方兴未艾的微单元结构气体探测器

介绍了微单元结构位置灵敏气体探测器的发展近况，探讨了其在生物医学中的应用前景及利用模拟计算软件辅助设计和研制气体探测器的方法。     

A 16-Channel high-resolution time and charge measurement module for the external target experiment in the CSR of HIRFL

High precision time measurement is required in the readout of the neutron wall and TOF walls in the ex- ternal target experiment of the Cooling Storage Ring （CSR） project in the Heavy Ion Research Facility in Lanzhou （HIRFL）. Considering the time walk correction, both time and charge are measured in the readout electronics. In this 16-channel measurement module, time and charge information are digitized by TDCs at the same time based on the Time-Over-Threshold （TOT） method; meanwhile, by employing high-density ASIC chips, the electronics complexity is effectively reduced. Test results indicate that this module achieves a time resolution better than 25 ps and a charge resolution better than 5% over the input amplitude range from 50 mV to 3V.     

Design and tests of the prototype a beam monitor of the CSR external target experiment

A prototype beam monitor was designed to provide tracking information for heavy-ion projectiles for the cool storage ring(CSR) external target experiment(CEE) at the Heavy Ion Research Facility in Lanzhou(HIRFL). High granularity and direct charge sensing are the main features of this device. It measures the beam position in a two-dimensional(2D) plane transverse to the beam direction on an event-by-event basis. The current design consists of two field cages inside a single vessel that operates ...     

Unavailability analysis of a lithium target system for a test facility

For an experimental facility like the International Fusion Materials Irradiation Facility, safety, performance and reliability are outstanding attributes. The results of an analysis aimed at estimating the unavailability figure of the target system and evaluating the expected performance of the plant, in terms of safe and reliable operation, are presented in this article. Starting points of the analysis have been the identification of relevant plant functions and relationships between plant systems and functions and the definition of relationships among the systems themselves. Fault tree technique has been adopted to address the topic: with regard to the reference configuration, systems boundaries and interfaces have been identified as well as the dependent failures between systems and components. Due to the novelty of the plant and its prototypical character, reliability data introduced in the numerical simulation underwent an accurate screening process among the current available databases, sometimes requiring the expert judgment assessment. Finally an uncertainty, importance and sensitivity analysis has been performed in order to add credit to the model and to highlight reliability-critical systems and components: results are analyzed to assess the compliance with the plant availability requirements and design criteria. Risk Spectrum code has been utilized for the system unavailability quantification.     

Structural design of beam transport system in SGIII facility target area

Beam transport system in ShenGuangIII (SGIII) facility target area brings 48 laser beams from main laser output to final optics assemblies (FOAs). This paper will present a summary of structural design of SGIII target area beam transport system, which include 276 transport mirrors and nearly 3000 m beam enclosures. The key performance of the beam transport system structural design includes stability, accuracy and cleanliness. To ensure the vibrational stability requirement, the beam transport system is located on stable platforms comprised of switchyard steel space frame and experimental area steel reinforced concrete building. The high fundamental frequency of the transport mirror system and vibrational isolation from thin tubes are designed to decrease the vibration response of the mirrors. An analytical method is proposed to evaluate the structural design on the drifting error of each laser beam obtained by accounting the dynamic responses of each optical elements of laser beam. The adjusting and fast replacement online requirements are satisfied by the structural design of line replaceable units (LRUs), the adjustable kinematic mounts, and the low-stress clamping of mirror mounts. The cleanliness is established in the process of designing, fabrication, and operation simultaneously. Testing results of the beam transport system that has been installed indicate that the structural design satisfies the performance requirements of the facility.     

A high-resolution small animal SPECT system developed at Tsinghua

An SPECT system dedicated to small animal imaging shall be of a millimeter spatial resolution or even better.This study was aimed at achieving 0.5-mm spatial resolution for a small animal SPECT system at low cost.It was developed from a single-head clinical SPECT scanner,with a seven-pinhole collimator and a four-degree-offreedom motion control stage.Several key techniques were developed,including high-resolution image reconstruction algorithm,high accuracy geometrical calibration method,and optimized system matrix derivation scheme.The system matrix was derived from Monte-Carlo simulation and de-noised by fitting each point spread function to a two dimensional Gaussian function.Experiments of point source and ultra micro hot rod phantom were conducted.With a spatial resolution of 0.5-0.6 mm,this system provides a practical way for low-cost high-resolution animal imaging on a clinic SPECT system.     

Information-analytical system for tracking the rehabilitation of a temporary storage facility for spent nuclear fuel and radioactive wastes in the village of Gremikha

An information-analytical system for solving various problems facing developers and implementing agencies at all stages of work has been developed at Russian Science Center Kurchatov Institute as part of a project for ecological rehabilitation of a temporary storage site located in the village of Gremikha for nuclear fuel and radioactive wastes. The information-analytical system accumulates all information on the project: technical characteristics of the objects, cartographic information, documentation, and information on the participants of the project, technologies, and equipment. The centralized storage of the initial data and the data obtained from examinations makes its use effective for all participants of the project. Analysis of the stored information and the formation of structured sets of data are necessary for planning further work on the project and choosing concrete design solutions, exchanging information between participants in the work, and providing information to state organs and the public.     

BEPC试验束数据获取系统改进及离线数据分析

运行在BEPC电子直线加速器上的试验束,主要利用在线探测器和离线数据分析选择单粒子事例,满足多种单粒子束流试验.本文介绍了试验束改进后的数据获取系统,以及离线数据分析中的飞行时间谱分析,单粒子判选和粒子击中位置定位等.     

晶体表面特性对PET探测器性能的影响

<正>电子发射断层成像(Positron Emission Tomography,PET)作为最灵敏和具有定量测量能力的功能分子影像技术,越来越广泛地应用于生物医学研究,如疾病的动物模型、新药物的研发和新治疗方法的评估等。提高探测器的性能是改进PET仪器性能的关键,PET探测器通常由分割的闪烁晶体阵列和光探测器组成,文中使用位置灵敏光电倍增管和不同晶体表面特性的硅酸钇镥((Lu,Y)2Si O5,LYSO)晶体阵列,对新型的双端读出三维PET探测器和传统的单端读出二维PET探测器的性能进行了测量。实验结果表明,对于双端读出PET探测器,两种晶体阵列提供相近的晶体分辨图和能量分辨率,但非抛光晶体阵列提供好的深度分辨率,双端读出PET探测器需要使用表面不抛光的晶体阵列;对单端读出PET探测器,抛光晶体阵列提供好的晶体分布图和能量分辨率,单端读出PET探测器需要使用表面抛光的晶体阵列。     

一种新型X射线相衬成像实验室系统

目前的X射线相衬成像研究大都采用同步辐射光源。光源点尺寸达微米量级的X射线管辐射具有较好的空间相干性，也可用于相衬成像研究。本文报道了一种基于纳聚焦x射线管的新型相衬成像实验室系统，光源点尺寸可达500nm。实验结果表明，该系统可对低Z样品如生物软组织、有机样品等的内部结构成清晰像，分辨率可达微米量级。与已有系统相比较，其空间分辨率和有效通量都有相当大的提高。锥形光束张角约为300，通过纵向扫描机构调节样品与光源点间距可调整投影放大率，从而降低对探测器分辨率的要求。适用于大样品研究，且可实现样品的横向二维扫描。在医学、生物学、材料科学及化学反应动力学等领域有重要应用前景。     

Characteristics of parallel-hole and pinhole collimators for nuclear medicine imaging

In this paper,the spatial resolution and geometry sensitivity of parallel- and pin-hole collimators in compact gamma camera are presented,and quantitatively compared by GEANT4 code in Monte-Carlo library.The results show that the geometry sensitivity for pinhole collimator rapidly drops with increasing the gamma source-to- collimator distance(SCD);and for parallel-hole collimator,mildly.Meanwhile,the spatial resolution for pin-hole collimator mildly deteriorates;and for parallel-hole collimator,severely.The pin-hole collimator for close imaging objects has higher geometry sensitivity than parallel-hole collimator.Our findings are helpful for setting compact gamma camera collimators in nuclear medicine imaging.     

Scan system for arbitrary-shaped samples at the synchrotron radiation facility

X-ray fluorescence (XRF) scan methodology is important for elemental mapping of samples at a synchrotron radiation facility.To save the experiment time and improve the experiment efficiency,one should develop an efficient XRF scan method.In this paper,a new scan mode is presented.It can map arbitrary-shaped areas without stopping the motors.The control and data acquisition system integrates motor controlling,detector triggering,and data acquisition and storage.The system realizes the arbitrary-shaped 2D-mapping and fluorescence data acquisition synchronously.SR-XRF mapping has been performed with a standard gold mask to verify the validity of this method at beamline BL15U1 of the Shanghai Synchrotron Radiation Facility.The results show that this method reduces the total scan time and improves the experiment efficiency.     

Safety assessment of the lithium target of the international fusion materials irradiation facility

This article presents the international fusion materials irradiation facility lithium target safety and thermal transient analysis, to evaluate the most important risk factors related to the system operation and to verify the fulfillment of the safety criteria. Main conclusions are that target safety is accomplished: hazards associated with lithium operation are confined within the IFMIF security boundaries and environmental impact is negligible, and the plant well answers to the simulated transients, being able to reach steady conditions in a condition of safety.     

近物所反冲谱仪端的转靶系统研制

介绍了中国科学院近代物理研究所研制的一套用于低熔点靶材料的转靶系统.靶盘上用于实验且厚度0.4-0.6 mg/cm2的C/Pb/C夹心靶,在束斑为0.785 cm2、流强～1 eμA、能量为5.84 MeV/u的24Mg7+束和流强～0.1pμA、能量4.95 MeV/u的64Ni19+束长时间照射下未损坏,照射总剂量...     

大面积位置灵敏中低能中子谱仪的时间刻度系统的研究

在利用飞行时间法测量中子位置和能量的大面积位置灵敏中子谱仪的研制过程中,提出了利用“绝对时间差”刻度的方法来测量各个电子学的相对时间,系统研究了对光电倍增管时间分辨影响的因素,其中包括光源的种类、光源的发光时间等,并得到使光电倍增管的时间分辨达到最佳60ps的实验条件。     

Analytical reconstruction scheme for the coarse-mesh solution generated by the spectral nodal method for neutral particle discrete ordinates transport model in slab geometry

Coarse-mesh numerical methods are very efficient in the sense that they generate accurate results in short computational time, as the number of floating point operations generally decrease, as a result of the reduced number of mesh points. On the other hand, they generate numerical solutions that do not give detailed information on the problem solution profile, as the grid points can be located considerably away from each other. In this paper we describe two steps for the analytical reconstruction of the coarse-mesh solution generated by the spectral nodal method for neutral particle discrete ordinates (S_N) transport model in slab geometry. The first step of the algorithm is based on the analytical reconstruction of the coarse-mesh solution within each discretization cell of the grid set up on the spatial domain. The second step is based on the angular reconstruction of the discrete ordinates solution between two contiguous ordinates of the angular quadrature set used in the S_N model. Numerical results are given so we can illustrate the accuracy of the two reconstruction techniques, as described in this paper.     

Development of a compact high resolution gamma-ray detector for E-CT applications

A compact gamma-ray detector with good spatial resolution for emission computed tomography (E-CT) applications has been developed. The detector is composed of NaI(Tl) scintillation pixels array and Hamamastu R2486-05 PSPMT. Having a pixel size of 2 mm × 2 mm and an overall dimension of 48.2 mm × 48.2mm × 5 mm, it has 484 pixels in a 22×22 matrix. An average spatial resolution of 2.5mm (FWHM) was achieved. The slope of position linearity is constant within 10% in a range of 40mm. After corrections, the average value of differential non-linearity and absolute non-linearity were 0.16mm and 0.535mm respectively, and a 17% at FWHM of total energy resolution for 241Am was obtained.     

A new TOF system for target recoil-ion momentum spectroscopy at IMP

A high resolution time measurement system with high data transfer rate was designed for the COLTRIMS (Cold Target Recoil-Ion Momentum Spectroscopy) system in Institute of Modern Physics,Chinese Academy of Sciences.It is used to measure the Time of Flight(TOF) with a high resolution for all 20 channels.Based on the PCI Extensions for Instrumentation(PXI) standard,the readout electronics system consists of one Clock-Trigger fan-out module and four TOF modules.Test results show that the system meets the demands of COLTRIMS,with a time resolution of better than 25 ps and a data transfer rate over 20 MB/s.     

SADHANA facility for simulation of natural convection in the SGDHR system of PFBR

The Prototype Fast Breeder Reactor (PFBR) is a 500 MWe sodium cooled pool type fast reactor being constructed at Kalpakkam, India. PFBR has all the reactor components immersed in the pool of sodium and the fission heat generated in the core, is removed by the sodium circulating in the pool. During normal operation this fission heat is transferred by primary sodium to secondary sodium, which in turn transfers the heat to water in the steam generator for producing steam. The removal of the decay heat generated in the reactor core after the reactor shutdown is also very important to maintain the structural integrity of reactor core components. PFBR employs two independent systems namely, Operational Grade Decay Heat Removal system (OGDHRS) and Safety Grade Decay Heat Removal System (SGDHRS) for decay heat removal. SGDHR system is a passive system working on natural convection to ensure the core coolability even under station blackout condition. It is very important to study the thermal hydraulic behavior of Safety Grade Decay Heat Removal system of PFBR to ensure its reliable operation. A scaled down model of the circuit, named SADHANA has been modeled, designed, constructed and commissioned for demonstration and evaluation of these systems. The facility has completed around 2000 h of high temperature operation. The performance of the experimental system is satisfactory and it meets all the design requirements. At 550 °C sodium pool temperature in test vessel the secondary sodium loop generated a sodium flow of 6.7 m³/h. These experiments have revealed the adequacy and capability of SGDHR system to remove the decay heat from the fast breeder reactor core after its shutdown.     

CSR系统终端中子墙光电倍增管时间型分压系统的应用研究

在兰州重离子加速器冷却储存环将要建设的外靶实验终端上，中子墙探测装置是用来开展放射性束物理以及利用放射性束开展非对称核物质性质研究的一个重要的实验设备。本文对应用于该实验装置上的光电倍增管分压系统进行了研究，给出了适合时间性能探测的时间型分压器设计参数以及测试结果。