From n_TOF and ISOLDE up to the LHC experiments, a remarkable common denominator of all CERN physics programmes is their interplay with central questions in astrophysics and cosmology. This edition of NPA-X will highlight novel opportunities in precision nucleosynthesis, neutron star physics, cosmic ray physics and chemical stellar evolution that arise from combining the latest observations...
In this presentation, I shall give an overview of neutron-induced cross section measurements at n_TOF, both past and present. A selection of the principal characteristics of the time-of-flight facility n_TOF at CERN is given together with several examples of measurements of interest to Nuclear Astrophysics.
Finally, I will present some ideas of possible future experiments, including the...
The GSI/FAIR facility close to Darmstadt, Germany offers a large suite of experimental possibilities with radioactive ions. Stable ions between hydrogen and uranium can currently be accelerated with the synchrotron SIS-18. Fragmentation on combination with a powerful fragment separator (FRS) enable the experiments with a wide range of radioactive isotopes. Single pass can be used to...
Heavy-ion storage rings connected to radioactive beam facilities offer a unique environment for nuclear physics experiments. However, so far they have been only coupled to in-flight fragmentation facilities, for example the ESR and the CRYRING at GSI Darmstadt/ Germany, the CSR at HIRF in Lanzhou/ China, and the Rare RI Ring at RIKEN Nishina Center in Japan.
Neutron capture reactions play a...
Neutron-induced reactions play an important role in several stellar nucleosynthesis scenarios. Experimental determination of their rates are limited by the available neutron flux at the relevant energies, sample size, especially in the case of unstable isotopes, and detection. The Soreq Applied Research Accelerator Facility (SARAF) enabled enhanced opportunities for such measurements by...
F. Hammache$^1$, P. Adsley$^{2,3,*}$, L. Lamia$^{4,5,6}$, D.~S. Harrouz$^1$, N. de Séréville$^{1}$, B. Bastin$^7$, T. Faestermann$^{8}$, C. Fougères$^7$, R. Hertenberger$^{9}$, M. La Cognata$^{5}$, A. Meyer$^{1}$, S. Palmerini$^{10,11}$, R.G. Pizzone$^{5}$, F. de Oliveira$^7$, S. Romano$^{4,5,6}$, A. Tumino$^{12,5}$, H.-F. Wirth$^{9}$
$^1$ Université Paris-Saclay, CNRS/IN2P3, IJCLab,...
The $^{13}$C(α,n)$^{16}$O reaction is the prevalent neutron source for the main s-process, taking place in thermally pulsing low mass AGB stars. The direct measurement of this reaction at stellar temperature (~ 90 MK), corresponding to a Gamow window between 140 - 230 keV, has so far not been possible due to the very low cross section at these energies.
The LUNA collaboration performed the...
Neutron-induced reactions remain at the forefront of experimental investigations for the understanding of stellar nucleosynthesis and chemical evolution of the Galaxy in the region of medium- and heavy-mass nuclides [1]. We report on measurements of the cross section of neutron capture reactions $^{74,80,82}$Se$(n,\gamma)$ and $^{138,140,142}$Ce$(n,\gamma)$ relevant, respectively, to the weak...
We will summarize the status of big-bang nucleosynthesis (BBN), which describes the production of the lightest nuclides during the first three minutes of cosmic time. We will emphasize the transformational influence of cosmic microwave background (CMB) experiments culminating today with Planck, which pin down the cosmic baryon density to exquisite precision. Standard BBN combines this with...
In addition to the insights gained by studying the galactic evolution of chemical elements, short lived radioisotopes contain additional information on astrophysical nucleosynthesis sites.
Meteorites can carry information about the nucleosynthetic conditions in the early Solar System using short lived radioisotopes [1][2], while detections of live isotopes of cosmic origin in the deep sea...
Globular clusters are key grounds for models of stellar evolution and early stages of the formation of galaxies. Abundance anomalies observed in the globular cluster NGC 2419, such as the enhancement of potassium and depletion of magnesium [1] can be explained in terms of an earlier generation of stars polluting the presently observed stars [2]. However, the nature and the properties of the...
The cross sections of nuclear reactions relevant for astrophysics are crucial ingredients to understand the energy generation inside stars and the synthesis of the elements. In stars, nuclear reactions take place at energies well below the Coulomb barrier. As a result, their cross sections are often too small to be measured in laboratories on the Earth’s surface, where the signal would be...
One of the crucial ingredients for the improvement of stellar models in the framework of nucleosynthesis studies is the accurate knowledge of neutron capture cross-sections for the different isotopes involved. This type of measurements can shed light on the discrepancies between observed and predicted isotopic abundances by the stellar models and thus help to constrain the stellar media...
Radiative-capture reactions leading to the formation of 7Be bear a particular interest in the field of nuclear astrophysics.
The most important ones are the 3He(α,γ)7Be and the 6Li(p,γ)7Be reactions.
The former is one of the primary sources of uncertainty in the prediction of the 7Be and 8B neutrino fluxes, being the first reaction of the 2nd and 3rd branch of the p−p chain. Despite its...
Obtaining reliable cross sections for neutron-induced reactions on unstable nuclei nuclei is crucial to our understanding of the stellar nucleosynthesis of heavy elements. However, the measurement of these cross sections is very complicated as both projectile and target are radioactive. The NECTAR (NuclEar reaCTions At storage Rings) project aims to circumvent these problems by using the...
Nuclear reactions play a key role in the framework of the Big Bang Nucleosynthesis. A network of 12 principal reactions has been identified as the main path which drives the elemental nucleosynthesis in the first twenty minutes of the history of the Universe. Among them an important role is played by neutron-induced reactions, which, from an experimental point of view, are usually a hard task...
Despite considerable progresses over the past few decades, the origin of trans-iron elements is not yet fully understood. In addition to the slow (s) and rapid (r) neutron capture processes, an intermediate neutron capture process (i-process) is thought to exist at neutron densities intermediate between the s- and r-processes. The existence of this process is supported by the observation of...
The short-lived radionuclides (SLRs) have a half-life ≤ 100 Myr. The excess abundance of their daughter nuclides in various meteoritic phases confirms the existence of SLRs in the early solar system (ESS). In this work, we have developed Galactic chemical evolution (GCE) models to understand the stellar sources of SLRs, $^{26}$Al, $^{36}$Cl, $^{41}$Ca, $^{53}$Mn, and $^{60}$Fe in the ESS. ...
Accreting neutron stars offer unique opportunities to study the properties of matter in extreme density environments and nuclear processes involving very unstable isotopes. X-ray burst are one of the rich observables that can be used to test models of accreting neutron stars. The burst are driven by thermonuclear reactions near the surface of the neutron star that proceed through (a,p) and...
How elements are made in the Universe is an open long-standing question. Several processes are invoked to explain the observed elemental abundances in our Solar System [1] and in our galaxy [2].
Complex astrophysical simulations are used to study the origin of the heavy elements and quantify the contribution of the r-process to the observed elemental abundances (see e.g. [3]). The r-process...
The lighter heavy elements of the first r-process peak, between strontium and silver, can be synthesized in the moderately neutron rich neutrino–driven ejecta of either core–collapse supernovae or neutron star mergers via the weak r–process [1]. This nucleosynthesis scenario exhibits uncertainties from the absence of experimental data from $(\alpha,xn)$ reactions on neutron–rich nuclei, which...
The r-process has been shown to be robust in reproducing the abundance distributions of heavy elements seen in ultra-metal poor stars. In contrast, observations of elements in the range 36 ≤ Z ≤ 47 display overabundances relative to r-process model predictions [1]. A proposed solution to this discrepancy is an additional source of early nucleosynthesis that preferentially produces the lighter...
The astrophysical origins of the heaviest stable elements that we observe today in the Solar System are still not fully understood. While thermonuclear supernovae (SNe Ia) are known to have forged about two-thirds of the iron content in the Solar System, recent studies have demonstrated that H-accreting white dwarfs (WDs) in a binary system exploding as SNe Ia could be an efficient p-process...
In massive-star binary systems, upon reaching later stages of stellar evolution one star can expand as a giant and envelope its companion. The enveloped companion, here a neutron star, can begin to accrete matter. The angular momentum of the accreting material will result in the formation of an accretion disk. Accretion onto common-envelope-phase neutron stars can result in material ejected...
$^{12}$C fusion reactions are among the most important in stellar evolution since they determine the destiny of massive stars. Over the past fifty years, massive efforts have been done to measure these reactions at low energies. However, existing data present several discrepancies between sets and large uncertainties specially at the lowest energies. Factors such as beam/environmental...
When stars approach the red giant branch, a deep convective envelope develops and the products of the CNO cycle appear at the stellar surface. In particular, the $\rm^{17}O$ is enhanced in RGB and AGB stars. Then, spectroscopic analyses of O isotopic ratios of these stars provide a powerful tool to investigate the efficiency of deep mixing processes, such as those powered by convective...
The presence of ${\rm ^{26}Al}$ (T$_{1/2}$=1.04 Myr) in the interstellar medium has been strongly debated through the years: its 1.809 MeV $\gamma$-ray line has been appointed as a tracer of the recent nucleosynthesis in our galaxy, and its presence have been found spread along Galactic plane. Observations support the idea that this isotope can been formed through nucleosynthesis in massive...
Facility for Research in Experimental Nuclear Astrophysics (FRENA), an upcoming tandem accelerator facility at Saha Institute of Nuclear Physics, Kolkata, India. This is a low energy (0.2-3 MV) high current facility primarily designed for nuclear astrophysical studies. Most of the astrophysical reactions have very low cross-sections with large error bars[1]. So the background studies in this...
Binding energies, proton-neutron paring and α-like quartetting in proton-rich nuclei
close to N=Z line
N. Sandulescu
National Institute of Physics annd Nuclear Engineering, 76900 Magurele-Bucharest, Romania
The modelling of nucleosynthesis processes triggered by rapid proton capture requires accurate predictions for the binding energies of...
Stellar explosions such as novae, supernovae, and X-ray bursts involve thermonuclear reactions on rare isotopes. Interpretation of observations such as the light curves from X-ray bursts, elemental abundances, or $\gamma$-rays from nuclear decay as well as predictions of nucleosynthesis are notably impacted by large uncertainties in the nuclear reaction rates. Many of these reactions either...
The NeuLAND (New Large-Area Neutron Detector) plastic scintillator based time of flight detector for 0.2-1.6 GeV neutrons is currently under construction at the Facility for Antiproton and Ion Research (FAIR), Darmstadt, Germany. In its final configuration, NeuLAND will consist of 3,000 2.7 m long plastic scintillator bars that are read out on each end by fast timing photomultipliers. Here,...
The subject of massive star explosions driven by a first-order hadron-quark matter phase transition has gained increasing attention in the community, e.g., providing a novel path to the existence of massive pulsars of 2 solar masses at birth [1] and the creation of ejected r-process material in these explosive events [2]. However, no final conclusions can yet be drawn from these results about...
Over the last decades huge efforts were made to determine the $^{12}$C($\alpha,\gamma$)$^{16}$O cross section, as it is key to understand the evolution of stars. Using direct methods with stable targets and a low-energy ion beam poses significant challenges to the experimental setup and data analysis. Center-of-mass energies down to 1 MeV were reached with sometimes large uncertainties of up...
For direct cross section measurements in nuclear astrophysics, in addition to suitable ion beams and detectors, also highly pure and stable targets are needed. Here, using a gas jet as a target offer an attractive approach that combines high stability even under significant beam load with excellent purity. Such a target is currently under construction at the Felsenkeller underground ion...
The $^{19}$F(p,$\alpha$)$^{16}$O reaction is important for understanding the fluorine abundance in the outer layers of asymptotic giant branch (AGB) stars and it might also play a role in hydrogen-deficient post-AGB star nucleosynthesis. Up to now, theoretical models overproduce F abundances in AGB stars with respect to the observed values, thus calling for further investigation of the...
A recent sensitivity study has shown that the 35K(p,γ)36Ca reaction is one of the ten (p,γ) reaction rates that could significantly impact the shape of the calculated X-ray burst light curve [1]. Its reaction rate used up to now in type I X-ray burst calculations was estimated using an old measurement for the mass of 36Ca and theoretical predictions for the partial decay widths of the first 2+...
Recent measurement of coherent π0 photoproduction on Pb lead to a most accurate determination of the neutron skin, constraining nuclear matter Equation of State (EoS) at around ρ~1ρ0. A natural next step is elucidating the nuclear EoS at higher densities to tune our understanding of the most violent process in the Universe - neutron stars mergers. It was demonstrated that at densities above...
The nuclear fission of very neuron-rich nuclei is essential for the termination of the r-process flow on the nuclear chart and the determination of the final abundances. Nevertheless, most of the available fission data for neutron-rich nuclei are based on theory predictions mostly by phenomenological treatments. In this study, we calculated a series of nuclear fission distribution for...
Nuclei in the $^{135}$I region have been identified as a possible bottleneck for the i process. Nuclear properties such as the Maxwellian-averaged cross section are indispensable tools when trying to explain nucleosynthetic processes, but the instability of the region prevents us from carrying out direct measurements. In order to investigate it, we propose an indirect approach.
At the Oslo...
In spite of decades of research, many observed nuclear abundances remain that can not be reproduced by p-process nucleosynthesis calculations [1].
This is mainly due to the lack of constraints for the involved nuclear physics models.
Previous studies have shown that key reactions affecting the abundance of the p-nucleus $^{168}$Yb are the $^{164,166}$Yb($\alpha, \gamma$) reactions and that...
The neutron activation method is well-suited to investigate neutron-capture
cross sections relevant for the main s-process component. Neutrons can be pro-
duced via the $^7$Li(p,n) reaction with proton energies of 1912 keV at e.g. Van de
Graaf accelerators, which results in a Maxwellian spectrum of neutrons corre-
sponding to a temperature of k$_\text{B}$T = 25 keV. This mimicks the...
The 3He(α,γ)7Be reaction plays a role in two distinct astrophysical scenarios, solar fusion processes as well as the Big Bang nucleosynthesis. The astrophysical S-factor of this reaction has been studied several times for energies above 0.3MeV and once for energies between 0.1MeV and 0.2MeV, but never directly for energies below 0.1MeV. The energies in between and below the measured range are...
Cross section measurements of ${}^{12,13}\mathrm{C}(\mathrm{p},\gamma){}^{13,14}\mathrm{N}$ have been performed at the Laboratory for Underground Nuclear Astrophysics (LUNA), where the low-background environment and high beam currents of the $400\,\mathrm{kV}$ accelerator allowed to obtain cross section data for these reactions at lower energies and with smaller statistical uncertainties than...
To calculate the reaction rate in the neutron capture processes it is common to work with the Maxwellian Average Cross Section (MACS), defined as the reaction rate scaled by the most probable neutron velocity of the Maxwell-Boltzmann distribution. For the s-process mainly, the MACS directly describes the reaction rate inside the stars, for a given temperature and neutron density. Hence, the...
$^{12}C(\alpha,\gamma)^{16}O$ has been, and still is, one of the central topic in nuclear astrophysics.\
Reason for this is that stellar models are very sensitive to the ratio $^{12}C/^{16}O$ produced by the helium buring stage. Knowing the value of the $^{12}C(\alpha,\gamma)^{16}O$ S-factor at the energy of astrophysical interest ($E_0\sim$ 300 keV) to a precision better than 10\% would...
Multinucleon-transfer (MNT) reactions have gained a lot of attention in the last decade following the theoretical prediction of larger than expected production cross sections for heavy neutron-rich nuclei [1] playing a key role in the astrophysical rapid neutron capture process (r process) [2]. At the Ion Guide Isotope Separator On-Line (IGISOL) facility [3] in the JYFL Accelerator Laboratory,...
Short-lived radionuclides, i.e. radioactive isotopes with half-lives of less than 100 Ma, were present as primordial isotopes in the proto-solar cloud and during the formation of our solar system. The origin of specific short-lived radionuclides is still a matter of dispute. Because of their comparatively short half-lives, these isotopes are no longer present in cosmic samples today, but are...
We perform microscopic Molecular Dynamics simulations to study crystallization in the outer crust of Neutron Stars (NSs). We study the energetics and pressure in the electron screened nuclear system using a consistent nuclear population in the inner and outer crust under the approximation of one the component plasma (OCP) and multicomponent plasma (MCP) assuming some nuclear species...
Neutron-induced charged particle reactions (n, p) and (n, α), especially on unstable proton-rich isotopes, play an important role in understanding explosive astrophysical scenarios and interpreting their remnants. In a recent publication [1], a novel approach is described to study experimental cross-sections of (n, p) and (n, α) reactions at explosive stellar temperatures for various nuclei...
The $^3$He($\alpha$,$\gamma$)$^7$Be nuclear reaction has been investigated in several times before [1]. The importance of this reaction is manifested in two astrophysical scenarios. It plays a role in the nucleosynthesis of the Big Bang (BBN) through the production of lithium and is also a branching reaction in the solar p-p chain. The astrophysically relevant energy range of this reaction in...
Black holes have ignited thought-provoking ideas for decades because of their peculiar origin of existence and very nature. Once only thought to be merely a mathematical curiosity, black holes have now become an integral part of Astrophysics and Astronomy that devour copious amounts of matter. Given the advancement from the first speculation to the latest research, an up-to-date review report...
The impression of mean field and spectator matter has been studied through the collision geometry dependence of reduced flow and elliptical flow in heavy-ion collisions (HICs) at intermediate energies using Isospin-dependent Quantum Molecular Dynamics (IQMD) model for the reaction of $^{50}_{20}$Ca+$^{50}_{20}$Ca and $^{197}_{79}$Au+$^{197}_{79}$Au at incident energy between 50 MeV/nucleon and...
Several reactions of light nuclei require a better understanding in Nuclear Astrophysics. The most relevant one is 12C(α,γ)16O. The reason for this is both, the unmitigated importance of the reaction, and the complexity of its cross section at the relevant energies of static helium burning (300 keV) which uncertainty is still undesirably large. As there is no state of natural parity to serve...
Big Bang Nucleosynthesis (BBN) accounts for the cosmic origin of the lightest elements, and deuterium (D/H) plays a key role in probing the physics of the early universe. The simplicity of BBN theory allows for few-percent-level precision of D/H prediction, which is not normally possible in nuclear astrophysics. Under such precision, the comparison between predicted and observed primordial D/H...
Bardeen–Cooper–Schrieffer theory explains how the heat capacity of the superfluid vanishes when the temperature approaches zero. Various mechanisms may suppress the pairing gap in the superfluid, leading to an increased heat capacity. In turn, this may translate to changing the cooling rate and the thermal evolution of neutron stars. The presence of a vortex in a superfluid neutron matter will...
The existence of most of the stable very neutron deficient nuclei - the $p$ nuclei - cannot be explained via neutron-capture reactions. Therefore, at least one other process has to exist in order to describe their origin, the $\gamma$ process. Since most photodisintegration reactions involved in the process are not directly accessible, reliable statistical model calculations are needed to...
The $^{17}$O(n,$\alpha$)$^{14}$C reaction is considered in astrophysical codes for its role in the astrophysically relevant "s(slow)-process" since it could act as a possible “neutron-poison” for the neutron induced nucleosynthesis thus influencing the final stellar abundances of some elements such as Fe, Ni or Sr. Thus, its reaction rate must be known in the energy region of interest for...
Muon are the subatomic particles. with very high speed(2.9*10^8).with this speed it can travel a distance of 456meters.But the muon formed in the atmosphere travel the distance of 15 km whish is shown by research.
This phenomenon is called muon paradox if we can differentiate between these special muon (of muon paradox which undergoes in time dilation and length contraction) and normal muon...
Observed supermassive black holes in the early universe have several proposed formation channels, in part because most of these channels are difficult to probe. One of the more promising channels, the directly collapse of a supermassive star, has several possible probes including the explosion of a helium supermassive star triggered by a general relativistic instability. We develop a...
$^{19}$F (p,$\alpha$) reaction is one of the crucial reactions in the CNO Cycle. It has the utmost importance in the astrophysical region particularly below the Coulomb barrier [1]. In an astrophysical scenario, the importance astrophysical S-factor is crucial for the understanding of discrepancies in fluorine nucleosynthesis [2-4] and the contribution of direct or resonance at such low...
Around half of the elemental abundances heavier than iron are created via the rapid neutron capture process (r-process). For nuclear masses $A>100$, there are two main peaks in the r-process abundances, located at $A\sim 130$ and $A\sim 195$. These peaks are associated with neutron shell closures. In contrast, the rare-earth peak (REP) is a small - but clear - peak around mass $A=160$,...
As the slowest reaction in the carbon-nitrogen cycle of hydrogen burning, the $^{14}$N($p,\gamma$)$^{15}$O reaction modulates the rate of energy generation in stars in the cycle and thus determines the time spent on the main sequence. Astrophysical challenges, such as the age determination of globular clusters or the solar-abundance problem can be targeted by improving the precision on the...
The isospin dependent nuclear saturation property has a salient role to play in understanding the matter behaviour at high density regimes. Very recently an improved value of neutron skin thickness of $^{208}\text{Pb}$ was reported in Lead Radius EXperiment-II (PREX-2) to be $R_{\text{skin}}=R_n - R_p=(0.283\pm 0.071)$ fm which corresponds to high estimations of nuclear symmetry energy...
The nucleosynthesis of elements heavier than iron in stars is one of the most relevant topics in nuclear astrophysics. The neutron-capture processes made most of the abundances of heavy elements in the solar system, but they are not able to make a number of rare proton-rich stable isotopes (p-nuclei) lying on the left side of the stability valley. The $\gamma$-process, i.e. a chain of...
Carbon burning is a fundamental process for the advanced stages of a massive star ($ M> 8M_\odot $) evolution. It mainly occurs through the $^{12}C+^{12}C$ fusion, however at temperatures higher than $ 10^9 K $ the $^{12}C+^{16}O $ fusion can become prevalent due to the increased abundance of $ ^ {16} O $ in the ashes of the helium burning. The $ ^{12}C + ^{16} O $ reaction also plays a role...
Present nuclear reaction network computations for astrophysical simulations involve many different types of rates, including neutron-capture reactions of interest for the modeling of heavy-element nucleosynthesis. While for many of them we still have to rely on theoretical calculations, an increasing number of experimentally-determined cross sections have now become available. In this...
Nucleosynthesis by the rapid neutron-capture process (r-process) produces elements heavier than iron via neutron-rich nuclides, observed in the solar system and stars with various metallicities. In the r-process, fission plays a fundamental role by recycling the matter during neutron irradiation and by shaping the final r-abundance distribution. Nevertheless, most of the fission data available...
We show the impact on AGB stellar nucleosynthesis of the maxwellian averaged capture cross sections determined at n_TOF over the past 20 years. We developed an automated procedure to derive MACSs from evaluated data libraries, which are subsequently used as input to stellar models computed by means of the FUNS code.
In this contribution, we present a number of s-process abundances obtained...
The nuclear fission of very neuron-rich nuclei is essential in the r-process for the termination of nucleosynthesis flows and the final abundances. Nevertheless, most of the available fission data for the r-process simulations are based on phenomenological calculations. In the present study, we investigate the theoretical uncertainty of nuclear fission related to the r-process. Focusing on the...
It has long been postulated that the onset of electron captures in degenerate high-density ONe cores of super-AGB stars would trigger a supernova, resulting in a collapse into a neutron star (NS). New models of these so-called electron capture supernovae (ECSNe) suggest that while the full collapse to a NS is still a possibility, the energy release by the electron-capture reactions can also...
Neutron-induced reactions play an important role in nuclear astrophysics in several scenario, such as Big Bang nucleosynthesis or heavy-element production via the s or r neutron capture processes [1]. To overcome some of the experimental difficulties typical of direct neutron cross section measurements, in the last years, the possibility of using the Trojan Horse Method (THM) to study...
Two significant anomalies have been recently observed in the emission of electron-positron
pairs in the 7Li(p,e− e+)8Be and 3H(p,e− e+)4He reactions [1, 2]. These anomalies have
been interpreted as the signature of the existence of a boson (hereafter referred to as X17)
of mass M_X17 = 16.8 MeV that could be a mediator of a fifth force, characterised by a
strong coupling suppression of...
Nucleosynthesis in Type I X-ray bursts (XRB) proceeds eventually through the rp-process near the proton drip-line. Several N=Z nuclei act as waiting points in the reaction network chain. Astrophysical calculations of XRB light curves depend upon the theoretical modelling of the beta decays of interest, with the N=Z and their second-neighbours N=Z+2 being key nuclei in this context.
Several...
Low Mass X-ray Binaries that transiently accrete matter onto their neutron stars are excellent laboratories for studying dense matter physics. These systems go in and out of the quiescence phase over observational timescales of decades. Monitoring the surface temperatures of neutron stars in this phase reveals a great deal of information about their structure and composition. However, to infer...
Approximately 30 stable nuclides on the neutron-deficient side of stability cannot be produced via the same neutron-capture driven mechanisms responsible for synthesizing all other elements heavier than iron. These “p-nuclei” are instead thought to originate from photodisintegration reactions on s- and r-process seed nuclei, which can occur in the extreme high-temperature environments of...
A kilonova is an electromagnetic transient powered by the radioactive decay of nuclei freshly
synthesized by the rapid neutron capture process (r-process). Its observation following the
gravitational wave event GW170817 provided the first evidence that the r-process operates in
neutron star mergers. Kilonova observations provide unique opportunities to learn about the in-
situ operation of...
The concepts of the nuclear level density (NLD) and $\gamma-$ray strength function (GSF) are two essential tools for the statistical description of excited nuclei and their $\gamma-$decay, used in numerous large-scale astrophysical calculations of abundances of elements in the universe. In this work, one of the widely used experimental techniques, the Oslo method was applied to the...
Experimental neutron capture rates of short-lived neutron-rich nuclei are of pivotal importance for our understanding of explosive nucleosynthesis. In this contribution we present an improved method for constraining neutron capture rates in exotic nuclei experimentally with beam intensities down to a few pps using the $\beta$-Oslo method.
While a powerful technique to access the most exotic...
Storage rings offer a unique approach to measure nuclear reactions using stored radioisotope beams impinging on ultra-pure internal targets. This approach has been pioneered at the ESR storage ring in GSI Laboratory (Germany).
The newly commissioned CRYRING, part of FAIR Phase-0, opens up new and ground-breaking possibilities for nuclear astrophysics at storage rings. CRYRING is the first...
Half the atomic nuclei heavier than iron are created through the s-process, i.e. a series of neutron captures and subsequent beta decays. Accordingly, the accuracy of neutron capture rates is of significant importance for these astrophysical calculations and for our understanding of the observed isotopic abundances [1]. In particular, fundamental input can be provided through the determination...
JRC Geel operates a neutron time-of-flight facility, based on an electron accelerator. At 11 flight paths experiments can be performed simultaneously, with available flight paths ranging from 5m to 400 m. Experimental setups to determine total and reaction cross sections ( capture, elastic and inelastic shattering, fission and charged particle reactions ) are available. Furthermore, during ...
The $^{22}\rm{Ne}(\alpha,\gamma)^{26}\rm{Mg}$ is an important reaction in stellar helium burning environments as it competes directly with one of the main neutron source for the s-process $^{22}\rm{Ne}(\alpha,n)^{25}\rm{Mg}$ reaction. The reaction rate of the $^{22}\rm{Ne}(\alpha,\gamma)^{26}\rm{Mg}$ reaction is dominated by low energy energy resonances at $E_{R}^{lab}$ = 0.65, 0.83 MeV. The...
$(\alpha,n)$ reactions provide a source for neutrons in many stellar environments, fueling the production of the heavy elements. The key $(\alpha,n)$ reactions for the $s$-process are thought to be $^{13}$C and $^{22}$Ne, but reactions on other nuclei, including $^{17,18}$O and $^{24,25}$Mg may also play important roles. In addition, $(\alpha,n)$ reactions are sources of background for...
Simulations of explosive nucleosynthesis in novae predict the production of the radioisotope $^{22}\text{Na}$. Its half-life of 2.6 yr makes it a very interesting astronomical observable by allowing space and time correlations with the astrophysical object. This radioisotope should bring constraints on nova models. It may also help to explain abnormal $^{22}\text{Ne}$ abundance observed in...
We report on a precise mass measurement of 69Co and 70Co performed at the IGISOL facility [1].
The nuclear structure above the N=40 subshell closure remained for long unclear due to lack of information on neutron-rich nuclei in this region. This region is known for shape coexistence and intruder states have been observed in neutron-rich cobalt isotopes toward N=40 [2]. The two-neutron...
Beta decay has a direct access to the absolute values of the Fermi and Gamow-Teller transition strengths. The comparison with complementary charge exchange reactions, such as the ($^3$He,t) reaction performed on the mirror stable targets at RCNP Osaka, allows us the investigation of fundamental questions related to the role of the isospin in atomic nuclei. A systematic study of...
Neutron capture cross-section measurements are fundamental in the study of astrophysical phenomena, such as the slow neutron capture (s-) process of nucleosynthesis operating in red-giant and massive stars. One of the best suited methods to measure neutron capture (n,γ) cross sections over the full stellar range of interest is the time-of-flight (TOF) technique.
TOF neutron capture...
Among the nucleosynthesis mechanism involving the heavy nuclei, the so-called slow (s-)process is one of the better known. Being responsible of about half of the element heavier than iron, many models were built in order to describe the process and the final element abundances.
The s-process take place in the inner layers of AGB stars, where the heavy elements are produced during interpulses...
Understanding the production and survival of $\mathrm{^{205}{Pb}}$ in stars is pivotal as $\mathrm{^{205}{Pb}}$ is the only short-lived radionuclide that is produced exclusively by the slow neutron capture process (s-process). The ratio of radioactive $\mathrm{^{205}{Pb}}$ to stable $\mathrm{^{204}{Pb}}$, when compared to the expected value from the continuous galactic nucleosynthesis, helps...
As standalone detections or in the context of multi-messengers signals, neutrinos offer opportunities to understand our Universe in unprecedented ways. Their weakly interacting nature provides information about the interior of cooling neutron stars, their mergers, and black hole accretion disks. Interpreting neutrino observations from compact objects relies on models of neutrino emission and...
The K600 magnetic spectrometer and the CAKE silicon detector array form a powerful tool for coincidence measurements in many nuclear physics measurements including nuclear astrophysics. These instruments have been used, among others, in studies measuring proton decays from $\alpha$-unbound states in $^{22}$Mg through the $^{24}$Mg(p,t)$^{22}$Mg reaction to study the...
Neutron-induced reactions are essential to the nucleosynthesis of the elements heavier than iron. Recent studies show that key (n,p) reactions, such as the $^{56}$Ni(n,p)$^{56}$Co and $^{64}$Ge(n,p)$^{64}$Ga, accelerate the so-called neutrino-p process ($\nu$p-process), enabling the process to create heavy elements between nickel (Ni) and tin (Sn) in type II Supernovae. The $\nu$p-process...
Among the reactions driving stellar evolution, $^{12}$C + $^{12}$C fusion gives the key ingredients during carbon burning. This system reveals many resonances [1], but also regions with suppressed fusion cross-sections [2,3]. The reaction was recently measured by the STELLA collaboration utilizing the gamma-particle coincidence technique for precise cross-section measurements reaching down to...
Thermonuclear reactions that power the stars take place at different energies according to their respective stellar environments. Such energies are well below the Coulomb barrier and the respective cross-sections are incredibly small, often below experimental reach. Modelling energy production in stars requires experimental data on cross-sections for low energies; these data are sparse. As a...
The carbon/oxygen (C/O) ratio at the end of stellar helium burning is the single most important input to stellar evolution theory. However, it is not known with sufficient accuracy, due to large uncertainties in the cross section of the 12C(a,g)16O reaction. We present results based on a new method, which is significantly different from the experimental efforts of the past four decades [1]....
Asymptotic giant branch (AGB) stars are responsible for the production of the main component, i.e. nuclei from Sr to Pb, of the solar s-process distribution. Despite tremendous advances in the theoretical modeling of these objects over the last few decades, many uncertainties remain. An example is represented by the still-unknown mechanism leading to the $^{13}$C neutron source. The...
This contribution highlights the importance of targetry in nuclear physics and astrophysics experiments. Three different stages are described: 1) production, purification and characterization of starting materials, with a concise description of the opportunity offered by PSI in this respect; 2) target manufacture, with emphasis on the last developments obtained at PSI; 3) characterization of...
The study of heavy-ion fusion reactions of light systems is essential for the understanding of the astrophysical reaction networks responsible for the energy production and elemental synthesis in stellar environments. At far sub-barrier energies, fusion is influenced by the hindrance phenomenon [1]. Fusion of light heavy-ions is characterised by a positive Q-value and establishing the presence...
Neutron-induced reactions on unstable nuclei play an important in nuclear astrophysics and for applications of nuclear technology. However, due to the radioactive nature of the nuclei involved, these reactions are extremely difficult or impossible to directly measure. The importance of these reactions has motivated the development of several indirect methods for constraining their properties,...
The $\rm ^7Be(p,\gamma)^8B$ represents one of the more important reaction for the prediction of high energy component of solar neutrino spectrum. The importance of this reaction triggered an intense experimental work over the last decades, where discrepancies were observed between the results of different measurements.
The origin of this discrepancy limit the overall precision and accuracy of...
By combining two unique facilities at GSI (Helmholtz Centre for Heavy Ion Research),
the fragment separator (FRS) and the experimental storage ring (ESR), the first direct measurement of a proton capture reaction of a stored radioactive isotope has been accomplished. The combination of sharp ion energy, ultra-thin internal gas target, and the ability to adjust energy of the beam in the ring...
