Knockout reaction induced by ~6 He at 61.2 MeV/u

A knockout reaction induced by ⁶He at 61.2 MeV/u was carried out at the HIRFL-RIBLL radioactive beam line. The α core fragments at forward angles were detected in coincidence with the recoiled protons at large angles. From this coincident measurement the valence nucleon knockout mechanism and the core knockout mechanism can be separated according to the polar angle correlation between the core fragments and the recoiled protons. It is demonstrated that, when reconstructing the resonant state of a weakly bound nucleus, the contamination resulting from the core knockout mechanism should be eliminated in order to obtain the correct structure information.     

用于辐射复合与双电子复合实验的低能离子闪烁探测器

为了在CSRm的电子冷却器上进行辐射复合以及双电子复合实验, 需要探测能量小于4 MeV/u的离子, 因此设计了新的置于超高真空环境的CsI(Tl)闪烁探测器, 探测器采用的光电倍增管为R7525(Hamamatsu）。 介绍了新闪烁探测器的结构, 并对其进行了性能测试。 测试结果表明, 该探测器对高、 低能离子均有良好的响应, 探测器的信号十分明显。 探测器的最高计数率可以达到106 ions/s, 并且探测器附近的真空度可达10-10 Pa量级, 能够满足辐射复合与双电子复合实验以及储存环对真空的要求, 为今后在CSRm上进行复合实验打下了良好的基础。 A new CsI(Tl) scintillation detector readout with R7525 PMT(Hamamatsu）is designed to detect low energy (<4 MeV/u) ions in radiative recombination and dielectronic recombination experiments at the main cooler storage ring in Lanzhou. The structure of the scintillator detector is described in this paper. The detector is tested with α source and ion beams, respectively. The signals from background, 200 MeV/u C6+ and alpha radioactive source are recorded and analyzed. The results show that the detector has good response to high and low energy ions. The maximum counting rate of the detector can reach 106 ions/s and the vacuum level near the detector can reach 10-10 Pa, both are good for recombination experiments. The installation of the new detector to CSRm is of great help for future radiative recombination and dielectronic recombination experiments.     

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.     

Characteristics of a 4-fold segmented clover detectore

Four high-purity germanium 4-fold segmented Clover detectors have been     

基于GEANT4的CsI(Tl)闪烁体探测器的Monte Carlo模拟

对闪烁光在晶体内的传输以及光电子倍增过程进行了建模,基于GEANT4软件包对CsI(T1)闪烁体探测器进行了蒙特卡罗模拟, 得到了不同形状、尺寸和包装的CsI(Tl)晶体测量γ射线的能谱。对比模拟和测试结果,两者得到了很好的符合,从而验证了模拟参数的合理性和可靠性。该模拟程序的建立为闪烁体探测器的设计提供了更精确的开发工具。 With the modeling of the light transportation in crystal and electron multiplication in the PMT, a Monte Carlo simulation of CsI(Tl) scintillator detector has been implemented with Geant4 toolkit. The energy spectra simulated with different crystal shape, size and wrappings are obtained. And the reliability of the simulation parameters is confirmed by comparing with the measurements. The simulation code can be used as an reliable tool for the design of scintillator detectors.     

Secondary electron time detector for mass measurements at CSRe

The Isochronous Mass Spectrometry is a high accurate mass spectrometer. A secondary electrons time detector has been developed and used for mass measurements. Secondary electrons from a thin carbon foil are accelerated by an electric field and deflected 180°by a magnetic field onto a micro-channel plate. The time detector has been tested with alpha particles and a time resolution of 197 ps （FWHM） was obtained in the laboratory. A mass resolution around 8×10^-6 for Am/m was achieved by using this time detector in a pilot mass measurement experiment.     

Characteristics of a 4-fold segmented clover detectore

Four high-purity germanium 4-fold segmented Clover detectors have been applied in the experiment of neutron-rich nucleus 21N. The performance of those four Clovers have been tested with radioactive sources and in-beam experiments, and the main results including energy resolution, peak-to-total ratios, the variation of the hit pattern distribution in different crystals of one Clover detector with the energy of γ ray, and absolute full energy peak detection effciency curve, were presented.     

A TOF-PET prototype with position sensitive PMT readout

A prototype of time-of-flight positron emission computed tomography (TOF-PET) has been developed for acquiring the coincident detection of 511 keV γ-rays produced from positron annihilation. It consists of two 80.5 mm×80.5 mm LYSO scintillator arrays (composed of 35×35 pixel finger crystals) with the position sensitive photomultiplier tubes R2487 as the readout. Each array is composed of 2 mm×2 mm×15 mm finger crystals and the average pixel pitch is 2.30 mm. The measured results indicate that the TOF information has the potential to significantly enhance the image quality by improving the noise variance in the image reconstruction. The best spatial resolution (FWHM) of the prototype for the pairs of 511 keV γ-rays is 1.98 mm and 2.16 mm in the x and y directions, respectively, which are smaller than the average pixel pitch of 2.30 mm.     

Characteristics of the sampling paddle modules of neutron wall from the cosmic ray test

In the construction of a large area neutron detector （neutron wall） that is used to detect neutrons at GeV energies, the performances of all the sampling paddle modules prepared for the neutron wall are investigated with a specially designed test bench. Tested by cosmic rays, an average intrinsic time resolution of 222.5 ps is achieved at the center of the modules. The light attenuation length and the effective speed of the light in the module are also investigated.