测量碳同位素与C靶反应总截面来确定其中子密度分布

发布时间：2018-04-05 11:47

本文选题：反应总截面　切入点：中子密度分布　出处：《中国科学院大学(中国科学院近代物理研究所)》2017年博士论文

【摘要】：原子核的半径和密度分布是原子核非常重要的基本特性。原子核半径以及密度分布对于理解原子核的内部结构以及验证描述原子核的理论模型都具有非常重要的意义。对原子核均方根半径的研究可以有效地促进手征核子-核子相互作用和三体核力、奇偶效应相关理论、平均场理论以及动力学模型等的研究。精确测量原子核的半径以及密度分布,特别是丰中子原子核的中子密度分布,不仅可以为确定中子皮和中子晕结构提供有力的实验证据,还可以为原子核性质及核物质状态方程提供可靠的实验数据。实验上通过对反应总截面(σR)、相互作用截面(σI)和电荷改变截面(σcc)的测量,结合理论计算来提取核半径与核密度分布。由于高能区的反应总截面对核的均方根半径敏感,而中低能区的反应总截面对核的稀薄外层的结构信息更加敏感,因而要确定丰中子核素中子密度分布需要精确测量其低能区的反应总截面。目前测量核反应总截面与核相互作用截面的常用方法有束流透射法(也叫束流衰减法)、弹性散射角分布测量法、Si堆栈望远镜法和4π-γ符合法。现有的碳同位素与C靶反应总截面实验数据点主要集中在高能区,较少的中低能区的数据也由于误差较大,提取的中子密度分布仍有很大的不确定性。本论文实验是和Tanihata研究小组合作,在日本大阪大学核物理研究中心的EN course终端完成的。实验中利用EN course产生了45MeV/nucleon的9-12Be、8,10-15B和10-18C核素用来轰击12C靶,利用束流穿透法测量了9-12Be、8,10-15B和10-18C在C靶上的反应总截面。本论文从实验上得到了10-17C的反应总截面,并结合现有的C同位素反应总截面实验数据,利用Glauber模型提取了这些同位素的中子密度分布。本论文实验中,反应靶前利用ΔE-TOF-Bρ方法对入射粒子进行鉴别,在反应靶后利用多重采用电离室(MUSIC)和NaI(Tl)探测器组成ΔE-E望远镜探测系统,用来探测并鉴别靶后的粒子。通过数据分析得到10-17C与12C靶的反应总截面分别为1073±19 mb,1107±13 mb(37MeV/nucleon),1137±14 mb,1258±63 mb,1242±20 mb,1603±72 mb,1284±32 mb和1317±21 mb。在Glauber模型计算中,根据已知的12C密度分布确定了模型中相互作用范围参数r0随入射能量的变化关系。其他C同位素的中子密度分布则根据该核素不同入射能量的反应总截面得到,它们的中子和物质的均方根半径由提取的密度分布计算所得。
[Abstract]:The radius and density distribution of the nucleus are very important basic properties of the nucleus.The nuclear radius and density distribution are very important to understand the inner structure of the nucleus and to verify the theoretical model of describing the nucleus.The study of the root-mean-square radius of nucleus can effectively promote the study of chiral nucleon-nucleon interaction and three-body nuclear force, the theory of odd-even effect, the mean field theory and the kinetic model.The accurate measurement of the radius and density distribution of the nucleus, especially the neutron density distribution of the neutron rich nucleus, can not only provide experimental evidence for determining the structure of the neutron skin and the neutron halo,It can also provide reliable experimental data for nuclear properties and equation of state of nuclear matter.The distribution of nuclear radius and density is extracted by measuring the total reaction cross section (蟽 Rn), interaction cross section (蟽 I) and charge change cross section (蟽 cc).Because the total cross section of the high energy region is sensitive to the root mean square radius of the nucleus, the total cross section of the middle and low energy region is more sensitive to the structural information of the thin outer layer of the nucleus.Therefore, to determine the neutron density distribution of neutron rich nuclide, it is necessary to accurately measure the total cross section of the reaction in the low energy region of neutron rich nuclide.At present, the commonly used methods for measuring the total cross section of nuclear reaction and nuclear interaction cross section are beam transmission method (also called beam attenuation method), elastic scattering angle distribution measurement method, Si stack telescope method and 4 蟺-纬 coincidence method.The existing experimental data points of total cross section of carbon isotope reaction with C target are mainly concentrated in the high energy region, and there is still a great uncertainty in the neutron density distribution of the extracted neutron because of the large error in the middle and low energy region.The experiment was carried out at en course terminal at the center of nuclear physics of Osaka University, Japan, in cooperation with Tanihata research team.In the experiment, en course was used to produce 9-12Bean810-15B and 10-18C nuclides of 45MeV/nucleon for bombarding 12C target. The total cross sections of 9-12Bean810-15B and 10-18C reaction on C target were measured by beam penetration method.In this paper, the total cross sections of 10 ~ (-17) C reaction are obtained experimentally, and the neutron density distributions of these isotopes are extracted by using the Glauber model combined with the available experimental data of the total cross sections of C isotopic reactions.In this paper, the 螖 E-TOF-B 蟻 method is used to identify the incident particles in front of the reaction target. After the reaction, the 螖 E-E telescope detection system is composed of multiple ionization chamber (MUSIC) and NaIK Tl detectors, which are used to detect and identify the particles after the target.The total cross sections of 10-17C and 12C target were 1073 卤19 mbN, 1107 卤13 mbU, 37 MeV / nucleon, 1137 卤14 mbN, 1258 卤63 mbN, 1242 卤20 mbC, 1603 卤72 mbN, 1284 卤32 mb and 1317 卤21 mbmb. respectively.In the calculation of Glauber model, according to the known density distribution of 12C, the relation of the interaction range parameter r0 with incident energy is determined.The neutron density distribution of other C isotopes is obtained according to the total cross sections of the reaction of the nuclides with different incident energies. The RMS radii of their neutrons and matter are calculated from the extracted density distributions.
【学位授予单位】：中国科学院大学(中国科学院近代物理研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O571

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