Showing 1–50 of 128 results for author: Gyürky, G

Detector characterization for a new $^{12}$C+$^{12}$C reaction study at LUNA

Authors: R. M. Gesùè, S. Turkat, J. Skowroński, M. Aliotta, L. Barbieri, F. Barile, D. Bemmerer, A. Best, A. Boeltzig, C. Broggini, C. G. Bruno, A. Caciolli, M. Campostrini, F. Casaburo, F. Cavanna, T. Chillery, G. F. Ciani, P. Colombetti, A. Compagnucci, P. Corvisiero, L. Csedreki, T. Davinson, D. Dell'Aquila, R. Depalo, A. Di Leva , et al. (28 additional authors not shown)

Abstract: The $^{12}$C+$^{12}$C fusion reaction plays a crucial role in stellar evolution, including the occurrence of supernova explosions, and in the synthesis of the chemical elements. However, our understanding of its cross section remains severely deficient, particularly below $E_\textrm{cm}=2.5$\,MeV, the energy range of interest for astrophysics. To address these unresolved issues, the LUNA collabora… ▽ More The $^{12}$C+$^{12}$C fusion reaction plays a crucial role in stellar evolution, including the occurrence of supernova explosions, and in the synthesis of the chemical elements. However, our understanding of its cross section remains severely deficient, particularly below $E_\textrm{cm}=2.5$\,MeV, the energy range of interest for astrophysics. To address these unresolved issues, the LUNA collaboration will conduct a dedicated study of the $^{12}$C+$^{12}$C reaction at the Bellotti Ion Beam Facility (Bellotti IBF) located deep underground within the Gran Sasso National Laboratory (LNGS) in Italy. Based on the combination of passive and active shields, this campaign aims to achieve unprecedented sensitivity in measuring the cross sections of the two key reaction channels, $^{12}$C($^{12}$C,$α$)$^{20}$Ne and $^{12}$C($^{12}$C,$p$)$^{23}$Na in the low-energy regime via $γ$-ray detection. Here, we report on a sensitivity study for the upcoming campaign with a focus on the characterization of two detectors, namely a HPGe detector and a NaI(Tl) array. Furthermore, their intrinsic contamination is thoroughly investigated since this could potentially influence the overall sensitivity. Assuming typical beam intensities of the Bellotti IBF, we will be able to investigate reaction rates significantly below 100 counts per day. In case of the $^{12}$C+$^{12}$C reaction we therefore expect to acquire experimental data well below the current limit of $E_\textrm{cm}=2.1\,$MeV. The results are supported by simulations to highlight the advantageous low-background environment, essential for high-precision nuclear astrophysics studies. △ Less

Submitted 7 January, 2026; originally announced January 2026.

Journal ref: J. Phys. G: Nucl. Part. Phys. 52 105103 (2025)

Nuclear Physics Mid Term Plan at LNGS

Authors: R. Buompane, F. Cavanna, C. Curceanu, A. D'Onofrio, A. Di Leva, A. Formicola, L. Gialanella, C. Gustavino, G. Imbriani, M. Junker, A. Marcianò, F. Marzaioli, R. Nania, F. Napolitano, K. Piscicchia, O. Straniero, C. Abia, M. Aliotta, D. Bemmerer, A. Best, A. Boeltzig, C. Bruno, A. Caciolli, A. Chieffi, G. Ciani , et al. (37 additional authors not shown)

Abstract: The Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Gran Sasso (LNGS) is one of the largest underground physics laboratory, a very peculiar environment suited for experiments in Astroparticle Physics, Nuclear Physics and Fundamental Symmetries. The newly established Bellotti Ion Beam facility represents a major advance in the possibilities of studying nuclear processes in an undergr… ▽ More The Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Gran Sasso (LNGS) is one of the largest underground physics laboratory, a very peculiar environment suited for experiments in Astroparticle Physics, Nuclear Physics and Fundamental Symmetries. The newly established Bellotti Ion Beam facility represents a major advance in the possibilities of studying nuclear processes in an underground environment. A workshop was organized at LNGS in the framework of the Nuclear Physics Mid Term Plan in Italy, an initiative of the Nuclear Physics Division of the Instituto Nazionale di Fisica Nucleare to discuss the opportunities that will be possible to study in the near future by employing state-of-the-art detection systems. In this report, a detailed discussion of the outcome of the workshop is presented. △ Less

Submitted 22 December, 2025; originally announced December 2025.

Exploring Stars in Underground Laboratories: Challenges and Solutions

Authors: Marialuisa Aliotta, Axel Boeltzig, Rosanna Depalo, György Gyürky

Abstract: For millennia, mankind has been fascinated by the marvel of the starry night sky. Yet, a proper scientific understanding of how stars form, shine, and die is a relatively recent achievement, made possible by the interplay of different disciplines as well as by significant technological, theoretical, and observational progress. We now know that stars are sustained by nuclear fusion reactions and ar… ▽ More For millennia, mankind has been fascinated by the marvel of the starry night sky. Yet, a proper scientific understanding of how stars form, shine, and die is a relatively recent achievement, made possible by the interplay of different disciplines as well as by significant technological, theoretical, and observational progress. We now know that stars are sustained by nuclear fusion reactions and are the furnaces where all chemical elements continue to be forged out of primordial hydrogen and helium. Studying these reactions in terrestrial laboratories presents serious challenges and often requires developing ingenious instrumentation and detection techniques. Here, we reveal how some of the major breakthroughs in our quest to unveil the inner workings of stars have come from the most unexpected of places: deep underground. As we celebrate 30 years of activity at the first underground laboratory for nuclear astrophysics, LUNA, we review some of the key milestones and anticipate future opportunities for further advances both at LUNA and at other underground laboratories worldwide. △ Less

Submitted 10 December, 2025; originally announced December 2025.

Comments: Invited review for Annual Reviews Nuclear Particle Science in 2022

Journal ref: Vol. 72 (2022) 177-204

Towards a comprehensive study of the 14N(p,g)15O astrophysical key reaction: Description of the experimental technique including novel target preparation

Authors: A. Compagnucci, A. Formicola, M. Campostrini, J. Cruz, M. Aliotta, C. Ananna, L. Barbieri, F. Barile, D. Bemmerer, A. Best, A. Boeltzig, C. Broggini, C. G. Bruno, A. Caciolli, F. Casaburo, F. Cavanna, G. F. Ciani, P. Colombetti, P. Corvisiero, L. Csedreki, T. Davinson, R. Depalo, A. Di Leva, Z. Elekes, F. Ferraro , et al. (24 additional authors not shown)

Abstract: While the 14N(p,g)15O reaction plays a key role in the hydrogen-burning processes in various stellar conditions, its reaction rate is not known with sufficient precision. Therefore, the first scientific project at the recently launched Bellotti Ion Beam Facility of the Laboratori Nazionali del Gran Sasso was the measurement of the 14N(p,g)15O reaction cross section in the proton energy range betwe… ▽ More While the 14N(p,g)15O reaction plays a key role in the hydrogen-burning processes in various stellar conditions, its reaction rate is not known with sufficient precision. Therefore, the first scientific project at the recently launched Bellotti Ion Beam Facility of the Laboratori Nazionali del Gran Sasso was the measurement of the 14N(p,g)15O reaction cross section in the proton energy range between 250 and 1500 keV. In this paper, the experimental techniques are summarized with special emphasis on the description of solid state nitrogen target production and characterization. The first results of the reaction yield measured at 55 deg detection angle are also presented. △ Less

Submitted 27 October, 2025; originally announced October 2025.

Journal ref: Eur. Phys. J. A 61 (2025) 191

Advances in Radiative Capture Studies at LUNA with a Segmented BGO Detector

Authors: Jakub Skowronski, Riccardo Maria Gesuè, Axel Boeltzig, Giovanni Francesco Ciani, Denise Piatti, David Rapagnani, Marialuisa Aliotta, Chemsedinne Ananna, Francesco Barile, Daniel Bemmerer, Andreas Best, Carlo Broggini, Carlo Giovanni Bruno, Antonio Caciolli, Matteo Campostrini, Francesca Cavanna, Paolo Colombetti, Alessandro Compagnucci, Piero Corvisiero, Laszlo Csedreki, Tom Davinson, Rosanna Depalo, Antonino Di Leva, Zoltan Elekes, Federico Ferraro , et al. (21 additional authors not shown)

Abstract: Studies of charged-particle reactions for low-energy nuclear astrophysics require high sensitivity, which can be achieved by means of detection setups with high efficiency and low backgrounds, to obtain precise measurements in the energy region of interest for stellar scenarios. High-efficiency total absorption spectroscopy is an established and powerful tool for studying radiative capture reactio… ▽ More Studies of charged-particle reactions for low-energy nuclear astrophysics require high sensitivity, which can be achieved by means of detection setups with high efficiency and low backgrounds, to obtain precise measurements in the energy region of interest for stellar scenarios. High-efficiency total absorption spectroscopy is an established and powerful tool for studying radiative capture reactions, particularly if combined with the cosmic background reduction by several orders of magnitude obtained at the Laboratory for Underground Nuclear Astrophysics (LUNA). We present recent improvements in the detection setup with the Bismuth Germanium Oxide (BGO) detector at LUNA, aiming to reduce high-energy backgrounds and to increase the summing detection efficiency. The new design results in enhanced sensitivity of the BGO setup, as we demonstrate and discuss in the context of the first direct measurement of the 65 keV resonance ($E_{x} = 5672$ keV) of the $^{17}$O($p,γ$)$^{18}$F reaction. Moreover, we show two applications of the BGO detector, which exploit its segmentation. In case of complex $γ$-ray cascades, e.g. the de-excitation of $E_{x} = 5672$ keV in $^{18}$F, the BGO segmentation allows to identify and suppress the beam-induced background signals that mimic the sum peak of interest. We demonstrate another new application for such a detector in form of in-situ activation measurements of a reaction with $β^{+}$ unstable product nuclei, e.g., the $^{14}$N($p,γ$)$^{15}$O reaction. △ Less

Submitted 7 October, 2025; originally announced October 2025.

Journal ref: J. Phys. G: Nucl. Part. Phys. 50 045201 (2023)

Status and future directions for direct cross-section measurements of the 13C(a,n)16O reaction for astrophysics

Authors: L. Csedreki, Gy. Gyürky, D. Rapagnani, G. F. Ciani, M. Aliotta, C. Anannad, L. Barbieri, F. Barile, D. Bemmerer, A. Best, A. Boeltzig, C. Broggini, C. G. Bruno, A. Caciolli, F. Casaburom, F. Cavannak, P. Colombetti, A. Compagnucci, P. Corvisiero, T. Davinson, R. Depalo, A. Di Leva, Z. Elekes, F. Ferraro, A. Formicola , et al. (23 additional authors not shown)

Abstract: The 13C(a,n)16O reaction is the main neutron source of the s-process taking place in thermally pulsing AGB stars and it is one of the main candidate sources of neutrons for the i-process in the astrophysical sites proposed so far. Therefore, its rate is crucial to understand the production of the nuclei heavier than iron in the Universe. For the first time, the LUNA collaboration was able to measu… ▽ More The 13C(a,n)16O reaction is the main neutron source of the s-process taking place in thermally pulsing AGB stars and it is one of the main candidate sources of neutrons for the i-process in the astrophysical sites proposed so far. Therefore, its rate is crucial to understand the production of the nuclei heavier than iron in the Universe. For the first time, the LUNA collaboration was able to measure the 13C(a,n)16O cross section at Ec.m.=0.23-0.3 MeV drastically reducing the uncertainty of the S(E)-factor in the astrophysically relevant energy range. In this paper, we provide details and critical thoughts about the LUNA measurement and compare them with the current understanding of the 13C(a,n)16O reaction in view of future prospect for higher energy measurements. The two very recent results (from the University of Notre Dame and the JUNA collaboration) published after the LUNA data represent an important step forward. There is, however, still room for a lot of improvement in the experimental study of the 13C(a,n)16O reaction, as emphasized in the present manuscript. We conclude that to provide significantly better constraints on the low-energy extrapolation, experimental data need to be provided over a wide energy range, which overlaps with the energy range of current measurements. Furthermore, future experiments need to focus on the proper target characterisation, the determination of neutron detection efficiency having more nuclear physics input, such as angular distribution of the 13C(a,n)16O reaction below Ea<0.8 MeV and study of nuclear properties of monoenergetic neutron sources and/or via the study of sharp resonances of 13C(a,n)16O. Moreover, comprehensive, multichannel R-matrix analysis with a proper estimate of uncertainty budget of experimental data are still required. △ Less

Submitted 2 October, 2025; originally announced October 2025.

Comments: 19 pages, 10 figures

Journal ref: Journal of Physics G: Nuclear and Particle Physics, 2024, Volume 51, Number 10

Nonresonant capture cross section measurement of the 29Si(p,gamma)30P reaction

Authors: Zs Mátyus, L Csedreki, Zs Fülöp, Z Halász, G G Kiss, T Szücs, Á Tóth, Gy Gyürky

Abstract: The isotopic ratios measured in meteoritic presolar grains are a crucial tool for tracing the nucleosynthetic origin of isotopes. In the case of silicon isotopes, two important indicators to establish the origin of presolar grains are the ratios 29Si/28Si and 30Si/28Si. To constrain theoretical predictions, the rates of key nuclear reactions influencing the abundances of 29Si and 30Si must be well… ▽ More The isotopic ratios measured in meteoritic presolar grains are a crucial tool for tracing the nucleosynthetic origin of isotopes. In the case of silicon isotopes, two important indicators to establish the origin of presolar grains are the ratios 29Si/28Si and 30Si/28Si. To constrain theoretical predictions, the rates of key nuclear reactions influencing the abundances of 29Si and 30Si must be well known. One such reaction is 29Si(p,gamma)30P which plays a role in classical nova explosions. The aim of the present work is to determine the nonresonant cross section of the 29Si(p,gamma)30P reaction, which has not been previously measured. The activation method was employed to measure the total cross section at four proton energies between Ep = 1000 and 1430 keV. The measured cross sections were found to be significantly (a factor of 4.3+-0.6) higher than those predicted by theoretical direct capture calculations, thereby impacting the reaction rates at low astrophysical temperatures, below about 30 MK. This higher nonresonant cross section - now based on experimental data - can be used in forthcoming nucleosynthesis calculations of classical novae. As a secondary result, the 16O(p,gamma)17F cross section was also obtained and found to be in good agreement with existing literature data. △ Less

Submitted 16 September, 2025; originally announced September 2025.

Comments: Accepted for publication in J. Phys. G

Improved direct measurement of low-energy resonances in the $^{21}$Ne(p,$γ$)$^{22}$Na reaction

Authors: R. S. Sidhu, F. Casaburo, E. Masha, M. Aliotta, C. Ananna, L. Barbieri, F. Barile, C. Baron, D. Bemmerer, A. Best, R. Biassisi, A. Boeltzig, R. Bonnel, C. Broggini, C. G. Bruno, A. Caciolli, M. Campostrini, F. Cavanna, T. Chillery, G. F. Ciani, P. Colombetti, A. Compagnucci, P. Corvisiero, L. Csedreki, T. Davinson , et al. (35 additional authors not shown)

Abstract: In the nova temperature range, 0.1 GK $< T <$ 0.4 GK, several low-energy resonances dominate the $^{21}$Ne(p,$γ$)$^{22}$Na reaction rate, which is currently affected by large uncertainties. We present a high-precision study of the resonances at $E^{\rm{lab}}_{\rm{r}}$ = 127.3, 271.4, 272.3, 291.5, and 352.6 keV, measured directly at the Laboratory for Underground Nuclear Astrophysics in Italy. The… ▽ More In the nova temperature range, 0.1 GK $< T <$ 0.4 GK, several low-energy resonances dominate the $^{21}$Ne(p,$γ$)$^{22}$Na reaction rate, which is currently affected by large uncertainties. We present a high-precision study of the resonances at $E^{\rm{lab}}_{\rm{r}}$ = 127.3, 271.4, 272.3, 291.5, and 352.6 keV, measured directly at the Laboratory for Underground Nuclear Astrophysics in Italy. The strengths of the 127.3, 271.4, and 291.5 keV resonances are consistent with previous measurements within 1$σ$. However, for the 272.3 keV and 352.6 keV resonances, we report strength values of (129.9 $\pm$ 5.8) meV and (14.9 $\pm$ 0.8) meV, respectively, more than a factor of 1.5 higher than literature values. In addition, we report on new branching ratios for the 127.3, 272.3, and 352.6 keV resonances, leading to updated decay schemes. Finally, we present a revised thermonuclear reaction rate and investigate its impact on the NeNa nucleosynthesis. △ Less

Submitted 28 May, 2025; originally announced May 2025.

Gas-cell development for nuclear astrophysics motivated studies on noble gas targets and the $^3$He($α$,$γ$)$^7$Be reaction

Authors: Á. Tóth, Z. Elekes, Zs. Fülöp, Gy. Gyürky, Z. Halász, M. M. Juhász, G. G. Kiss, S. R. Kovács, Zs. Mátyus, T. N. Szegedi, T. Szücs

Abstract: In many astrophysical scenarios, alpha induced reactions on noble gas nuclei play a crucial role. Studying these reactions in the laboratory requires the noble gas atoms to be confined in a sufficient amount to allow the reactions. At Atomki thin-windowed gas-cell targets were developed and improved for studying alpha induced reactions on noble gases. Several stages of the gas-cell design used for… ▽ More In many astrophysical scenarios, alpha induced reactions on noble gas nuclei play a crucial role. Studying these reactions in the laboratory requires the noble gas atoms to be confined in a sufficient amount to allow the reactions. At Atomki thin-windowed gas-cell targets were developed and improved for studying alpha induced reactions on noble gases. Several stages of the gas-cell design used for activation experiments and lately a version to be used for particle scattering experiments will be presented. A new experimental study of the $^3$He($α$,$γ$)$^7$Be reaction with one of the activation gas-cell targets was performed. This reaction plays an important role both in the solar pp-chains and in big bang nucleosynthesis. The reaction cross section was measured in the past in several works, however, there are still energy regions lacking experimental data, rendering the extrapolations towards the astrophysically relevant energies uncertain. New experimental total cross section of the $^3$He($α$,$γ$)$^7$Be reaction was thus determined here in the energy range of $E_\mathrm{c.m.} = 2600-3000$ keV in about 50 keV energy steps. These results confirm the overall trend, and also the absolute scale set by the only one previous measurement in this energy range. In addition, two pilot experiments with the scattering cell were performed aiming to study the $^4$He($α$,$α$)$^4$He and $^{124}$Xe($α$,$α$)$^{124}$Xe reactions at $E_α= 18$ MeV. These studies benchmark the performance of the cell and detection system both for light and heavy noble gas targets. △ Less

Submitted 25 November, 2025; v1 submitted 28 April, 2025; originally announced April 2025.

Comments: Revised, accepted version

Measurement of $β$-particles to determine cross sections relevant to the weak r-process

Authors: Sándor R. Kovács, Tibor Norbert Szegedi, Ákos Tóth, Attila Németh, Manoj Kumar Pal, Edit Szilágyi, Mihály Braun, György Gyürky, Zoltán Elekes, Zoltán Halász, Tamás Szücs, Gábor Gyula Kiss

Abstract: The neutron-rich isotopes with 30 $\leq$ Z $\leq$ 45 are thought to be synthesised in neutrino-driven winds after the collapse of a massive star. This nucleosynthesis scenario, called the weak r-process, is studied using nuclear reaction network calculations. The accuracy of the nucleosynthesis simulations is strongly influenced by the reliability of the nuclear physics input parameters used. Rece… ▽ More The neutron-rich isotopes with 30 $\leq$ Z $\leq$ 45 are thought to be synthesised in neutrino-driven winds after the collapse of a massive star. This nucleosynthesis scenario, called the weak r-process, is studied using nuclear reaction network calculations. The accuracy of the nucleosynthesis simulations is strongly influenced by the reliability of the nuclear physics input parameters used. Recently, it has been demonstrated that ($α$,n) reactions play a particularly important role in the weak r-process, but their rates -- computed from the cross sections -- are only known with large uncertainties in the astrophysically relevant temperature range. The half-lives of the products of some key reactions are such that, in principle, the cross sections can be studied using the activation technique. In many cases, however, the $β$-decay of the reaction products leads to the ground state of the daughter nucleus, hence no gamma emission occurs. The purpose of this manuscript is to present our setup with which we determine the cross sections by measuring the yield of $β$-particles emitted during radioactive decay. The $^{86}$Kr($α$,n)$^{89}$Sr reaction cross-section measurement is used, as a case study. △ Less

Submitted 25 March, 2025; originally announced March 2025.

Comments: Accepted for publication in NIMA

Journal ref: Nuclear Instruments and Methods in Physics Research Section A 1073, 170272 (2025)

A Comparative Analysis of R-Matrix Fitting: ${}^{12}$C$(p,γ)$${}^{13}$N as Test Case

Authors: J. Skowronski, D. Piatti, D. Rapagnani, M. Aliotta, C. Ananna, L. Barbieri, F. Barile, D. Bemmerer, A. Best, A. Boeltzig, C. Broggini, C. G. Bruno, A. Caciolli, M. Campostrini, F. Casaburo, F. Cavanna, G. F. Ciani, P. Colombetti, A. Compagnucci, P. Corvisiero, L. Csedreki, T. Davinson, R. Depalo, A. Di Leva, Z. Elekes , et al. (27 additional authors not shown)

Abstract: In nuclear astrophysics, the accurate determination of nuclear reaction cross sections at astrophysical energies is critical for understanding stellar evolution and nucleosynthesis. This study focuses on the $^{12}$C($p, γ$)$^{13}$N reaction, which takes part in the CNO cycle and is significant for determining the $^{12}$C/$^{13}$C ratio in stellar interiors. Data from various studies, including r… ▽ More In nuclear astrophysics, the accurate determination of nuclear reaction cross sections at astrophysical energies is critical for understanding stellar evolution and nucleosynthesis. This study focuses on the $^{12}$C($p, γ$)$^{13}$N reaction, which takes part in the CNO cycle and is significant for determining the $^{12}$C/$^{13}$C ratio in stellar interiors. Data from various studies, including recent LUNA measurements, reveal high discrepancies in cross section values, underscoring the need for robust fitting approaches. Utilizing the R-matrix theory, we compare different frequentist and Bayesian methodologies for estimating reaction cross sections and their uncertainties. The analysis evaluates the strengths and weaknesses of different statistical techniques, highlighting the importance of systematic uncertainty treatment and the estimate of covariance matrix estimation to enhance the reliability and reproducibility of uncertainty estimates in nuclear astrophysics. △ Less

Submitted 22 February, 2025; v1 submitted 19 February, 2025; originally announced February 2025.

Characterization of the LUNA neutron detector array for the measurement of the 13C(a,n)16O reaction

Authors: L. Csedreki, G. F. Ciani, J. Balibrea-Correa, A. Best, M. Aliotta, F. Barile, D. Bemmerer, A. Boeltzig, C. Broggini, C. G. Bruno, A. Caciolli, F. Cavanna, T. Chillery, P. Colombetti, P. Corvisiero, T. Davinson, R. Depalo, A. Di Leva, Z. Elekes, F. Ferraro, E. M. Fiore, A. Formicola, Zs. Fulop, G. Gervino, A. Guglielmetti , et al. (24 additional authors not shown)

Abstract: We introduce the LUNA neutron detector array developed for the investigation of the 13C(a,n)16O reaction towards its astrophysical s-process Gamow peak in the low-background environment of the Laboratori Nazionali del Gran Sasso (LNGS). Eighteen 3He counters are arranged in two different configurations (in a vertical and a horizontal orientation) to optimize neutron detection effciency, target han… ▽ More We introduce the LUNA neutron detector array developed for the investigation of the 13C(a,n)16O reaction towards its astrophysical s-process Gamow peak in the low-background environment of the Laboratori Nazionali del Gran Sasso (LNGS). Eighteen 3He counters are arranged in two different configurations (in a vertical and a horizontal orientation) to optimize neutron detection effciency, target handling and target cooling over the investigated energy range Ea;lab = 300 - 400 keV (En = 2.2 - 2.6 MeV in emitted neutron energy). As a result of the deep underground location, the passive shielding of the setup and active background suppression using pulse shape discrimination, we reached a total background rate of 1.23 +- 0.12 counts/hour. This resulted in an improvement of two orders of magnitude over the state of the art allowing a direct measurement of the 13C(a,n)16O cross-section down to Ea;lab = 300 keV. The absolute neutron detection efficiency of the setup was determined using the 51V(p,n)51Cr reaction and an AmBe radioactive source, and completed with a Geant4 simulation. We determined a (34+-3) % and (38+-3) % detection efficiency for the vertical and horizontal configurations, respectively, for En = 2.4 MeV neutrons. △ Less

Submitted 7 November, 2024; originally announced November 2024.

Comments: 8 pages, 5 figures, to be published in NIMA

Journal ref: Nuclear Inst. and Methods in Physics Research, A 994 (2021) 165081

Measurement of the E_p = 416.9 keV resonance strength in the 29Si(p,gamma)30P reaction

Authors: Zs. Mátyus, L. Csedreki, Zs. Fülöp, Z. Halász, G. G. Kiss, T. Szücs, Á Tóth, Gy. Gyürky

Abstract: Silicon isotopic ratios measured in meteoritic presolar grains can provide useful information about the nucleosynthesis origin of these isotopes if the rates of nuclear reactions responsible for their production are known. One of the key reactions determining the Si isotopic abundances is 29Si(p,gamma)30P. Its reaction rate is not known with sufficient precision due in part to some ambiguous reson… ▽ More Silicon isotopic ratios measured in meteoritic presolar grains can provide useful information about the nucleosynthesis origin of these isotopes if the rates of nuclear reactions responsible for their production are known. One of the key reactions determining the Si isotopic abundances is 29Si(p,gamma)30P. Its reaction rate is not known with sufficient precision due in part to some ambiguous resonance strength values. In the present work, the strength of the E_p = 416.9 keV resonance has been measured with high precision using the activation technique. The new strength of omega_gamma = 219 +- 16 meV can be used in updated reaction rate estimations and astrophysical models. △ Less

Submitted 4 November, 2024; originally announced November 2024.

Comments: Accepted for publication in European Physical Journal A

First direct measurement of the 64.5 keV resonance strength in $^{17}$O(p,$γ$)$^{18}$F reaction

Authors: R. M. Gesuè, G. F. Ciani, D. Piatti, A. Boeltzig, D. Rapagnani, M. Aliotta, C. Ananna, L. Barbieri, F. Barile, D. Bemmerer, A. Best, C. Broggini, C. G. Bruno, A. Caciolli, M. Campostrini, F. Casaburo, F. Cavanna, P. Colombetti, A. Compagnucci, P. Corvisiero, L. Csedreki, T. Davinson, G. M. De Gregorio, D. Dell'Aquila, R. Depalo , et al. (28 additional authors not shown)

Abstract: The CNO cycle is one of the most important nuclear energy sources in stars. At temperatures of hydrostatic H-burning (20 MK $<$ T $<$ 80 MK) the $^{17}$O(p,$γ$)$^{18}$F reaction rate is dominated by the poorly constrained 64.5~keV resonance. Here we report on the first direct measurements of its resonance strength and of the direct capture contribution at 142 keV, performed with a new high sensiti… ▽ More The CNO cycle is one of the most important nuclear energy sources in stars. At temperatures of hydrostatic H-burning (20 MK $<$ T $<$ 80 MK) the $^{17}$O(p,$γ$)$^{18}$F reaction rate is dominated by the poorly constrained 64.5~keV resonance. Here we report on the first direct measurements of its resonance strength and of the direct capture contribution at 142 keV, performed with a new high sensitivity setup at LUNA. The present resonance strength of $ωγ_{(p, γ)}$\textsuperscript{bare} = (30 $\pm$ 6\textsubscript{stat} $\pm$ 2\textsubscript{syst})~peV is about a factor of 2 higher than the values in literature, leading to a $Γ$\textsubscript{p}\textsuperscript{bare} = (34 $\pm$ 7\textsubscript{stat} $\pm$ 3\textsubscript{syst})~neV, in agreement with LUNA result from the (p,$α$) channel. Such agreement strengthen our understanding of the oxygen isotopic ratios measured in red giant stars and in O-rich presolar grains. △ Less

Submitted 6 August, 2024; originally announced August 2024.

Low energy alpha-nucleus optical potential studied via (a,n) cross section measurements on Te isotopes

Authors: Zs. Mátyus, Gy. Gyürky, P. Mohr, A. Angyal, Z. Halász, G. G. Kiss, Á Tóth, T. Szücs, Zs. Fülöp

Abstract: In several processes of stellar nucleosynthesis, like the astrophysical gamma-process, nuclear reactions involving alpha particles play an important role. The description of these reactions necessitates the knowledge of the alpha-nucleus optical model potential (AOMP) which is highly ambiguous at low, astrophysical energies. This ambiguity introduces a substantial uncertainty in the stellar models… ▽ More In several processes of stellar nucleosynthesis, like the astrophysical gamma-process, nuclear reactions involving alpha particles play an important role. The description of these reactions necessitates the knowledge of the alpha-nucleus optical model potential (AOMP) which is highly ambiguous at low, astrophysical energies. This ambiguity introduces a substantial uncertainty in the stellar models for predicting elemental and isotopic abundances. The experimental study of the AOMP is thus necessary which can be implemented by measuring the cross section of alpha-induced nuclear reactions. At low energies, (a,n) reactions are suitable for such a purpose. Therefore, in the present work, the (a,n) cross sections of four Te isotopes have been measured, mostly for the first time, and compared with theoretical predictions. The (a,n) cross sections of 120,122,124,130Te have been measured in the energy range between about 10 and 17 MeV using the activation method. The detection of the gamma radiation following the decay of the radioactive reaction products were used to determine the cross sections. The measured cross sections are compared with statistical model calculations obtained from the widely used TALYS nuclear reaction simulation code. Predictions using various available AOMPs are investigated. It is found that the recently developed Atomki-V2 AOMP provides the best description for all studied reactions and this potential also reproduces well the total reaction cross sections from elastic scattering experiments, when they are available in literature. We recommend therefore to use the astrophysical reaction rates based on this potential for nucleosynthesis models of heavy elements. △ Less

Submitted 3 June, 2024; originally announced June 2024.

Comments: Accepted for publication in Phys. Rev. C

First measurement of the low-energy direct capture in 20Ne(p, γ)21Na and improved energy and strength of the Ecm = 368 keV resonance

Authors: E. Masha, L. Barbieri, J. Skowronski, M. Aliotta, C. Ananna, F. Barile, D. Bemmerer, A. Best, A. Boeltzig, C. Broggini, C. G. Bruno, A. Caciolli, M. Campostrini, F. Casaburo, F. Cavanna, G. F. Ciani, A. Ciapponi, P. Colombetti, A. Compagnucci, P. Corvisiero, L. Csedreki, T. Davinson, R. Depalo, A. Di Leva, Z. Elekes , et al. (26 additional authors not shown)

Abstract: The $\mathrm{^{20}Ne(p, γ)^{21}Na}$ reaction is the slowest in the NeNa cycle and directly affects the abundances of the Ne and Na isotopes in a variety of astrophysical sites. Here we report the measurement of its direct capture contribution, for the first time below $E\rm_{cm} = 352$~keV, and of the contribution from the $E^{\rm }_{cm} = 368$~keV resonance, which dominates the reaction rate at… ▽ More The $\mathrm{^{20}Ne(p, γ)^{21}Na}$ reaction is the slowest in the NeNa cycle and directly affects the abundances of the Ne and Na isotopes in a variety of astrophysical sites. Here we report the measurement of its direct capture contribution, for the first time below $E\rm_{cm} = 352$~keV, and of the contribution from the $E^{\rm }_{cm} = 368$~keV resonance, which dominates the reaction rate at $T=0.03-1.00$~GK. The experiment was performed deep underground at the Laboratory for Underground Nuclear Astrophysics, using a high-intensity proton beam and a windowless neon gas target. Prompt $γ$ rays from the reaction were detected with two high-purity germanium detectors. We obtain a resonance strength $ωγ~=~(0.112 \pm 0.002_{\rm stat}~\pm~0.005_{\rm sys})$~meV, with an uncertainty a factor of $3$ smaller than previous values. Our revised reaction rate is 20\% lower than previously adopted at $T < 0.1$~GK and agrees with previous estimates at temperatures $T \geq 0.1$~GK. Initial astrophysical implications are presented. △ Less

Submitted 7 November, 2023; originally announced November 2023.

Comments: 8 pages, 4 figures, accepted to PRC (letter)

Experimental $^7$Be production cross section from the $^7$Li(p,n)$^7$Be reaction at E$_p = 3.5-13$ MeV

Authors: Á. Tóth, Gy. Gyürky, E. Papp, T. Szücs

Abstract: The $^7$Li(p,n)$^7$Be reaction is widely used as neutron source for neutron induced reaction cross section measurements, and for $^7$Be radioactive source production. There are two prominent structures in the excitation function, a narrow resonance between $E_\mathrm{p}= 2.2-2.3$ MeV, and a broad peak, around $E_\mathrm{p}= 5$ MeV. There are tension between the experimental data sets both in the p… ▽ More The $^7$Li(p,n)$^7$Be reaction is widely used as neutron source for neutron induced reaction cross section measurements, and for $^7$Be radioactive source production. There are two prominent structures in the excitation function, a narrow resonance between $E_\mathrm{p}= 2.2-2.3$ MeV, and a broad peak, around $E_\mathrm{p}= 5$ MeV. There are tension between the experimental data sets both in the position and the width of this latter structure, as well as in the absolute scale of the data. In the present work the $^7$Li(p,n)$^7$Be reaction is investigated using the activation technique, with the aim of providing comprehensive cross section data covering the second structure and connecting prior literature data sets. The irradiations were performed with the Atomki cyclotron accelerator with pairs of thin foil targets, thus with precisely controlled reaction energy in the range of E$_\mathrm{p} = 3.5-13$ MeV. After the irradiations the activity of the samples was measured using a high-purity germanium detector. The energy uncertainty of the new data points is much smaller than in any of the previous works, while the cross section uncertainty is comparable with the most precise literature data. A consistent data set was obtained connecting the most recent and most precise literature data sets. With the new data the absolute magnitude of the $^7$Li(p,n)$^7$Be reaction cross section is constrained and became more precise. △ Less

Submitted 3 November, 2023; v1 submitted 12 October, 2023; originally announced October 2023.

Comments: typos corrected

Journal ref: Nuclear Physics A, 1041, January 2024, 122778

New proton-capture rates on carbon isotopes and their impact on the astrophysical $^{12}\mathrm{C}/{}^{13}\mathrm{C}$ ratio

Authors: J. Skowronski, A. Boeltzig, G. F. Ciani, L. Csedreki, D. Piatti, M. Aliotta, C. Ananna, F. Barile, D. Bemmerer, A. Best, C. Broggini, C. G. Bruno, A. Caciolli, M. Campostrini, F. Cavanna, P. Colombetti, A. Compagnucci, P. Corvisiero, T. Davinson, R. Depalo, A. Di Leva, Z. Elekes, F. Ferraro, A. Formicola, Zs. Fülöp , et al. (21 additional authors not shown)

Abstract: The ${}^{12}\mathrm{C}/{}^{13}\mathrm{C}$ ratio is a significant indicator of nucleosynthesis and mixing processes during hydrogen burning in stars. Its value mainly depends on the relative rates of the ${}^{12}\mathrm{C}(p,γ){}^{13}\mathrm{N}$ and ${}^{13}\mathrm{C}(p,γ){}^{14}\mathrm{N}$ reactions. Both reactions have been studied at the Laboratory for Underground Nuclear Astrophysics (LUNA) in… ▽ More The ${}^{12}\mathrm{C}/{}^{13}\mathrm{C}$ ratio is a significant indicator of nucleosynthesis and mixing processes during hydrogen burning in stars. Its value mainly depends on the relative rates of the ${}^{12}\mathrm{C}(p,γ){}^{13}\mathrm{N}$ and ${}^{13}\mathrm{C}(p,γ){}^{14}\mathrm{N}$ reactions. Both reactions have been studied at the Laboratory for Underground Nuclear Astrophysics (LUNA) in Italy down to the lowest energies to date ($E_\mathrm{c.m.} = 60\,\mathrm{keV}$) reaching for the first time the high energy tail of hydrogen burning in the shell of giant stars. Our cross sections, obtained with both prompt $γ$-ray detection and activation measurements, are the most precise to date with overall systematic uncertainties of $7-8\%$. Compared with most of the literature, our results are systematically lower, by $25\%$ for the ${}^{12}\mathrm{C}(p,γ){}^{13}\mathrm{N}$ reaction and by $30\%$ for ${}^{13}\mathrm{C}(p,γ){}^{14}\mathrm{N}$. We provide the most precise value up to now of $(3.6 \pm 0.4)$ in the $20-140\,\mathrm{MK}$ range for the lowest possible ${}^{12}\mathrm{C}/{}^{13}\mathrm{C}$ ratio that can be produced during H burning in giant stars. △ Less

Submitted 30 August, 2023; originally announced August 2023.

Comments: Submitted to Phys. Rev. Lett

Journal ref: Phys. Rev. Lett. 131, 162701 (2023)

Experimental determination of the $^3$He($α$,$γ$)$^7$Be reaction cross section above the $^7$Be proton separation threshold

Authors: Á. Tóth, T. Szücs, T. N. Szegedi, Gy. Gyürky, Z. Halász, G. G. Kiss, Zs. Fülöp

Abstract: The $^3$He($α$,$γ$)$^7$Be reaction plays a major role both in the BBN producing the majority of the primordial $^7$Li, and in the pp-chain, where it is the branching point. As a few-nucleon system, this reaction is often used to validate ab-initio theoretical calculations and/or test R-matrix theory and code implementations. For the latter, experimental data in an extended energy range is of cruci… ▽ More The $^3$He($α$,$γ$)$^7$Be reaction plays a major role both in the BBN producing the majority of the primordial $^7$Li, and in the pp-chain, where it is the branching point. As a few-nucleon system, this reaction is often used to validate ab-initio theoretical calculations and/or test R-matrix theory and code implementations. For the latter, experimental data in an extended energy range is of crucial importance to test the fit and extrapolation capabilities of the different codes. The $^3$He($α$,$γ$)$^7$Be reaction cross section has been measured by several groups up to the first resonance ($E_{c.m.} \approx 3$ MeV) in the reaction. However, only one dataset exists above the $^7$Be proton separation threshold measured in a narrow energy range ($E_{c.m.} = 4.0-4.4$ MeV). In this work we extend the available experimental capture cross section database to the energy range of known $^7$Be levels. The activation method was used. The experiment was performed using a thin-window gas cell with two high-purity Al foils as entrance and exit windows. The activity of the $^7$Be nuclei implanted in the exit/catcher foil was measured by detecting the yield of the emitted $γ$~rays using shielded high-purity germanium detectors. New experimental $^3$He($α$,$γ$)$^7$Be reaction cross section data were obtained for the first time in the $E_{c.m.}=4.3-8.3$ MeV energy region. The new dataset with about 0.2 MeV step covers the energy range of known levels and particle separation thresholds. No prominent structures are observer around the $^7$Be levels. The reaction cross section is slowly increasing with increasing energy. Above the $^6$Li$+p_1$ threshold, a decrease starts in the cross section trend. The overall structure of the cross section suggest a broad resonance peaking around $E_x=7.5$ MeV $^7$Be excitation energy, with a width of 8 MeV. △ Less

Submitted 3 August, 2023; v1 submitted 14 July, 2023; originally announced July 2023.

Comments: Typos are corrected, mainly in Table II., second column where the numerical values were incorrectly entered before

Cross section measurement of the 12C(p,gamma)13N reaction with activation in a wide energy range

Authors: Gy. Gyürky, L. Csedreki, T. Szücs, G. G. Kiss, Z. Halász, Zs. Fülöp

Abstract: The CNO cycle is one of the fundamental processes of hydrogen burning in stars. The first reaction of the cycle is the radiative proton capture on 12C and the rate of this 12C(p,gamma)13N reaction is related to the 12C/13C ratio observed e.g. in the Solar System. The low-energy cross section of this reaction was measured several times in the past, however, the experimental data are scarce in a wid… ▽ More The CNO cycle is one of the fundamental processes of hydrogen burning in stars. The first reaction of the cycle is the radiative proton capture on 12C and the rate of this 12C(p,gamma)13N reaction is related to the 12C/13C ratio observed e.g. in the Solar System. The low-energy cross section of this reaction was measured several times in the past, however, the experimental data are scarce in a wide energy range especially around the resonance at 1.7 MeV. In the present work the 12C(p,gamma)13N cross section was measured between 300 and 1900 keV using the activation method. This method was only used several decades ago in the low-energy region. As the activation method provides the total cross section and has uncertainties different from those of the in-beam gamma-spectroscopy technique, the present results provide a largely independent data set for future low-energy extrapolations and thus for astrophysical reaction rate calculations. △ Less

Submitted 10 March, 2023; originally announced March 2023.

Comments: Accepted for publication in European Physical Journal A

Cross section measurement of the 144Sm(alpha,n)147Gd reaction for studying the alpha-nucleus optical potential at astrophysical energies

Authors: Gy. Gyürky, P. Mohr, A. Angyal, Z. Halász, G. G. Kiss, Zs. Mátyus, T. N. Szegedi, T. Szücs, Zs. Fülöp

Abstract: Nuclear reactions involving alpha particles play an important role in various astrophysical processes such as the gamma-process of heavy element nucleosynthesis. The poorly known low-energy alpha-nucleus optical (AOMP) potential is a key parameter to estimate the rates of these reactions. The AOMP can be tested by measuring the cross section of alpha-scattering as well as alpha-induced reactions.… ▽ More Nuclear reactions involving alpha particles play an important role in various astrophysical processes such as the gamma-process of heavy element nucleosynthesis. The poorly known low-energy alpha-nucleus optical (AOMP) potential is a key parameter to estimate the rates of these reactions. The AOMP can be tested by measuring the cross section of alpha-scattering as well as alpha-induced reactions. Low energy elastic alpha-scattering on 144Sm has recently been measured with high precision. The aim of the present work was to complement that work by measuring the (a,n) cross sections on 144Sm at low energies. The experimental data shall be used to constrain the AOMP. From this potential the 144Sm(a,g)148Gd reaction rate can be derived with reduced uncertainties. The 144Sm(a,n)147Gd reaction was studied by bombarding Sm targets with alpha-beams provided by the cyclotron accelerator of Atomki. The cross section was determined using the activation method. The gamma-radiation following the decay of the 147Gd reaction product was measured with a HPGe detector. The experimental data are analyzed within the statistical model. The cross section was measured in the alpha-energy range between 13 and 20 MeV in 1 MeV steps, i.e., from close above the (a,n) threshold. The results were compared with statistical model calculations using various approaches and parametrizations for the AOMP, and excellent agreement was obtained for two recent potentials. However, these potentials cannot reproduce literature data for the 144Sm(a,g)148Gd reaction with the same accuracy. Constraints for the AOMP were derived from an analysis of the new 144Sm(a,n)147Gd data and literature data for 144Sm(a,g)148Gd. These constraints enable a determination of the reaction rate of the 144Sm(a,g)148Gd reaction with significantly reduced uncertainties of less than a factor of two. △ Less

Submitted 6 February, 2023; originally announced February 2023.

Comments: Accepted for publication in Phys. Rev. C

First direct limit on the 334 keV resonance strength in the $^{22}$Ne(α,γ)$^{26}$Mg reaction

Authors: D. Piatti, E. Masha, M. Aliotta, J. Balibrea-Correa, F. Barile, D. Bemmerer, A. Best, A. Boeltzig, C. Broggini, C. G. Bruno, A. Caciolli, F. Cavanna, T. Chillery, G. F. Ciani, A. Compagnucci, P. Corvisiero, L. Csedreki, T. Davinson, R. Depalo, A. di Leva, Z. Elekes, F. Ferraro, E. M. Fiore, A. Formicola, Zs. Fülöp , et al. (22 additional authors not shown)

Abstract: In stars, the fusion of $^{22}$Ne and $^4$He may produce either $^{25}$Mg, with the emission of a neutron, or $^{26}$Mg and a $γ$ ray. At high temperature, the ($α,n$) channel dominates, while at low temperature, it is energetically hampered. The rate of its competitor, the $^{22}$Ne($α$,$γ$)$^{26}$Mg reaction, and, hence, the minimum temperature for the ($α,n$) dominance, are controlled by many n… ▽ More In stars, the fusion of $^{22}$Ne and $^4$He may produce either $^{25}$Mg, with the emission of a neutron, or $^{26}$Mg and a $γ$ ray. At high temperature, the ($α,n$) channel dominates, while at low temperature, it is energetically hampered. The rate of its competitor, the $^{22}$Ne($α$,$γ$)$^{26}$Mg reaction, and, hence, the minimum temperature for the ($α,n$) dominance, are controlled by many nuclear resonances. The strengths of these resonances have hitherto been studied only indirectly. The present work aims to directly measure the total strength of the resonance at $E$_{r}$\,=\,$334$\,$keV (corresponding to $E$_{x}$\,=\,$10949$\,$keV in $^{26}$Mg). The data reported here have been obtained using high intensity $^4$He$^+$ beam from the INFN LUNA 400 kV underground accelerator, a windowless, recirculating, 99.9% isotopically enriched $^{22}$Ne gas target, and a 4$π$ bismuth germanate summing $γ$-ray detector. The ultra-low background rate of less than 0.5 counts/day was determined using 67 days of no-beam data and 7 days of $^4$He$^+$ beam on an inert argon target. The new high-sensitivity setup allowed to determine the first direct upper limit of 4.0$\,\times\,$10$^{-11}$ eV (at 90% confidence level) for the resonance strength. Finally, the sensitivity of this setup paves the way to study further $^{22}$Ne($α$,$γ$)$^{26}$Mg resonances at higher energy. △ Less

Submitted 7 September, 2022; originally announced September 2022.

Comments: Submitted to Eur. Phys. J. A

Journal ref: Eur. Phys. J. A 58, 194 (2022)

Activation cross section measurement of the 14N(p,gamma)15O astrophysical key reaction

Authors: Gy. Gyürky, Z. Halász, G. G. Kiss, T. Szücs, Fülöp

Abstract: 14N(p,gamma)15O is one of the key reactions of nuclear astrophysics playing a role in various stellar processes and influencing energy generation of stars, stellar evolution and nucleosynthesis. For a reliable reaction rate calculation the low energy cross section of 14N(p,gamma)15O must be known with high accuracy. Owing to the unmeasurable low cross sections, theoretical calculations are unavoid… ▽ More 14N(p,gamma)15O is one of the key reactions of nuclear astrophysics playing a role in various stellar processes and influencing energy generation of stars, stellar evolution and nucleosynthesis. For a reliable reaction rate calculation the low energy cross section of 14N(p,gamma)15O must be known with high accuracy. Owing to the unmeasurable low cross sections, theoretical calculations are unavoidable. High precision experimental cross section data are needed in a wide energy range in order to provide the necessary basis for low energy extrapolations. In the present work the total 14N(p,gamma)15O cross section was measured with a method complementary to the available data sets. The cross section was measured with activation, based on the detection of the annihilation radiation following the beta+ decay of the reaction product 15O. This method, which provides directly the astrophysically important total cross section, was never used for the 14N(p,gamma)15O cross section measurement in the studied energy range. The non-resonant cross section was measured between 550 keV and 1400 keV center-of-mass energies with total uncertainty of about 10%. The results were compared with literature data using an R-matrix analysis. It is found that the cross sections measured in this work are in acceptable agreement with the two recent measurements only if the weak transitions - not measured in those works - are included. The present data set, being largely independent from the other available data, can be used to constrain the extrapolated cross sections to astrophysical energies and helps to make the astrophysical model calculations more reliable. △ Less

Submitted 25 January, 2022; originally announced January 2022.

Comments: Accepted for publication in Phys. Rev. C as a letter

Direct measurement of the 13C(α,n)16O cross section into the s-process Gamow peak

Authors: G. F. Ciani, L. Csedreki, D. Rapagnani, M. Aliotta, J. Balibrea-Correa, F. Barile, D. Bemmerer, A. Best, A. Boeltzig, C. Broggini, C. G. Bruno, A. Caciolli, F. Cavanna, T. Chillery, P. Corvisiero, S. Cristallo, T. Davinson, R. Depalo, A. DiLeva, Z. Elekes, F. Ferraro, E. Fiore, A. Formicola, Zs. Fulop, G. Gervino , et al. (23 additional authors not shown)

Abstract: One of the main neutron sources for the astrophysical s-process is the reaction 13C(α,n)16O, taking place in thermally pulsing Asymptotic Giant Branch stars at temperatures around 90 MK. To model the nucleosynthesis during this process the reaction cross section needs to be known in the 150-230keV energy window (Gamow peak). At these sub-Coulomb energies cross section direct measurements are sever… ▽ More One of the main neutron sources for the astrophysical s-process is the reaction 13C(α,n)16O, taking place in thermally pulsing Asymptotic Giant Branch stars at temperatures around 90 MK. To model the nucleosynthesis during this process the reaction cross section needs to be known in the 150-230keV energy window (Gamow peak). At these sub-Coulomb energies cross section direct measurements are severely affected by the low event rate, making us rely on input from indirect methods and extrapolations from higher-energy direct data. This leads to an uncertainty in the cross section at the relevant energies too high to reliably constrain the nuclear physics input to s-process calculations. We present the results from a new deep-underground measurement of 13C(α,n)16O, covering the energy range 230-300keV, with drastically reduced uncertainties over previous measurements and for the first time providing data directly inside the s-process Gamow peak. Selected stellar models have been computed to estimate the impact of our revised reaction rate. For stars of nearly solar composition, we find sizeable variations of some isotopes, whose production is influenced by the activation of close-by branching points that are sensitive to the neutron density, in particular the two radioactive nuclei 60Fe and 205Pb, as well as 152Gd △ Less

Submitted 1 October, 2021; originally announced October 2021.

Comments: 7 pages, 4 figures, accepted on PRL on 17th August 2021

Measurement of the 91Zr(p,gamma)92mNb cross section motivated by type Ia supernova nucleosynthesis

Authors: Gy. Gyürky, Z. Halász, G. G. Kiss, T. Szücs, R. Huszánk, Zs. Török, Zs. Fülöp, T. Rauscher, C. Travaglio

Abstract: The synthesis of heavy, proton rich isotopes is a poorly understood astrophysical process. Thermonuclear (type Ia) supernova explosions are among the suggested sites and the abundance of some isotopes present in the early solar system may be used to test the models. 92Nb is such an isotope and one of the reactions playing a role in its synthesis is 91Zr(p,gamma)92Nb. As no experimental cross secti… ▽ More The synthesis of heavy, proton rich isotopes is a poorly understood astrophysical process. Thermonuclear (type Ia) supernova explosions are among the suggested sites and the abundance of some isotopes present in the early solar system may be used to test the models. 92Nb is such an isotope and one of the reactions playing a role in its synthesis is 91Zr(p,gamma)92Nb. As no experimental cross sections were available for this reaction so far, nucleosynthesis models had to solely rely on theoretical calculations. In the present work the cross section of 91Zr(p,gamma)92mNb has been measured at astrophysical energies by activation. The results excellently confirm the predictions of cross sections and reaction rates for 91Zr(p,gamma)92Nb, as used in astrophysical simulations. △ Less

Submitted 23 August, 2021; originally announced August 2021.

Comments: Accepted for publication in Journal of Physics G

Journal ref: Journal of Physics G: Nuclear and Particle Physics 48 (2021) 105202

High precision half-life measurement of $^{95}$Ru, $^{95}$Tc and $^{95m}$Tc with $γ$-spectroscopy

Authors: T. N. Szegedi, Á. Tóth, G. G. Kiss, Gy. gyürky

Abstract: The precise knowledge of the half-life of the reaction product is of crucial importance for a nuclear reaction cross section measurement carried out with the activation technique. The cross section of the $^{92}$Mo($α$,n)$^{95}$Ru reaction was measured recently using this experimental approach. The preliminary results indicated that the literature half-life of $^{95}$Ru, derived about half a centu… ▽ More The precise knowledge of the half-life of the reaction product is of crucial importance for a nuclear reaction cross section measurement carried out with the activation technique. The cross section of the $^{92}$Mo($α$,n)$^{95}$Ru reaction was measured recently using this experimental approach. The preliminary results indicated that the literature half-life of $^{95}$Ru, derived about half a century ago, is overestimated. Therefore, the half-lives of $^{95}$Ru and its daughter isotope $^{95}$Tc and $^{95m}$Tc have been measured with high precision using $γ$-spectroscopy. The results are t$_{1/2}$=1.6033 $\pm$ 0.0044 h for $^{95}$Ru, t$_{1/2}$ = 19.258 $\pm$ 0.026 h for $^{95}$Tc and t$_{1/2}$ = 61.96 $\pm$ 0.24 d for $^{95m}$Tc. The precision of the half-life values has been increased, consequently the recently measured $^{92}$Mo($α$,n)$^{95}$Ru activation cross section will become more precise. △ Less

Submitted 5 October, 2020; v1 submitted 2 October, 2020; originally announced October 2020.

Journal ref: Eur. Phys. J. A 56 (2020) 182

Low Energy measurement of the $^{96}\mathrm{Zr}(α,n)^{99}\mathrm{Mo}$ reaction cross section and its impact on weak r-process nucleosynthesis

Authors: G. G. Kiss, T. N. Szegedi, P. Mohr, M. Jacobi, Gy. Gyürky, R. Huszánk, A. Arcones

Abstract: Lighter heavy elements beyond iron and up to around silver can form in neutrino-driven ejecta in core-collapse supernovae and neutron star mergers. Slightly neutron-rich conditions favour a weak r-process that follows a path close to stability. Therefore, the beta decays are slow compared to the expansion time scales, and ($α$,n) reactions become critical to move matter towards heavier nuclei. The… ▽ More Lighter heavy elements beyond iron and up to around silver can form in neutrino-driven ejecta in core-collapse supernovae and neutron star mergers. Slightly neutron-rich conditions favour a weak r-process that follows a path close to stability. Therefore, the beta decays are slow compared to the expansion time scales, and ($α$,n) reactions become critical to move matter towards heavier nuclei. The rates of these reactions are calculated with the statistical model and their main uncertainty, at energies relevant for the weak r-process, is the $α$+nucleus optical potential. There are several sets of parameters to calculate the $α$+nucleus optical potential leading to large deviations for the reaction rates, exceeding even one order of magnitude. Recently the $^{96}$Zr($α$,n)$^{99}$Mo reaction has been identified as a key reaction that impacts the production of elements from Ru to Cd. Here, we present the first cross section measurement of this reaction at energies (6.22 MeV $\leq$ E$_\mathrm{c.m.}$ $\leq$ 12.47 MeV) relevant for the weak r-process. The new data provide a stringent test of various model predictions which is necessary to improve the precision of the weak r-process network calculations. The strongly reduced reaction rate uncertainty leads to very well-constrained nucleosynthesis yields for $Z = 44 - 48$ isotopes under different neutrino-driven wind conditions. △ Less

Submitted 2 March, 2021; v1 submitted 28 September, 2020; originally announced September 2020.

Determination of luminosity for in-ring reactions: A new approach for the low-energy domain

Authors: Y. M. Xing, J. Glorius, L. Varga, L. Bott, C. Brandau B. Bruckner, R. J. Chen, X. Chen, S. Dababneh, T. Davinson, P. Erbacher, S. Fiebiger, T. Gassner, K. Gobel, M. Groothuis, A. Gumberidze, G. Gyurky, M. Heil, R. Hess, R. Hensch, P. Hillmann, P. -M. Hillenbrand, O. Hinrichs, B. Jurado, T. Kausch, A. Khodaparast , et al. (37 additional authors not shown)

Abstract: Luminosity is a measure of the colliding frequency between beam and target and it is a crucial parameter for the measurement of absolute values, such as reaction cross sections. In this paper, we make use of experimental data from the ESR storage ring to demonstrate that the luminosity can be precisely determined by modelling the measured Rutherford scattering distribution. The obtained results ar… ▽ More Luminosity is a measure of the colliding frequency between beam and target and it is a crucial parameter for the measurement of absolute values, such as reaction cross sections. In this paper, we make use of experimental data from the ESR storage ring to demonstrate that the luminosity can be precisely determined by modelling the measured Rutherford scattering distribution. The obtained results are in good agreement with an independent measurement based on the x-ray normalization method. Our new method provides an alternative way to precisely measure the luminosity in low-energy stored-beam configurations. This can be of great value in particular in dedicated low-energy storage rings where established methods are difficult or impossible to apply. △ Less

Submitted 27 August, 2020; originally announced August 2020.

Comments: 8 pages, 5 figures

Journal ref: Nuclear Inst. and Methods in Physics Research, A 982 (2020) 164367

Successful prediction of total $α$-induced reaction cross sections at astrophysically relevant sub-Coulomb energies using a novel approach

Authors: P. Mohr, Zs. Fülöp, Gy. Gyürky, G. G. Kiss, T. Szücs

Abstract: The prediction of stellar ($γ$,$α$) reaction rates for heavy nuclei is based on the calculation of ($α$,$γ$) cross sections at sub-Coulomb energies. These rates are essential for modeling the nucleosynthesis of so-called $p$-nuclei. The standard calculations in the statistical model show a dramatic sensitivity to the chosen $α$-nucleus potential. The present study explains the reason for this dram… ▽ More The prediction of stellar ($γ$,$α$) reaction rates for heavy nuclei is based on the calculation of ($α$,$γ$) cross sections at sub-Coulomb energies. These rates are essential for modeling the nucleosynthesis of so-called $p$-nuclei. The standard calculations in the statistical model show a dramatic sensitivity to the chosen $α$-nucleus potential. The present study explains the reason for this dramatic sensitivity which results from the tail of the imaginary $α$-nucleus potential in the underlying optical model calculation of the total reaction cross section. As an alternative to the optical model, a simple barrier transmission model is suggested. It is shown that this simple model in combination with a well-chosen $α$-nucleus potential is able to predict total $α$-induced reaction cross sections for a wide range of heavy target nuclei above $A \gtrsim 150$ with uncertainties below a factor of two. The new predictions from the simple model do not require any adjustment of parameters to experimental reaction cross sections whereas in previous statistical model calculations all predictions remained very uncertain because the parameters of the $α$-nucleus potential had to be adjusted to experimental data. The new model allows to predict the reaction rate of the astrophysically important $^{176}$W($α$,$γ$)$^{180}$Os reaction with reduced uncertainties, leading to a significantly lower reaction rate at low temperatures. The new approach could also be validated for a broad range of target nuclei from $A \approx 60$ up to $A \gtrsim 200$. △ Less

Submitted 6 June, 2020; originally announced June 2020.

Comments: 6 pages, 3 figures; 6 pages supplement with 3 additional figures and 3 tables; Physical Review Letters, accepted for publication

Electron capture of Xe$^{54+}$ in collisions with H${_2}$ molecules in the energy range between 5.5 MeV/u and 30.9 MeV/u

Authors: F. M. Kröger, G. Weber, M. O. Herdrich, J. Glorius, C. Langer, Z. Slavkovská, L. Bott, C. Brandau, B. Brückner, K. Blaum, X. Chen, S. Dababneh, T. Davinson, P. Erbacher, S. Fiebiger, T. Gaßner, K. Göbel, M. Groothuis, A. Gumberidze, Gy. Gyürky, S. Hagmann, C. Hahn, M. Heil, R. Hess, R. Hensch , et al. (41 additional authors not shown)

Abstract: The electron capture process was studied for Xe$^{54+}$ colliding with H$_2$ molecules at the internal gas target of the ESR storage ring at GSI, Darmstadt. Cross section values for electron capture into excited projectile states were deduced from the observed emission cross section of Lyman radiation, being emitted by the hydrogen-like ions subsequent to the capture of a target electron. The ion… ▽ More The electron capture process was studied for Xe$^{54+}$ colliding with H$_2$ molecules at the internal gas target of the ESR storage ring at GSI, Darmstadt. Cross section values for electron capture into excited projectile states were deduced from the observed emission cross section of Lyman radiation, being emitted by the hydrogen-like ions subsequent to the capture of a target electron. The ion beam energy range was varied between 5.5 MeV/u and 30.9 MeV/u by applying the deceleration mode of the ESR. Thus, electron capture data was recorded at the intermediate and in particular the low collision energy regime, well below the beam energy necessary to produce bare xenon ions. The obtained data is found to be in reasonable qualitative agreement with theoretical approaches, while a commonly applied empirical formula significantly overestimates the experimental findings. △ Less

Submitted 10 May, 2020; v1 submitted 5 May, 2020; originally announced May 2020.

Journal ref: Phys. Rev. A 102, 042825 (2020)

Setup commissioning for an improved measurement of the D(p,gamma)3He cross section at Big Bang Nucleosynthesis energies

Authors: V. Mossa, K. Stöckel, F. Cavanna, F. Ferraro, M. Aliotta, F. Barile, D. Bemmerer, A. Best, A. Boeltzig, C. Broggini, C. G. Bruno, A. Caciolli, L. Csedreki, T. Chillery, G. F. Ciani, P. Corvisiero, T. Davinson, R. Depalo, A. Di Leva, Z. Elekes, E. M. Fiore, A. Formicola, Zs. Fülöp, G. Gervino, A. Guglielmetti , et al. (22 additional authors not shown)

Abstract: Among the reactions involved in the production and destruction of deuterium during Big Bang Nucleosynthesis, the deuterium-burning D(p,gamma)3He reaction has the largest uncertainty and limits the precision of theoretical estimates of primordial deuterium abundance. Here we report the results of a careful commissioning of the experimental setup used to measure the cross-section of the D(p,gamma)3H… ▽ More Among the reactions involved in the production and destruction of deuterium during Big Bang Nucleosynthesis, the deuterium-burning D(p,gamma)3He reaction has the largest uncertainty and limits the precision of theoretical estimates of primordial deuterium abundance. Here we report the results of a careful commissioning of the experimental setup used to measure the cross-section of the D(p,gamma)3He reaction at the Laboratory for Underground Nuclear Astrophysics of the Gran Sasso Laboratory (Italy). The commissioning was aimed at minimising all sources of systematic uncertainty in the measured cross sections. The overall systematic error achieved (< 3 %) will enable improved predictions of BBN deuterium abundance. △ Less

Submitted 29 April, 2020; originally announced May 2020.

Comments: 11 pages, 11 figures

A new approach to monitor 13C-targets degradation in situ for 13C(alpha,n)16O cross-section measurements at LUNA

Authors: G. F. Ciani, L. Csedreki, J. Balibrea-Correa, A. Best, M. Aliotta, F. Barile, D. Bemmerer, A. Boeltzig, C. Broggini, C. G. Bruno, A. Caciolli, F. Cavanna, T. Chillery, P. Colombetti, P. Corvisiero, T. Davinson, R. Depalo, A. Di Leva, L. Di Paolo, Z. Elekes, F. Ferraro, E. M. Fiore, A. Formicola, Zs. Fulop, G. Gervino , et al. (24 additional authors not shown)

Abstract: Direct measurements of reaction cross-sections at astrophysical energies often require the use of solid targets able to withstand high ion beam currents for extended periods of time. Thus, monitoring target thickness, isotopic composition, and target stoichiometry during data taking is critical to account for possible target modifications and to reduce uncertainties in the final cross-section resu… ▽ More Direct measurements of reaction cross-sections at astrophysical energies often require the use of solid targets able to withstand high ion beam currents for extended periods of time. Thus, monitoring target thickness, isotopic composition, and target stoichiometry during data taking is critical to account for possible target modifications and to reduce uncertainties in the final cross-section results. A common technique used for these purposes is the Nuclear Resonant Reaction Analysis (NRRA), which however requires that a narrow resonance be available inside the dynamic range of the accelerator used. In cases when this is not possible, as for example the 13C(alpha,n)16O reaction recently studied at low energies at the Laboratory for Underground Nuclear Astrophysics (LUNA) in Italy, alternative approaches must be found. Here, we present a new application of the shape analysis of primary gamma rays emitted by the 13C(p,g)14N radiative capture reaction. This approach was used to monitor 13C target degradation {\em in situ} during the 13C(alpha,n)16O data taking campaign. The results obtained are in agreement with evaluations subsequently performed at Atomki (Hungary) using the NRRA method. A preliminary application for the extraction of the 13C(alpha,n)16O reaction cross-section at one beam energy is also reported. △ Less

Submitted 3 March, 2020; v1 submitted 23 January, 2020; originally announced January 2020.

Comments: 10 pages, 6 figures, to be published in EPJ A

Journal ref: The European Physical Journal A volume 56, Article number: 75 (2020)

Stable beam experiments in wide energy ranges serving low energy nuclear astrophysics

Authors: Gy. Gyürky

Abstract: In experimental nuclear astrophysics it is common knowledge that reaction cross sections must be measured in the astrophysically relevant, low energy ranges or at least as close to them as possible. In most of the cases, however, it is impossible to reach such low energies. The reactions must therefore be studied at higher energies and the cross sections must be extrapolated to lower ones. In this… ▽ More In experimental nuclear astrophysics it is common knowledge that reaction cross sections must be measured in the astrophysically relevant, low energy ranges or at least as close to them as possible. In most of the cases, however, it is impossible to reach such low energies. The reactions must therefore be studied at higher energies and the cross sections must be extrapolated to lower ones. In this paper the importance of cross section measurements in wide energy ranges are emphasized and a few examples are shown from the areas of hydrogen burning processes and heavy element nucleosynthesis. △ Less

Submitted 18 December, 2019; originally announced December 2019.

Comments: Invited talk at the Nuclear Physics in Astrophysics IX conference. Accepted for publication in Journal of Physics: Conference Series

Cross section of $α$-induced reactions on $^{197}$Au at sub-Coulomb energies

Authors: T. Szücs, P. Mohr, Gy. Gyürky, Z. Halász, R. Huszánk, G. G. Kiss, T. N. Szegedi, Zs. Török, Zs. Fülöp

Abstract: Statistical model calculations have to be used for the determination of reaction rates in large-scale reaction networks for heavy-element nucleosynthesis. A basic ingredient of such a calculation is the a-nucleus optical model potential. Several different parameter sets are available in literature, but their predictions of a-induced reaction rates vary widely, sometimes even exceeding one order of… ▽ More Statistical model calculations have to be used for the determination of reaction rates in large-scale reaction networks for heavy-element nucleosynthesis. A basic ingredient of such a calculation is the a-nucleus optical model potential. Several different parameter sets are available in literature, but their predictions of a-induced reaction rates vary widely, sometimes even exceeding one order of magnitude. This paper presents the result of a-induced reaction cross-section measurements on gold which could be carried out for the first time very close to the astrophysically relevant energy region. The new experimental data are used to test statistical model predictions and to constrain the a-nucleus optical model potential. For the measurements the activation technique was used. The cross section of the (a,n) and (a,2n) reactions was determined from g-ray counting, while that of the radiative capture was determined via X-ray counting. The cross section of the reactions was measured below E$_a=20.0$~MeV. In the case of the $^{197}$Au(a,2n)$^{199}$Tl reaction down to 17.5~MeV with 0.5-MeV steps, reaching closer to the reaction threshold than ever before. The cross section of $^{197}$Au(a,n)$^{200}$Tl and $^{197}$Au(a,g)$^{201}$Tl was measured down to E$_a=13.6$ and 14.0~MeV, respectively, with 0.5-MeV steps above the (a,2n) reaction threshold and with 1.0-MeV steps below that. The new dataset is in agreement with the available values from the literature, but is more precise and extends towards lower energies. Two orders of magnitude lower cross sections were successfully measured than in previous experiments which used g-ray counting only, thus providing experimental data at lower energies than ever before. The new precision dataset allows us to find the best-fit a-nucleus optical model potential and to predict cross sections in the Gamow window with smaller uncertainties. △ Less

Submitted 22 October, 2019; originally announced October 2019.

Comments: Accepted for publication in Phys. Rev. C

Journal ref: Phys. Rev. C 100, 065803 (2019)

Resonance strengths in the 14N(p,gamma)15O astrophysical key reaction measured with activation

Authors: Gy. Gyürky, Z. Halász, G. G. Kiss, T. Szücs, A. Csík, Zs. Török, R. Huszánk, M. G. Kohan, L. Wagner, Zs. Fülöp

Abstract: The 14N(p,gamma)15O reaction plays a vital role in various astrophysical scenarios. Its reaction rate must be accurately known in the present era of high precision astrophysics. The cross section of the reaction is often measured relative to a low energy resonance, the strength of which must therefore be determined precisely. The activation method, based on the measurement of 15O decay, has not be… ▽ More The 14N(p,gamma)15O reaction plays a vital role in various astrophysical scenarios. Its reaction rate must be accurately known in the present era of high precision astrophysics. The cross section of the reaction is often measured relative to a low energy resonance, the strength of which must therefore be determined precisely. The activation method, based on the measurement of 15O decay, has not been used in modern measurements of the 14N(p,gamma)15O reaction. The aim of the present work is to provide strength data for two resonances in the 14N(p,gamma)15O reaction using the activation method. The obtained values are largely independent from previous data measured by in-beam gamma-spectroscopy and are free from some of their systematic uncertainties. Solid state TiN targets were irradiated with a proton beam provided by the Tandetron accelerator of Atomki using a cyclic activation. The decay of the produced 15O isotopes was measured by detecting the 511 keV positron annihilation gamma-rays. The strength of the Ep = 278 keV resonance was measured to be 13.4 +- 0.8 meV while for the Ep = 1058 keV resonance the strength is 442 +- 27 meV. The obtained Ep = 278 keV resonance strength is in fair agreement with the values recommended by two recent works. On the other hand, the Ep = 1058 keV resonance strength is about 20% higher than the previous value. The discrepancy may be caused in part by a previously neglected finite target thickness correction. As only the low energy resonance is used as a normalization point for cross section measurements, the calculated astrophysical reaction rate of the 14N(p,gamma)15O reaction and therefore the astrophysical consequences are not changed by the present results. △ Less

Submitted 17 July, 2019; originally announced July 2019.

Comments: Accepted for publication in Phys. Rev. C

Cross section of $^3$He($α$,$γ$)$^7$Be around the $^7$Be proton separation threshold

Authors: T. Szücs, G. G. Kiss, Gy. Gyürky, Z. Halász, T. N. Szegedi, Zs. Fülöp

Abstract: The $^3$He($α$,$γ$)$^7$Be reaction is a widely studied nuclear reaction; however, it is still not understood with the required precision. It has a great importance both in Big Bang nucleosynthesis and in solar hydrogen burning. The low mass number of the reaction partners makes it also suitable for testing microscopic calculations. Despite the high number of experimental studies, none of them ad… ▽ More The $^3$He($α$,$γ$)$^7$Be reaction is a widely studied nuclear reaction; however, it is still not understood with the required precision. It has a great importance both in Big Bang nucleosynthesis and in solar hydrogen burning. The low mass number of the reaction partners makes it also suitable for testing microscopic calculations. Despite the high number of experimental studies, none of them addresses the $^3$He($α$,$γ$)$^7$Be reaction cross sections above 3.1-MeV center-of-mass energy. Recently, a previously unobserved resonance in the $^6$Li(p,$γ$)$^7$Be reaction suggested a new level in $^7$Be, which would also have an impact on the $^3$He($α$,$γ$)$^7$Be reaction in the energy range above 4.0 MeV. The aim of the present experiment is to measure the $^3$He($α$,$γ$)$^7$Be reaction cross section in the energy range of the proposed level. For this investigation the activation technique was used. A thin window gas-cell target confining $^3$He gas was irradiated using an $α$ beam. The $^7$Be produced was implanted into the exit foil. The $^7$Be activity was determined by counting the $γ$ rays following its decay by a well-shielded high-purity germanium detector. Reaction cross sections have been determined between $E_{cm} = 4.0 - 4.4$ MeV with 0.04-MeV steps covering the energy range of the proposed nuclear level. One lower-energy cross-section point was also determined to be able to compare the results with previous studies. A constant cross section of around 10.5 $μ$barn was observed around the $^7$Be proton separation energy. An upper limit of 45 neV for the strength of a $^3$He($α$,$γ$)$^7$Be resonance is derived. △ Less

Submitted 5 May, 2019; originally announced May 2019.

Comments: Accepted for publication in Physical Review C

Journal ref: Phys. Rev. C 99; 055804 (2019)

High precision half-life measurement of $^{125}$Cs and $^{125}$Xe with γ-spectroscopy

Authors: T. N. Szegedi, G. G. Kiss, I. Öksüz, T. Szücs, Gy. Gyürky, Z. Elekes, E. Somorjai, Zs. Fülöp

Abstract: In order to provide data for the simulation of the astrophysical $γ$-process, the cross section measurement of the $^{124}$Xe(p,$γ$)$^{125}$Cs reaction is in progress at MTA Atomki using the activation technique. Precise information on the decay characteristics of the reaction products is of crucial importance for measurements carried out using this method. The half-lives of the produced $^{125}$C… ▽ More In order to provide data for the simulation of the astrophysical $γ$-process, the cross section measurement of the $^{124}$Xe(p,$γ$)$^{125}$Cs reaction is in progress at MTA Atomki using the activation technique. Precise information on the decay characteristics of the reaction products is of crucial importance for measurements carried out using this method. The half-lives of the produced $^{125}$Cs and its daughter $^{125}$Xe are published in previous works, but with large uncertainties and ambiguous values. To make these nuclear parameters more precise, the half-lives have been re-measured with high precision using $γ$-spectroscopy. The obtained new half-life values are t$_{1/2}$ = 44.35 $\pm$ 0.29 minutes for $^{125}$Cs and t$_{1/2}$ = 16.87 $\pm$ 0.08 hours for $^{125}$Xe. △ Less

Submitted 3 May, 2019; originally announced May 2019.

Half-life measurement of 65Ga with gamma-spectroscopy

Authors: Gy. Gyürky, Z. Halász, G. G. Kiss, T. Szücs, Zs. Fülöp

Abstract: The literature half-life value of 65Ga is based on only one experiment carried out more than 60 years ago and it has a relatively large uncertainty. In the present work this half-life is determined based on the counting of the gamma-rays following the beta-decay of 65Ga. Our new recommended half-life is 15.133 +- 0.028 min which is in agreement with the literature value but almost one order of mag… ▽ More The literature half-life value of 65Ga is based on only one experiment carried out more than 60 years ago and it has a relatively large uncertainty. In the present work this half-life is determined based on the counting of the gamma-rays following the beta-decay of 65Ga. Our new recommended half-life is 15.133 +- 0.028 min which is in agreement with the literature value but almost one order of magnitude more precise. △ Less

Submitted 26 March, 2019; originally announced March 2019.

Journal ref: Applied Radiation and Isotopes 148 (2019) 87

The activation method for cross section measurements in nuclear astrophysics

Authors: Gy. Gyürky, Zs. Fülöp, F. Käppeler, G. G. Kiss, A. Wallner

Abstract: The primary aim of experimental nuclear astrophysics is to determine the rates of nuclear reactions taking place in stars in various astrophysical conditions. These reaction rates are important ingredient for understanding the elemental abundance distribution in our solar system and the galaxy. The reaction rates are determined from the cross sections which need to be measured at energies as close… ▽ More The primary aim of experimental nuclear astrophysics is to determine the rates of nuclear reactions taking place in stars in various astrophysical conditions. These reaction rates are important ingredient for understanding the elemental abundance distribution in our solar system and the galaxy. The reaction rates are determined from the cross sections which need to be measured at energies as close to the astrophysically relevant ones as possible. In many cases the final nucleus of an astrophysically important reaction is radioactive which allows the cross section to be determined based on the off-line measurement of the number of produced isotopes. In general, this technique is referred to as the activation method, which often has substantial advantages over in-beam particle- or gamma-detection measurements. In this paper the activation method is reviewed from the viewpoint of nuclear astrophysics. Important aspects of the activation method are given through several reaction studies for charged particle, neutron and gamma-induced reactions. Various techniques for the measurement of the produced activity are detailed. As a special case of activation, the technique of Accelerator Mass Spectrometry in cross section measurements is also reviewed. △ Less

Submitted 8 March, 2019; originally announced March 2019.

Comments: Review paper accepted for publication in European Physical Journal A

Journal ref: Eur. Phys. J. A 55 (2019) 41

Approaching the Gamow window with stored ions: Direct measurement of $^{124}$Xe(p,$γ$) in the ESR storage ring

Authors: J. Glorius, C. Langer, Z. Slavkovská, L. Bott, C. Brandau, B. Brückner, K. Blaum, X. Chen, S. Dababneh, T. Davinson, P. Erbacher, S. Fiebiger, T. Gaßner, K. Göbel, M. Groothuis, A. Gumberidze, G. Gyürky, M. Heil, R. Hess, R. Hensch, P. Hillmann, P. -M. Hillenbrand, O. Hinrichs, B. Jurado, T. Kausch , et al. (41 additional authors not shown)

Abstract: We report the first measurement of low-energy proton-capture cross sections of $^{124}$Xe in a heavy ion storage ring. $^{124}$Xe$^{54+}$ ions of five different beam energies between 5.5 AMeV and 8 AMeV were stored to collide with a windowless hydrogen target. The $^{125}$Cs reaction products were directly detected. The interaction energies are located on the high energy tail of the Gamow window f… ▽ More We report the first measurement of low-energy proton-capture cross sections of $^{124}$Xe in a heavy ion storage ring. $^{124}$Xe$^{54+}$ ions of five different beam energies between 5.5 AMeV and 8 AMeV were stored to collide with a windowless hydrogen target. The $^{125}$Cs reaction products were directly detected. The interaction energies are located on the high energy tail of the Gamow window for hot, explosive scenarios such as supernovae and X-ray binaries. The results serve as an important test of predicted astrophysical reaction rates in this mass range. Good agreement in the prediction of the astrophysically important proton width at low energy is found, with only a 30% difference between measurement and theory. Larger deviations are found above the neutron emission threshold, where also neutron- and $γ$-widths significantly impact the cross sections. The newly established experimental method is a very powerful tool to investigate nuclear reactions on rare ion beams at low center-of-mass energies. △ Less

Submitted 6 February, 2019; originally announced February 2019.

Journal ref: Phys. Rev. Lett. 122, 092701 (2019)

Direct capture cross section and the $E_p$ = 71 and 105 keV resonances in the $^{22}$Ne($p,γ$)$^{23}$Na reaction

Authors: F. Ferraro, M. P. Takács, D. Piatti, F. Cavanna, R. Depalo, M. Aliotta, D. Bemmerer, A. Best, A. Boeltzig, C. Broggini, C. G. Bruno, A. Caciolli, T. Chillery, G. F. Ciani, P. Corvisiero, T. Davinson, G. D'Erasmo, A. DiLeva, Z. Elekes, E. M. Fiore, A. Formicola, Zs. Fülöp, G. Gervino, A. Guglielmetti, C. Gustavino , et al. (19 additional authors not shown)

Abstract: The $^{22}$Ne($p,γ$)$^{23}$Na reaction, part of the neon-sodium cycle of hydrogen burning, may explain the observed anticorrelation between sodium and oxygen abundances in globular cluster stars. Its rate is controlled by a number of low-energy resonances and a slowly varying non-resonant component. Three new resonances at $E_p$ = 156.2, 189.5, and 259.7 keV have recently been observed and confirm… ▽ More The $^{22}$Ne($p,γ$)$^{23}$Na reaction, part of the neon-sodium cycle of hydrogen burning, may explain the observed anticorrelation between sodium and oxygen abundances in globular cluster stars. Its rate is controlled by a number of low-energy resonances and a slowly varying non-resonant component. Three new resonances at $E_p$ = 156.2, 189.5, and 259.7 keV have recently been observed and confirmed. However, significant uncertainty on the reaction rate remains due to the non-resonant process and to two suggested resonances at $E_p$ = 71 and 105 keV. Here, new $^{22}$Ne($p,γ$)$^{23}$Na data with high statistics and low background are reported. Stringent upper limits of 6$\times$10$^{-11}$ and 7$\times$10$^{-11}$\,eV (90\% confidence level), respectively, are placed on the two suggested resonances. In addition, the off-resonant S-factor has been measured at unprecedented low energy, constraining the contributions from a subthreshold resonance and the direct capture process. As a result, at a temperature of 0.1 GK the error bar of the $^{22}$Ne($p,γ$)$^{23}$Na rate is now reduced by three orders of magnitude. △ Less

Submitted 3 October, 2018; originally announced October 2018.

Comments: Submitted to Phys. Rev. Lett

Journal ref: Phys. Rev. Lett. 121, 172701 (2018)

Effect of beam energy straggling on resonant yield in thin gas targets: The cases $^{22}$Ne(p,γ)$^{23}$Na and $^{14}$N(p,γ)$^{15}$O

Authors: D. Bemmerer, F. Cavanna, R. Depalo, M. Aliotta, M. Anders, A. Boeltzig, C. Broggini, C. Bruno, A. Caciolli, P. Corvisiero, T. Davinson, Z. Elekes, F. Ferraro, A. Formicola, Zs. Fülöp, G. Gervino, A. Guglielmetti, C. Gustavino, Gy. Gyürky, R. Menegazzo, V. Mossa, F. R. Pantaleo, P. Prati, D. A. Scott, O. Straniero , et al. (3 additional authors not shown)

Abstract: When deriving resonance strengths using the thick-target yield approximation, for very narrow resonances it may be necessary to take beam energy straggling into account. This applies to gas targets of a few keV width, especially if there is some additional structure in target stoichiometry or detection efficiency. The correction for this effect is shown and tested on recent studies of narrow reson… ▽ More When deriving resonance strengths using the thick-target yield approximation, for very narrow resonances it may be necessary to take beam energy straggling into account. This applies to gas targets of a few keV width, especially if there is some additional structure in target stoichiometry or detection efficiency. The correction for this effect is shown and tested on recent studies of narrow resonances in the $^{22}$Ne(p,γ)$^{23}$Na and $^{14}$N(p,γ)$^{15}$O reactions. △ Less

Submitted 29 June, 2018; originally announced June 2018.

Comments: Submitted to Europhys. Lett

Journal ref: Europhys. Lett. 122 (2018) 52001

alpha-induced reactions on 115In: cross section measurements and statistical model analysis

Authors: G. G. Kiss, T. Szucs, P. Mohr, Zs. Torok, R. Huszank, Gy. Gyurky, Zs. Fulop

Abstract: [Background] Alpha-nucleus optical potentials are basic ingredients of statistical model calculations used in nucleosynthesis simulations. While the nucleon+nucleus optical potential is fairly well known, for the alpha+nucleus optical potential several different parameter sets exist and large deviations, reaching sometimes even an order of magnitude, are found between the cross section predictions… ▽ More [Background] Alpha-nucleus optical potentials are basic ingredients of statistical model calculations used in nucleosynthesis simulations. While the nucleon+nucleus optical potential is fairly well known, for the alpha+nucleus optical potential several different parameter sets exist and large deviations, reaching sometimes even an order of magnitude, are found between the cross section predictions calculated using different parameter sets. [Purpose] A measurement of the radiative alpha-capture and the alpha-induced reaction cross sections on the nucleus 115In at low energies allows a stringent test of statistical model predictions. Since experimental data is scarce in this mass region, this measurement can be an important input to test the global applicability of alpha+nucleus optical model potentials and further ingredients of the statistical model. [Methods] The reaction cross sections were measured by means of the activation method. The produced activities were determined by off-line detection of the gamma-rays and characteristic x-rays emitted during the electron capture decay of the produced Sb isotopes. The 115In(alpha,gamma)119Sb and 115In(alpha,n)118Sbm reaction cross sections were measured between Ec.m. = 8.83 MeV - 15.58 MeV, and the 115In(alpha,n)118Sbg reaction was studied between Ec.m. = 11.10 MeV - 15.58 MeV. The theoretical analysis was performed within the statistical model. △ Less

Submitted 19 May, 2018; originally announced May 2018.

Journal ref: Phys. Rev. C 97, 055803 (2018)

Investigation of $α$-induced reactions on Sb isotopes relevant to the astrophysical $γ$-process

Authors: Z. Korkulu, N. Özkan, G. G. Kiss, T. Szücs, Gy. Gyürky, Zs. Fülöp, R. T. Güray, Z. Halász, T. Rauscher, E. Somorjai, Zs. Török, C. Yalçın

Abstract: The aim of the present work is to measure the $^{121}$Sb($α,γ$)$^{125}$I, $^{121}$Sb($α$,n)$^{124}$I, and $^{123}$Sb($α$,n)$^{126}$I reaction cross sections. The $α$-induced reactions on natural and enriched antimony targets were investigated using the activation technique. The ($α$,$γ$) cross sections of $^{121}$Sb were measured and are reported for first time. To determine the cross section of t… ▽ More The aim of the present work is to measure the $^{121}$Sb($α,γ$)$^{125}$I, $^{121}$Sb($α$,n)$^{124}$I, and $^{123}$Sb($α$,n)$^{126}$I reaction cross sections. The $α$-induced reactions on natural and enriched antimony targets were investigated using the activation technique. The ($α$,$γ$) cross sections of $^{121}$Sb were measured and are reported for first time. To determine the cross section of the $^{121}$Sb($α$,$γ$)$^{125}$I, $^{121}$Sb($α$,n)$^{124}$I, and $^{123}$Sb($α$,n)$^{126}$I reactions, the yields of $γ$-rays following the $β$-decay of the reaction products were measured. For the measurement of the lowest cross sections, the characteristic X-rays were counted with a LEPS (Low Energy Photon Spectrometer) detector. The cross section of the $^{121}$Sb($α$,$γ$)$^{125}$I, $^{121}$Sb($α$,n)$^{124}$I and $^{123}$Sb($α$,n)$^{126}$I reactions were measured with high precision in an energy range between 9.74 MeV to 15.48 MeV, close to the astrophysically relevant energy window. The results are compared with the predictions of statistical model calculations. The ($α$,n) data show that the $α$ widths are predicted well for these reactions. The ($α$,$γ$) results are overestimated by the calculations but this is due to the applied neutron- and $γ$ widths. Relevant for the astrophysical reaction rate is the $α$ width used in the calculations.While for other reactions the $α$ widths seem to have been overestimated and their energy dependence was not described well in the measured energy range, this is not the case for the reactions studied here. The result is consistent with the proposal that additional reaction channels, such as Coulomb excitation, may have led to the discrepancies found in other reactions. △ Less

Submitted 21 March, 2018; originally announced March 2018.

Journal ref: Phys. Rev. C 97, 045803 (2018)

A high-efficiency gas target setup for underground experiments, and redetermination of the branching ratio of the 189.5 keV $\mathbf{^{22}Ne(p,γ)^{23}Na}$ resonance

Authors: F. Ferraro, M. P. Takács, D. Piatti, V. Mossa, M. Aliotta, D. Bemmerer, A. Best, A. Boeltzig, C. Broggini, C. G. Bruno, A. Caciolli, F. Cavanna, T. Chillery, G. F. Ciani, P. Corvisiero, L. Csedreki, T. Davinson, R. Depalo, G. D'Erasmo, A. Di Leva, Z. Elekes, E. M. Fiore, A. Formicola, Zs. Fülöp, G. Gervino , et al. (20 additional authors not shown)

Abstract: The experimental study of nuclear reactions of astrophysical interest is greatly facilitated by a low-background, high-luminosity setup. The Laboratory for Underground Nuclear Astrophysics (LUNA) 400 kV accelerator offers ultra-low cosmic-ray induced background due to its location deep underground in the Gran Sasso National Laboratory (INFN-LNGS), Italy, and high intensity, 250-500 $μ$A, proton an… ▽ More The experimental study of nuclear reactions of astrophysical interest is greatly facilitated by a low-background, high-luminosity setup. The Laboratory for Underground Nuclear Astrophysics (LUNA) 400 kV accelerator offers ultra-low cosmic-ray induced background due to its location deep underground in the Gran Sasso National Laboratory (INFN-LNGS), Italy, and high intensity, 250-500 $μ$A, proton and $α$ ion beams. In order to fully exploit these features, a high-purity, recirculating gas target system for isotopically enriched gases is coupled to a high-efficiency, six-fold optically segmented bismuth germanate (BGO) $γ$-ray detector. The beam intensity is measured with a beam calorimeter with constant temperature gradient. Pressure and temperature measurements have been carried out at several positions along the beam path, and the resultant gas density profile has been determined. Calibrated $γ$-intensity standards and the well-known $E_p$ = 278 keV $\mathrm{^{14}N(p,γ)^{15}O}$ resonance were used to determine the $γ$-ray detection efficiency and to validate the simulation of the target and detector setup. As an example, the recently measured resonance at $E_p$ = 189.5 keV in the $^{22}$Ne(p,$γ$)$^{23}$Na reaction has been investigated with high statistics, and the $γ$-decay branching ratios of the resonance have been determined. △ Less

Submitted 12 February, 2018; originally announced February 2018.

Comments: 11 pages, 11 figures, accepted in Eur. Phys. Journal A

Journal ref: Eur. Phys. J. A (2018) 54: 44

Nuclear physics uncertainties of the astrophysical gamma-process studied through the 64Zn(p,alpha)61Cu and 64Zn(p,gamma)65Ga reactions

Authors: Gy. Gyürky, Zs. Fülöp, Z. Halász, G. G. Kiss, T. Szücs

Abstract: In a recent work, the cross section measurement of the 64Zn(p,alpha)61Cu reaction was used to prove that the standard alpha-nucleus optical potentials used in astrophysical network calculation fail to reproduce the experimental data at energies relevant for heavy element nucleosynthesis. In the present paper the analysis of the obtained experimental data is continued by comparing the results with… ▽ More In a recent work, the cross section measurement of the 64Zn(p,alpha)61Cu reaction was used to prove that the standard alpha-nucleus optical potentials used in astrophysical network calculation fail to reproduce the experimental data at energies relevant for heavy element nucleosynthesis. In the present paper the analysis of the obtained experimental data is continued by comparing the results with the predictions using different parameters. It is shown that the recently suggested modification of the standard optical potential leads to a better description of the data. △ Less

Submitted 8 February, 2018; originally announced February 2018.

Comments: Proceedings of the Nuclear Physics in Astrophysics VII conference, York, UK, 2015

Journal ref: Journal of Physics: Conf. Series 940 (2017) 012005

Cross section of $α$-induced reactions on iridium isotopes obtained from thick target yield measurement for the astrophysical $γ$ process

Authors: T. Szücs, G. G. Kiss, Gy. Gyürky, Zs. Fülöp, Z. Halász, T. Rauscher

Abstract: The stellar reaction rates of radiative $α$-capture reactions on heavy isotopes are of crucial importance for the $γ$ process network calculations. These rates are usually derived from statistical model calculations, which need to be validated, but the experimental database is very scarce. This paper presents the results of $α$-induced reaction cross section measurements on iridium isotopes carrie… ▽ More The stellar reaction rates of radiative $α$-capture reactions on heavy isotopes are of crucial importance for the $γ$ process network calculations. These rates are usually derived from statistical model calculations, which need to be validated, but the experimental database is very scarce. This paper presents the results of $α$-induced reaction cross section measurements on iridium isotopes carried out at first close to the astrophysically relevant energy region. Thick target yields of $^{191}$Ir($α$,$γ$)$^{195}$Au, $^{191}$Ir($α$,n)$^{194}$Au, $^{193}$Ir($α$,n)$^{196m}$Au, $^{193}$Ir($α$,n)$^{196}$Au reactions have been measured with the activation technique between E$_α= 13.4$ MeV and 17 MeV. For the first time the thick target yield was determined with X-ray counting. This led to a previously unprecedented sensitivity. From the measured thick target yields, reaction cross sections are derived and compared with statistical model calculations. The recently suggested energy-dependent modification of the $α$+nucleus optical potential gives a good description of the experimental data. △ Less

Submitted 30 November, 2017; originally announced November 2017.

Comments: Accepted for publication in Physics Letters B

Journal ref: Phys. Lett. B 776 (2018) 396

Cross section measurement of the astrophysically important 17O(p,gamma)18F reaction in a wide energy range

Authors: Gy. Gyürky, A. Ornelas, Zs. Fülöp, Z. Halász, G. G. Kiss, T. Szücs, R. Huszánk, I. Hornyák, I. Rajta, I. Vajda

Abstract: The 17O(p,g)18F reaction plays an important role in hydrogen burning processes in different stages of stellar evolution. The rate of this reaction must therefore be known with high accuracy in order to provide the necessary input for astrophysical models. The cross section of 17O(p,g)18F is characterized by a complicated resonance structure at low energies. Experimental data, however, is scarce… ▽ More The 17O(p,g)18F reaction plays an important role in hydrogen burning processes in different stages of stellar evolution. The rate of this reaction must therefore be known with high accuracy in order to provide the necessary input for astrophysical models. The cross section of 17O(p,g)18F is characterized by a complicated resonance structure at low energies. Experimental data, however, is scarce in a wide energy range which increases the uncertainty of the low energy extrapolations. The purpose of the present work is therefore to provide consistent and precise cross section values in a wide energy range. The cross section is measured using the activation method which provides directly the total cross section. With this technique some typical systematic uncertainties encountered in in-beam gamma-spectroscopy experiments can be avoided. The cross section was measured between 500 keV and 1.8 MeV proton energies with a total uncertainty of typically 10%. The results are compared with earlier measurements and it is found that the gross features of the 17O(p,g)18F excitation function is relatively well reproduced by the present data. Deviation of roughly a factor of 1.5 is found in the case of the total cross section when compared with the only one high energy dataset. At the lowest measured energy our result is in agreement with two recent datasets within one standard deviation and deviates by roughly two standard deviations from a third one. An R-matrix analysis of the present and previous data strengthen the reliability of the extrapolated zero energy astrophysical S-factor. Using an independent experimental technique, the literature cross section data of 17O(p,g)18F is confirmed in the energy region of the resonances while lower direct capture cross section is recommended at higher energies. The present dataset provides a constraint for the theoretical cross sections. △ Less

Submitted 9 March, 2017; originally announced March 2017.

Comments: Accepted for publication in Phys. Rev. C. Abstract shortened in order to comply with arxiv rules

Journal ref: Phys. Rev. C 95, 035805 (2017)

Origin of meteoritic stardust unveiled by a revised proton-capture rate of $^{17}$O

Authors: M. Lugaro, A. I. Karakas, C. G. Bruno, M. Aliotta, L. R. Nittler, D. Bemmerer, A. Best, A. Boeltzig, C. Broggini, A. Caciolli, F. Cavanna, G. F. Ciani, P. Corvisiero, T. Davinson, R. Depalo, A. Di Leva, Z. Elekes, F. Ferraro, A. Formicola, Zs. Fülöp, G. Gervino, A. Guglielmetti, C. Gustavino, Gy. Gyürky, G. Imbriani , et al. (12 additional authors not shown)

Abstract: Stardust grains recovered from meteorites provide high-precision snapshots of the isotopic composition of the stellar environment in which they formed. Attributing their origin to specific types of stars, however, often proves difficult. Intermediate-mass stars of 4-8 solar masses are expected to contribute a large fraction of meteoritic stardust. However, no grains have been found with characteri… ▽ More Stardust grains recovered from meteorites provide high-precision snapshots of the isotopic composition of the stellar environment in which they formed. Attributing their origin to specific types of stars, however, often proves difficult. Intermediate-mass stars of 4-8 solar masses are expected to contribute a large fraction of meteoritic stardust. However, no grains have been found with characteristic isotopic compositions expected from such stars. This is a long-standing puzzle, which points to serious gaps in our understanding of the lifecycle of stars and dust in our Galaxy. Here we show that the increased proton-capture rate of $^{17}$O reported by a recent underground experiment leads to $^{17}$O/$^{16}$O isotopic ratios that match those observed in a population of stardust grains, for proton-burning temperatures of 60-80 million K. These temperatures are indeed achieved at the base of the convective envelope during the late evolution of intermediate-mass stars of 4-8 solar masses, which reveals them as the most likely site of origin of the grains. This result provides the first direct evidence that these stars contributed to the dust inventory from which the Solar System formed. △ Less

Submitted 1 March, 2017; originally announced March 2017.

Journal ref: Published on Nature Astronomy 1, 0027 (2017)

Statistical model analysis of $α$-induced reaction cross sections of $^{64}$Zn at low energies

Authors: P. Mohr, Gy. Gyürky, Zs. Fülöp

Abstract: Background $α$-nucleus potentials play an essential role for the calculation of $α$-induced reaction cross sections at low energies in the statistical model. Uncertainties of these calculations are related to ambiguities in the adjustment of the potential parameters to experimental elastic scattering angular distributions (typically at higher energies) and to the energy dependence of the effective… ▽ More Background $α$-nucleus potentials play an essential role for the calculation of $α$-induced reaction cross sections at low energies in the statistical model. Uncertainties of these calculations are related to ambiguities in the adjustment of the potential parameters to experimental elastic scattering angular distributions (typically at higher energies) and to the energy dependence of the effective $α$-nucleus potentials. Purpose The present work studies cross sections of $α$-induced reactions for $^{64}$Zn at low energies and their dependence on the chosen input parameters of the statistical model calculations. The new experimental data from the recent Atomki experiments allow for a $χ^2$-based estimate of the uncertainties of calculated cross sections at very low energies. Method The recent data for the ($α$,$γ$), ($α$,$n$), and ($α$,$p$) reactions on $^{64}$Zn are compared to calculations in the statistical model. A survey of the parameter space of the widely used computer code TALYS is given, and the properties of the obtained $χ^2$ landscape are discussed. Results The best fit to the experimental data at low energies shows $χ^2/F \approx 7.7$ per data point which corresponds to an average deviation of about 30% between the best fit and the experimental data. Several combinations of the various ingredients of the statistical model are able to reach a reasonably small $χ^2/F$, not exceeding the best-fit result by more than a factor of 2. Conclusions The present experimental data for $^{64}$Zn in combination with the statistical model calculations allow to constrain the astrophysical reaction rate within about a factor of 2. However, the significant excess of $χ^2/F$ of the best-fit from unity asks for further improvement of the statistical model calculations and in particular the $α$-nucleus potential. △ Less

Submitted 9 January, 2017; originally announced January 2017.

Comments: 10 pages, 3 figures, to appear in Phys. Rev. C