Measurement of the response function and the detection efficiency of an organic liquid scintillator for neutrons between 1 and 30 MeV

The light output function of a φ50.8 mm×50.8 mm BC501A scintillation detector was measured in the neutron energy region of 1 to 30 MeV by fitting the pulse height (PH) spectra for neutrons with the simulations from the NRESP code at the edge range. Using the new light output function, the neutron detection efficiency was determined with two Monte-Carlo codes, NEFF and SCINFUL. The calculated efficiency was corrected by comparing the simulated PH spectra with the measured ones. The determined efficiency was verified at the near threshold region and normalized with a Proton-Recoil-Telescope (PRT) at the 8-14 MeV energy region.     

用于中国散裂中子源多功能反射谱仪的高气压多丝正比室探测器的研制

中国散裂中子源需要建设一台多功能反射谱仪中子探测器,满足在10年运行期间内,50%(@2A)以上的探测效率、好于2 mm的二维位置分辨、200 mm×200 mm的灵敏面积、3倍的n/γ分辨能力及良好的二维成像性能.基于此要求,探测器因此采用基于高气压~3He气体的多丝正比室,并以满足反射谱仪的探测效率、位置分辨、长期稳定工作和n/y分辨能力为目标进行探测器的设计.本文经过模拟和实验计算得出:以9 mm厚的铝合金入射窗、铝丝密封的高气压腔体和6 bar~3He+2.5 bar C_3H_8的工作气体的设计,可满足探测器对2 A中子10年运行期间内54%以上的探测效率要求;探测器对中子的位置分辨可达到1.4 mm左右;设计的气体净化系统,拥有2 L/min的气流速度可有效去除探测器内的负电性杂质气体,气体循环净化后可提高探测器约27%的气体增益,保证探测器长期稳定的运行;通过对~(252)Cf中子源的能谱测量和成像测量,得出探测器的n/γ分辨能力在5倍以上和均匀的成像结果.研制的探测器满足反射谱仪需求,并已在中国散裂中子源反射谱仪靶站就位联调.     

X-ray tube spectra measurement and correction using a CdTe detector and an analytic response matrix for photon energies up to 160 keV

The aims of our work were: i) to measure selected normalized X-ray beam spectra with the commercially available cadmium telluride detector based spectrometry system; ii) to construct the approximate response matrix of the detector using a simple algebraic model approach; iii) to reconstruct the physical energy spectra from the measured instrumental spectra using the detector response matrix; iv) to compare the obtained spectra parameters with the published and reference data in order to verify the model and to optimize the measurement setup if necessary. In particular, the spectra of five “narrow-spectrum series” beams, namely N60 to N150, were measured with a spectrometry system consisting of the Amptek XR-100T X-ray semiconductor detector and the PX5 multichannel analyser. Two different measuring geometries were used. The response matrix R(E, E′) of the detector was constructed which quantifies the energy dependence of the relative detection efficiency of the detector, the probabilities of the escape effects, and the probability of the Compton effect. A single matrix operation was applied to recover the physical energy spectra from the measured instrumental ones. The parameters of the corrected spectra were compared with the published and reference data. Despite the fact that the effect of incomplete charge collection was not implemented in the detector model, a fully satisfying quantitative correspondence was observed between the measured corrected spectra and the available reference data.     

中国散裂中子源小角中子散射谱仪探测器研制

中子小角散射探测器是小角散射（SANS）谱仪的关键设备之一,探测器要求有足够大的探测面积、较高的探测效率及较好的空间分辨率,能够在真空腔中稳定地工作并可在腔体内前后移动。综合考虑,SANS探测器采用120只8 mm直径位置灵敏3He管,组成有效面积1 000 mm（X）×1 020 mm（Y）的二维探测器阵列。探测器阵列分为10个模块,每一个模块功能完全独立,包括12只3He管及其对应的读出电子学和数据获取系统。读出电子学位于探测器背面的回字形密闭腔体内,由CSNS电子学组自主研发。SANS探测器从设计、选型、样机、调试到安装历时三年,中子束流实验结果显示探测器探测效率大于50%（@2Å）,空间分辨率好于10 mm（FWHM）,完全达到设计要求,目前正在中国散裂中子源小角散射谱仪运行使用。     

兰州充气谱仪的焦平面探测系统

在兰州充气谱仪上,设计安装了一套新的焦平面探测系统,该系统包括飞行时间(TOF) 探测器、盒型硅(Si-box) 探测器阵列和反符合(Veto) 探测器3 部分。Si-box 探测器阵列是由3 块位置灵敏硅探测器(PSSD) 和8 块周边硅探测器(SSD) 构成,它对注入核的 衰变的探测效率达到80% 左右。Si-box 探测器阵列与TOF 探测器关联可以有效区分注入信号和 衰变信号。Veto 探测器与Si-box 探测器阵列和TOF 探测器关联可以反符合掉高能轻粒子对注入信号和 衰变信号的干扰。简要介绍了PSSD 的能量和位置刻度方法。这套探测器系统已经应用于40Ca+175Lu 和40Ca+169Tm 的实验。实验结果表明,该探测器系统具备很好的本底抑制能力,能够给出干净的a衰变能谱,结合能量-时间-位置关联测量方法可以实现对单原子的探测和鉴别,总体上达到了预期的设计要求。A new designed focal plane detection system was mounted at the gas-filled recoil separator at Institute of Modern Physics, Chinese Academy of Sciences, which consisted of a time-of-flight (TOF) detector, a silicon-box (Sibox) detector array and a silicon veto detector. Three position sensitive silicon detectors (PSSD) were surrounded by eight side silicon detectors (SSD) without position sensitive, forming a box of the detector open from the front side. The detection efficiency for -decays of implanted nuclei was about 80%. The anticoincidence condition for the signals from the TOF detector and Si-box detector array was used to distinguish between the pulses originating from the implanted nuclei and their -decays. The veto detector information was used to discriminate events due to high-energy charged particles．External energy calibration and position calibration of PSSD are described concisely in this work. This systemhas been used in experiments of 40Ca+175Lu and 40Ca+169Tm. Clean a-decay spectra obtained in these reactions indicated the detection system has a good performance in background suppression. Evaporation residues can be identified by the energy-time-position correlation method. On the whole, the new designed focal plane detection system has achieved thedesign requirements.     

THE INVESTIGATION OF THE HIGH DENSITY MULTIWIRE PROPORTIONAL CHAMBER AS A DETECTOR FOR NEUTRAL PARTICLES

This paper describes a position sensitive multiwire proportional chamber with effective area of 200×200mm². The chamber combining with multi-layer lead γ-ray converter form a high density multiwire proportional chamber γ-ray detector. The lead converter is made in auniformly arranged matrix of 0.9mm diameter holes on a 1.1mm pitch. For 511keV photons the detection efficiency is 5.6%, and the spatial resolution is 1mm. The detector has been used in the investigation of positron camera, it also offers possibility for X-ray detection.     

Performance optimization of a deep-sea scintillation gamma detector

Processes attendant to the propagation of gammas in the sea water, in the wall of an immersed detector, and in a scintillator are simulated by the Monte Carlo method. The Compton spectra recorded by a deep-sea scintillation detector are simulated as a function of the wall thickness for two design versions of the detector. From the photoabsorption peak, the properties of wall materials, V-95 and steel 40, are compared. The background spectra of gammas generated in the scintillator are calculated. It is shown that a reasonable increase in the dimensions of the detector (without increasing those of the scintillator) improves the gamma detection efficiency.     

Influence of electron irradiation on properties of semi-insulating GaAs detectors

The effects of electron beam irradiation on electrical and spectrometric properties of semi-insulating (SI) GaAs detectors were studied. The electric properties were monitored by reverse and forward current–voltage characteristics. In general, a breakdown voltage decrease with the dose was observed. However, some samples showed a local increase in the breakdown voltage at doses between 5 and 10?kGy. The detector spectrometric properties (the charge collection efficiency (CCE), the energy resolution and the detection efficiency) were evaluated from measured spectra of the ²⁴¹Am radionuclide gamma source before and after electron irradiation. The CCE and energy resolution showed minor changes after irradiation. The detection efficiency noticed an initial increase (up to a dose of 5?kGy) followed by a permanent decrease. At 30?kGy, the overall degradation of detector functionality was observed with all samples.     

基于虚拟点探测器的虚拟点源效率刻度技术

主要针对尺寸为?75 mm×25 mm的241Am标准体源HPGe探测器探测效率展开研究,通过LabSOCS软件模拟及蒙卡计算研究发现,使用同一种结构类型的探测器测量特定形状的体源,其虚拟点探测器位置与虚拟点源位置满足线性、二次函数、指数等关系。针对确定的探测器,通过点源在对称轴线上不同高度位置实验就可以标定出虚拟点探测器位置,再结合它们的线性函数进一步计算出虚拟点源位置,最后将点源放置于虚拟点位置刻度即可得到体源的探测效率。因此,该技术方法首次提出通过虚拟点探测器位置找到了虚拟点源的位置,是一种全新的刻度方法,已达到实际应用的程度,可以大面积推广应用该技术成果。     

基于10B4C转换体的多层多丝正比室中子探测器模拟

随着国内高通量中子源及中子散射谱仪的快速发展,对高探测效率、高位置分辨、低伽玛灵敏度的位置灵敏型热中子探测器需求日益迫切。目前国际上中子散射谱仪大多数采用了基于3He的热中子探测器,由于当前3He价格昂贵,寻求3He替代型热中子探测器的相关研究任务紧迫。提出了一种基于10B₄C转换体的多层多丝正比室新型二维位置灵敏型热中子探测器,并利用蒙特卡罗模拟软件Geant4和Garfield++对其探测效率、位置分辨、n/γ抑制比等性能展开了详细的模拟研究。结果表明,当多丝正比室单元为40层,阈值为200 keV时,热中子（E=0.025 eV）探测效率可达到~54%,位置分辨为2.6 mm （FWHM）,n/γ抑制比为~107,可以满足大多数中子散射谱仪的需求,为此类探测器设计及实验研究提供了理论依据。As the development of high flux neutron sources and neutron scattering spectrometers in China, more and more neutron detectors with high detection efficiency, high position resolution, high time resolution and low gamma sensitivity are need ungently. 3He based neutron detector is one of the best options. Recently, because of the 3He gas shortage and its expensive price, we must find a new replacement of 3He. A two-dimensional position sensitive neutron detector based on multi-layer Multi Wires Proportional Chambers (mMWPC) with 10B₄C converter was proposed in this paper. The neutron detection efficiency, position resolution and γ compression were simulated with Geant4 and Garfield++. The results show that with 40 layers of neutron convertor, high themal neutron (E=0.025 eV) detection of~54%, best position resolution of 2.6 mm (FWHM) and high n/γ rejection ratio of~107 with the threshold of 200 keV can be achieved, which can meet the requirements of most spectrometers. This simulation results lay a good foundation for the next step of detector construction and test.     

GdBr3:Ce in glass matrix as nuclear spectroscopy detector

An alumina-silica glass cylinder with cerium-activated gadolinium bromide, 2.5 cm in diameter and 3 cm long was cast to form a scintillation detector for spectral analysis of nuclear radiation, especially gamma rays. The detector, operated with a conventional photomultiplier tube and associated power supply, amplifier, and multichannel analyzer, shows for the first time for this material system a set of spectra that include well-defined full-energy gamma-ray peaks from 59.5 keV to 2500 keV. The full-energy peaks were characterized in terms of pulse height linearity, resolution, and counting efficiency. Energy spectral resolution also was demonstrated for alpha particles, beta particles, and ²³⁹Pu/Be neutrons. Gamma-ray detection efficiency was comparable to a conventional NaI(Tl) detector of similar volume but peak resolution at 662 keV in this new detector type was currently only 27%, compared to about 7% for the NaI(Tl) detector. Improved light output and thus resolution is being sought by optimizing glass compositions and processing.     

一种基于MEMS光栅光调制器的近红外光谱探测系统

基于微机电系统技术的近红外光谱探测系统已成为了近红外光谱仪研究的一个新方向。文章提出了一种基于光栅光调制器的新型近红外光谱探测系统。该系统采用微加工技术制造的光栅光调制器阵列与单点近红外探测器相结合使用的方法进行光谱探测。设计了该光谱探测系统的光学结构, 论述了系统光谱探测原理, 并使用经表面微加工工艺得到的光栅光调制器器件进行了系统分辨本领、波长准确性、系统稳定性、器件响应频率等特征参数测试实验。结果表明,该探测系统在1 320到1 400 nm波长范围内,分辨本领小于10 nm, 波长准确性小于1 nm, 系统稳定性小于0.5%, 光栅光调制器的响应频率为5kHz。实验结果证明了该近红外光谱探测系统的可行性, 为研制基于微机电系统光栅光调制器的微型化近红外光谱仪提供了理论基础及实验指导。     

散裂中子源高气压二维位置灵敏3He探测器的实验研究

为满足中国散裂中子源多功能反射谱仪中子探测器的基本物理要求:有效面积达到200 mm×200 mm、探测效率大于50%（2Å）、位置分辨好于2 mm等,中国科学院高能物理研究所研制了3He高气压二维多丝正比室位置灵敏中子探测器。该探测器采用二维多丝室结构,腔体内充3He/C₃H₈（6 atm/2.5 atm）的组合气体。本文首先利用Am/Be中子源完成对探测器全面积均匀性测试,均匀性指标达到了95.1%;探测器在中国散裂中子源的20号束流线站安装后,对其进行了在束测量,通过飞行时间选取波长2.8Å的慢中子,测量了探测器二维位置分辨和二维成像性能。在X方向（垂直于阳极丝的方向）的位置分辨为0.99 mm,Y方向（平行于阳极丝的方向）的位置分辨为1.36 mm,探测器具有很好的二维位置分辨和二维成像能力。测量结果表明探测器满足反射谱仪的研制要求。     

Two-dimensional thermal neutron detector

A two-dimensional thermal neutron detector for neutron diffraction experiments has been developed and designed at the St. Petersburg Nuclear Physics Institute, Russian Academy of Sciences. The detector is based on a multiwire proportional chamber with cathode-strip delay line readout. The detector aperture is 170 × 300 mm² and the anode wire spacing is 4 mm. The chamber is filled with a 1.5 atm ³He + 2 atm CF₄ gas mixture. To conserve high purity of the gas mixture, all electrodes are made of quartz glass. The spatial resolution of the detector is 2.5 mm and the detection efficiency is 60% for 9 Å neutrons.     

用于GPPD谱仪的大面积闪烁体中子探测器性能测试

中国散裂中子源（Chinese Spallation Neutron Source,CSNS）的建成为中子散射技术的发展和应用奠定了基础。通用粉末衍射谱仪（general purpose powder diffractometer,GPPD）是CSNS一期建设的三条谱仪之一。研制了用于GPPD的大面积闪烁体探测器阵列,在CSNS的BL20中子束线上开展了探测器关键性能参数的实验测试。测试结果显示,对波长为1.4 Å和2.8 Å的中子,其探测效率分别为（38.5±1.7）%和（56.1±1.1）%,模拟与实验相结合,给出对2 Å的中子,其探测效率约为（46.1±2.0）%,有效面积内的探测效率不均匀度约为19.6%,经优化后可以降低到14.9%;探测器位置分辨可以达到4.0 mm×4.0 mm,最高计数率约79 kHz。探测器单元的整体性能指标能满足GPPD的物理需求。     

CdZnTe像素探测器的电输运性能

碲锌镉(CdZnTe)是一种性能优异的室温核辐射半导体探测器材料,广泛应用于核安全、核医学以及空间科学等领域.然而,传统的CdZnTe平面探测器受制于"空穴拖尾"效应的影响,探测性能有待改善.采用改进的垂直布里奇曼法生长的In掺杂Cd_(0.9)Zn_(0.1)Te单晶制备出单载流子收集的4×4像素阵列探测器,通过电流-电压(I-V)测试和γ射线能谱响应测试,研究了像素探测器的电学性能和载流子电输运性能,随之与相应的CdZnTe平面探测器进行了性能对比.结果表明,CdZnTe像素探测器的电阻率约为1.73×10~(10)?·cm,且施加100 V偏压后单像素点的最大漏电流小于2.2 nA;当施加偏压升高至300 V时,单像素点对~(241)Am@59.5 keV的γ射线的最佳能量分辨率可达5.78%,探测性能优于相同条件下制备的CdZnTe平面探测器.     

使用曲面微通道板和感应电荷位置灵敏阳极的软X射线-极紫外光子计数成像探测器研究

本项目对我国空间探测的极紫外(EUV)波段大视场相机所需求的球面光子计数成像探测器的关键技术进行了研究。首先,建立了光阴极材料次级电子产出模型,利用该模型计算了软X射线-EUV波段常用的光电阴极材料—碱卤化物的次级电子产出,分析了微通道板(MCP)的次级电子产出。建立了测量MCP量子探测效率的装置,并推导出MCP量子探测效率的计算公式,测量了MCP在软X射线-EUV波段的量子效率以及MCP量子效率随掠入射角的变化。其次,建立了球面实芯微通道板的制备装置,利用高温热成型方法制备出曲率半径为150 mm球面MCP,利用光刻技术制备出有效直径为48 mm的楔条形感应电荷位置灵敏阳极,在此基础上集成了一套使用球面MCP和感应电荷位置灵敏阳极的两维光子计数成像探测器。再次,研制出包括快速前端模拟电路与后续数字电路的成像读出电路,编制了能矫正图像畸变的图像实时采集和处理软件。最后,建立了MCP探测器空间分辨率、图像线性的检测装置,对研制出的探测器性能进行了检测,检测结果表明:探测器的各项技术指标完全满足要求。     

A stopping layer concept to improve the spatial resolution of gas-electron-multiplier neutron detector

In recent years, gas electron multiplier (GEM) neutron detectors have been developing towards high spatial resolution and high dynamic counting range. We propose a novel concept of an Al stopping layer to enable the detector to achieve sub-millimeter (sub-mm) spatial resolution. The neutron conversion layer is coated with the Al stopping layer to limit the emission angle of ions into the drift region. The short track projection of ions is obtained on the signal readout board, and the detector would get good spatial resolution. The spatial resolutions of the GEM neutron detector with the Al stopping layer are simulated and optimized based on Geant4GarfieldInterface. The spatial resolution of the detector is 0.76 mm and the thermal neutron detection efficiency is about 0.01% when the Al stopping layer is 3.0 μ m thick, the drift region is 2 mm thick, the strip pitch is 600 μ m, and the digital readout is employed. Thus, the GEM neutron detector with a simple detector structure and a fast readout mode is developed to obtain a high spatial resolution and high dynamic counting range. It could be used for the direct measurement of a high-flux neutron beam, such as Bragg transmission imaging, very small-angle scattering neutron detection and neutron beam diagnostic.     

Differential non-destructive image current detection in a fourier transform quadrupole ion trap

Dual-detector differential non-destructive Fourier transform detection in a quadrupole ion trap is shown to improve signal intensity and reduce noise compared with spectra recorded using a single detector. A larger area detector in each end-cap electrode is machined to fit its hyperbolic shape and so minimize field imperfections on the z-axis. Argon, acetophenone and bromobenzene spectra were recorded to allow a comparison between single- and dual-detector (differential) modes of detection and to demonstrate the improvement achieved with differential detection. Copyright 1999 John Wiley & Sons, Ltd.     

The Monte-Carlo simulation on a scintillator neutron detector

A simulation of the properties of the shifting scintillator neutron detector using 6LiF/ZnS(Ag) scintillation screens is performed.The simulation results show that the light attenuation length of standard BC704 scintillator is about 0.65 mm.Its thermal neutron detection efficiency,gamma sensitivity and intrinsic spatial resolution can achieve around 50.0%,10 5and 0.18 mm(along X-axis) respectively.For the detector,air coupling position resolution is better than the silicone oil coupling.Some of the simulation results are compared with experimental results.They are in agreement.This work will be helpful for constructing neutron detector for high intensity powder diffractometer at Chinese spallation neutron source.