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New experimental measurement of natSe(n, γ) cross section between 1 eV to 1 keV at the CSNS Back-n facility 下载免费PDF全文
Xin-Rong Hu 《中国物理 B》2022,31(8):80101-080101
The 74Se is one of 35 p-nuclei, and 82Se is a r-process only nucleus, and their (n, γ) cross sections are vital input parameters for nuclear astrophysics reaction network calculations. The neutron capture cross section in the resonance range of isotopes and even natural selenium samples has not been measured. Prompt γ-rays originating from neutron-induced capture events were detected by four C6D6 liquid scintillator detectors at the Back-n facility of China Spallation Neutron Source (CSNS). The pulse height weighting technique (PHWT) was used to analyze the data in the 1 eV to 100 keV region. The deduced neutron capture cross section was compared with ENDF/B-VIII.0, JEFF-3.2, and JENDL-4.0, and some differences were found. Resonance parameters were extracted by the R-matrix code SAMMY in the 1 eV-1 keV region. All the cross sections of natSe and resonance parameters are given in the datasets. The datasets are openly available at http://www.doi.org/10.11922/sciencedb.j00113.00019. 相似文献
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The thermonuclear~(19)F(p,α_0)16O reaction rate in the temperature region 0.007–10 GK has been derived by re-evaluating the available experimental data, together with the low-energy theoretical R-matrix extrapolations.Our new rate deviates by up to about 30% compared to the previous results, although all rates are consistent within the uncertainties. At very low temperature(e.g. 0.01 GK) our reaction rate is about 20% lower than the most recently published rate, because of a difference in the low energy extrapolated S-factor and a more accurate estimate of the reduced mass used in the calculation of the reaction rate. At temperatures above ~1 GK, our rate is lower, for instance, by about 20% around 1.75 GK, because we have re-evaluated the previous data(Isoya et al., Nucl. Phys.7, 116(1958)) in a meticulous way. The present interpretation is supported by the direct experimental data. The uncertainties of the present evaluated rate are estimated to be about 20% in the temperature region below 0.2 GK,and are mainly caused by the lack of low-energy experimental data and the large uncertainties in the existing data.Asymptotic giant branch(AGB) stars evolve at temperatures below 0.2 GK, where the~(19)F(p,α)16O reaction may play a very important role. However, the current accuracy of the reaction rate is insufficient to help to describe, in a careful way, the fluorine over-abundances observed in AGB stars. Precise cross section(or S factor) data in the low energy region are therefore needed for astrophysical nucleosynthesis studies. 相似文献
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近年来随着海水养殖业的发展,因海水养殖而对环境造成的污染得到人们的重视,联合养殖系统作为一种环境友好的养殖方法,成为目前海水养殖的研究热点.本文综述了联合养殖系统中"藻塘"和"食藻动物塘"的研究进展,并对其未来发展方向进行了预测. 相似文献
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柳卫平 李志宏 何建军 唐晓东 连钢 郭冰 苏俊 李云居 崔保群 孙良亭 武启 安竹 谌阳平 陈治钧 杜先超 符长波 甘林 贺国珠 AlexanderHeger 侯素青 黄翰雄 黄宁 江历阳 ShigeruKubono 李荐民 李阔昂 李涛 MariaLugaro 罗小兵 马少波 韩治宇 李鑫悦 马田丽 梅东明 南威克 南巍 陈晨 张昊 张龙 曹富强 钱永忠 秦久昌 任杰 谭万鹏 IsaoTanihata 王鹏 王硕 王友宝 许世伟 颜胜权 曾志 于祥庆 岳骞 曾晟 张环宇 张辉 杨丽桃 张立勇 张宁涛 张奇玮 张涛 方晓 张笑鹏 张雪珍 陈云华 祁宁春 吴世勇 郭绪元 周济芳 何胜明 宁金华 岳剑锋 《原子核物理评论》2020,37(3):283-290
锦屏深地核天体物理(JUNA)实验项目将利用中国锦屏深地实验室(CJPL)的良好条件,在天体物理伽莫夫能量窗口开展核天体关键反应$^{25}{\rm{Mg}}({\rm{p}},{\rm{\gamma}})^{26}{\rm{Al}}$ 、$^{19}{\rm{F}}({\rm{p}},\alpha)^{16}{\rm{O}}$ 、$^{13}{\rm{C}}(\alpha, {\rm{n}})^{16}{\rm{O}}$ 和$^{12}{\rm{C}}(\alpha,{\rm{\gamma}})^{16}{\rm{O}}$ 的直接测量,为理解恒星演化和元素起源提供新的数据。目前,已经在地面上对加速器装置、束流稳定性、靶、探测器以及电子学进行了系统的测试。地面实验内容包括高纯锗探测器效率刻度,$^{25}{\rm{Mg}}({\rm{p}}, {\rm{\gamma}})^{26}{\rm{Al}}$ 在304 keV的共振强度测量,$^{19}{\rm{F}}({\rm{p}}, \alpha)^{16}{\rm{O}}$ 的截面测量,聚乙烯作为慢化体的中子探测器的设计、加工和效率刻度,靶的设计和稳定性检测等。JUNA项目整体进展顺利,地面实验已取得一系列关键进展和初步成果。在不远的将来,JUNA项目将有序开展地下实验,完成设定目标,也将促进更广泛的国际合作,助力于天体演化中的若干重大科学问题的解决。 相似文献
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在低温核天体物理环境下,如静态核稳定燃烧阶段的核反应都发生较低的能区,其伽莫夫窗口内的核反应截面非常小,这就需要加速器提供较强束流才能完成核反应截面的直接测量。最近在中国科学院近代物理的320 kV高压平台上建立了低能核天体物理实验室以及相应的研究平台。驱动该平台的是一个14.5 GHz的永磁铁型ECR离子源,它能够提供非常强的束流离子。对于质子和氦离子,离子源出口的最大流强可以达到100 eμA,在实验终端上可以获得大约30 eμA的流强。基于此强流加速器装置,我们建立了核天体物理实验测量装置,包括靶室以及带电粒子和伽玛射线探测器等设备。利用已知的核反应对探测器性能和实验方法进行了一系列测试。同时,展示了近年来取得的一些主要实验结果。最后,对该平台上开展工作的前景进行了展望,并指出基于该地面装置的低能核反应研究所积累的技术及经验对于我国锦屏深地核天体物理JUNA项目的重要意义。For the hydrostatic stable burning in stars, the Gamow window is well below the Coulomb barriers for the charged-particle-induced nuclear reaction involved. Such nuclear reaction occurs through the quantum-mechanics tunneling effect, and its cross section drops rapidly approaching the Gamow window. An accelerator which can provide intense beam current is thus required to directly measure the reactions at low energies. An experimental setup for low-energy nuclear astrophysics studies has been recently established at a 320 kV high-voltage platform of the Institute of Modern Physics (IMP), Lanzhou, China. The driver machine of this platform is a very strong ECR ion source employing all-permanent magnets, which can typically supply up to about 100 eμA proton, alpha and many other heavy ions, and ultimately about 30 eμA currents can be achieved at the experimental terminal. The experimental setup includes a target chamber, and the charged-particle and γ-ray HPGe detectors. This work describes the setup established, characteristics of detectors, methodologies, and test results of several reactions with known cross sections. Furthermore, some important results published are shown briefly. We believe that the experimental technologies developed and experiences accumulated at this above-ground platform will be extremely helpful for the Jinping Underground Nuclear Astrophysics laboratory (JUNA) project in China. 相似文献
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张立勇 许世伟 何建军 H. Yamaguchi S. Kubono Y. Wakabayashi 陈思泽 胡钧 马朋 Y. Togano T. Hashimoto D. Kahl T. Teranishi 陈若富 王宏伟 田文栋 郭冰 S. Hayakawa N. Iwasa T. Yamada T. Komatsubara 《原子核物理评论》2013,30(4):385-390
在X 射线暴高温高密度的环境中,18Ne( α, p)21Na 很可能是由热CNO 循环突破到rp 过程的一个重要反应。到目前为止,人们测得的反应率还存在很大的不确定性。实验中用CRIB(CNS RadioactiveIon Beam separator) 提供的21Na 放射性束轰击8.8 mg/cm2 的聚乙烯厚靶,利用放置在θlab = 14°,0°,14° 处的3 套硅条探测器望远镜阵列对反冲轻粒子进行鉴别和测量,测得在一段能区(Ex = 5:5 9:2MeV) 内21Na(p, p)21Na 的激发函数。通过对21Na(p, p) 共振弹性散射截面进行R矩阵拟合,得到了22Mg共振能级的自旋宇称以及质子宽度等信息,从而为计算18Ne( α,, p)21Na 反应率提供了实验参数。The 18Ne(α ,p)21Na reaction is thought to be one of the key breakout reaction from the hot CNO cycle to the rp-process in X-ray bursts. Over stellartemperatures achieved in XRBs, this rate has not been sufficiently determined.The experiment was performed using CRIB (CNS Radioactive Ion Beam separator) at the Center for Nuclear Study (CNS) of the University of Tokyo. An 89 MeV 21Na radioactive ion beam was produced and bombarded an 8.8 mg/cm2 thick polyethylene target. The recoiled light particles were detected with three Micron silicon ΔE-E telescopes centered at angles of θlab = 0°; +14° and 14°with respect to the beam direction, respectively. The 21Na+p elastic-scattering excitation functions were reconstructed with a thick-target method over energies Ex = 5:5 9:2 MeV. The resonance parameters have been determined through an R-matrix analysis,which will be used to evaluate the 18Ne( α, p)21Na reaction rate. 相似文献
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Nuclear reactions in stars occur between nuclei in the high-energy tail of the energy distribution and are sensitive to possible deviations from the standard equilibrium thermal-energy distribution, the well-known Maxwell-Boltzmann Distribution (MBD). Strong constraints on such deviations were made previously with the detailed helioseismic information of the solar structure. With a small deviation parameterized with a factor exp[-δ (E/kT)2], it was shown δ restricted between -0.005 and +0.002. These constraints have been carefully re-examined in the present work. We find that a normalization factor was missed in the previous modified MBD. In this work, the normalization factor c is calculated as a function of δ. It shows the factor c is almost unity within the range 0< δ ≤0.002, which supports the previous conclusion. However, it demonstrates that δ cannot take a negative value from the normalization point of view. As a result, a stronger constraint on δ is defined as 0≤ δ ≤0.002. The astrophysical implication on the solar neutrino fluxes is simply discussed based on a positive δ value of 0.003. The reduction of the 7Be and 8B neutrino fluxes expected from the modified MBD can possibly shed alternative light on the solar neutrino problem. In addition, the resonant reaction rates for the 14N(p, γ)15O reaction are calculated with a standard MBD and a modified MBD, respectively. It shows that the rates are quite sensitive even to a very small δ. This work demonstrates the importance and necessity of experimental verification or testing of the well-known MBD at high temperatures. 相似文献
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胡钧 何建军 # 许世伟 陈志强 张雪荧 王建松 于祥庆 苏俊 李二涛 王宏伟 田文栋 李龙 张立勇 杨彦云 马朋 章学恒 胡正国 郭忠言 徐星 袁小华 鲁皖 余玉洪 臧永东 唐述文 叶瑞平 陈金达 金仕纶 杜成名 王世陶 马军兵 刘龙祥 白真 雷祥国 孙志宇 李湘庆 张玉虎 周小红 徐瑚珊 《原子核物理评论》2011,28(4):428-432
实验通过17F+p共振弹性散射研究了复合核18Ne激发态中与天体核反应14O(α, p)17F相关的共振态性质。利用兰州放射性束流线(RIBLL)对弹核碎裂反应产生的放射性束17F进行了分离和提纯。经过降能后,能量为4.22 AMeV 的17F束流轰击在T2终端的厚氢靶(CH2)n上。 两套∆E-E Si探测器望远镜放置在两个不同的探测角度θlab≈2.3°和14°上,对反冲质子的角度和能量进行了测量。实验观测到了复合核18Ne的几条质子共振能级。通过R-Matrix理论程序对激发函数进行拟合,得到了共振态的能量、 自旋、 宇称和衰变宽度等共振参数。Resonant properties in18Ne relevant to the stellar reaction of 14O(α, p)17F have been investigated through a resonant elastic scattering of 17F+p. The 17F RI beam was produced via a projectile fragmentation reaction, and subsequently separated and purified by Radioactive Ion beam Line in Lanzhou(RIBLL). After a series of energy degradation,a 4.22 AMeV 17F beam bombarded a thick(CH2)ntarget at T2 terminal. Energy and angle of the recoiled protons were measured by two sets of ∆E-E silicon telescope at θlab≈2.3°,14° respectively. Several resonances in 18Ne were observed,and their resonant parametersincluding energy,spin parity and decay width have been determined by an R-Matrix analysis of the experimental excitation function. 相似文献
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