Study of the data analysis process of the neutron wall with simulation

We study the response function of the neutron wall for 300 MeV neutrons with GEANT4 simulations. The methods to find the correct neutron incident position and time are discussed, and the neutron emission angle and energy are reconstructed and compared with the simulation.     

Study of Borromean halo nuclei by the neutron wall with simulation

The model of three-body Borromean halo nuclei breakup was described by using standard phase space distributions and the Monte Carlo simulation method was established to resolve the detection problem of two neutrons produced from breakup reaction on the neutron wall detector. For ⁶He case,overall resolution σE_k for the Gaussian part of the detector response and the detection efficiency including solid angle acceptance with regard to the excitation energy E_k are obtained by the simulation of two neutrons from ⁶He breakup into the neutron wall. The effects of the algorithm on the angular and energy correlations of the fragments are briefly discussed.     

基于SiPM读出的塑料闪烁体探测器时间性能研究

研究了基于硅光电倍增管(SiPM)双端读出的面积为10 cm ×10 cm的薄塑料闪烁体探测器的时间性能。239Pu放射源测试结果显示:(1)在多支SiPM串连读出方式下，随着SiPM数量的增加，探测器时间分辨逐渐变好；(2)在固定12支SiPM数量不变的情况下，并联支路越多，探测器时间分辨越差；(3)采用快时间塑料闪烁体并增加其厚度，可有效提高探测器时间分辨；(4)采用比束斑尺寸更大的塑料闪烁体，可有效提高探测器时间分辨的位置均匀性；(5)对于1 mm厚的EJ232塑料闪烁体探测器，在单端12支SiPM串行连接的情况下，可获得好于131 ps的时间分辨。这一研究对RIBLL2起始时间探测器的升级改造具有重要的指导意义。     

HIRFL-CSR ETF多层CsI(Tl)望远镜探测器能量刻度方法

在兰州重离子加速器冷却储存环（HIRFL-CSR）的外靶终端（ETF）,设计建造了一套多层CsI（Tl）望远镜探测器,用于对轻质量带电粒子的鉴别。这套探测器由7层CsI（Tl）晶体组成,每一层晶体光输出信号由4个光电倍增管分别在晶体4角读出。由于CsI（Tl）晶体对于重离子的响应是非线性的,且与入射离子的种类有关,这些因素使得对这台探测器的能量刻度需要做专门的研究。利用RIBLL2提供的能量在200 s~300 MeV/u的次级束流对探测器进行了测试,并针对第一片CsI（Tl）晶体的光输出以及所有CsI（Tl）晶体光输出的和的刻度方法分别进行了探索。在此能区下,第一片CsI（Tl）晶体猝灭现象可以近似忽略,即光输出与能量沉积近似呈线性。对于所有晶体光输出的和,利用一个经验公式对其进行刻度,利用这种刻度方法计算得到的光输出的值与实验测量值之间的差别小于5%。A multi-layer CsI(Tl) telescope has been designed and constructed at External Target in Facility (ETF) terminal of the Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou(HIRFL-CSR), and is used for identifying light charged particles. The detector consists of seven layers of CsI(Tl) crystals, and the signals of each crystal are read out by four photomultipliers at the corners. Since the response of the CsI(Tl) crystal to the heavy ions is non-linear and also depends on the species of the incident ions, the energy calibration method of the telescope must be carefully studied. With the help of the secondary beams selected by RIBLL2 in the energy ranges from 200 to 300 MeV/u, the telescope has been tested and the energy calibration method for the first-layer crystal together with the whole telescope has been investigated. In this energy region, the quench effect in the first-layer crystal can be neglected and a linear expression can be used to represent the relation between the light output and the energy deposition in the crystal. To the total light output of the telescope, an empirical formula is used for the energy calibration. The difference between the calculated results and the experiment data is globally less than 5%.     

Fragmentation of stable and neutron-rich 12-16C into boron fragments at approximately 240 MeV/nucleon

The elemental fragmentation cross sections of boron fragments produced by stable and neutron-rich^12-16C beams with a carbon target were systematically measured at an incident beam energy of approximately 240 MeV/nucleon.The measured cross sections were found to increase as the projectile mass number increases.The observed feature is explained qualitatively based on the abrasion-ablation two-stage reaction model and is compared quantitatively with predictions from various reaction models,including empirical and statistical models.All models agree with the measured cross sections within a factor of 2.     

Si-Csl（TI）望远镜探测系统用于大动态范围空间重离子鉴别与测量的研究

太阳极轨射电望远镜（SPORT）是一颗从事太阳活动研究的卫星。重离子探测仪是其中的高能粒子探测仪的关键组成部分。鉴于重离子探测仪对多种类离子（2 ≤ Z ≤ 26）的鉴别和大范围能段（8～300 MeV/u）的测量需求,中国科学院近代物理研究所设计并研制了一套Si-CsI（Tl）望远镜探测系统样机,这套望远镜系统由1个Si探测器、1个入射面为正六边形的CsI（Tl）晶体及其专用电子学系统构成。利用兰州重离子加速器冷却储存环系统（HIRFL-CSR）提供的高品质束流对这套望远镜探测系统样机进行了在束测试,完成了种类为2 ≤ Z ≤ 18的重离子直接测量与鉴别,利用直接测量的重离子,进行外推得到,最高测量要求的300MeV/u Fe离子也在设计要求的范围内。实验结果显示这套望远镜探测器样机满足空间中对大范围能段重离子探测的设计需求,该套方案为SPORT计划中的重离子探测仪的设计及建造奠定了很好的技术基础。Solar Polar Orbit Radio Telescope (SPORT) project, aimed at solar activities and solar atmosphere, is a satellite-borne apparatus which is composed by many sub-payloads and is under development in China. High Energy Heavy Ion Telescope (HEHIT) is one of most key sub-payloads in this project, and the main purpose of HEHIT is to identify space heavy ions (2 ≤ Z ≤ 26) with a broad energy range (8～300 MeV/u). In this paper, a prototype telescope of HEHIT, which includes a silicon detector, a CsI(Tl) crystal with regular hexagonal incident plane and customized electronic system, has been developed in the Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS). To obtain the performance of the prototype telescope, this telescope was tested with high quality beams provided by the accelerator of Heavy Ions Facility and Cooler-Storage-Ring in Lanzhou (HIRFL-CSR). The heavy ions ranging from Z =2 to Z =18 were clearly identified and measured from the beam test and an extrapolation was also done reasonably and it showed that the prototype detector could meet the requirement of t Fe(Z =26) with energy up to 300 MeV/u. In a word, this prototype telescope could satisfy the requirements of the measured heavy ions in the future SPORT project and this scheme of telescope will provide a favorable technique in the future design and construction of HEHIT.     

A time-of-flight system for the external target facility

A time-of-flight system with a plastic scintillator coupled to photomultipliers is developed for the external target facility (ETF). This system can satisfy the requirement of an ultrahigh vacuum (～10^-9 mbar), a high counting rate (～10⁶ particles per second) and a magnetic field environment. In the beam test experiment, a total time resolution of 580 ps FWHM was obtained for the whole system, and nuclei with a mass of up to 80 could be identified using this system.     

一种基于SiPM的新型起始时间探测器研制

本文介绍了一种新型起始时间探测器的研制。该探测器的灵敏面积为60 mm×60 mm,利用120根直径为1 mm的塑料闪烁光纤分成两层错位紧致排布,且上下相邻的3根光纤作为一个探测单元,每个探测单元均采用硅光电倍增管从双端读出信号。采用90Sr放射源对单根光纤进行了性能测试,结果表明,闪烁光沿着光纤方向的有效传播速度约为17 cm/ns,对应的时间分辨优于600 ps。此外,利用中国科学院近代物理研究所第二条放射性束流线（RIBLL2）提供的240 MeV/u的15N次级束研究了该探测器的性能。束流测试结果表明:该探测器的时间分辨为（150±15）ps,纵向位置分辨为（1.8±0.2）cm,并且结合该探测器以及RIBLL2束流线外靶实验终端上的其他探测器,可以对实验中产生的5 ≤ Z ≤ 8的各种同位素进行非常好的粒子鉴别。     

基于ASIC芯片的硅微条阵列探测器多通道前端电子学模块设计

描述了为兰州重离子加速器冷却储存环(HIRFL-CSR)外靶实验系统硅微条阵列探测器而设计的前端电子学模块。该模块采用专用ASIC芯片,可以处理96路能量信号。对前端电子学模块的性能进行了测试,结果表明,该模块在0.1～0.7 V范围内的积分非线性好于0.3%;其电子学分辨好于0.45%,最大串扰小于10%;通道一致性测试结果好于1.3%;在室温下连续工作24 h后,零点峰位最大漂移为1.48 m V。     

粗糙表面接触的层级模型

真实的材料加工表面的粗糙度往往跨越了多个尺度。本研究建立了一种新的粗糙表面层级接触模型。对于较大尺度部分，截断过滤短波长的粗糙度，然后运用连续介质力学的方法计算出相应的近似接触面积和局部压力的分布；对于较小尺度部分，本研究基于分形理论，利用二维Cantor集来描述层叠的短波长微凸峰，然后对在较大尺度得到的近似接触面积进行细化修正，计算出了最终的接触面积。为了验证所建立的模型，将得到的整体接触响应与有限元法计算结果进行了比较。结果表明，该模型能够充分预测粗糙表面的弹性接触响应，而且大大降低了多尺度粗糙表面接触力学建模的计算规模。这对进一步研究跨尺度粗糙表面之间的接触和摩擦具有重要意义。