The 22 Ne(α, γ) 26 Mg is an important reaction in stellar helium burning environments as it compe... more The 22 Ne(α, γ) 26 Mg is an important reaction in stellar helium burning environments as it competes directly with one of the main neutron sources for the s-process, the 22 Ne(α, n) 25 Mg reaction. The reaction rate of the 22 Ne(α, γ) 26 Mg is dominated by the low energy resonances at E lab α = 650 and 830 keV respectively. The E lab α = 830 keV resonance has been measured previously, but there are some uncertainties in the previous measurements. We confirmed the measurement of the E lab α = 830 keV resonance using implanted 22 Ne targets. We obtained a resonance strength of ωγ = 35 ± 4 µeV , and provide a weighted average of the present and previous measurements of ωγ = 35 ± 2 µeV with reduced uncertainties compared to previous studies. We also attempted to measure the strength of the predicted resonance at E lab α = 650 keV directly for the first time and found an upper limit of ωγ < 0.15 µeV for the strength of this resonance. In addition, we also studied the E lab P = 851 keV resonance in 22 Ne(p, γ) 23 Na, and obtained a resonance strength of ωγ = 9.2 ± 0.7 eV with significantly lower uncertainties compared to previous measurements.
Proceedings of International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos - IX — PoS(NIC-IX), 2010
The astrophysically-relevant region of the level structure of 19 Ne around the proton threshold r... more The astrophysically-relevant region of the level structure of 19 Ne around the proton threshold remains incomplete when considering that analogs for several states in the mirror nucleus 19 F have not yet been identified in 19 Ne. This structure is particularly important to understanding the eventual fate of the long-lived radioisotope 18 F in explosive environments like novae and xray bursts, where rates of proton-induced reactions on 19 F depend critically on the properties of 19 Ne excited states above threshold. To study this system, a measurement of the 17 O(3 He, n) 19 Ne
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The astrophysical p-process is an important way of nucleosynthesis to produce the stable and prot... more The astrophysical p-process is an important way of nucleosynthesis to produce the stable and proton-rich nuclei beyond Fe which can not be reached by the s- and r-processes. In the present study, the impact of nuclear ingredients, especially the nuclear potential, level density and strength function, to the astrophysical re-action rates of (p,γ), (α,γ), (γ,p), and (γ,α) reactions are systematically studied. The calculations are performed basad on the modern reaction code TALYS for about 3000 stable and proton-rich nuclei with 12≤Z≤110. In particular, both of the Wood-Saxon potential and the microscopic folding potential are taken into account. It is found that both the capture and photonuclear reaction rates are very sensitive to the nuclear potential, thus the better determination of nuclear potential would be important to reduce the uncertainties of reaction rates. Meanwhile, the Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility is being developed, which will provide ...
The Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility, under construction in Magurel... more The Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility, under construction in Magurele near Bucharest in Romania, will provide high-intensity and high-resolution gamma ray beams that can be used to address hotly debated problems in nuclear astrophysics. For this purpose, a silicon strip detector array (named ELISSA) will be realized in a common effort by ELI-NP and Laboratori Nazionali del Sud (INFN-LNS), in order to measure excitation functions and angular distributions over a wide energy and angular range. An experimental campaign is ongoing in order to test the feasibility of the future study at ELI-NP. With this aim, an experiment has been approved at INFN-LNS in order to measure the \(^{19}\)F(p,\(\alpha _{\pi }\))\(^{16}\)O reaction at astrophysical energies using a prototype of the ELISSA array. Moreover, an exploratory experiment to measure the \(^{7}\)Li(\(\gamma \),\(^{3}\)H)\(^{4}\)He reaction has been performed at High Intensity Gamma Source (HI\(\gamma \)S)....
The Al(p,α)Mg reaction, which drives the destruction of Al and the production of Mg in stellar hy... more The Al(p,α)Mg reaction, which drives the destruction of Al and the production of Mg in stellar hydrogen burning, has been investigated via the Trojan Horse Method (THM), by measuring the H(Al,αMg)n three-body reaction. The experiment covered a broad energy range (Ec.m. ≤ 1.5 MeV), aiming to investigate those of interest for astrophysics. The results confirm the THM as a valuable technique for the experimental study of fusion reactions at very low energies and suggests the presence of a rich pattern of resonances in the energy region close to the Gamow window of stellar hydrogen burning (70-120 keV), with potential impact on astrophysics. To estimate such an impact a second run of the experiment is needed, since the background due the three-body reaction hampered to collect enough data to resolve the resonant structures and extract the reaction rate. PACS. PACS-key discribing text of that key – PACS-key discribing text of that key
Journal of Physics G: Nuclear and Particle Physics, 2021
The study of stellar burning began just over 100 years ago. Nonetheless, we do not yet have a det... more The study of stellar burning began just over 100 years ago. Nonetheless, we do not yet have a detailed picture of the nucleosynthesis within stars and how nucleosynthesis impacts stellar structure and the remnants of stellar evolution. Achieving this understanding will require precise direct measurements of the nuclear reactions involved. This report summarizes the status of direct measurements for stellar burning, focusing on developments of the last couple of decades, and offering a prospectus of near-future developments.
The 7 Li(γ , t) 4 He ground state cross section was measured for the first time using monoenerget... more The 7 Li(γ , t) 4 He ground state cross section was measured for the first time using monoenergetic γ rays with energies between 4.4 and 10 MeV at the High Intensity Gamma-ray Source. The reaction is important for the primordial Li problem and for testing our understanding of the mirror α-capture reactions 3 H(α, γ) 7 Li and 3 He(α, γ) 7 Be. Although over the last 30 years most measurements of the 3 H(α, γ) 7 Li reaction have concentrated in an energy range below E γ = 3.65 MeV, measurements at higher energies could potentially restrict the extrapolation to astrophysically important energies. The experimental arrangement for measuring the 7 Li(γ , t) 4 He reaction included a large-area silicon detector array and several beam characterization instruments. The experimental astrophysical S factor of 3 H(α, γ) calculated from the present data was fitted using the R-matrix formalism. The results are in disagreement with previous experimental measurements in the same energy range but the extrapolated S factor agrees with the potential model calculation and lower energy experimental data.
Proceedings of 10th Symposium on Nuclei in the Cosmos — PoS(NIC X), 2009
The 18 Ne(α,p) 21 Na reaction plays a crucial role in the (α,p) process, which leads to the rapid... more The 18 Ne(α,p) 21 Na reaction plays a crucial role in the (α,p) process, which leads to the rapid proton capture process in X-ray bursts. The reaction rate depends upon properties of 22 Mg levels above the α threshold at 8.14 MeV. Despite recent studies of these levels, only the excitation energies are known for most with no constraints on the spins. We have studied the 24 Mg(p,t) 22 Mg reaction at the Oak Ridge National Laboratory (ORNL) Holifield Radioactive Ion Beam Facility (HRIBF), and by measuring the angular distributions of outgoing tritons, we provide the first experimental constraints on the spins of astrophysically-important 18 Ne(α,p) 21 Na resonances.
Proceedings of 10th Symposium on Nuclei in the Cosmos — PoS(NIC X), 2009
The magnitude of the 15 N(n, γ) 16 N reaction rate in asymptotic giant branch stars depends direc... more The magnitude of the 15 N(n, γ) 16 N reaction rate in asymptotic giant branch stars depends directly on the neutron spectroscopic factors of low-lying 16 N levels. A new study of the 15 N(d, p) 16 N reaction is reported populating the ground and first three excited states in 16 N. The preliminary spectroscopic factors are near unity as expected from shell model calculations, resolving a longstanding discrepancy with previous experiments. The data and analysis are presented.
Proceedings of 11th Symposium on Nuclei in the Cosmos — PoS(NIC XI), 2011
The rate of the 25 Al(p,γ) 26 Si reaction in novae is important to the production of galactic 26 ... more The rate of the 25 Al(p,γ) 26 Si reaction in novae is important to the production of galactic 26 Al, an important astronomical observable for its 1.809 MeV gamma ray. 26 Al has been catalogued near massive stars and found in presolar grains. The 25 Al proton capture reaction serves to bypass 26 Al g.s. production since the subsequent 26 Si beta decay preferentially populates instead the isomeric state of 26 Al. Several recent studies have aimed to locate and characterize the first = 0 resonances in 26 Si above the 25 Al+p threshold, which would dominate the reaction rate at nova temperatures. We have studied several resonances in 25 Al(p,γ) 26 Si via the 28 Si(p,t) 26 Si* reaction at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. In addition to measuring the angular distributions of the tritons, a partial implementation of the Oak Ridge Rutgers University Barrel Array (ORRUBA) was used to measure the coincident protons emitted from the decay of states in 26 Si above the proton threshold. We observe that the first = 0 state above the proton threshold decays essentially 100% of the time via proton emission, resulting in a proton branching ratio consistent with one.
Present and future gamma-beam facilities represent a great opportunity to validate and evaluate t... more Present and future gamma-beam facilities represent a great opportunity to validate and evaluate the cross-sections of many photonuclear reactions at near-threshold energies, whose data mostly come from theoretical calculations. We developed a Monte Carlo (MC) software that makes use of the validated tracking Geant4 libraries and the n-body event generator of ROOT libraries in order to provide a fast, realiable and complete MC tool to be used for nuclear physics experiments, with a particular focus on photo-nuclear processes. We discuss the results of the MC simulations performed in order to evaluate the effects of the electromagnetic background, the straggling of the emitted particles due to the target thickness and the resolution of the silicon detectors. Finally we present the preliminary results on some nuclear reactions involved in the p-process, which will be studied with ELISSA and the GBS at ELI-NP.
The Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility, underconstruction in Magurele... more The Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility, underconstruction in Magurele near Bucharest in Romania, will provide high-intensity andhigh-resolution gamma ray beams that can be used to address hotly debated problems in nuclear astrophysics, such as the accurate measurements of the cross sections of the24Mg(γ,α)20Ne reaction For this purpose, a silicon strip detector array (named ELISSA) will be realized in acommon effort by ELI-NP and Laboratori Nazionali del Sud (INFN-LNS), in order to measure excitation functions and angular distributions over a wide energy and angular range. A prototype of ELISSA was built and tested at INFN-LNS in Catania (Italy) with the support of ELI-NP. In this occasion, we have carried out experiments with alpha sources and with a 11 MeV 7Li beam that show up a very good energy resolution (better than 1%) and very good position resolution, of the order of 1 mm. Moreover, a threshold of 150 keV can be easily achieved with no cooling.
The 22 Ne(α, γ) 26 Mg is an important reaction in stellar helium burning environments as it compe... more The 22 Ne(α, γ) 26 Mg is an important reaction in stellar helium burning environments as it competes directly with one of the main neutron sources for the s-process, the 22 Ne(α, n) 25 Mg reaction. The reaction rate of the 22 Ne(α, γ) 26 Mg is dominated by the low energy resonances at E lab α = 650 and 830 keV respectively. The E lab α = 830 keV resonance has been measured previously, but there are some uncertainties in the previous measurements. We confirmed the measurement of the E lab α = 830 keV resonance using implanted 22 Ne targets. We obtained a resonance strength of ωγ = 35 ± 4 µeV , and provide a weighted average of the present and previous measurements of ωγ = 35 ± 2 µeV with reduced uncertainties compared to previous studies. We also attempted to measure the strength of the predicted resonance at E lab α = 650 keV directly for the first time and found an upper limit of ωγ < 0.15 µeV for the strength of this resonance. In addition, we also studied the E lab P = 851 keV resonance in 22 Ne(p, γ) 23 Na, and obtained a resonance strength of ωγ = 9.2 ± 0.7 eV with significantly lower uncertainties compared to previous measurements.
Proceedings of International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos - IX — PoS(NIC-IX), 2010
The astrophysically-relevant region of the level structure of 19 Ne around the proton threshold r... more The astrophysically-relevant region of the level structure of 19 Ne around the proton threshold remains incomplete when considering that analogs for several states in the mirror nucleus 19 F have not yet been identified in 19 Ne. This structure is particularly important to understanding the eventual fate of the long-lived radioisotope 18 F in explosive environments like novae and xray bursts, where rates of proton-induced reactions on 19 F depend critically on the properties of 19 Ne excited states above threshold. To study this system, a measurement of the 17 O(3 He, n) 19 Ne
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The astrophysical p-process is an important way of nucleosynthesis to produce the stable and prot... more The astrophysical p-process is an important way of nucleosynthesis to produce the stable and proton-rich nuclei beyond Fe which can not be reached by the s- and r-processes. In the present study, the impact of nuclear ingredients, especially the nuclear potential, level density and strength function, to the astrophysical re-action rates of (p,γ), (α,γ), (γ,p), and (γ,α) reactions are systematically studied. The calculations are performed basad on the modern reaction code TALYS for about 3000 stable and proton-rich nuclei with 12≤Z≤110. In particular, both of the Wood-Saxon potential and the microscopic folding potential are taken into account. It is found that both the capture and photonuclear reaction rates are very sensitive to the nuclear potential, thus the better determination of nuclear potential would be important to reduce the uncertainties of reaction rates. Meanwhile, the Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility is being developed, which will provide ...
The Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility, under construction in Magurel... more The Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility, under construction in Magurele near Bucharest in Romania, will provide high-intensity and high-resolution gamma ray beams that can be used to address hotly debated problems in nuclear astrophysics. For this purpose, a silicon strip detector array (named ELISSA) will be realized in a common effort by ELI-NP and Laboratori Nazionali del Sud (INFN-LNS), in order to measure excitation functions and angular distributions over a wide energy and angular range. An experimental campaign is ongoing in order to test the feasibility of the future study at ELI-NP. With this aim, an experiment has been approved at INFN-LNS in order to measure the \(^{19}\)F(p,\(\alpha _{\pi }\))\(^{16}\)O reaction at astrophysical energies using a prototype of the ELISSA array. Moreover, an exploratory experiment to measure the \(^{7}\)Li(\(\gamma \),\(^{3}\)H)\(^{4}\)He reaction has been performed at High Intensity Gamma Source (HI\(\gamma \)S)....
The Al(p,α)Mg reaction, which drives the destruction of Al and the production of Mg in stellar hy... more The Al(p,α)Mg reaction, which drives the destruction of Al and the production of Mg in stellar hydrogen burning, has been investigated via the Trojan Horse Method (THM), by measuring the H(Al,αMg)n three-body reaction. The experiment covered a broad energy range (Ec.m. ≤ 1.5 MeV), aiming to investigate those of interest for astrophysics. The results confirm the THM as a valuable technique for the experimental study of fusion reactions at very low energies and suggests the presence of a rich pattern of resonances in the energy region close to the Gamow window of stellar hydrogen burning (70-120 keV), with potential impact on astrophysics. To estimate such an impact a second run of the experiment is needed, since the background due the three-body reaction hampered to collect enough data to resolve the resonant structures and extract the reaction rate. PACS. PACS-key discribing text of that key – PACS-key discribing text of that key
Journal of Physics G: Nuclear and Particle Physics, 2021
The study of stellar burning began just over 100 years ago. Nonetheless, we do not yet have a det... more The study of stellar burning began just over 100 years ago. Nonetheless, we do not yet have a detailed picture of the nucleosynthesis within stars and how nucleosynthesis impacts stellar structure and the remnants of stellar evolution. Achieving this understanding will require precise direct measurements of the nuclear reactions involved. This report summarizes the status of direct measurements for stellar burning, focusing on developments of the last couple of decades, and offering a prospectus of near-future developments.
The 7 Li(γ , t) 4 He ground state cross section was measured for the first time using monoenerget... more The 7 Li(γ , t) 4 He ground state cross section was measured for the first time using monoenergetic γ rays with energies between 4.4 and 10 MeV at the High Intensity Gamma-ray Source. The reaction is important for the primordial Li problem and for testing our understanding of the mirror α-capture reactions 3 H(α, γ) 7 Li and 3 He(α, γ) 7 Be. Although over the last 30 years most measurements of the 3 H(α, γ) 7 Li reaction have concentrated in an energy range below E γ = 3.65 MeV, measurements at higher energies could potentially restrict the extrapolation to astrophysically important energies. The experimental arrangement for measuring the 7 Li(γ , t) 4 He reaction included a large-area silicon detector array and several beam characterization instruments. The experimental astrophysical S factor of 3 H(α, γ) calculated from the present data was fitted using the R-matrix formalism. The results are in disagreement with previous experimental measurements in the same energy range but the extrapolated S factor agrees with the potential model calculation and lower energy experimental data.
Proceedings of 10th Symposium on Nuclei in the Cosmos — PoS(NIC X), 2009
The 18 Ne(α,p) 21 Na reaction plays a crucial role in the (α,p) process, which leads to the rapid... more The 18 Ne(α,p) 21 Na reaction plays a crucial role in the (α,p) process, which leads to the rapid proton capture process in X-ray bursts. The reaction rate depends upon properties of 22 Mg levels above the α threshold at 8.14 MeV. Despite recent studies of these levels, only the excitation energies are known for most with no constraints on the spins. We have studied the 24 Mg(p,t) 22 Mg reaction at the Oak Ridge National Laboratory (ORNL) Holifield Radioactive Ion Beam Facility (HRIBF), and by measuring the angular distributions of outgoing tritons, we provide the first experimental constraints on the spins of astrophysically-important 18 Ne(α,p) 21 Na resonances.
Proceedings of 10th Symposium on Nuclei in the Cosmos — PoS(NIC X), 2009
The magnitude of the 15 N(n, γ) 16 N reaction rate in asymptotic giant branch stars depends direc... more The magnitude of the 15 N(n, γ) 16 N reaction rate in asymptotic giant branch stars depends directly on the neutron spectroscopic factors of low-lying 16 N levels. A new study of the 15 N(d, p) 16 N reaction is reported populating the ground and first three excited states in 16 N. The preliminary spectroscopic factors are near unity as expected from shell model calculations, resolving a longstanding discrepancy with previous experiments. The data and analysis are presented.
Proceedings of 11th Symposium on Nuclei in the Cosmos — PoS(NIC XI), 2011
The rate of the 25 Al(p,γ) 26 Si reaction in novae is important to the production of galactic 26 ... more The rate of the 25 Al(p,γ) 26 Si reaction in novae is important to the production of galactic 26 Al, an important astronomical observable for its 1.809 MeV gamma ray. 26 Al has been catalogued near massive stars and found in presolar grains. The 25 Al proton capture reaction serves to bypass 26 Al g.s. production since the subsequent 26 Si beta decay preferentially populates instead the isomeric state of 26 Al. Several recent studies have aimed to locate and characterize the first = 0 resonances in 26 Si above the 25 Al+p threshold, which would dominate the reaction rate at nova temperatures. We have studied several resonances in 25 Al(p,γ) 26 Si via the 28 Si(p,t) 26 Si* reaction at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. In addition to measuring the angular distributions of the tritons, a partial implementation of the Oak Ridge Rutgers University Barrel Array (ORRUBA) was used to measure the coincident protons emitted from the decay of states in 26 Si above the proton threshold. We observe that the first = 0 state above the proton threshold decays essentially 100% of the time via proton emission, resulting in a proton branching ratio consistent with one.
Present and future gamma-beam facilities represent a great opportunity to validate and evaluate t... more Present and future gamma-beam facilities represent a great opportunity to validate and evaluate the cross-sections of many photonuclear reactions at near-threshold energies, whose data mostly come from theoretical calculations. We developed a Monte Carlo (MC) software that makes use of the validated tracking Geant4 libraries and the n-body event generator of ROOT libraries in order to provide a fast, realiable and complete MC tool to be used for nuclear physics experiments, with a particular focus on photo-nuclear processes. We discuss the results of the MC simulations performed in order to evaluate the effects of the electromagnetic background, the straggling of the emitted particles due to the target thickness and the resolution of the silicon detectors. Finally we present the preliminary results on some nuclear reactions involved in the p-process, which will be studied with ELISSA and the GBS at ELI-NP.
The Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility, underconstruction in Magurele... more The Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility, underconstruction in Magurele near Bucharest in Romania, will provide high-intensity andhigh-resolution gamma ray beams that can be used to address hotly debated problems in nuclear astrophysics, such as the accurate measurements of the cross sections of the24Mg(γ,α)20Ne reaction For this purpose, a silicon strip detector array (named ELISSA) will be realized in acommon effort by ELI-NP and Laboratori Nazionali del Sud (INFN-LNS), in order to measure excitation functions and angular distributions over a wide energy and angular range. A prototype of ELISSA was built and tested at INFN-LNS in Catania (Italy) with the support of ELI-NP. In this occasion, we have carried out experiments with alpha sources and with a 11 MeV 7Li beam that show up a very good energy resolution (better than 1%) and very good position resolution, of the order of 1 mm. Moreover, a threshold of 150 keV can be easily achieved with no cooling.
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