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Optical potentials are an essential ingredient in theories for nuclear reactions [1]. They characterize initial and final states, determine transmission coefficients and often provide the terms needed for transition operators responsible for the reaction. Over the last decade, significant progress has been made in obtaining optical potentials from ab-initio many-body calculations (e.g. [2,3]). Depending on the method used, these optical potentials have different properties and, in most cases, still fall short compared to phenomenological potentials in describing elastic scattering.
Concurrently to the ab-initio developments, we have also developed state-of-the-art methodology, using Bayesian Statistics, to understand the uncertainties these potentials carry and how these propagate to reaction observables [4,5,6,7,8]. It is now possible to make predictions of confidence intervals for reaction observables and use a variety of statistical tools to determine which observables are best to constrain specific optical potential parameters and determine the data that provides maximum information [9]. It is also possible to emulate large-scale breakup calculations to enable uncertainty quantification in complex reactions [10].
In this presentation, we will provide an overview of these recent developments and provide an outlook on promising future applications.
[1] C. Hebborn et al., J. Phys. G submitted (arXiv:2210.07293)
[2] J. Rotureau et al., Phys. Rev. C 98, 044625 (2018)
[3] T. Whitehead et al., Phys. Rev. Lett. 127, 182502 (2021)
[4] G.B. King et al., Phys. Rev. Lett. 122, 232502 (2019)
[5] A. Lovell et al., J. Phys. G 48, 014001 (2020)
[6] M. Catacora-Rios et al., Phys. Rev. C 100, 064615 (2019)
[7] T. Whitehead et al., Phys. Rev. C 105, 054611 (2022)
[8] M. Catacora-Rios et al., Phys. Rev. C submitted (arXiv:2212.10698)
[9] M. Catacora-Rios et al., Phys. Rev. C 104, 064611 (2021)
[10] O. Surer et al., Phys. Rev. C 106, 024607 (2022)
After nearly sixty years since its introduction, the phenomenological bell-shape Perey–Buck spatial nonlocality in the optical model potential for nucleon–nucleus scattering has remained unaccounted for from a microscopic standpoint. In this article we provide a quantitative account for such nonlocality considering fully nonlocal optical potentials
in momentum space. The framework is based on a momentum-space in-medium folding model, where infinite nuclear matter g matrices in Brueckner–Hartree–Fock approximation are folded to the target one-body mixed density. The study is based on chiral next-to-next-to-next-to-leading order (N3LO) as well as Argonne nucleon–nucleon bare interaction models. Applications focus on Ca(p, p) scattering at beam energies in the range 11–200 MeV, resulting in the identification of a separable structure of the momentum-space optical potential of a form we coin as JvH, with a nonlocality form factor as one of its terms. The resulting nonlocaliy form factor features a bell-shape with nonlocality range between 0.86 and 0.89 fm, for both proton and neutron beams at energies below 65 MeV. An analytic toy model is introduced to elucidate the underlying mechanism for the nonlocality in the optical model, providing an estimate of its range based on the Fermi motion of the target nucleons and the long-range part of the NN interaction.
A microscopic description of the nucleus-nucleus reaction system has been attempted.
The double-folding model with effective nucleon-nucleon interaction is widely successful to describe nucleus-nucleus scatterings.
However, we need a special prescription for the microscopic description of the $\alpha$-nucleus scatterings, for example for the application of the strong renormalization factor or the change of the local density approximation.
Namely, $\alpha$ scattering and heavy-ion scattering are not described in the same framework.
We consider the reason as follows.
Almost the effective nucleon-nucleon interactions reflect the property in the nuclear matter.
However, the $\alpha$ particle is far from the condition of the nuclear matter.
Then, we should reconsider describing the $\alpha$ scattering with such nucleon-nucleon interaction.
In this work, we provide a complex density-dependent $\alpha$-nucleon (DD-$\alpha N$) interaction to construct the $\alpha$-nucleus potential in the wide ranges of the incident energy and the target nucleus.
The $\alpha$-nucleus potential is obtained by folding the present DD-$\alpha N$ interaction with the point nucleon density obtained by the mean-field model (HF+BCS).
The present DD-$\alpha N$ interaction is based on the phenomenological optical potential to reproduce the p + $^4$He elastic scattering.
Namely, the $\alpha$-nucleon system is considered to be an elementary process.
The real part of the p + $^4$He potential has a form of the double Woods-Saxon (WS) type.
The short-range WS potential has a role in repulsive behavior at high energy.
However, the present density dependence of the DD-$\alpha N$ interaction is phenomenologically fixed to reproduce the $\alpha$-nucleus elastic scattering.
The $\alpha$-nucleus potential with the present DD-$\alpha N$ interaction well reproduces the experimental data.
Realistic nuclear reaction cross-section models are an essential ingredient of reliable heavy-ion transport codes. Such codes are used for risk evaluation of manned space exploration missions as well as for ion-beam therapy dose calculations and treatment planning \cite{luoni}.
Within the community of basic research in nuclear reactions, reaction cross section data compared to theoretical calculations, mostly performed within the Glauber model \cite{59} with folded potentials (f.p.) \cite{SL,S2}, have been used for many years \cite{dvp,kox}. Also since the beginning of physics with RIBs the method has been applied to deduce density distributions of exotic nuclei as well as their root mean square radii (rms) \cite{tanih1,tanih,ozawa,Ca+12C,fitbeta,take,hor1,hor2}. On the other hand in order to improve the calculations of nucleus-nucleus folded potentials, usually called double folded potentials (d.f) Satchler and Love \cite{SL} proposed the calculate single folded (s.f) potentials using projectile densities together with phenomenological nucleon target potentials. In this talk we will show that for $^9$Be and $^{12}$C very good agreement with experimental data can be found using nucleon-target (n-T) phenomenological potentials which we have obtained fitting the n+T cross section in a very large energy range and also the nucleus-target (N-T) cross sections at high energy. The advantage of s.f. potentials is to avoid the dependence on the target density choice as well as the choice of the parameters to describe the free n-n-amplitude in the Glauber model.
Electromagnetic form factors are quantities that describe the internal structure of complexe objects. They are measured through elementary reactions of annihilation and scattering involving leptons and hadrons. Unexpected features appeared in the recent very precise data on electromagnetic proton form factors. In the scattering region, a series of measurements of electron proton elastic scattering based on the Akhiezer-Rekalo recoil polarization methods, showed that the proton electromagnetic form factor ratio has a steep dependence on the transferred momentum with possibly a zero crossing (!) while earlier it was assumed that electric and magnetic form factors have similar dipole dependence. In the annihilation region investigated at electron-positron colliders, the evidence was found of regular oscillations in the generalized proton form factor. The electric and magnetic form factors of the proton have also been individually determined for the first time as well as hyperon time-like form factors. The data will be discussed in terms of an advanced representation of form factors in unified space and time regions [1]. This model assumes a region of quantum vacuum at small internal distances, allows to coherently describe all existing data and to make predictions for future experiments [2].
[1] E.A. Kuraev, E.Tomasi-Gustafsson and A. Dbeyssi, Phys.Lett. B712 (2012) 240
[2] E. Tomasi-Gustafsson, S. Pacetti, Phys. Rev. C106 (2022) 3, 035203
At BESIII, the electromagnetic form factors (EMFFs) and the pair production cross sections of various baryons have been studied. The proton EMFF ratio |GE/GM| is determined precisely and line-shape of |GE| is obtained for the first time. The recent results of neutron EMFFs at BESIII show great improvement comparing with previous experiments. Cross sections of various baryon pairs (Lambda, Sigma, Xi, Lambdac) are studied from their thresholds. Anomalous enhancement behavior on the Lambda and Lambdac pair are observed.
Recently, the BESIII experiment renewed the interest in baryon form factors by measuring the modulus and phase of the ratio between the electric and the magnetic Λ form factors with unprecedented accuracy. The BESIII measurement together with older, less precise data, can be analyzed by means of a dispersive procedure based on analyticity and a set of first-principle constraints. Such a dispersive procedure shows the unique ability to determine for the first time the complex structure of the ratio knowing its modulus and phase measured by the BESIII collaboration at only one energy point. Different classes of solutions are obtained, and in all cases, the time-like and space-like behaviors show interesting properties: space-like zeros or unexpected large determinations for the phase. More data at different energies would be crucial to enhance the predictive power of the dispersive procedure and to unravel further remarkable features of the Λ baryon.
The theory of heavy ion double charge exchange (DCE) reactions is recapitulated as discussed in the recent review articles [1,2]. Leaving aside the higher order mean-field driven multi-particle transfer contributions, the competition of two interfering (semi-)direct reaction mechanisms is emphasized, given by nucleon-nucleon (NN) Double Single Charge Exchange (DSCE) and Meson-Nucleon Majorana DCE (MDCE).
The DSCE mechanism amounts to a conventional distorted wave two-step reaction. As was shown in [2,3] the reaction amplitude can be transformed by suitable recoupling techniques into a form corresponding in structure to the nuclear matrix elements (NME) of $2\nu 2\beta$ decay, albeit with a transition operator defined by strong interaction. The second order DSCE response functions are described by the polarization tensor formalism in Quasiparticle Random Phase Approximation (QRPA).
Different to the DSCE mechanism the MDCE mode is formally a one—step DW mechanism but monitored by the coherent exchange of pairs of charged mesons between projectile and target. Each of these mesons undergoes a single charge exchange reaction, thereby initiating short—range correlations through the intranuclear exchange of neutral mesons. The MDCE reaction corresponds to a combination of an off-shell ($\pi^+,\pi^-$) reaction in one of the ions and a complementary ($\pi^-,\pi^+$) reaction in the other ion. Altogether, the MDCE process proceeds by a dynamically generated effective rank-2 isotensor interaction. Theoretically, this requires to evaluating box diagrams extending over the two colliding nuclei.
The elementary MDCE vertices differ significantly from the conventional SCE and DSCE charge exchange vertices. While the latter are given by NN isovector interactions e.g. by the exchange of virtual charged pions, the MDCE process is driven by the (off-shell) isovector pion-nucleon T-matrix, governed by excitations of nucleon resonances as e.g. $\Delta_{33}(1232)$ [6]. From a nuclear structure point of view, the MDCE operator induces two--particle-two--hole ($p^2n^{-2}$) and ($n^2p^{-2}$) DCE transitions in either of the interacting nuclei. The MDCE vertices are of a striking similarity to the NMEs of $0\nu 2\beta$ decay, where the Majorana neutrinos are replaced by neutral pions.
The physics aspects of DSCE and MDCE processes are illustrated on examples of SCE [5] and DCE [2,3] response functions and cross sections. Results are compared to recent data measured by the NUMEN collaboration at LNS Catania as discussed in detail in [1].
\section{References}
\begin{enumerate}
\item F. Cappuzzello, H. Lenske et al., Shedding light on nuclear aspects of neutrinoless double beta decay by heavy-ion double charge exchange reactions, Prog. Part. Nucl. Phys. 128 (2023) 103999.
\item H. Lenske, F. Cappuzzello, M. Cavallaro, and M. Colonna, Heavy Ion Charge Exchange Reactions and Beta Decay, Prog. Part. Nucl. Phys., 109:103716, 2019.
\item H. Lenske, J. Bellone, M. Colonna, and D. Gambacurta, Nuclear Matrix Elements for Heavy Ion Sequential Double Charge Exchange Reactions. Universe, 7(4):98, 2021.
\item J. Bellone, S. Burrello, M. Colonna, J.-A. Lay, and H. Lenske, Two-step description of heavy ion double charge exchange reactions. Phys. Lett. B, 807:135528, 2020.
\item H. Lenske, J. Bellone, M. Colonna, and J.-A. Lay, Theory of Single Charge Exchange Heavy Ion Reactions, Phys. Rev., C98:044620, 2018.
\item H. Lenske, M. Dhar, Th. Gaitanos, and Xu Cao, Baryons and baryon resonances in nuclear matter, Prog. Part. Nucl. Phys. 98 (2018) 119
\end{enumerate}
Multistep Direct (MSD) and Multistep Compound (MSC) mechanisms when combined account for emission of nucleons from a composite nucleus before it attains compound nucleus equilibrium. In spite being better founded than exciton model or other classical pre-equilibrium models, MSD and MSC were only occasionally employed in practical calculations. Initially, it was due to higher complexity of these quantum-mechanical theories and higher computational cost. Both these factors, however, are not major obstacles today since MSD (TUL) and MSC (NVWY) were implemented in the EMPIRE code by the end of the last century and modern computational capabilities make such calculations feasible on a single-processor laptop. The major cause of avoiding MSD/MSC in practical calculations (e.g., nuclear data evaluations) was the fact that these two models tend to underestimate the middle-energy range of neutron spectra.
In our recent work we were able to overcome this deficiency and obtain very good reproduction of experimentally measured neutron spectra coming from neutron interaction with Ta181 and Pu239 targets. The default MSD/MSC calculations on Ta181 are already acceptable. Similar result with exciton model requires DWBA calculations to a large number of fake levels embedded in the continuum to simulate MSD mechanism. This success comes, however, at the price of turning off gradual absorption to the MSC chain. This is at odds with the fundamental distinction between MSD and MSC mechanisms that should proceed through the chain of open (P-space) and closed (Q-space) respectively. By blocking gradual absorption we allow the first stage of MSC to be fully populated from the incident channel. This ignores the fact that at high enough incident energies creation of a bound three-quasiparticle state is energetically impossible.
We will discuss various attempts of addressing the problem that, so far, remains open.
Implications of a microscopic modeling of direct and pre-quilibrium
mechanisms on the neutron + actinides reaction observables.
Modeling of medium energy nuclear reaction requires the precise
description of the direct, pre-equilibrium and compound decay
mechanisms. Direct and pre-quilibrium mechanisms
modeled from microscopic approach needs a description
of target neutron, proton and charge matter and transition densities.
Development of microscopic models is crucial
as they provide predictions where experimental
data are missing to constrain phenomenological models
or when phenomenological models are unsatisfactory.
Here, we focus on direct and pre-equilibrium mechanisms
described within the semi-microscopic Jeukenne Leujeune Mahaux folding model with Hartree-Fock-Bogoliubov and Quasi-Particle Random Phase Approximation nuclear structure input. Applications were performed
for elastic and inelastic scattering of nucleon and alpha particles
on spherical and axially deformed targets. The coupled channel approach
is used in the deformed targets case. It is extended to the description of the first step of the pre-equilibrium emission.
For neutron scattering off actinides, and other deformed targets, this
microscopic model provides a good description of the high energy neutron spectrum, without relying
on "pseudo-states". This follows the collectivity
predicted in the QRPA approach for low excitation energy.
The pre-equilibrium model provides the spin distribution of the residual nucleus which can decay emitting a second neutron, a gamma cascade, or fissionning. The implication of the pre-equlibrium model prediction on a set of observables (n,f), (n,n'), (n,n'$\gamma$), (n,2n) will be discussed for actinides and other deformed targets.
Finally, this approach is applied to predict spin distributions for
a large number of nuclei in the mass range A=16-240. A parametrization
of the spin distribution was extracted from these results
and from an alternative microscopic approach developed in LANL,
that can be associated to the exciton model. Applications will be discussed.
Nucleon-induced pre-equilibrium reactions are recognized to consist almost exclusively of direct reactions in which incident nucleons induce excitations over a wide range of energy in the target nucleus. At low energies, one step reactions dominate. As the incident energy increases, multi-step reactions become important too. Although quantum mechanical models of these reactions were introduced long ago, [1-3] their computational difficulty has limited their application to calculations including at most two steps, [2,4-7] in most cases, and four steps in a particular simplified model. [8]
Some twenty years ago, Kawai and collaborators used the Wigner transform to rewrite the multi-step direct reaction series directly as a sum of cross sections rather than squared amplitudes. [9-13] Such a transformation can be performed exactly, if one makes the usual assumption that amplitudes involving different numbers of collisions are incoherent. They further simplified the expressions for the cross sections by rewriting the incoming and outgoing waves, as well as intermediate propagators, in terms of classical trajectories and quantum absorption factors. Calculations have been extended up to third order and provide promising results when compared to experimental data. [14-15] However, the calculations continue to be computationally demanding.
We show how the semiclassical multi-step series can be evaluated using Monte Carlo methods. Nucleon-nucleon collisons occur according to the random selection of a nucleon’s absorption factor along its classical trajectory. In a more precise model, the particle and hole excited in a collision would be selected randomly from a sum of Wigner densities. We simplify this by selecting them from a local Fermi distribution, which furnishes distributions similar to those of Kikuchi and Kawai. [16] We assume that the particles produced continue to propagate and possibly collide again before leaving the nucleus. We assume that holes collide in place, to possibly produce other particles and holes. The resulting model has a striking resemblance to the DDHMS model of Blann and Chadwick. [17-18] However, it goes beyond that model by including the dependence on impact parameter and quantum absorption and transmission factors, as well as permitting the inclusion of curved trajectories and providing a path for improvement of the description of the nucleon-nucleon interaction used.
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The investigation of many astrophysical processes is dependent upon understanding of nuclear reaction rates. Examples include X-ray bursts from accreting neutron stars [1] and white dwarfs in binary star systems, which detonate nova or supernova explosions, and may rotate in decreasing orbits, producing gravitational waves [2].
However, nuclear capture reactions of astrophysical interest occur at extremely low energies, taking place at the Gamow energy within the stellar environment. Hence, they are hard to study experimentally due to Coulomb repulsion. They may also involve compound resonances stemming from a delicate interplay of many quantum states in the colliding bodies. The multi-channel algebraic scattering (MCAS) method is one that addresses both of these challenges; it has a history of successfully modelling narrow compound resonance structures, incorporating as many channels as are important for a given problem, but is also proven in recreating the low-energy, non-resonant elastic scattering cross sections needed for these astrophysics problems [3].
This talk will provide an overview of MCAS’ techniques of modelling elastic scattering reactions, how these may be extended to capture reactions, and current work in this area.
[1] R. H. Cyburt, A. M. Amthor, A. Heger, et al., ApJ 830, 55 (2016).
[2] A. J. Ruiter, K. Belczynski, S. A. Sim, I. R. Seitenzahl, and D. Kwiatkowski,
MNRAS 440, L101 (2014).
[3] S. Karataglidis, K. Amos, P. R. Fraser, and L. Canton, A New Development at the Intersection of Nuclear Structure and Reaction Theory (Springer-Nature, 2019)
Collective and single-particle excitations have been studied in many aspects in nuclear physics. However, most studies focus on the excitations of a nucleus as an isolated system. In this study, we focus on the collective and single-particle excitations of a projectile nucleus in a scattering system, e.g., breakup reactions of T($^{31}$Ne,$^{30}$Ne+$n$), where T is a target.
$^{31}$Ne is the so-called “deformed halo” where a neutron is weakly bound to the deformed core nucleus $^{30}$Ne. During the early stage of the research on $^{31}$Ne, the large Coulomb breakup cross section [1] and the large interaction cross section [2] were measured for $^{31}$Ne unexpectedly, encouraging many theoretical researchers. Note that in the simple shell-model picture, the last neutron of $^{31}$Ne ($N=21$) occupies the $f_{7/2}$ orbital, and the halo structure never develops. In Ref. [3], the measured interaction cross sections were analyzed in the microscopic framework based on the double-folding model with the densities calculated by antisymmetrized molecular dynamics (AMD). The result reproduced the cross sections systematically, suggesting that $^{31}$Ne is the deformed halo in which the valence neutron is strongly coupled to the excited core ($^{30}$Ne$^*$). In 2014, the spin parity $J^\pi=3/2^-$ and the separation energy $S_n=0.15_{-0.10}^{+0.16}$ MeV were experimentally deduced from the inclusive nuclear- and Coulomb-dominated breakup reactions [C($^{31}$Ne,$^{30}$Ne) and Pb($^{31}$Ne,$^{30}$Ne)] [4]. The ground-state properties of $^{31}$Ne have been thus determined by experimental and theoretical efforts in the past 15 years. Now, our interest goes to the unbound excited states of $^{31}$Ne. In fact, in the recent study based on AMD [5], it was found that the first excited state ($5/2^-$ state) is dominated by the core-excited component with the small decay width. It is interesting to analyze how this property appears in the breakup observables.
In this study, we investigate the unbound excited states of $^{31}$Ne through exclusive breakup reactions T($^{31}$Ne,$^{30}$Ne+$n$+$\gamma$). We adopt the extended version of the continuum-discretized coupled-channels (CDCC) method with core excitation [6]. $^{31}$Ne is described as a neutron and an active core by the particle-rotor model, which considers the mixing of core-excited components in both the ground and unbound excited states (static core excitation). The reaction part is solved by CDCC, which can treat the core-ground channel [$^{31}$Ne+T→$^{30}$Ne(gs)+$n$+T] and the core-excited channel [$^{31}$Ne+T→$^{30}$Ne$^*$+$n$+T] on an equal footing (dynamic core excitation). The corresponding cross sections are properly calculated in this framework. As a result, the $5/2^-$ resonant breakup cross section is strongly enhanced by the dynamic core excitation (collective excitation). In the presentation, we will discuss how the static and dynamic core excitations affect the resultant cross sections.
[1] T. Nakamura et al., Phys. Rev. Lett. 103, 262501 (2009).
[2] M. Takechi et al., Nucl. Phys. A 834, 412c-415c (2010).
[3] K. Minomo et al., PRL 108, 052503 (2012).
[4] T. Nakamura et al., PRL 112, 142501 (2014).
[5] R. Takatsu et al., arXiv:2212.00980v1.
[6] R. de Diego et al., Phys. Rev. C 89, 064609 (2014).
Transport models to describe the evolution of heavy-ion collisions are indispensable to extract information on the equation-of-state of nuclear matter and on medium properties of hadrons from such experiments in the intermediate energy range from several 100 MeV to a few GeV per nucleon. Of particular interest today is the high-density behavior of the nuclear symmetry energy, which is of relevance for the understanding of astrophysical objects and processes. The highly complex and non-linear transport equations are commonly solved by simulations, which involve choices of strategies, which are not necessarily determined by the underlying equations. Thus it has occurred that studies using different transport models have deduced differing conclusions from the same data. In order to understand these differences and to reduce the systematical uncertainties of transport analyses of heavy-ion collisions, we have, within the Transport Model Evaluation Project (TMEP), undertaken an extensive study of comparing transport codes under various controlled conditions, also providing benchmark calculations and identifying sensitive simulation strategies (an intermediate review is given in H. Wolter et al., Progr. Part. Nucl. Phys. 125 (2022) 103962). Here, we will discuss the present status and future projects of this effort.
Charge-exchange reactions offer the possibility to explore the features of the isospin and spin-isospin channels of the nuclear interaction and associated nuclear structure properties. For instance, they have been recently exploited to measure, in inverse kinematics, the spin-isospin response of neutron drip-line nuclei and to scrutinize the nature of the tetraneutron system.
Owing to the analogies between the vertices of the strong and weak interactions in the isospin and spin-isospin channels, charge-exchange reactions are often investigated also to deduce information on nuclear transition matrix elements (NME) relevant for beta decay. In particular, double charge exchange (DCE) reactions could allow to probe NMEs similar to the ones involved in neutrino-less double beta decay.
In this contribution we discuss new developments related to the theoretical description of DCE reactions with heavy ions. In particular, we model the latter as a sequential meson-exchange, corresponding to a double single charge exchange (DSCE) reaction mechanism. The crucial role of the ion-ion elastic interactions, in the entrance and exit channels, is discussed. Within a DWBA treatment, this allows to single out reaction and structure components from the DCE reaction cross section and to isolate the corresponding NMEs of projectile and target. Several nuclear structure models (QRPA, IBM-like and shell models) are adopted for the evaluation of the NMEs and results are compared with each other. The correlation between the DCE NMEs and the ones characterizing neutrino-less double beta decay is explored.
Calculations are performed for the reactions 40Ca(18O,18Ne)40Ar,
76Se(18O,18Ne)76Ge and 76Ge(Ne20,20O)76Se, and results are compared to the data measured at LNS-Catania and published by the NUMEN Collaboration. This analysis also allows one to estimate the possible contribution of more complex DCE mechanisms, implying a correlation between the two charge-changing nucleons, and/or competing reaction channels associated with multi-nucleon transfer.
References:
- J.I.Bellone et al., Phys. Lett. 807, 135528 (2020).
- H.Lenske, J.I.Bellone, M. Colonna, D.Gambacurta, Universe 7, 98 (2021).
- F.Cappuzzello et al., Progr. in Part. and Nucl. Phys. 128, 103999 (2023).
A full understanding of the reaction mechanisms involved in double and single charge exchange nuclear reactions is mandatory for the purposes of the NUMEN project. The main goal is to extract data driven information on nuclear matrix elements of neutrino-less double-beta decay from measured cross section of heavy-ion induced double charge exchange reactions.
An interesting benchmark to test the capability of state-of-the-art nuclear reaction and nuclear structure theories is the network of nuclear reactions involved in the $^{18}$O + $^{12}$C collision at 15.3 AMeV incident energy.
The experiment has been performed at the INFN-LNS using the K800 Superconducting Cyclotron and the MAGNEX magnetic spectrometer. The experimental results and the theoretical analysis for the single charge exchange, elastic and inelastic scattering, one-neutron addition and one-proton removal nuclear reactions will be discussed during the conference.
The main purpose of this work is to describe the newly extracted experimental cross-sections in a full comprehensive theoretical framework in which the reaction channels are treated all together. The many aspects that play a relevant role in the description of the single charge exchange reaction mechanism are the choice and tuning of the optical potential, the role of the couplings with the low-lying excited states of the involved nuclei, the single-particle and many-body properties of the nuclear wave functions and the competition between the direct and the sequential reaction mechanisms.
B. Gnoffo1,2, S. Pirrone2, G. Politi1,2, G. Cardella2, E. De Filippo2, E. Geraci1,2, C. Maiolino3, N. S. Martorana1,3, A. Pagano2, E. V. Pagano3, M. Papa2, F. Risitano4,2, F. Rizzo1,3 P. Russotto3 and M. Trimarchi4,2
1 Dipartimento di Fisica e Astronomia “Ettore Majorana”, Università degli Studi di Catania-Catania, Italy
2 INFN, Sezione di Catania-Catania, Italy
3 INFN, Laboratori Nazionali del Sud–Catania, Italy
4 Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra, Università degli Studi di Messina - Messina, Italy
An investigation of the influence of the isospin on the thermometric characteristics, in the reactions 78Kr+40Ca and 86Kr+48Ca at 10 AMeV [1,2,3] will be presented. The experiment was performed at the INFN Laboratori Nazionali del Sud (LNS) in Catania by using the beams delivered by the Superconductive Cyclotron and the 4π multidetector CHIMERA [4,5]. The isospin effects on the decay modes of the two produced composite systems and on the competition between statistical and dynamical break-up of the projectile have been studied. The thermal evaporation from both compound nucleus (CN) and Quasi-Projectile (PLF) have been investigated by extracting the temperature with two different thermometric methods, namely the slope thermometer, with the alpha particles as probe, and the double isotope yields ratio thermometer [6]. The results of the analysis suggest the influence of the N/Z ratio on the system (CN or PLF) temperature, regardless of the nature of the method used for its determination. In fact, in the neutron rich system, a lower value of temperature has been observed for the Quasi-Projectile and a higher one has been found for the compound system, with respect to the ones observed for the neutron poor system. This trend is confirmed by the comparison with the calculations of GEMINI++ statistical model.
We modeled an unprecedentedly large dataset of complete fusion cross section data using a novel artificial intelligence approach. Our analysis aims especially to unveil, in a data-driven way, nuclear structure effects on the fusion between heavy ions and to suggest a universal formula capable to describe all previously available data. The study focused on light-to-medium-mass nuclei, where incomplete fusion phenomena are more difficult to occur and less likely to contaminate the data. The method used to derive the models exploits a state-of-the-art hybridization of genetic programming and artificial neural networks and is capable to derive an analytical expression that serves to predict integrated cross section values. For the first time, we analyzed a comprehensive set of nuclear variables, including quantities related to the nuclear structure of projectile and target. In this talk, we describe the derivation of two computationally simple models that can satisfactorily describe, with a reduced number of variables and only a few parameters, a large variety of light-to-intermediate-mass collision systems in an energy domain ranging approximately from the Coulomb barrier to the oncet of multi-fragmentation phenomena. The underlying methods are particularly innovative and are of potential use for a broad domain of applications in the nuclear field.
Deficiencies in describing the elastic and especially inelastic components of the deuteron breakup (BU) motivate the actual full parametrization of the available deuteron data [1] better than TENDL-2021 deuteron sub-library [2] based on the widely-used TALYS nuclear model code system [3]. Various merely phenomenological descriptions of the available direct-reaction $(d,p)$ stripping data are also yet adopted [4] while microscopic calculation of inclusive BU and DR cross sections ({\it e.g.}, [5]) are still numerically tested. On the other hand, due consideration of all elastic-breakup (EB), breakup-fusion (BF), direct-reaction (DR), pre-equilibrium emission (PE), and evaporation from fully equilibrated compound nucleus (CN) processes ({\it e.g.}, [6]), has been found crucial [7] for a consistent analysis of the deuteron-reaction data and even high production of proton-rich nuclei [8], while insufficient treatment and separation between different reaction mechanisms such as DR and BU components [9] may be related to deviations between measurements and advanced surrogate reaction studies [10].
Nevertheless, suitable account of all available excitation-function of deuterons on $A\sim$90 nuclei up to 60 MeV has been proved by consistent analysis of elastic scattering and consequent optical-potential validation, EB and BU parametrization [11] checked by microscopical Continuum-Discretized Coupled-Channels (CDCC) formalism calculations, BF enhancement of various $(d,x)$ reaction cross sections, DR results using DWBA spectroscopic factors from data analysis of available particle-emission angular distributions, as well as PE+CN statistical decay. This approach involved for the target nuclei $^{27}$Al, $^{51,nat}$V, $^{50,52,53,54,nat}$Cr, $^{55}$Mn, $^{54,56,57,58,nat}$Fe, $^{59}$Co, $^{58,60,61,62,64,nat}$Ni, $^{63,65,nat}$Cu, $^{90,91,92,94,96,nat}$Zr, and $^{93}$Nb ([12] and Refs. therein), pointed out the BU enhanced role with the target-nucleus mass/charge increase as well as the BU dominance around the Coulomb barrier for heavy nuclei as, {\it e.g.}, $^{231}$Pa [13].
The overall agreement between the measured and calculated data validates this model approach while the comparison with the global predictions underlines the effects of overlooking the BF enhancement as well as the stripping and pick-up processes. This is particularly important for the $(d,p)$, $(d,2p)$, and $(d,xn)$ excitaton functions on target nuclei from $^{27}$Al to $^{100}$Mo where the role of the stripping and breakup mechanism is evidenced as the reason of the apparent discrepancies. Thus, the essential role of the stripping mechanism in $(d,p)$ and $(d,n)$ reactions is played by the BF processes for the $(d,2p)$, $(d,2n)$, and $(d,3n)$ reactions, all of them being of interest for the evaluation of the H and neutron production({\it e.g.}, [14]).
Actually, the key advantage of the consistent theoretical approach of the deuteron interactions, supported by advanced codes associated to the nuclear reaction mechanisms, is especially its predictive power. Therefore, update of the theoretical framework of deuteron-nucleus interaction will improve the evaluation predictions for target nuclei and incident energies where data are still missing but strongly requested by the current engineering design projects.
[1] J. Engle {\it et al.}, Nuclear Data Sheets {\bf 155}, 56 (2019).
[2] A.J. Koning {\it et al.}, Nuclear Data Sheets {\bf 155}, 1 (2019).
[3] A.J. Koning, S. Hilaire, and S. Goriely, https://www-nds.iaea.org/talys/tutorials/talys_v1.96.pdf.
[4] F. T\' ark\' anyi {\it et al.}, Eur. Phys. J. A {\bf 57}, 21 (2021); {\it ibid.} {\bf 57}, 223 (2021).
[5] Y.S. Neoh {\it et al.}, Phys. Rev. C {\bf 94}, 044619 (2016); K. Ogata and K. Yoshida, {\it ibid.} {\bf 94}, 051603(R) (2016).
[6] M. Avrigeanu {\it et al.}, Phys. Rev. C {\bf 89}, 044613 (2014); {\it ibid.} {\bf 94}, 014606 (2016).
[7] V. Jha, V. Parkar, and S. Kailas, Physics Reports {\bf 845}, 1 (2020).
[8] H. Wang {\it et al.}, Communications Physics {\bf 2}, 78 (2019).
[9] M. Avrigeanu and V. Avrigeanu, J. Phys. Conf. Ser. {\bf 724}, 012003 (2016).
[10] J.J. Cowan {\it et al.}, Rev. Mod. Phys. {\bf 93}, 015002 (2021).
[11] M. Avrigeanu {\it et al.}, Fus. Eng. Design {\bf 84}, 418 (2009); Phys. Rev. C {\bf 95}, 024607 (2017);
Eur. Phys. J. A {\bf 58}:3 (2022).
[12] E.~\v Sime\v ckov\'a {\it et al.}, Phys. Rev. C {\bf 104}, 044615 (2021).
[13} M. Avrigeanu, V. Avrigeanu, and A. J. Koning, Phys. Rev. C {\bf 85}, 034603 (2012).
[14] N. Zimber {\it et al.}, J. Nucl. Mat. {\bf 535}, 152160 (2020).
Deuteron is expected to be an effective particle for nuclear transmutation. One of the key nuclear reactions to be studied is the inclusive $(d,d^{\prime}x)$ reaction, in which only the energy and angle of the emitted deuteron are specified. In general, the description of the inclusive reaction is very difficult because of the vast number of nuclear states involved. Although phenomenological calculations can be performed using the exciton model [1] or its improved model [2], these models cannot incorporate the effect of the changes in the kinematics of incident particle due to the distortion by the target nucleus.
In this study, the double differential cross section (DDX) of the inclusive $(d,d^{\prime}x)$ reaction is described with the semiclassical distorted wave model (SCDW) [3-6], which contains no free adjustable parameters. SCDW achieves a description of the inclusive reaction, by representing the nuclear response in a simple local Fermi gas model. As a remarkable feature, SCDW can incorporate the effect of the refraction of the incoming and outgoing particles caused by the nuclear distortion.
In this presentation, we will explain the description of the $(d,d^{\prime}x)$ reaction with SCDW and clarify the importance of the refraction effect for reproducing DDX data of the $(d,d^{\prime}x)$ reaction.
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Proton-nucleus inelastic scattering is an experimental probe for excitation spectrum of the target nucleus. On the other hand, the experimental data for neutron-nucleus inelastic scattering is scarce and thus one needs a robust theoretical framework to study it. Our work uses microscopic nuclear structure calculations for spherical nuclei to obtain nucleon-nucleus scattering potentials to calculate cross sections for these processes. \
We implement Jeukenne, Lejeune, Mahaux (JLM) semimicroscopic folding approach [1,2,3] where the medium effects on nuclear interaction are parameterized in nuclear matter to obtain a local energy-dependent nucleon-nucleon interaction in a medium at positive energies. We solve the nuclear ground state using Hartree-Fock-Bogoliubov many-body method, and by approximating interaction between nucleons within a nucleus as Gogny D1M potential [4]. The vibrational excited states of the target nucleus are calculated using quasi-particle random phase approximation method. We calculate the nucleon-nucleus optical and transition potentials by folding in microscopic ground state and transition densities with the JLM potential. \
We will present the results for elastic and inelastic scattering cross sections for Zr90, Zr94 and Zr96 using our scattering potentials for proton and neutron incident energies from 10-30 MeV. We will also discuss the application of this approach to computing $(n, \gamma)$ cross sections using surrogate method. \
References
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In the experiment performed 40 years ago at the University of Maryland, it was reported that the cross section of the $^{16}$O($p,pd$)$^{14}$N reaction [1] is almost half that of the $^{16}$O($p,2p$)$^{15}$N reaction [2]. This result may indicate that the existence probability of the deuteron in $^{16}$O is surprisingly high and that there are $pn$ correlation including the deuteron ``cluster.'' To describe this reaction, it is important to treat the fragility of the deuteron properly. The deuteron can be easily broken up by the incident proton in the elementary process. In addition, the knocked-out deuteron is expected to go through transition between the bound and breakup states by the final-state interactions (FSIs). Furthermore, the deuteron broken up in the elementary process can reform a deuteron by the FSIs. These processes are not included in the distorted wave impulse approximation (DWIA) framework [3], which is the standard reaction model for describing the knockout reactions as employed in the ($p,pd$) analysis of Ref. [2]. Therefore, even if measurement results of deuteron knockout reactions are systematically obtained, it is not possible to conclude clearly whether deuterons exist in nuclei or not by the DWIA analysis. Thus, a reaction model beyond DWIA is necessary.
In this presentation, we are going to report the numerical results calculated with such a reaction model, CDCCIA, which we have been constructing [4]. In CDCCIA, the elementary processes of the ($p,pd$), i.e., the $p$-$d$ elastic scattering and the $d$($p,p$)$pn$ reaction, are described with an impulse picture employing a nucleon-nucleon effective interaction. In addition, the three-body scattering waves in the final state of the
($p,pd$) reaction are calculated with the continuum-discretized coupled-channels method (CDCC) [5--7]. We will shown that the deuteron reformation significantly changes the explicit cross section of the ($p,pd$) reaction through the interference between the elastic and breakup channels of deuteron. Our conclusion is that including these processes is important to quantitatively discuss the ($p,pd$) cross sections in view of the deuteron formation in nuclei.
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We discuss the first theoretical identification of a low-energy enhancement (LEE) in the magnetic dipole $\gamma$-ray strength function of heavy nuclei. The LEE has been a subject of intense experimental and theoretical interest [1] since its discovery, and, if the LEE persists in heavy neutron-rich nuclei, it would have profound implications for our understanding of r-process nucleosynthesis. Standard shell-model methods used to study the LEE in medium-mass nuclei are computationally intractable in heavy nuclei. We combined beyond-mean-field many-body methods in the shell-model framework to identify the LEE in heavy nuclei.
The shell model Monte Carlo (SMMC) method [2] is a powerful method to calculate thermal observables in model spaces that are many orders of magnitude larger than those that can be addressed in conventional methods, but it cannot be used to calculate directly $\gamma$SFs. In SMMC, it is only possible to calculate the imaginary-time response function, whose inverse Laplace transform is the $\gamma$SF. However, this transform is numerically ill-defined. The standard method to carry out numerically the analytic continuation is the maximum-entropy method whose success depends crucially on a good choice of a prior strength function.
The static path plus random-phase approximation (SPA+RPA) reproduces well SMMC state densities [3]. We implemented an extension of the SPA+RPA [4] to calculate $\gamma$SFs in the framework of the CI shell model for a pairing plus quadrupole Hamiltonian [5]. We then use the SPA+RPA $\gamma$SF as a prior in a maximum-entropy method that reproduces the SMMC imaginary-time response function [5].
The SPA+RPA becomes computationally expensive for the interactions used in SMMC, and instead we use as prior strength the SPA $\gamma$SF [6,7]
We applied these methods in chains of samarium [5] and neodymium [6,7] isotopes and identified a LEE in their M1 $\gamma$SF. We also observed a scissors mode and a spin-flip mode that are built on top of excited states. We discuss how these modes change in the crossover from spherical to deformed heavy nuclei.
This work was supported in part by the U.S. DOE grant No. DE-SC0019521.
[1] J. E. Mitdbo, A. C. Larsen, T. Renstrom, F. L. Bello Garrote, and E. Lime, Phys. Rev. C 98, 064321 (2018), and references therein.
[2] For a recent review, see Y. Alhassid, in Emergent Phenomena in Atomic Nuclei from Large-Scale Modeling: a Symmetry-Guided Perspective, edited by K. D. Launey (World Scientific, Singapore, 2017), pp. 267-298.
[3] P. Fanto and Y. Alhassid, Phys. Rev. C 103, 064310 (2021).
[4] H. Attias and Y. Alhassid, Nucl. Phys. A 625, 565 (1997); R. Rossignoli and P. Ring, Nucl. Phys. A 633, 613 (1998).
[5] P. Fanto and Y. Alhassid, arXiv:2112.13772.
[6] A. Mercenne, P. Fanto, and Y. Alhassid, to be published (2023).
[7] D. DeMartini, P. Fanto, and Y. Alhassid, to be published (2023).
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\title{Nuclear reactions as a tool to study the microscopic structure of pygmy and giant resonances}
\author{N. Tsoneva}
\affil{\small{Extreme Light Infrastructure (ELI-NP)$,$ Horia Hulubei National Institute for R$\&$D in Physics and Nuclear Engineering (IFIN-HH), Str. Reactorului No. 30, 077125 Bucharest-M$\check{a}$gurele, Romania}}
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\abstract{An advanced microscopic approach based on the energy density functional theory and the quasiparticle-phonon model has been implemented in studies of pygmy and giant resonances \cite{NT16,Len19}. In addition, the nuclear structure model is extended by a reaction theory for the calculation of (d,p)- and (d,p$\gamma$) reaction cross-sections in order to investigate the microscopic structure of the pygmy dipole resonance and its collectivity \cite{Spi20,Wei21}. Besides the single-particle nature of the excited states, various properties of the low-energy dipole strength emerge from the analysis of ($\gamma$,$\gamma'$) spectral distributions and branching ratios, from which the role of the quasicontinuum is investigated \cite{Wei21,Tso22}. Unprecedented access to the theoretical wave functions demonstrating the one-particle, one-hole neutron origin of the pygmy dipole resonance in the studied nuclei was achieved. The current studies will support day-one gamma-above-neutron-threshold experiments at ELI-NP targeting ground-state $\gamma$ decays of giant and pygmy resonances, as well as studies by multi-step $\gamma$ decays through low-lying states.}
\begin{thebibliography}{99}
\bibitem{NT16} N. Tsoneva, H. Lenske, \textit{Physics of Atomic Nuclei} \textbf{79} (2016) 885–903 and refs. therein.
\bibitem{Len19}Horst Lenske and Nadia Tsoneva, \textit{European Physical Journal} A, \textbf{55} (2019) 238.
\bibitem{Spi20} M. Spieker, A. Heusler, B. A. Brown, T. Faestermann, R. Hertenberger, G. Potel, M. Scheck, N. Tsoneva, M. Weinert, H.-F. Wirth, and A. Zilges, Phys.Rev.Lett. 125 (2020) 102503.
\bibitem{Wei21} M. Weinert, M. Spieker, G. Potel, N. Tsoneva, M. M\"uscher, J. Wilhelmy, and A. Zilges, submitted to Phys. Rev. Lett. (2021).
\bibitem{Tso22}T. Shizuma, S. Endo, A. Kimura, R. Massarczyk, R. Schwengner, R. Beyer, T. Hensel, H. Hoffmann, A. Junghans, K. Römer, S. Turkat, A. Wagner, and N. Tsoneva
Phys. Rev. C 106, 044326 (2022).
\end{thebibliography}
\end{document}
The abstract is attached as a pdf file
Multihundred MeV proton accelerators are promising sites for the large scale production of medical radionuclides due to the high production rates enabled by their high-intensity beam capabilities and the long range of high-energy protons. However, the ability to reliably conduct isotope production at these accelerators and model relevant (p,x) reactions in the 100–200 MeV range is hampered by a lack of measured data. The current suite of predictive reaction-modeling codes is only accurate to within approximately 20% for (p,x) and (n,x) reaction channels where a large body of experimental measurements currently exist. In cases where few data exist, these codes often exhibit discrepancies anywhere within a factor of 2–50. In order to address this deficiency, stacked-target irradiations were performed at LBNL, LANL, and BNL, measuring proton-induced reactions on niobium, arsenic, and lanthanum targets from threshold to 200 MeV.
Reaction modeling at these energies is typically unsatisfactory due to few prior published data and many interacting physics models. Therefore, a detailed assessment of the TALYS code was performed with simultaneous parameter adjustments applied according to a standardized procedure. Particular attention was paid to the formulation of the two-component exciton model in the transition between the compound and preequilibrium regions, with a linked investigation of level density models for nuclei off of stability and their impact on modeling predictive power. This assessment has revealed a systematic trend in how residual product excitation functions for high-energy proton-induced reactions on spherical nuclei are miscalculated in the current exciton model scheme. Additionally, adjustments made to the TALYS ldmodel 4 (Goriely) and ldmodel 6 (HFB+Gogny) level densities illustrate the reliance of reaction modeling upon well-characterized models of the nuclear level density at high excitation energy [1, 2].
[1] M. B. Fox, A. S. Voyles, J. T. Morrell, L. A. Bernstein, J. C. Batchelder, E. R. Birnbaum, C. S. Cutler, A. J. Koning, A. M. Lewis, D. G. Medvedev, F. M. Nortier, E. M. O’Brien, and C. Vermeulen, “Measurement and modeling of proton-induced reactions on arsenic from 35 to 200 MeV,” Physical Review C, vol. 104, p. 064615, dec 2021.
[2] M. B. Fox, A. S. Voyles, J. T. Morrell, L. A. Bernstein, A. M. Lewis, A. J. Koning, J. C. Batchelder, E. R. Birnbaum, C. S. Cutler, D. G. Medvedev, F. M. Nortier, E. M. O’Brien, and C. Vermeulen, “Investigating high-energy proton-induced reactions on spherical nuclei: Implications for the preequilibrium exciton model,” Physical Review C, vol. 103, p. 034601, mar 2021.
With very few exceptions, direct measurements of neutron capture cross sections on
radionuclides have not been possible. A number of indirect methods have been pursued such as
the surrogate method [1], the γ-ray strength function method [2,3], the Oslo method [4-7] and the
β-Oslo method [8]. Substantial effort has been devoted to quantify the usually large systematic
errors that accompany the results from these techniques. A new instrument has been recently
developed at the Los Alamos Neutron Science Center (LANSCE) to provide more accurate data
on several radionuclides relevant to nuclear criticality safety, radiochemical diagnostics,
astrophysics, nuclear forensics and nuclear security, by measuring the transmission of neutrons
through radioactive samples and studying resonance properties. The Device for Indirect Capture
on Radionuclides (DICER) [9-11] and associated radionuclide production at the Isotope
Production Facility (IPF) [12, 13], both at LANSCE, as well radioactive sample fabrication, have
been under development the last few years. A description of the new apparatus, preliminary data
on a few mid-weight stable isotopes and efforts on radionuclide measurements will be presented.
References
1. J. E. Escher et al., Phys. Rev. Lett. 121, 052501 (2018)
2. H. Utsunomiya et al., Phys. Rev. C 82, 064610 (2010)
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9. P.E. Koehler, Springer Proceedings in Physics, 254 (2021) p. 187
10. P.E Koehler, LA-UR-18-22995 (2018)
11. A. Stamatopoulos et al., Nucl. Instrum. Meth. A, 1025 (2022) 166166
12. K.F. Johnson et al., LA-UR-04-4570 (2004)
13. https://lansce.lanl.gov/facilities/ipf/index.php
3He induced reactions allow to investigate the spectroscopy of high excitation energy regions of light compound nuclei that can be formed in low energy reactions [Lom21]. We recently performed a new experiment of this type, HELICA, with the solid-state hodoscope OSCAR [Del18] at the AN-2000 accelerator of the Laboratori Nazionali di Legnaro (INFN-LNL). In the experiment, a 3He beam, with energies ranging from about 1400 keV to 2200 keV was delivered to a thin 13C target. Thanks to the excellent identification capabilities of the HELICA setup, several nuclear reactions, including 13C(3He,p)15N, 13C(3He,d)14N, 13C(3He,alpha)12C, leading the residual nucleus to several excited states, were correctly identified. The latter, in particular, is an excellent probe for the detailed spectroscopy of the 16O compound nucleus. In the talk, we show preliminary angular distributions and excitation functions of the cross section for the 13C(3He,a0), 13C(3He,a1), 13C(3He,a2) reactions in a broad angular domain, and discuss the impact on the spectroscopy of 16O. The preliminary values of the branching ratios between the transitions populating the ground state and the Hoyle state show an energy dependence that suggest the occurrence of a strongly clustered state in 16O at about 24 MeV excitation energy.
References
[Del18] D. Dell’Aquila et al., Nucl. Instr. Meth. Phys. Res. A 877 (2018) 227
[Lom21] I. Lombardo et al., J. Phys. G: Nucl. Part. Phys. 48 (2021) 065101
The 19F(p,α0)16O and the 19F(p,απ)16O reactions play a key role in the description of astrophysical phenomena and nuclear structure, allowing to study the behavior of the 20Ne compound nucleus. In addition, in the domain of nuclear astrophysics, the competition between 19F(p,α) and 19F(p,γ) reactions at sub-coulomb energies is of paramount importance to determine possible escape paths from the ordinary CNOF cycle. Nowadays, available literature data lack some information around the 1.3 MeV region for the απ reaction, while at higher energies, around 1.6 MeV, there is a strong disagreement between different data sets for the α0 measurements.
This work is focused onto providing new data on both reaction channels and on deepening knowledge on the spectroscopy of 20Ne excited states. The new experiment was performed at the Singletron electrostatic accelerator in Catania. Excitation functions were obtained at backward polar angles for both reaction channels; we were able to unambiguously separate the contribution of the απ peak, with respect to the close lying α1 peak (80 keV energy difference). To avoid problems related to the stoichiometry of 19F in the target, we adopted an internal normalization protocol based on the analysis of the elastic peak on 19F. The obtained 19F(p,α0) differential cross sections were compared with other data reported in the literature. Reaction data were then transformed into absolute integrated cross section and analyzed in the framework of a comprehensive R-Matrix fit. The results of the fitting procedure and of the subsequent extraction of partial widths for the explored reaction channels will be discussed on the light of theoretical predictions concerning α cluster states in 20Ne in the excitation energy region Ex = 13-15 MeV.
The $^{18}$O + $^{48}$Ti reaction was studied at the energy of 275 MeV for the first time within the NUMEN [1] and NURE [2] experimental campaigns with the aim of investigating the complete net of reaction channels potentially involved in the $^{48}$Ti $\rightarrow$ $^{48}$Ca double charge exchange (DCE) transition. The $^{48}$Ca nucleus is indeed one of the candidates for neutrinoless double beta (0$\nu\beta\beta$) decay and the study of DCE and other competing nuclear reaction channels is important to constrain theories on the nuclear matrix elements. Among the nuclear reactions, the study of one- and two-nucleon transfer reactions has a prominent role within the project. Understanding the degree of competition between successive nucleon transfer and DCE reactions is crucial for the description of the meson exchange mechanism. Moreover, study of elastic scattering is of paramount importance for probing the nucleus-nucleus potential. The latter is a key ingredient for precise theoretical calculations for all the reaction channels mentioned above. To this extent, angular distribution measurements for all the available reaction channels in the $^{18}$O + $^{48}$Ti collision were pursued at the MAGNEX facility [3] of INFN-LNS in Catania. This contribution provides an overview on the analysis of elastic and inelastic scattering [4], one-nucleon [5,6] and two-nucleons transfer reactions, while preliminary results on the analysis of the DCE reaction will be also presented.
[1] F. Cappuzzello et al., Eur. Phys. J. A 54, 72 (2018).
[2] M. Cavallaro et al., Proceedings of Science BORMIO2017:015 (2017).
[3] F. Cappuzzello et al., Eur. Phys. J. A 52, 167 (2016).
[4] G. A. Brischetto, Il Nuovo Cimento 45C, 96 (2022).
[5] O. Sgouros et al., Phys. Rev. C 104, 034617 (2021).
[6] O. Sgouros, Il Nuovo Cimento 45C, 70 (2022).
High-energy photons are primarily produced as bremsstrahlung by electron accelerators. These photons produce neutrons, photoneutrons, via photonuclear reactions from the interactions with accelerator components. The yield, energy, and angular distribution data of the photoneutrons are fundamental parameters for the shielding design of electron accelerators. To date, plenty of studies have been conducted on neutron emission in photonuclear reactions [1,2,3]. In [2,3], the photoneutron energy spectra for 17 MeV polarized beam from medium-heavy targets were measured. The results indicate that the spectra consist of low-energy and high-energy components. The angular distribution of the low-energy component is isotropic, whereas that of the high-energy component is dependent on the interaction angle between the photon polarization and neutron emission. The photonuclear reaction cross-section for the Giant Dipole Resonance (GDR) photon absorption mechanism of various targets was reviewed in [1]. Heavy targets such as Ta, W, Au, Pb, and Bi have cross section peaks at photon energies of around 13 MeV. It is interesting to see what differences are observed on the photoneutron spectra emitted from these heavy materials with two different incident photon energies: one at the peak and the other above the peak. Hence, our group recently measured the photoneutron spectra for 13 MeV and 17 MeV linearly polarized photons at angles ranging from 30° to 150° on Ta, W, Au, Pb, and Bi targets.
Our experiment was carried out at NewSUBARU facility, BL-01, Hyogo, Japan. The experimental setup for the photoneutron measurement and data acquisition system was identical to that reported previously [2,3]. The 13 MeV and 17 MeV horizontally polarized photon beams were produced by the collision of a polarized laser and 0.85 GeV and 0.97 GeV electrons, respectively, at the backscattering angle. Targets were cylinders with 1 cm thicknesses for Ta, W, and Au, and 2 cm for Pb and Bi. We used six liquid scintillation detectors (NE213, 5 inches × 5 inches L) positioned at 30°, 60°, 90°, 120°, and 150° horizontally and 90° vertically to the photon beam direction. Because of the high sensitivity of NE213 to photoneutrons and gamma rays in the background, the pulse shape discrimination (PSD) technique was used. The time-of-flight (TOF) method was applied to obtain photoneutron energy spectra. In this talk, the photoneutron energy spectra from Ta, W, Au, Pb, and Bi with 13 MeV and 17 MeV photons will be presented and compared.
References
1) Varlamov, A.V., et al, Atlas of giant dipole resonances. Parameters and Graphs of Photonuclear Reaction Cross Sections. INDC (NDS)-394, IAEA NDS, Vienna, Austria, 1999, pp.1-311.
2) Tuyet, T.K., et al, Energy and angular distribution of photo-neutrons for 16.6 MeV polarized photon on medium–heavy targets, Nucl. Instrum. Meth. A, vol.989, 2021, 164965.
3) Kirihara, Y., et al, Neutron emission spectrum from gold excited with 16.6 MeV linearly polarized monoenergetic photons, vol.57, no.4, J. Nucl. Sci. Technol., 2020, pp.444-456.
The production mechanism of light (anti-)(hyper)nuclei at LHC energies is still under debate given the extreme conditions at which they are formed. The ALICE experiment so far has performed several measurements not only in Pb-Pb collisions but also in p-Pb and pp collisions, thus providing a wider look at the production mechanisms in different scenarios. A review of the measurements of light (anti)nuclei from small to high-density colliding systems will be shown and comparisons with models will be discussed.
The NeNa-MgAl cycles are involved in the synthesis of Ne, Na, Mg, and Al isotopes. The 20Ne(p,γ)21Na (Q = 2431.68 keV) reaction is the first and slowest reaction of the NeNa cycle and it controls the speed at which the entire cycle proceeds. At the state of the art, the uncertainty on the 20Ne(p,γ)21Na reaction rate affects the production of the elements in the NeNa cycle. In particular, in the temperature range from 0.1 GK to 1 GK, the rate is dominated by the 366 keV resonance corresponding to the excited state of EX = 2797.5 keV and by the direct capture component. The present study focus on the study of the 366 keV resonance and the direct capture below 400 keV. At LUNA (Laboratory for Underground Nuclear Astrophysics) the 20Ne(p, γ)21Na reaction has been measured using the intense proton beam delivered by the LUNA 400 kV accelerator and a windowless differential-pumping gas target. The products of the reaction are detected with two high-purity germanium detectors. The experimental details and preliminary results on the 366 keV resonance and on the direct capture component at very low energies will be shown, together with their possible impact on the 20Ne(p,γ)21Na reaction rate.
The mixing phenomena in both, the Red Giant Branch (RGB) and Asymptotic Giant Branch (AGB) stars, can be studied by using the $^{12}$C/$^{13}$C ratio in the stellar atmosphere, an important indicator of the stellar nucleosynthesis. Since both nuclei take part in the CNO cycle, the reaction rate of both, $^{12}$C$(p,\gamma)^{13}$N and $^{13}$C$(p,\gamma)^{14}$N, are the main ingredients to evaluate the ratio $^{12}$C/$^{13}$C. The cross-sections of both the reactions have been measured at the Laboratory for Underground Nuclear Astrophysics (LUNA) reaching the lowest energies up to date ($E_{p} = 65$ keV) and entering into the high energy tail of the hydrogen burning shell in massive stars. In order to efficiently characterize any possible systematic effect, both reactions were measured with two independent setups and by using several detection techniques, namely prompt-$\gamma$ detection, total absorption spectroscopy and activation counting. The results are systematically lower with respect to the literature. The new data are the most precise up to date with an estimated systematic uncertainty in the 7 - 8% range. Finally, based on these cross-sections the lowest possible $^{12}$C/$^{13}$C ratio during hydrogen burning has been calculated with the highest precision up to date.
The experimental yields of fragment mass and charge distributions for the neutron-induced fission of 30 actinide nuclei are well described in the model [1,2], which considers the fissioning scission system consisting of two heavy fragments and α-particle between them. The α-particle has its origin in the neck nucleons. The yield of fission fragments in the model is linked to the number of states over the barrier of the saddle point, which is between the contacting and well-separated fission fragments. The quadrupole deformations of heavy fragments are taken into account in the model. The correlation between the values of the equilibrium quadrupole deformation parameter of the fragments and the yield of these fragments is shown. The yields of 9020 fission fragment data points produced in 30 neutron-induced fission reactions considered in our model are described up to a factor of ∼7.8. The values of the averaged total kinetic energy for the neutron-induced fission of considered nuclei are well agreed with the available experimental data.
The values of the ground-state deformation parameters play important role in the description of the nuclide, mass, and charge distributions because the deformation energy gives contribution to the total potential energy of the three-body system. Due to this, it is possible to define the values of the ground-state deformation parameters in neutron-rich fragment nuclei by using the sensitivity of the fragment yield on the values of these parameters. The mass, charge, and nuclide yields are described by fitting the values of the equilibrium quadrupole deformation of nuclei related to the fission fragments in the model.
The fragment mass distribution is considered without division on symmetric and different asymmetric fission modes. In contrast to this, there is the three-body configuration in the scission point, which is responsible for the characteristics of the fission fragments yields. The fission fragment yields depend on the heights of corresponding saddle points and the values of the equilibrium quadrupole deformation of fragment nuclei.
[1] V.Yu. Denisov, I.Yu. Sedykh, Eur. Phys. J. A 57, 129 (2021).
[2] V.Yu. Denisov, Eur. Phys. J. A 58, 188 (2022) (2022).
Anton P. Tonchev1,4, Anthony P.D. Ramirez1, Ron C. Malone1, Jack A. Silano1, Roger Henderson1, Mark A. Stoyer1, Nicolas Schunck1, Matthew E. Gooden2, Jerry Wilhelmy2, Werner Tornow3,4, Calvin R. Howell3,4,Sean Finch3,4
1 Lawrence Livermore National Laboratory, Livermore, California 94550, USA
2 Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545, USA
3 Triangle Universities Nuclear Laboratory, Durham, North Carolina, 27708, USA
4 Department of Physics, Duke University, Durham North Carolina, 27708, USA
Fission product yields (FPY) are essential ingredients for addressing questions relevant to a range of basic and applied physics. Examples include the cosmic nucleosynthesis processes that created the elements from iron to uranium, decay heat release in nuclear reactors, reactor neutrino studies, radioisotope production, development of advanced reactor and transmutation systems, and many national security applications. While new applications will require accurate energy-dependent FPY data over a broad set of incident neutron energies, the current evaluated FPY data files contain only three energy points: thermal, fast, and 14-MeV incident energies. The goal of this study is to provide high-precision and energy dependent FPY data using monoenergetic neutron beams with energies between 0.5 and 15 MeV.
Absolute cumulative fission product yields have been determined for about 100 fission products representing 40 mass chains during neutron-induced fission of 235U, 238U, and 239Pu. Using rapid belt-driven irradiated target transfer system (RABITTS) [1] and irradiations with varying duration, gamma-ray decay history of fission products between 1 second to a few days have been measured. The number of fissions during the irradiation times was determined via a dual fission ionization chamber loaded with thin electroplated foils with the same actinide material. The obtained new FPY data provides a more complete picture of the FPY landscape - from the initial distribution produced directly by fission, through the complex, time-dependent evolution of the yields from beta-decay and neutron emission [2]. This work also provides a unique capability to bridge short-lived fission product yields [3] to our measured cumulative fission yields [4]. An overview of the recent experimental results obtained by the LLNL-LANL-TUNL collaboration will be presented. The FPY results will be discussed in terms of their energy and target-mass dependency.
[1] S. Finch et al., Nuc. Instrum. Meth A 1025, 166127 (2022).
[2] A. Tonchev et al., EPJ Web of Conference 239, 03001 (2020).
[3] A.P.D. Ramirez et al., Manuscript submitted for publication.
[4] M. Gooden et al., Nucl. Data Sheets 131, 319 (2016).
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.
Despite the recent experimental and theoretical progress in the investigation of the nuclear fission process, a complete description still represents a challenge in nuclear physics because it is a very complex dynamical process, whose description involves the coupling between intrinsic and collective degrees of freedom as well as different quantum-mechanical phenomena. Due to this complexity and the use of different reaction mechanisms to induce the fission process, as well as the definition of different fission observables which were often biased by the experimental conditions, many contradictory results and conclusions exist in literature [1]. In the last decade, unprecedented fission experiments have been carried out at the GSI-FAIR facility using the inverse kinematics technique in combination with state-of-the-art detectors especially designed to measure the fission products with high detection efficiency and acceptance [2,3]. For the first time in the long-standing history of fission, it was possible to simultaneously measure and identify both fission fragments in mass and atomic numbers and obtain many correlations among them sensitive to the fission dynamics [2,4] and the nuclear structure at the scission point [5,6]. Recently, these measurements have been improved by combining the previous experimental setup with the calorimeter CALIFA (CALorimeter for In-Flight detection of $\gamma$-rays and high energy charged pArticles) [7] and the neutron detector NeuLAND (New LArge Neutron Detector) [8] developed by the R3B collaboration, which allow us to measure the gamma-rays and light particles in coincidence with the fission fragments. In this talk I will show the results obtained in all these experiments, summarizing as well the new ideas for the future fission experiments at the GSI-FAIR facility.
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We present the fission fragment decay calculation results by the nuclear reaction model code, TALYS, that adopts the Hauser-Feshbach statistical decay theory to the de-excitation of fission fragments evaporating by emitting neutron and $\gamma$. TALYS incorporates so-called "Fission Fragment Database" which consists of yield $Y$, charge $Z$, mass $A$, excitation energy $E_x$, spin $J$, and parity $\Pi$, {\it i.e.}, $Y_{\rm ff}(Z,A,E_x,J,\Pi)$. The data are prepared for TALYS' input by the other fission models such as GEF, HF3D, and SPY. We examine the fission fragment data produced by the GEF code. The calculated independent fission product yield $Y_{\rm I}(A)$, average prompt fission neutron emission $\bar\nu$, neutron multiplicity distribution $P(\nu)$, and prompt fission neutron spectra will be discussed.
The fast proton-induced fission cross-sections of 238U have been analyzed from the threshold up to 70 MeV. Calculations were performed on fission variables such as cross-sections, mass distributions, and prompt neutron emission. For the analysis, Talys and programs written by authors were used to describe the fission process using a Brosa model. As a result, we estimate the contribution of different nuclear reaction mechanisms (direct, pre-equilibrium, compound nucleus) to cross-sections, prompt neutron production, and other fission parameters. Different nuclear reaction mechanisms contribute to the interaction of fast protons with any target nucleus, excited residual nuclei by mean of (p,p’), (p,xn), (p,xp), (p,xa) (x=1,2,…,n) and other processes. In the case of 238U, excited residual nuclei can also fission, contributing in this way to the investigated variables and isotope production. Theoretical results were compared with previous experimental data found in the literature. The comparison allowed us to extract parameters of the optical potential, fission barrier height and width, and type of nucleus deformation. Fission cross sections and yields for produced fission isotopes (as Mo, I, Xe, Sr and other fission fragments) along the whole energy range were determined for all types of incident channels and then agreed with available data from the EXFOR database.
References
[1] C. Oprea, A. Mihul, A. Oprea, European Physics Journal–Web of Conference, 211, 04008 (2019)
[2] C. Oprea, A. Mihul, A. I. Oprea, I. Gruia, O. D. Maslov, A. G. Belov, M. V. Gustova, Il Nuovo Cimento, 42C, 2 - 3, 138 (2019)
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The role of angular momentum in fission has generated a great deal of attention recently. Recent data has shown that, while the fission fragment spins may be thought to emerge highly correlated, the resulting measured fragment spins were shown to be largely uncorrelated. This talk will summarize some of the advances made with the fission simulation model FREYA which is well suited for studying the role of angular momentum in fission because it can easily simulate a variety of scenarios for generating fragment spin and determine the observational consequences.
The work of R.V. was performed under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. The work of J.R. was performed under the auspices of the US Department of Energy by Lawrence Berkeley National Laboratory under Contract DE-AC02-05CH11231.
Nuclear fission produces fragments whose spins are correlated both mutually
and with the fission direction. The character and degree of the correlations
depend on the time scales of the various rotational modes in the evolving
dinuclear complex prior to scission. The expected rotational dynamics is
discussed based on the nucleon-exchange mechanism.
Photon angular correlations can reveal information about the orientations
of the fission fragment angular momenta. Identified stretched E2 collective
transitions in even-even fission product nuclei are particularly suitable
because they do not change the orientation of the nuclear spin and the
associated angular distribution relative to the direction of a fission fragment
reflects the orientation of the fragment spins relative to the fission axis.
Furthermore, if the photon helicities can be determined, the distribution of
the opening angle between E2 photons from even-even partner fragments reveals
the mutual correlation of the fragment spins, demonstrating the potential power
of helicity measurements in fission.
Isomeric states have been observed in about 150 of the hundreds of isotopes that can be produced in the fission of major actinides. These isomers can be populated directly through fission, and the isomeric yield ratio (IYR) represents the relative population of the excited state(s) and the ground state (GS) independent yield.
Due to the underlying nuclear structure, the isomeric state often undergoes β decay and populates very different states in the daughter nucleus compared to the GS decay. This has important implications for the determination of the reactor antineutrino flux. The yields of certain fission products have been shown to play a particularly important role in the calculation of reactor antineutrino spectra with the summation method [1,2]. However, an exhaustive study of the impact of IYRs was never reported.
An evaluation of experimental isomeric yields was recently published [4], that provided recommended IYRs for 42 nuclides produced in low-energy neutron-induced fission. In this work, we present a comprehensive study of the extent to which IYRs affect the antineutrino flux predictions with the summation method using two different approaches. First, we estimated how the newly published recommended IYRs change the antineutrino spectra of all major actinides of interest for reactor antineutrino spectra (235,238U,239,241Pu). Then we individually looked at the contribution of each fission product with a known isomer, and studied how a different IYR value would affect the calculated antineutrino spectra.
A result from the first study, the antineutrino spectrum obtained with the newly evaluated IYRs was calculated as the ratio to the one obtained with the unmodified JEFF-3.3 yields [5,6]. While essentially no effect on the antineutrino spectrum is observed below 5 MeV, changes on the order of 1%-2% for each fuel type become evident between 5 and 7 MeV. These grow to as much as 30% above 7 MeV. The changes show consistently an increase in the antineutrino yield when the newly evaluated isomeric yields are used, compared to the original JEFF-3.3 values.
In the second phase of this work, we performed a sensitivity analysis to identify which IYRs the antineutrino spectrum is most dependent on. This looked beyond the experimentally determined values from Ref. [4], and allowed us to identify a number of fission products whose IYR might considerably affect the antineutrino spectrum in proximity to the bump region, and for which no direct yield measurement has been reported to date.
References
[1] Sonzogni, A.A., et al. Phys Rev Lett 116.13 (2016): 132502.
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[3] An, Feng Peng, et al. Phys Review Lett 116.6 (2016): 061801.
[4] C.J. Sears, et al. Nucl Data Sheets 173 (2021): 118.
[5] Mills, R.W. EPJ Web of Conf Vol. 146 (2017).
[6] Plompen, A.J., et al. Eur Phys Jour A 56.7 (2020): 1.
While nuclear fission has been extensively studied for over 80 years, this phenomenon still lacks a complete and fully microscopic description. One of its most intriguing properties are the spin distributions of the fission fragments (FFs), quantities that are not directly observable in experiment yet play an important role in determining the properties of the neutrons and gammas emitted from the FFs, which are essential experimental tools for understanding and characterizing fission.
In my presentation I will cover the first microscopic extractions of the FF spin distributions, starting with a summary of the microscopic framework, namely the time-dependent density functional theory or equivalently time-dependent density functional theory, then touch upon the projection procedure used to obtain the spin distributions. I will show qualitative results obtained for nuclear systems 240Pu, 236U, and 252Cf. Finally, I will summarize the progress on ongoing extensions including fission fragment (FF) charge and mass distributions, and the FF particle projected energy spectra.
The advent of the LHC as antimatter factory has enabled an unprecedented effort to measure the production of light (anti)nuclei from pp to heavy-ion collisions, providing input for a detailed study of nucleosynthesis in high-energy interactions. The production of these bound states, however, is not modelled in commonly-used event generators. To fill this gap, we developed a coalescence afterburner to be used within Monte Carlo generator inputs to model the production of light (anti)nuclei in hadronic interactions on an event-by-event basis.
In this work, the event generators as PYTHIA8.3 and EPOS are preliminarily tuned to describe (anti)proton yields as measured at the LHC. This input is fed to a Wigner function-based coalescence afterburner that forms a nucleus when two or more nucleons are close in phase space, depending on the momentum distribution of the nucleons, the nucleus wave function, and the size of the nucleon emitting source. The results are discussed in comparison to ALICE data and in the perspective to apply the model for estimating the fluxes of cosmic antinuclei for indirect dark matter searches with space-based experiments like AMS and GAPS.
Measurements and theoretical studies show that thunderclouds can act as particle accelerators in nature. Terrestrial gamma ray flashes (TGFs) are bursts of gamma rays with energies ranging from below 10 keV to about 40 MeV. They last for microseconds and occurring in bursts separated by hundreds of microseconds, all events lasting up to the order of milliseconds. There also exist gamma ray glows, with durations up to several minutes. To explain a TGFs and gamma ray glows, a phenomenon called relativistic runaway electron avalanche (RREA) is frequently used. RREAs are large populations of high energetic electrons formed by avalanche growth driven by electric fields in Earth’s atmosphere. The electrons, which are traveling at speeds very close to the speed of light, collide with nuclei of atoms in the atmosphere and release their energy in the form bremsstrahlung. The produced gamma rays can further trigger photo-nuclear reactions in the air and in soil. The electron avalanches can cause local high dose levels so airplane crew and passengers flying near thunderstorms can therefore be exposed to “dangerously” high levels of radiation due to the RREA electrons. Since the energies of the RREAs are up to several tens of MeV, they can also trigger reactions with atoms of the air and in the soil. In this paper we present the project CRREAT (Research Centre of Cosmic Rays and Radiation Events in Atmosphere), which measures the lightning and the ionizing radiation during thunderstorms and the radiation field at aviation altitudes and at low earth orbits (LEO). This paper gives also an overview of possible sources of ionizing radiation and phenomena during thunderstorms, and discuss how RREA induced increased radiation fields at aviation altitudes could be simulated using the general-purpose 3D Monte Carlo code PHITS.
Due to electromagnetic properties, thunderclouds can act as particle accelerators in nature. The electrons accelerated in the thunderclouds can reach energies up to tens of MeV, and create a number of different phenomena: Terrestrial gamma-ray flashes (TGFs), Terrestrial Neutron Flashes (TNFs), Terrestrial Ground Enhancements (TGEs), and Relativistic Runaway Electron Avalanches (RREA). RREAs are large populations of high energetic electrons formed by avalanche growth driven by electric fields in Earth’s atmosphere. The electron avalanches propagate through the matter and are decelerated and deflected by particles in the atmosphere. The remaining energy is emitted as gamma rays known as bremsstrahlung. The produced gamma rays can further trigger photo-nuclear reactions in air and soil. The matter then may remain activated.
The project CRREAT (Research Centre of Cosmic Rays and Radiation Events in Atmosphere) is studying different phenomena related to thunderstorms in different ways, in situ and at laboratories, including exposing different soil samples with 20 MeV electron beams at the Microtron accelerator in Prague. The electron beam experiments were performed to see what radionuclides might be produced during the reactions of high energetic electrons with different soils. Measurements of the radionuclides produced in the exposed samples were performed using a High Purity Germanium (HPGe) detector. This simple geometry of source and sample was also simulated using the general-purpose 3D Monte Carlo code PHITS, and a comparison of the measured and the simulated data will be presented.
FLUKA [1-3] is a general-purpose Monte Carlo code for the simulation of radiation transport used, among other applications, for the assessment of single-event-upset (SEU) production in electronic devices. FLUKA predictions for SEUs induced by protons below 10 MeV in commercial RAM modules significantly underestimate experimental values [4], due in part to the present lack of a nuclear elastic scattering model in FLUKA for protons below 10 MeV.
In order to overcome this limitation, the Coulomb and nuclear elastic scattering of protons on nuclei has been revisited within the distorted-wave Born approximation (DWBA), relying on spin-dependent optical potential models for protons of up to 200 MeV in the vicinity of nuclei [5,6], and accounting for the contribution of the compound elastic channel in the first few MeV above the Coulomb barrier [7]. A numerical database of differential cross sections for the elastic scattering of protons with energies from Coulomb barrier up to 200 MeV on targets ranging from Z=2 to Z=100 has been evaluated. To minimize memory requirements, an effective parametrized expression based on the (diffuse) black-disk limit [8] has been fitted to the numerical database, reducing it to a handful of energy-dependent coefficients, while still capturing the most relevant features in the differential cross section and providing a systematic means of disentangling Coulomb and nuclear elastic scattering. An efficient sampling scheme relying on the aforementioned parametrization has been implemented. This model supersedes the legacy model for nuclear elastic scattering of protons presently employed in the code (currently just above 10 MeV), dating back to the 1970s [9].
The model presented here substantially improves the agreement between FLUKA predictions and experimental cross sections for the production of SEUs in RAM modules under irradiation by protons below 10 MeV. Furthermore, it also gives an overall better description of large-angle nuclear elastic collisions of protons up to 200 MeV compared to the effective model presently in use in the code.
[1] https://fluka.cern
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[4] Coronetti A., PhD thesis, JYU Dissertations series, number 453, Jyväskylä, ISSN 2489-9003, ISBN 978-951-39-8915-6 (2021).
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[8] Dremin I.M., Phys. Uspekhi, 56 (1) 3-28 (2013).
[9] Ranft J., Part. Accel., 3 129-161 (1972).
Antiproton-nucleus reaction is a versatile tool. It can be used to study fundamental behavior of antimatter (e.g., at CERN AD facility), neutron halo and skin of atomic nuclei (e.g., PUMA project), hyperon-antihyperon interaction (project at GSI FAIR), to name but a few.
Since final state interactions are also important in such reactions and that the intranuclear cascade code INCL is known to do it well, it is naturally that its developers have been asked to add this new projectile to the list.
Therefore, recent results of the new INCL version with antiproton as projectile are presented
with comparisons to experimental data in wide energy range.
Influence of various input parameters, such as annihilation distance, total cross-section, Sp/Sn ratio (ratio of probabilities to annihilate on a neutron or a proton), potential, as well as annihilation final states and secondary antiparticle production, is discussed in both scenarios of annihilation, i.e., at rest and in-flight.
The new version will be made available also in GEANT4, allowing to simulate future complex experiments involving pbar.
Electromagnetic processes such as photon absorption or gamma decay play a critical role in the reaction networks involved in nucleosynthesis or radiochemistry. Since direct experimental data is often lacking for many of the nuclei relevant for such applications, developing a predictive theory of these electromagnetic processes is especially important. Microscopic approaches built from fundamental models of nuclear forces and quantum many-body methods offer the advantage to describe in a consistent manner both nuclear ground-state properties, nuclear decays such as gamma or beta decay, and even more complex processes such as fission. In this talk I will give a status report of a LLNL project to perform large-scale calculations of gamma-strength functions, beta-decay rates and level densities within the general framework of nuclear density functional theory with Skyrme forces. This approach is an attempt to generalize recent studies with the Gogny force from the CEA-Bruxelles collaboration, and with the relativistic mean field by the Zagreb group.
We calculate the electric dipole (E1) and the magnetic dipole (M1) giant resonances with noniterative finite amplitude methods and demonstrate how the fully microscopic density functional theory predicts the giant resonances without any phenomenological parameters. Then, we calculate neutron capture reactions based on the statistical Hauser-Feshbach theory with the result of E1 and M1 transitions and find that the capture cross sections for deformed nuclei are enhanced due to the contribution from the low energy M1 scissors mode.
In nuclear reactions induced by low-energy charged particles, atomic electrons can participate in the process by screening the nuclear charge and so, effectively reduce the repulsive Coulomb barrier. Consequently, the measured cross section is enhanced by an effect called electron screening. In numerous experiments, different research groups [1-4] have reported extremely high values for the electron screening potential, much higher than the prediction based on an available theoretical model [5].
Nevertheless, even as a considerable amount of experimental data was collected over the past twenty years, a suitable theory, which can give an explanation of this effect, has not yet been found. However, electron screening is very important in nuclear astrophysics. For nucleosynthesis calculations, precise reaction rates should be known at very low energies where screening effects cannot be neglected and for a proper application, electron screening must be included in most calculations related to the nucleosynthesis of elements. However, this is impossible because we simply do not know enough about this effect. Furthermore, it is believed that electron screening in stellar plasmas differs from the laboratory screening because the atoms in the stellar interiors are in most cases in highly stripped states and the nuclei are immersed in a sea of almost free electrons, which tend to cluster closer to the nucleus than in atoms. The only thing that can be done at present is to try to better understand electron screening under the laboratory conditions and then to draw a parallel with the stellar plasma.
Lately, our group was focusing on studying the electron screening effect in palladium targets. The experimental study of the electron screening effect was performed using the 2~MV Tandetron accelerator at Jo\v{z}ef Stefan Institute. We measured the $^{1}$H($^{7}$Li,${\alpha}$)$^{4}$He, $^{1}$H($^{19}$F,${\alpha}$${\gamma}$)$^{16}$O and $^{2}$D($^{19}$F,p)$^{20}$F reaction rates on two differently prepared hydrogen and deuterium containing palladium foils. In one of our targets we measured no screening, and in the second one we measured a high screening potential for all three reactions, that is an order of magnitude above the theoretical model. Contrary to the theoretical predictions, our research suggested that the reason behind this difference is linked to a dependence of electron screening potential on the host's crystal lattice structure and the location of the target nuclei in the metallic lattice.
The latest results from our research and an applied methodology will be presented.
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The concept of “theragnostics” in nuclear medicine, ideally, involves the diagnosis and treatment of a
patient using radioisotopes of the same element, to ensure what you image is what you treat. The
concept is currently being followed by means of diagnosis with 68Ga, followed by radionuclide therapy
using 177Lu.
Researchers are pursuing the idea utilizing the same element, but different radioisotopes thereof for
diagnosis and therapy. Over the last decade, much research has been performed at Paul Scherrer
Institute with radioisotopes of scandium and terbium, respectively. The radiotheragnostics principle
was demonstrated with the use of cyclotron-produced 44Sc (as well as 43Sc) for tumour diagnosis, while
47Sc was produced for preclinical therapy studies. Four radioisotopes of terbium are deemed
interesting for nuclear medical purposes: 152Tb and 155Tb can be used for diagnostic purposes via
positron emission tomography (PET) and single photon emission computed tomography (SPECT),
respectively, while 149Tb and 161Tb are interesting therapeutic radionuclides due to their α- and βemission, respectively.
The radionuclides in question are in various stages of development, with some in its early stages due
to lack of facilities capable of producing them, while terbium-161 is being prepared for clinical trials.
An outlook will include possibilities of producing novel radionuclides with new facilities/installations
in future.
The MEDICIS facility is a unique facility located at CERN dedicated to the production of non-conventional radionuclides for research and development in medical imaging, diagnostics and radiation therapy. Located in a laboratory equipped to safely handle unsealed radioactive samples, it comprises a dedicated isotope separator beam line, a target irradiation station at the 1.4 GeV Proton Synchroton Booster (PSB), or alternatively receives activated targets from external institutes e.g. during CERN Long Shut-Downs. The target is heated up at high temperatures to allow for the diffusion and effusion of the produced atoms out of the target that are subsequently ionized. The ions are accelerated and sent through an off-line mass separator. The radionuclide of interest is mass-separated and implanted into a thin metallic collection foil. After collection, followed by a radiochemistry process when necessary, the batch is prepared to be dispatched to a research center for further processing and usage. Since its commissioning in December 2017, the facility has provided novel radionuclides including, but not limited to, Ba-128/Cs-128, Tb-149, Sm-153, Tb-155, Tm-165/Er-165, Er-169, Yb-175 and Ac-225 with high specific activity values, some for the first time, to research institutes part of the collaboration. CERN-MEDICIS’ research and development around the topics of production, extraction and mass-separation is in constant evolution. The facility also contributes in the education and training of young researchers. Moreover, MEDICIS is one of the pillars of PRISMAP, a network of world-leading European facilities including nuclear reactors, medium- and high-energy accelerators, radiochemical laboratories and biomedical facilities. PRISMAP acts as a European platform for medical radionuclides and supports the ongoing research on nuclear therapy and molecular imaging by providing immediate access to novel radionuclides. This presentation will provide a general overview of the facility and its operation as well as address recent achievements and developments together with the challenges that such a facility faces.
The scientific community interest in the production of the theranostic 47Sc, as underlined in the IAEA Coordinated Research Project (CRP) on 67Cu, 47Sc and 186Re [1], is due to its medically favourable decay characteristics (Eγ=159.381 keV Iγ=68.3%, Eβ-,mean=162.0 keV Iβ-=100%) suitable for therapeutic purposes and SPECT cameras for diagnosis. Moreover, 47Sc has a quite long half-life (T1/2 = 3.3492 d) allowing the radiolabelling operations for radiopharmaceuticals production but also the monitoring of the biodistribution of monoclonal antibodies, paving the way to radioimmunotherapy applications.
In case of medical applications it is crucial to optimize the production of 47Sc, to avoid as much a possible the co-production of contaminant isotopes. At INFN-LNL (Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali di Legnaro), in the framework of the LARAMED project (LAboratory of RAdionuclides for MEDicine) [2], the most favourable conditions for the cyclotron-based production of this radioisotope using proton beams are investigated. The study of the 47Sc production employing enriched 48Ti target is carried out as part of the PASTA project (Production with Accelerator of Sc-47 for Theranostic Applications), funded by INFN for the years 2017/2018 [3, 4]. Instead, the use of enriched 49Ti and 50Ti targets is an aim of the REMIX project (Research on Emerging Medical radIonuclides from the X-sections), funded by INFN for the years 2021/2023. The enriched targets are manufactured at INFN-LNL through the use of the HIVIPP technique (HIgh energy VIbrational Powder Plating) [5]. Since the LARAMED bunkers are still under completion, irradiation runs are performed at the ARRONAX facility (Nantes, France) where a similar high-energy and high-intensity cyclotron able to provide a 70 MeV proton beam is operating [6].
In this work the preliminary results of the production cross-sections using enriched 48Ti, 49Ti and 50Ti targets are presented and compared. Considering the goal of the medical application, not only 47Sc but also the contaminants’ cross-sections are examined, since they can contribute to the radiation deposited in the human body. Particular attention is paid to the Sc-isotopes which cannot be chemical separated with a focus on 46Sc, whose half-life (T1/2 = 83.79 d) is longer than 47Sc one. Results are also compared with the previous literature data where available.
[1] A. Jalilian et al. 2021 IAEA Activities on 67Cu, 186Re, 47Sc Theranostic radionuclides and Radiopharmaceuticals, Current Radiopharmaceuticals.
[2] J. Esposito et al. 2019 LARAMED: a LAboratory for Radioisotopes of MEDical interest, Molecules 24(1), 20 - 10.3390/molecules24010020.
[3] G. Pupillo et al. 2019 Production of 47Sc with natural vanadium targets: results of the PASTA project, Journal of Radioanalytical and Nuclear Chemistry 297(3) - 10.1007/s10967-019-06844-8
[4] G. Pupillo et al. 2019 Preliminary results of the PASTA project (2019) Colloquia: EuNPC 2018, IL NUOVO CIMENTO 42 C 139 - 10.1393/ncc/i2019-19139-1
[5] H. Skliarova et al. (2020) HIVIPP deposition and characterization of isotopically enriched Titanium-48 targets for nuclear cross-section measurements, Nuclear Inst. and Methods in Physics Research, A.
[6] F. Haddad et al. 2008 ARRONAX, a high-energy and high-intensity cyclotron for nuclear medicine, European Journal of Nuclear Medicine and Molecular Imaging, 35:1377-1387.
Radionuclide $^{47}$Sc (T$_{1/2}$ = 3.35 d) represents a promising element for innovative radiopharmaceutical compounds suitable for theranostic applications, however an efficient and convenient production route has still to be identified. In this work we simulate the reactions $^{50}$Ti(p,α)$^{47}$Sc and $^{49}$Ti(d,α)$^{47}$Sc in view of a cyclotron production of $^{47}$Sc on enriched Titanium targets. Pre-clinical and clinical applications demand a production route with high quality, minimizing the co-production of contaminants that could affect the purity of the radiolabeled compound.
The theoretical analysis has been carried out with the nuclear reaction code TALYS and the model variability of the reaction mechanisms has been investigated. Modeling the relevant cross sections, including the production of the main contaminants, namely $^{46}$Sc (T$_{1/2}$ = 83.79 d) and $^{48}$Sc (T$_{1/2}$ = 43.67 h), allows to select the energy interval which maximizes the production yield and the purity, for both targets. Simulations improvements are needed to reproduce the data with a high level of accuracy required for a precise estimate of yields, activities, and purities. For this purpose an optimization strategy has been adopted, based on the genetic algorithm approach.
The results indicate that both channels, $^{50}$Ti(p,n)$^{47}$Sc and $^{49}$Ti(d,α)$^{47}$Sc, are promising reactions for a possible production of $^{47}$Sc by hospital (low-energy) cyclotrons.
Terbium has gained the attention of the community since it is the only element in the periodic table with four isotopes ($^{149}$Tb, $^{152}$Tb, $^{155}$Tb and $^{161}$Tb) that can be used for many clinical applications [1]. In particular, the isotope $^{155}$Tb, with the emission of Auger-electron and $\gamma$ rays, suitable respectively for therapy and for SPECT imaging, is a promising key player in the field of radiopharmaceutical production.
Different nuclear reactions can be evaluated for direct or indirect production of $^{155}$Tb by varying projectiles and targets with different enrichments. In particular, in this work we investigate and compare two $^{155}$Tb generators by considering protons on $^{nat}$Tb and alpha particles on $^{nat}$Gd. Both routes, can be studied using intermediate energy cyclotrons for the production of $^{155}$Dy, the precursor of $^{155}$Tb. The production is followed by two radiochemical separations: initially to isolate dysprosium nuclides from the target, and finally terbium nuclides from their dysprosium parents. The timings of the two separations are crucial to optimize yields and purity of the sample and different scenarios have been considered.
The two production routes are analyzed with the nuclear reaction code TALYS [2], in which different theoretical models are available. The code allows to use state-of-art implementations of the optical potential, of the level density and of the preequilibrium processes: by varying the parameters of the models it is possible to improve the agreement between the calculated cross sections and the available experimental data using techniques similar to those presented in Refs. [3][4].
After a reliable description of the cross sections is obtained, realistic theoretical simulations for the production of $^{155}$Tb are performed by varying the irradiation conditions and the times of the radiochemical separations, as suggested in Refs. [5][6]. Yields and purities of $^{155}$Tb are calculated and optimal solutions are compared for the two reactions, showing that the use of $^{nat}$Tb, as a target, is preferable in view of possible preclinical/clinical applications.
References:
[1] C. Müller et al., J. Nucl. Med, 53(12):1951–1959, 2012.
[2] A. J. Koning, S. Hilaire, and M. C. Duijvestijn. In International Conference on Nuclear Data for Science and Technology, pages 211–214. EDP Sciences, 2007.
[3] F. Barbaro et al., Phys. Rev. C, 104:044619, 2021.
[4] M. B. Fox et al., Phys. Rev. C, 104(6):064615, 2021.
[5] G. F. Steyn et al., Nucl. Instrum. Methods Phys. Res. B, 319:128–140, 2014.
[6] A. N. Moiseeva et al., Nucl. Med. Biol., 106:52–61, 2022.
At least part of the demand for medical radionuclides currently produced via fission of $^{235}$U in dedicated reactors could be met in the future by alternative accelerator-based production routes via photonuclear and light-ion reactions, thus addressing supply chain issues that arise from the operation of ageing reactors and nuclear proliferation concerns, as well as offering easier separation of the end-products and a reduced reliance on a limited number of large producers.
In this context, a programme to study photon- and neutron-induced reactions of medical interest, as well as accelerator-based methods of medical radionuclide production, has been instituted at JRC-Geel. Making use of existing as well as new infrastructure, this activity focuses on both established radionuclides, such as $^{99m}$Tc and its parent $^{99}$Mo (used in SPECT imaging), and emerging radionuclides, such as $^{225}$Ac (relevant for targeted alpha therapy). The recently renewed MONNET 3.5 MV Tandem accelerator provides light ion beams for reaction-based quasi-mono-energetic neutron production, and has been used for the study of $^{99}$Mo production via neutron irradiation of molybdenum nanoparticles. At the same time, a new electron beamline that can deliver quasi-mono-energetic beams has been commissioned at the GELINA electron linac, and will be primarily dedicated to the study of photonuclear reactions and for medical radioisotope production studies via photon irradiation.
In this work we present an overview of the medical radionuclide activities at JRC-Geel, including a description of existing and newly commissioned infrastructure, with particular attention to the design, development and future improvements to the new GELINA electron beamline. Future perspectives of the programme are also discussed.
An innovative neutron Time-of-Flight facility (n_TOF) is operative since 2001 at CERN, with two experimental areas, 20 m and 200 m flight paths.
Neutrons in the wide energy range, from thermal to a few GeV, are generated by spallation of 20 GeV/c protons on a lead target. The high instantaneous neutron flux, low duty cycle, high resolution and low background make this facility unique for high-accuracy and high-resolution cross-section measurements relevant to Nuclear Astrophysics, Nuclear Technology and fundamental Nuclear Physics. Thanks to its features, n_TOF is particularly suited for measurements on radioactive isotopes, such as those involved in the branching of s-process nucleosynthesis, as well as in projects of nuclear waste incineration and for the design of Generation IV nuclear reactors.
To match the convenient characteristics of the neutron beam, the facility has been complemented with state-of-the-art detector and data acquisition systems. In particular, for the measurements of capture reactions, a high-performance 4 total absorption calorimeter made of 40 BaF2 crystals has been built and extensively used, while innovative gas detectors have been developed for measurements of fission cross-sections.
Since the start of operations several measurements have been performed, on light elements, fission fragments and actinides. The high-quality data collected so far of n_TOF provide new insight on the processes of stellar nucleosynthesis and constitute the basis for more accurate data files to be used for the design of advanced nuclear energy systems.
During the CERN long shutdown, a new spallation target has been installed in the facility, it allowed to increase the neutron flux in the second experimental area of a factor two, and to further expand the range of measurements that can be performed at n_TOF. Furthermore, a new experimental area (NEAR station) in proximity of the spallation target has been made, the NEAR station is used to perform activation measurements.
In this talk, the n_TOF facility will be described, together with the main features of the detectors used for capture, fission and (n, charge particle) cross section measurements. An overview of the recent results will be given and the perspective of the new measurements will be presented.
The Experimental Nuclear Reaction Database (EXFOR) database is composed of the numerical data compiled by the international collaboration within the Nuclear Reaction Data Centre (NRDC).
Even though it is digitized and has been used everywhere, the EXFOR format is still under the restrictions of a punch card legacy. It prevents users from using EXFOR data directly by plotting packages such as matplotlib, a Python package used for data plotting and visualization.
Over the past decades, the Open Science movements known as FAIR (Findable, Accessible, Interoperable, Reusable) and digital transformation have gained considerable traction in many scientific fields. The IAEA Nuclear Data Section is expected continue providing free and unrestricted access to its basic nuclear data databases including EXFOR as well as data files and related software by following the FAIR Principles.
As a first trial, we are developing the EXFOR parser to convert EXFOR to JSON and provide data via REST APIs and new interface. In this presentation, we will give an overview and some examples of our developments which would be useful for scientists working on nuclear reaction mechanisms.