HIRFL-CSRm内靶实验终端CsI(Tl)电磁量能器性能模拟

基于GEANT4模拟了HIRFL-CSRm内靶实验终端的CsI(Tl)电磁量能器系统, 给出了CsI电磁量能器的最佳设计参数及可能达到的性能. 结果表明, 设计的CsI(Tl)电磁量能器系统能够满足所研究的物理要求.     

双维位置灵敏CsI(Tl)闪烁探测器

介绍了一种双维位置灵敏CsI(Tl)闪烁探测器, 利用GEANT4对它进行了蒙特卡罗模拟, 得到了RIB 17N的位置分布谱及探测器的空间位置分辨,　模拟结果与实验测量值很好地吻合。给出了影响探测器分辨的主要因素及改进方案。A two dimensional position sensitive CsI(Tl) scintillation detector readout with PSPMT was introduced. The performance of detector was simulated by using Monte Carlo code GEANT4. The position spectrum of RIB 17N and the detector’s position resolution were obtained, and the simulation results accorded with the experimental ones. The main factors, which can affect performance of the detector, and some planned detector improvements were presented.     

CsI（Tl）+Si-APD探测器的性能测试

介绍了Si-APD的工作原理并对Si-APD中的暗电流进行了理论分析。基于RIBLL上产生的放射性核束流,使用CsI（Tl）+Si-APD探测器对中能重离子进行了能量测试。测试结果显示,CsI（Tl）+Si-APD探测器测量20 MeV/u的重离子时,可得到3%的能量分辨;同时还发现Si-APD中的暗电流大小以及入射粒子的能量大小都会对探测器的能量分辨产生影响。In this paper, the working principle of Si-APD was introduced and the dark current of Si-APD was analyzed theoretically. The intermediate energy heavy ions, which are produced on the RIBLL(Radioactive Ion Beam Line in Lanzhou), were measured with CsI(Tl)+Si-APD detector. The energy resolution of CsI(Tl)+Si-APD detector is about 3% for heavy ions with energy around 20 MeV/u. It is also found that the energy resolution of detector can be in uenced by the dark current of Si-APD and the energy of incident particles.     

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.     

CsI(Tl)晶体量能器中硅光二极管的核计数器效应研究

研究了由于电磁簇射在CsI(Tl)晶体后端的泄漏而引起的硅光二极管“核计数器”效应. 通过GEANT模拟和实验测量分析其在BESⅢ的CsI(Tl)晶体量能器中对能量测量的影响.     

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%.     

Measurement of spatial resolution of the micro-CT system

The performance test is an important and necessary work for the micro-CT (computed tomography) system. The focal spot size of the micro focus X-ray tube is measured. The method of measuring the spatial resolution of micro-CT is introduced. A line-pair resolution of 28.2 lp/mm at the 10% modulation transfer function (MTF) level can be achieved with 14.7 μm spot size, 12.3 μm voxel size and a 25 mm field of view. In addition, a tungsten wire with the diameter of 5 μm can be detected by the system.     

Performance assessment of CsI(Tl) screens on varioussubstrates for X-ray imaging

Thallium-doped cesium iodide (CsI(Tl)) screens are widely used in X-ray imaging devices because of the columnar structure of the CsI(Tl) layer, but few reports focus on the optical role of the substrate in the screen system. In this paper, four substrates including fused silica (SiO₂), silver-film coated SiO₂, graphite (C) and fiber optic plate (FOP) are used to fabricate CsI(Tl) screens by thermal evaporation. Their imaging performance is evaluated by relative light output (RLO), modulation transfer function (MTF), normalized noise power spectrum (NNPS) and noise equivalent quanta (NEQ). The results reveal that although CsI(Tl) film on graphite plate yields images with the lowest light output, it presents relatively higher spatial resolution and better signal-to-noise characteristics. However, films on SiO₂ plate obtain low MTF but high NNPS curves, whether they are coated with silver film or not. Furthermore, scintillation screens on FOP have bright images with low NNPS and high NEQ, but have the lowest MTF. By controlling the substrate optical features, CsI(Tl) films can be tailored to suit a given application.     

A Module Test of CCDA： an Array to Select the Centrality of Collisions in Heavy Ion Collisions

A test result of a module for the collision centrality detector array （CCDA）, a simple detector array for the event classification of the centrality, is presented. The CsI（Tl） module has PMTs on both ends to read out signals. The beam test results indicate that it provides a good light charged particles （LCP） identification and a reasonable energy resolution. The energy spectra of LCPs are compared with the GEANT simulation.     

Measurement of spatial resolution of the micro-CT system

The performance test is an important and necessary work for the micro-CT （computed tomography） system. The focal spot size of the micro focus X-ray tube is measured. The method of measuring the spatial resolution of micro-CT is introduced. A line-pair resolution of 28.2 lp/mm at the 10% modulation transfer function （MTF） level can be achieved with 14.7 μm spot size, 12.3 μm voxel size and a 25 mm field of view. In addition, a tungsten wire with the diameter of 5 μm can be detected by the system.     

一种应用于HIRFL-CSR上的非拦截式剩余气体电离束流剖面探测器(英文)

兰州重离子加速器冷却储存环主环（CSRm）上成功应用了一种剩余气体电离剖面探测器（IPM）,这种新型非拦截式剖面探测器的应用服役对CSRm的束流冷却研究及常规调束的实时剖面监测具有重要意义。IPM探测器通过收集束流与剩余气体之间的电离产物（气体离子或电子）,利用偏转静电场将电离产物加速至多重微通道板（MCP）,并在其上进行电子放大,放大的信号电子随后在荧光屏（P46等）上进行电子-光子转换,最终含有束流剖面信息的投影光子被真空靶室外的CCD相机获取。在正式应用于CSRm之前,IPM探测器还在分离扇回旋加速器直线（SSC Linac）上进行了束流实验,并与传统单丝扫描剖面探测器进行了对比。IPM探测器与单丝刮束器的剖面测量结果相近,并且具有较好的信噪比和约60 μm的较高空间分辨率。这种IPM探测器可以利用电阻串联进行均匀分压,较便捷地应用于真空度较低的直线加速器,还可以改造为分离电极单独供压的结构,应用在超高真空需要烘烤的环形加速器。最后还介绍了一种全新紧凑型结构的IPM探测器设计,该设计利用一套IPM探测器实现束流横向水平与垂直两个方向的剖面测量功能,这种紧凑型IPM结构尤其在空间紧缺型的强流直线加速器上具有重大的应用价值。A new non-intercepting beam profile monitor, residual gas Ionization Profile Monitor (IPM), has been developed and tested at the main Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou (HIRFL-CSRm). It has been successfully used for studies of electron cooling mechanisms, as well as profile monitoring under normal-mode operation in HIRFL-CSRm. The IPM measures the distribution of ions resulting from the residual gas ionization during the beam passage. The gas ions are collected and multiplied by tandem-type MCPs and a phosphor screen, and eventually captured by a commercial CCD camera outside the vacuum chamber. Before formally applied in HIRFL-CSRm, the IPM was tested and compared with a conventional wire scanner profile monitor at Sector Separated Cyclotron Linac (SSC Linac). Both results show good agreement. Besides, the IPM has higher signal to noise ratio than the wire scanner. It also has a very high spatial resolution of around 60 μm. This monitor can be used for low vacuum like Linac with resistance for bias voltage, or for ultra-high vacuum with discrete electrodes for bias voltage where the bakeout process is essential. Furthermore, a novel and compact design of one IPM with capability of detecting both horizontal and vertical profile is proposed. This compact IPM is quite suitable for non-invasive profile diagnostics at space shortage and high-current Linac.     

HIRFL-CSRm内靶实验终端上TPC性能的Monte-Carlo研究

基于Monte Carlo方法对HIRFL CSRm上的TPC的性能进行了模拟.研究了磁场、读出电极几何尺寸、灵敏丝距以及读出电极平面与灵敏丝平面之间的距离等参数对TPC性能的影响,给出了TPC的一些最佳设计参数. Based on Monte-Carlo method the time projection chamben s (TPC s) performance at HIRFL-CSRm has been simulated. We have already studied the effect of magnetic field, wire space, the size of readout pad and the distance between the pad plane and the wire plane on the performance of TPC. At the same time some important results are given for designing TPC.     

PROTOTYPE OF END CAP SHOWER COUNTERAND ITS BEAM TEST

A gas sampling Em Shower counter of the lead-SQS tube sandwich type was constructed and tested. The Shower counter uses Aluminium tubes and anode readout. Energy resolution σ/E is 15.5% at E_e=1GeV. Range of the energy response linearity is 0—2GeV. This paper describes the beam test and the performance studied under various conditions.     

18/8型不锈钢中σ-相的形成

本文叙述在含钼、钛的18/8型不锈钢中σ-相形成的过程及其对钢的性能的影响。金相及X线衍射分析证实:在复相铬镍不锈钢中,铁素体分解成σ-相以在850℃为最快。应用特殊的侵蚀剂及高倍的金相检查,发现σ-相的沉淀开始发生于铁素体相界;伴随着σ-相的形成,其周围铁素体重结晶为奥氏体。由于σ-相的形成,钢的硬度增加,韧性显著降低,因而严重地影响了钢的安全使用,但是适当的热处理可以恢复其原来的组织及性能。     

Tune调制对HIRFL-CSRm动力学孔径影响的模拟研究

 通过引进包含tune调制的传输矩阵，模拟计算了由四极铁电源纹波所引起的tune调制对HIRFL-CSRm动力学孔径的影响。模拟计算中，对HIRFL-CSRm实际(lattice)跟踪1.0×10⁶圈。从结果可以看出，动力学孔径随调制振幅的增大迅速减小，大体呈线性变化；动力学孔径随调制tune值的变化在研究范围内也有变化，变化的范围在0.049~0.089 m之间。     

Characteristics of the 2 m long scintillation counters measured by detecting 90 MeV protons

The characteristics of scintillation counters measured in a 90-MeV proton beam have been presented. Two-meter long scintillators BC-404 and BC-408, which were viewed from both ends with photoelectron multipliers R1828-01 (PMT) have been used. Both the amplitude and time distributions of the PMT signals are well described by the Gaussian function. It turned out that the amplitude resolution σ(А)/А weakly depends on the type of scintillator and the proton position along the counter, and lies in the interval between 4 and 5%. The best time resolution σ(T) is about 50 ps near the counter ends and 63 ps at the center.     

兰州重离子加速器冷却储存环上强子物理研究计划及现状

An internal target experiment at HIRFL-CSRm is planned for hadron physics, which focuses on hadron spectroscopy, polarized strangeness production and medium effect. A conceptual design of Hadron Physics Lanzhou Spectrometer (HPLUS) is discussed. Related computing framework involves event generation, simulation, reconstruction and final analysis. The R & D works on internal target facilities and sub-detectors are presented briefly.     

CSRm束流径向和轴向振荡的耦合

 介绍了由于磁铁的安装误差和螺线管的存在而造成的束流径向和轴向的耦合，以及耦合对束流稳定的影响。结合CSRm结构的典型参数分析得出：二极磁铁和四极磁铁在纵向角安装偏差为-0.5~0.5 mrad；有螺线管存在的情况下，工作点落在和共振线时，将导致束流不稳定而大量损失，落在差共振线时，束流稳定。通过模拟计算发现：螺线管产生的耦合远大于磁铁的纵向角安装偏差产生的耦合。     

RIBLL2上放射性次级束粒子鉴别能力的提升

为了提升兰州重离子加速器冷却存储环(HIRFL-CSR)中放射性次级束流装置(RIBLL2)的粒子鉴别能力,在其F1色散面上研发、安装了一套可测量核反应产物起始时间和位置等信息的新型高性能探测器,并发展了一种利用测量的位置及飞行时间等实验数据提取束线光学参数从而修正粒子磁刚度的实验方法。使用F1色散面上的新型探测器,再结合粒子磁刚度修正方法,首次在RIBLL2-ETF分离器上实现了全动量接收度下300 MeV/nucleon 78Kr弹核碎裂产物的清楚鉴别,结果显示:对于较重的75As33+,其电荷分辨σ_Z~0.19、质核比分辨σ_A/Z~5.8×10?3。这一结果,有效提升了RIBLL2粒子鉴别能力,增加了奇异核收集效率,使研究范围由低质量核区(A<40)拓展到了中等质量核区(A~80),这将有效促进RIBLL2上放射性次级束物理实验的发展。     

HIRFL-CSRm纵向随机冷却-槽形滤波冷却模拟研究

 通过Fokker Planck方程,对拟在HIRFL-CSRm上建造的纵向槽形滤波器（notch filter）的冷却机理进行了研究,得出了冷却原理及冷却时间的表达式,并对影响冷却时间和冷却效果的因素进行了模拟和讨论,模拟结果表明,噪信比越小,冷却时间越短,冷却效果越好;带宽越宽冷却越快。该研究为具体纵向冷却系统的设计和优化提供了依据。