Measurement of the 20 and 90 keV resonances in the ${}^{18}{\rm O}(p,α){}^{15}$N reaction via THM
M. La Cognata, C. Spitaleri, A. M. Mukhamedzhanov, B. Irgaziev, R. E. Tribble, A. Banu, S. Cherubini, A. Coc, V. Crucillá, V. Goldberg, M. Gulino, G. G. Kiss, L… 展开作者
M. La Cognata, C. Spitaleri, A. M. Mukhamedzhanov, B. Irgaziev, R. E. Tribble, A. Banu, S. Cherubini, A. Coc, V. Crucillá, V. Goldberg, M. Gulino, G. G. Kiss, L. Lamia, J. Mrazek, R. G. Pizzone, S. M. R. Puglia, G. G. Rapisarda, S. Romano, M. L. Sergi, G. Tabacaru, L. Trache, W. Trzaska, A. Tumino
The $^{18}{\rm O}(p,α)^{15}{\rm N}$ reaction is of primary importance in several astrophysical scenarios, including fluorine nucleosynthesis inside AGB stars as well as oxygen and nitrogen isotopic ratios in meteorite grains. Thus the indirect measurement of the low energy region of the $^{18}{\rm O}(p,α)^{15}{\rm N}$ reaction has been performed to reduce the nuclear uncertainty on theoretical predictions. In particular the strength of the 20 and 90 keV resonances have been deduced and the change in the reaction rate evaluated.
Big Bang Nucleosynthesis results refined via the Trojan Horse Method
Laboratori Nazionali del Sud, INFN（南方国家实验室，意大利核物理研究所）；Dipartimento di Fisica e Astronomia ‘Ettore Majorana’, Universitá di Catania（卡塔尼亚大学埃托雷·马约拉纳物理与天文学系）；Centro Siciliano di Fisica Nucleare e Struttura della Materia (CSFNSM)（西西里核物理与物质结构中心）；Sezione di Napoli, INFN（意大利核物理研究所那不勒斯分部）；Dipartimento di Fisica e Astronomia ’Galileo Galilei’,Universitá degli Studi di Padova（帕多瓦大学伽利略·伽利莱物理与天文学系）；Sezione di Padova, INFN（意大利核物理研究所帕多瓦分部）
The $^{13}{\rm C}(α,n)^{16}{\rm O}$ reaction is considered to be the main neutron source responsible for the production of heavy nuclides (from ${\rm Sr}$ to ${\rm Bi}$) through slow $n$-capture nucleosynthesis ($s$-process) at low temperatures during the asymptotic giant branch (AGB) phase of low mass stars ($\lesssim 3-4\;{\rm M}_{\odot}$, or LMSs). In recent years, several direct and indirect measurements have been carried out to determine the cross section at the energies of astrophysical interest (around $190\pm40\;{\rm keV}$). However, they yield inconsistent results causing a highly unc…
$\rm S^*(E)$ measurement of the $\rm {}^{12}C({}^{12}C,α){}^{20}Ne$ reaction at astrophysical energies via the Trojan horse method with $\rm ^{16}O$ quasi-free breakup
Institute of Radiation Technology, Beijing Academy of Science and Technology（北京辐射技术研究所，北京 Akademija 科学技术研究院）；Department of Nuclear Physics, China Institute of Atomic Energy（原子能科学研究院核物理系）；School of Physics and Materials Science, Anhui University（安徽大学物理与材料科学学院）
Indirect Measurement of the $\rm S^*(E)$ Factor for $\rm {}^{12}C({}^{12}C,\mathit{p}){}^{23}Na$ at Gamow Energies via the Trojan Horse Method with Near-0 degree Spectator Detection
Institute of Radiation Technology, Beijing Academy of Science and Technology（北京应用技术研究院辐射技术研究所）
The 27Al(p,a)24Mg reaction, which drives the destruction of 27Al and the production of 24Mg in stellar hydrogen burning, has been investigated via the Trojan Horse Method (THM) by measuring the 2H(27Al,a24Mg)n three-body reaction. The experiment covered a broad energy range (-0.5 MeV < E_cm < 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 suggest the presence of a rich pattern of resonances in the energy region close to the Gamow window of stellar hydr…
Multi-Model Analysis of the Astrophysical $S(E)$ Factor for the $^{9}\mathrm{Be}(p,α)^{6}\mathrm{Li}$ Reaction and Its Impact on Astrophysical Reaction Rates
School of Physics, Anhui University（安徽大学物理学院）；School of Physics, Southern University of Science and Technology（南方科技大学物理学院）；College of Physics and Optoelectronic Engineering, Shenzhen University（深圳大学物理与光电工程学院）；Institute of Radiation Technology, Beijing Academy of Science and Technology（北京市科学技术研究院辐射技术研究所）；Department of Nuclear Physics, China Institute of Atomic Energy（中国原子能科学研究院核物理系）
The $^{22}$Ne(p,$γ$)$^{23}$Na reaction is included in the neon-sodium cycle of hydrogen burning. A number of narrow resonances in the Gamow window dominates the thermonuclear reaction rate. Several resonance strengths are only poorly known. As a result, the $^{22}$Ne(p,$γ$)$^{23}$Na thermonuclear reaction rate is the most uncertain rate of the cycle. Here, a new experimental study of the strengths of the resonances at 436, 479, 639, 661, and 1279 keV proton beam energy is reported. The data have been obtained using a tantalum target implanted with $^{22}$Ne. The strengths $ωγ$ of the resonance…
Angular correlation spectra of $e^+e^-$ pairs produced in the $^{7}$Li($p$,$γ$)$^{8}$Be nuclear reaction have been studied at the sharp $E_p$= 441 keV resonance as well as at $E_p$= 650 keV, 800 keV and 1100 keV proton beam energies. The spectra measured at the resonance can be understood through the M1 internal pair creation process, but in the case of the off-resonance regions (direct proton capture) significant anomalies were observed in the $e^+e^-$ angular correlations supporting the X17 hypothetical particle creation and decay.
In this paper we discuss the $R$-matrix approach to treat the subthreshold resonances for the single-level and one channel, and for the single-level and two channel cases. In particular, the expression relating the ANC with the observable reduced width, when the subthreshold bound state is the only channel or coupled with an open channel, which is a resonance, is formulated. Since the ANC plays a very important role in nuclear astrophysics, these relations significantly enhance the power of the derived equations. We present the relationship between the resonance width and the ANC for the gener…
In nuclear astrophysics, the experimental scenario is still unclear for BBN relevant energies from 30-300 keV. Here, we report our measurements of cross section and astrophysical S(E) factor for pd capture reaction using proton beam energies 66 keV, 116 keV and 166 keV. Realistic GEANT4 simulations were carried out in order to estimate the energy dependent efficiency of the detector. The measured cross section and astrophysical S(E) factor for three new incident proton energies are found to be in good agreement, within the errors, with the values reported in the literature.
Background. The $^{12}$C$(α,γ)^{16}$O reaction plays a fundamental role in astrophysics and needs to be known with accuracy better than 10%. Cascade $γ$ transitions through the excited states of $^{16}$O are contributing to the uncertainty. Purpose. To constrain the contribution of the 0$^+$ (6.05 MeV) and 3$^-$ (6.13 MeV) cascade transitions. Method. The $α$ Asymptotic Normalization Coefficient for these states were measured using the $α$-transfer reaction $^{12}$C$(^6$Li,$d)^{16}$O at sub-Coulomb energies. Results. The 0$^+$ and 3$^-$ cascade transitions contribution was found to be 1.96$\pm…
The origin of fluorine is a widely debated issue. Nevertheless, the ^{15}N(α,γ)^{19}F reaction is a common feature among the various production channels so far proposed. Its reaction rate at relevant temperatures is determined by a number of narrow resonances together with the DC component and the tails of the two broad resonances at E_{c.m.} = 1323 and 1487 keV. Measurement through the direct detection of the 19F recoil ions with the European Recoil separator for Nuclear Astrophysics (ERNA) were performed. The reaction was initiated by a 15N beam impinging onto a 4He windowless gas target. Th…
A current challenge for ab initio calculations is systems that contain large continuum contributions such as 8Be. We report on new measurements of radiative decay widths in this nucleus that test recent Green's function Monte Carlo calculations. Traditionally, γ ray detectors have been utilized to measure the high energy photons from the 7Li(p, γ)αα reaction. However, due to the complicated response function of these detectors it has not yet been possible to extract the full γ ray spectrum from this reaction. Here we present an alternative measurement using large area Silicon detectors to dete…
A high-power Liquid-Lithium Target (LiLiT) was used for the first time for neutron production via the thick-target 7Li(p,n)7Be reaction and quantitative determination of neutron capture cross sections. Bombarded with a 1-2 mA proton beam at 1.92 MeV from the Soreq Applied Research Accelerator Facility (SARAF), the setup yields a 30-keV quasi-Maxwellian neutron spectrum with an intensity of 3-5e10 n/s, more than one order of magnitude larger than present near-threshold 7Li(p,n) neutron sources. The setup was used here to determine the 30-keV Maxwellian averaged cross section (MACS) of 94Zr and …
The thermonuclear rate of the $^{29}$Si(p,$γ$)$^{30}$P reaction impacts the $^{29}$Si abundance in classical novae. A reliable reaction rate is essential for testing the nova paternity of presolar stardust grains. At present, the fact that no classical nova grains have been unambiguously identified in primitive meteorites among thousands of grains studied is puzzling, considering that classical novae are expected to be prolific producers of dust grains. We investigated the $^{29}$Si $+$ $p$ reaction at center-of-mass energies of $200$ $-$ $420$~keV, and present improved values for resonance en…
The $^{17}$O(p,$α$)$^{14}$N reaction plays a key role in various astrophysical scenarios, from asymptotic giant branch stars to classical novae. It affects the synthesis of rare isotopes such as $^{17}$O and $^{18}$F, which can provide constraints on astrophysical models. A new direct determination of the $E_{\rm R}~=~64.5$~keV resonance strength performed at the Laboratory for Underground Nuclear Astrophysics accelerator has led to the most accurate value to date, $ωγ= 10.0 \pm 1.4_{\rm stat} \pm 0.7_{\rm syst}$~neV, thanks to a significant background reduction underground and generally impro…
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 wi…
Orientation effect of increasing the enhancement factor of DD reaction in CVD-Diamond was investigated by simulation. It is obtained that the flux peaking effect up to 2.2 times increases the relative enhancement factor for a parallel beam and up to 1.2 times for the deuteron beam with angular divergence equals 3 critical channeling angles. Qualitative agreement with the experiment was obtained.
In this Letter we report on the first inverse kinematics measurement of key resonances in the ${}^{22}\text{Ne}(p,γ)^{23}\text{Na}$ reaction which forms part of the NeNa cycle, and is relevant for ${}^{23}$Na synthesis in asymptotic giant branch (AGB) stars. An anti-correlation in O and Na abundances is seen across all well-studied globular clusters (GC), however, reaction-rate uncertainties limit the precision as to which stellar evolution models can reproduce the observed isotopic abundance patterns. Given the importance of GC observations in testing stellar evolution models and their depend…
The 16O nucleus was investigated through the 15N(p,α)12C reaction at excitation energies from Ex = 12 231 to 15 700 keV using proton beams from a 5 MeV Van de Graaff accelerator at beam energies of Ep = 331 to 3800 keV. Alpha decay from resonant states in 16O was strongly observed for ten known excited states in this region. The candidate 4-alpha cluster state at Ex = 15.1 MeV was investigated particularly intensely in order to understand its particle decay channels.
At temperatures below 0.1 GK the $^{19}$F$(p,γ)^{20}$Ne reaction is the only breakout path out of the CNO cycle. Experimental studies of this reaction are challenging from a technical perspective due to copious $γ$-ray background from the far stronger $^{19}$F$(p,α)^{16}$O reaction channel. Here we present the first inverse kinematics study of the $^{19}$F$(p,γ)^{20}$Ne reaction, in which we measure the strength of the 323-keV resonance. We find a strength value of $ωγ= 3.3^{+1.1}_{-0.9}$ meV, which is a factor of two larger than the most recent previous study. The discrepancy is likely the re…
The study of d(d,p)t reaction is very important for the nucleosynthesis in both standard Big Bang and stellar evolution, as well as for the future fusion reactors planning of energy production. The d(d,p)t bare nucleus astrophysical S(E) factor has been measured indirectly at energies from about 400 keV down to several keV by means of the Trojan horse method applied to the quasi-free process $\rm {}^2H({}^6Li,pt){}^4He$ induced at a lithium beam energy of 9.5 MeV, which is closer to the zero quasi-free energy point. An accurate analysis leads to the determination of the $\rm S_{bare}(0)=56.7 \…
The $^{22}$Ne($α$,n)$^{25}$Mg reaction is the dominant neutron source for the slow neutron capture process ($s$-process) in massive stars and contributes, together with the $^{13}$C($α$,n)$^{16}$O, to the production of neutrons for the $s$-process in Asymptotic Giant Branch (AGB) stars. However, the reaction is endothermic and competes directly with the $^{22}$Ne($α,γ)^{26}$Mg radiative capture. The uncertainties for both reactions are large owing to the uncertainty in the level structure of $^{26}$Mg near the alpha and neutron separation energies. These uncertainties are affecting the s-proce…
In the present experiment we measure the forward-emitted angle-integrated neutron spectrum of the 7Li(p,n)7Be reaction via time-of-flight neutron spectrometry. The proton beam is shaped to a Gaussian-like distribution with energies close to the reaction threshold upstream the thick lithium target. The angle-integrated neutron spectrum resembles a Maxwellian or stellar neutron spectrum at kT=30 keV.
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}$\,=\,$334$\,$k…
Re-evaluation of the $^{22}$Ne($p$,$γ$)$^{23}$Na reaction rate: $R-$matrix analysis of the non-resonant capture and effect of the 8945 keV (${7/2}^{-}$) resonance strength
The CNO cycle is the main energy source in stars more massive than our sun, it defines the energy production and the cycle time that lead to the lifetime of massive stars, and it is an important tool for the determination of the age of globular clusters. One of the largest uncertainties in the CNO chain of reactions comes from the uncertainty in the $^{14}$N$(p,γ)^{15}$O reaction rate. This uncertainty arises predominantly from the uncertainty in the lifetime of the sub-threshold state in $^{15}$O at $E_{x}$ = 6792 keV. Previous measurements of this state's lifetime are significantly discrepan…
The abundances of sodium and oxygen are observed to be anti-correlated in all well-studied globular clusters. Asymptotic giant branch (AGB) stars undergoing hot bottom burning (HBB) are thought to be prime candidates for producing sodium-rich oxygen-poor material and expelling it into the cluster ISM. The 22Ne(p,gamma)23Na reaction has been shown to strongly influence the amount of 23Na produced during HBB. This reaction is also important for classical novae nucleosynthesis, with sensitivity studies showing that the abundances of several isotopes in the Ne-Al region are significantly altered w…
Investigation of alpha-induced reactions on 127I for the astrophysical gamma process
为了给天体物理γ过程的模拟提供截面数据，用活化技术研究了α-诱发的~（127）I反应。精确测量了536.1keV γ跃迁的相对强度，其不确定度由13%降低到4%。通过测量特征X射线的产额，首次确定了127 I（α，γ）~（131）Cs反应的截面接近天体物理相关的能量区域，能量为9.50 <Ec. m。< 15.15由于反应模型的改进，$ MeV. The 127I(alpha,n)130Cs reaction was studied in the range 9.62 < Ec.m. < 15.15 MeV by measuring the yield of the 536.1 keV gamma-ray and at the lower part of this energy range by counting the characteristic X-rays. A comparison of the resulting cross sections to predictions of statistical model calculations confirmed the predictions of the astrophysically relevant averaged alpha width. Nevertheless, the newly derived stell…
Mono-energetic gamma-beams ($Δ\sim 10$ eV) based on thermal neutron capture, in a nuclear reactor, using the V(n, $γ$) and Fe(n,$γ$) reactions, were utilized for generating fast neutron sources from lead and thallium respectively, via the $^{207}$Pb($γ$,n) and $^{205}$Tl($γ$,n) reactions. It so happened that one of the incident gamma-lines of the V source, E$_γ$ = 7163 keV, photoexcites by chance a resonance level in $^{207}$Pb, which emits neutrons at an energy of 423 keV. In a similar manner, the incident $γ$-line at E$_γ$ = 7646 keV of the Fe(n, $γ$) source photoexcites by chance a resonanc…
$β$ decay of $^{26}$P was used to populate the astrophysically important $E_x=$5929.4(8) keV $J^π=3{^+}$ state of $^{26}$Si. Both $β$-delayed proton at 418(8) keV and gamma ray at 1742(2) keV emitted from this state were measured simultaneously for the first time with corresponding absolute intensities of 11.1(12)\% and 0.59(44)\%, respectively. Besides, shell model calculations with weakly bound effects were performed to investigate the decay properties of other resonant states and a spin-parity of $4^+$ rather than $0^+$ was favored for the $E_x=$5945.9(40) keV state. Combining the experimen…
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 radiative capture cross sections of $^{12}$C($α$,$γ$)$^{16}$O and derived reaction rates are calculated from the direct capture potential model. The resulting $S$-factor at low energies is found to be dominated by $E$2 transition to the $^{16}$O ground state. The $E$1 and $E$2 $S$-factors at $E_{c.m.}=0.3$ MeV are $S_{E1}\approx3$ keV~b and $S_{E2}=150^{+41}_{-17}$ keV~b, respectively. The sum of the cascade transition through the excited state of $^{16}$O is $S_{\rm casc}= 18\pm4.5$ keV~b. The derived reaction rates at low temperatures seem to be concordant with those from the previous ev…
The ${}^{12}\mathrm{C}(α,γ){}^{16}\mathrm{O}$ reaction plays a key role in the evolution of stars with masses of $M >$ 0.55 $M_\odot$. The cross-section of the ${}^{12}\mathrm{C}(α,γ){}^{16}\mathrm{O}$ reaction within the Gamow window ($E_\textrm{c.m.}$ = 300 keV, $T_\textrm9$ = 0.2) is extremely small (about $10^{-17}$ barn), which makes the direct measurement in a ground-based laboratory with existing techniques unfeasible. Up until now, the cross-sections at lower energies can only be extrapolated from the data at higher energies. However, two subthreshold resonances, located at $E_x$ = 7.1…
The reaction network in the neutron-deficient part of the nuclear chart around $A \sim 100$ contains several nuclei of importance to astrophysical processes, such as the p-process. This work reports on the results from recent experimental studies of the radiative proton-capture reactions $^{112,114}\mathrm{Cd}(p,γ)^{113,115}\mathrm{In}$. Experimental cross sections for the reactions have been measured for proton beam energies residing inside the respective Gamow windows for each reaction, using isotopically enriched $^{112}\mathrm{Cd}$ and $^{114}\mathrm{Cd}$ targets. Two different techniques,…
