cross sections for (n,a) reactions, from slow neutrons resonance neutrons up to some MeV’s, in the frame of Hauser – Feshbach formalism (HFF), were evaluated using computer codes realized by authors. The main element of HFF is represented by the transmission coefficients for incident and emergent channels. Transmission coefficients were calculated by applying a quantum-mechanical approach based on reflection factor.
        Starting from 0.5 MeV up to 14 MeV, a separation in the contribution of different nuclear reaction mechanisms related to discrete and continuum states were realized with the help of Talys computer codes. It was demonstrated that the main contribution to the cross sections is given by compound nucleus processes followed by direct processes. Also, nuclear data, as parameters of optical potential, nuclear states densities and others were extracted.
        The computed cross sections and strength functions are compared with experimental data in order to explain possible nonstatistical effects reported previously by some authors on the distributions of alpha widths.
        Cross sections, asymmetry effects and strength functions at the EG-5 and IREN basic facilities of FLNP - JINR by using a double gridded ionization chamber were measured. By recent measurements cross sections for 5 and 6 MeV of 147Sm(n,a) reaction were obtained. Because the values of cross sections are very low (hundreds of microbarns) their measurements are very difficult. The cross sections experimental data are very well described by the performed theoretical model evaluations. A high forward-backward asymmetry effect was also measured but it was not yet confirmed by the theoretical models computations.
        Strength functions, as prescribed by theory, are expected to be constant. In the neutron energy range of some hundred of eV’s the strength functions were measured and a significant decreasing was evidenced. A qualitative explanation suggested by authors is based on the following suppositions: a) nuclear reaction is going only through compound processes b) a radius modification in the emergent channel is possible. Considering these two suppositions, our theoretical model approach describes satisfactorily the experimental data obtained for strength functions.
        This year further measurements on cross sections neutron energy dependence in a wide energy range with the extraction of new nuclear data are proposed to be accomplished. The experiments are possible to be effectuated at JINR basic facilities. The theoretical analysis realized in this study is representing a new proposal for 147Sm experiments at IREN neutron resonance facility.

        Speaker: Dr Cristiana Oprea (JINR)
      • 79
        Neutron width statistics in a realistic resonance-reaction model

        The statistical model of compound nucleus reactions is widely used to calculate reaction observables for basic nuclear science, astrophysics, and nuclear technology. The prediction that neutron resonance reduced widths are distributed according to the Porter-Thomas distribution (PTD) is a cornerstone of the statistical model. Consequently, the recently measured deviations from the PTD for neutron resonance widths in $s$-wave neutron scattering off Pt isotopes [1] have generated much interest, and several explanations have been proposed within the statistical model [2-4]. We discuss a recent study of the neutron width statistics for $s$-wave neutron scattering off $^{194}$Pt within a model that combines a realistic description of the neutron channel with the usual statistical description of the internal compound nucleus states [5]. Our model enables us to calculate resonance widths and reaction cross sections within a unified framework. We explored a reasonably large range of the model parameters around a baseline set taken from the literature and tuned to evaluated and experimental data. Our main conclusion is that the PTD provides an excellent description of the reduced neutron width distribution, provided that the correct secular energy dependence of the average neutron width is used in the calculation of the reduced widths. Our result indicates that the effects of the nonstatistical interaction of the internal states through the neutron channel are not significant in this reaction. Within our parameter range, there can be a near-threshold bound or virtual state of the neutron channel that leads to an energy dependence of the average neutron width that differs from the usual $\sqrt{E}$ form, as proposed in Ref. [2]. In this case, the reduced width distribution extracted using the $\sqrt{E}$ dependence is significantly broader than the PTD. We provide a narrow range of the model parameters within which such a near-threshold bound or virtual state may occur and identify measurable signatures of its existence.

        [1] P. E. Koehler, F. Bečvár, M. Krtička, J. A. Harvey, and K. H. Guber, Phys. Rev. Lett. 105, 072502 (2010).

        [2] H. A. Weidenmüller, Phys. Rev. Lett. 105, 232501 (2010).

        [3] G. L. Celardo, N. Auerbach, F. M. Izrailev, and V. G. Zelevinsky, Phys. Rev. Lett. 106, 042501 (2011).

        [4] A. Volya, H. A. Weidenmüller, and V. Zelevinsky, Phys. Rev. Lett. 115, 052501 (2015).

        [5] P. Fanto, G. F. Bertsch, and Y. Alhassid, arXiv:1710.00792.

        Speaker: Paul Fanto (Yale University)
      • 80
        Transfer reactions induced with 56Ni: np pairing and N=28 shell closure

        Transfer reactions have been proven to be a powerful tool to understand nuclear structure. Two different physical aspects are being investigated with the use of transfer reactions on $^{56}Ni$, which is a $N=Z$ unstable doubly magic nucleus.

        $i)$ To probe the gap of $N=28$, we study the spectroscopy of the $N=29$ and $N=27$ isotones by the $(d,t)$, $(p,d)$ and $(d,p)$ one nucleon transfer reactions on $^{56}Ni$ ($N=28$ isotone) and extract information on the single-particle configuration around the Fermi surface.

        $ii)$ To study the $np$ pairing in the self-conjugate nucleus $^{56}Ni$, we have measured the two-nucleon transfer reactions $^{56}Ni(p,^3He)^{54}Co$ and $^{56}Ni(d,α)^{54}Co$. In the $(p,^3He)$ reaction, the ratio of the population of the $T=0$ and $T=1$ states indicates a predominance of $T=1$ pairing. The selectivity of the $(d,α)$ reaction enables the investigation of the $T=0$ channel with better precision.

        During spring 2014 the experiment aiming to these studies took place at GANIL-Caen, France. The radioactive beam of $^{56}Ni$ at $30MeV/u$ was produced by fragmentation of $^{58}Ni$ and purification. Measurements were performed in inverse kinematics on CH$_2$ and CD$_2$ targets. The experiment included a 4π coverage for the study of the charged projectiles with the MUST2 and TIARA detectors, while 4 clovers of EXOGAM were also used for γ-particle coincidences in order to identify the populated state of the residue. The analysis of the $^{56}Ni(d,t)^{55}Ni$ and $^{56}Ni(d,p)^{57}Ni$ reactions yield the differential cross-section for transfer reaction to the ground state and the excited states of 55Ni and $^{57}Ni$ giving information about the shell closure and depicting the Fermi surface of $^{56}Ni$. I will present the angular distribution and compare with the results for the $(p,dγ)$, $(d,tγ)$ and $(d,pγ)$ reactions, as well as with DWBA calculations. The results for the transfer reaction $^{56}Ni(d,α)^{54}Co$ will be also presented, completing the information about the strength of the isoscalar $np$ pairing in the closure of the $fp$ shell.

        Speaker: Anastasia Georgiadou (Institut de Physique Nucléaire d'Orsay (IPN))
      • 81
        Multinucleon transfer processes in the $^{197}$Au+$^{130}$Te system studied with a high-resolution kinematic coincidence

        The production of neutron-rich nuclei in the mass region A ~ 200, in particular along the neutron closed shell N = 126, has recently received strong attention since these nuclei are fundamental to understand different physical aspects, from the shell evolution far from stability to the investigation of the path chosen by the r-process to synthesize the heavy elements. The difficulties in accessing this region with reactions between stable beams and in identifying such heavy nuclei in A and Z with the present techniques are the main reasons why few experimental data exist so far. Moreover secondary processes, like particle evaporation and transfer-induced fission, may play a non-negligible role when heavy nuclei are involved and may significantly shift the final yield distributions to lower masses.
        Multinucleon (MNT) transfer reactions at energies close to the Coulomb barrier have been indicated as a promising mechanism to produce neutron-rich nuclei around the N = 126 region of the nuclide chart. In some recent experiments the study of the mechanism and the probability for the production of neutron-rich heavy nuclei with MNT reactions was attempted by employing either γ-particle coincidences, high-efficiency but low-resolution particle-particle coincidences or radiochemical methods.
        In this context we performed an experiment to study multinucleon transfer reactions at near-barrier energies in the $^{197}$Au+$^{130}$Te system employing a novel method which consists in the simultaneous detection of light and heavy transfer products where one of the reaction partners (the light one) is identified with high resolution. We exploited the performance of the PRISMA spectrometer to identify isotopes in the tellurium region, while the coincident Au-like partners were detected with a dedicated set-up, the NOSE, specifically built and coupled to PRISMA. We chose the neutron-rich $^{130}$Te to populate neutron transfer channels leading primarily to neutron-rich Au isotopes. The use of inverse kinematics allowed to achieve high efficiency and resolutions for both partners in spite of the low bombarding energy.
        The A, Z and Q value distributions of the light partner of the reaction were determined through an event-by-event trajectory reconstruction in PRISMA. The cross sections for neutron transfer channels were extracted and compared with the ones calculated with the GRAZING code. The mass of the coincident heavy partner was determined from the correlated scattering angle and Time-of-Flight in NOSE, by assuming the reaction binary in character. This allowed, via a high resolution mass-mass correlation and the comparison with Monte Carlo simulations, to study the final mass distribution of the heavy partner and the effect of secondary processes. This also allowed to extract the requirements that are needed in order to have a clear identification in mass A and charge Z of the heavy reaction products.
        The experimental method and results and the comparison with theoretical calculations will be presented.

        Speaker: Franco Galtarossa (INFN, Legnaro (IT))
      • 82
        Shell-model studies of the astrophysical mirror rp-reactions $^{34}$S(p,$\gamma$)$^{35}$Cl and $^{34g,m}$Cl(p,$\gamma$)$^{35}$Ar

        The two mirror rp-reactions $^{34}$S(p,$\gamma$)$^{35}$Cl and
        $^{34g,m}$Cl(p,$\gamma$)$^{35}$Ar were studied via a shell-model approach.
        At energies in the resonance region
        near the proton-emission threshold many negative-parity states appear.
        We present results of calculations in a full (0$+$1)$ \hbar \omega $
        model space which addresses this problem. Energies, spectroscopic
        factors and proton-decay widths are calculated for input into the
        reaction rates. Comparisons are also made with a recent experimental
        determination of the reaction rate for the first reaction. The
        thermonuclear $^{34g,m}$Cl(p,$\gamma$)$^{35}$Ar reaction rates
        are unknown because of a lack of experimental data. The rates for
        transitions from the ground state of $^{34}$Cl as well as from the
        isomeric first excited state of $^{34}$Cl are explicitly calculated taking
        into account the relative populations of the two states. These reaction rates
        were then used in post processing studies using NucNet Tools to
        understand the impact on classical nova nucleosynthesis.

        Speaker: Prof. Werner Richter (Universrty of Stellenbosch)
    • 5:10 PM