Design of a Preamplifier Card for the Photomultiplier Tubes of a Gamma Camera

The service provided by the GC(Gamma Cameras)in the Nuclear Medicine departments fails because of their breakdown,generally due to the associated electronics and not to the physical detection components.For this reason,it was decided to develop an electronic system that allows the recovery and optimization of disused GC,starting with the design of the preamplifier for a PMT(photomultiplier tube).The circuit was designed and simulated and the list of components necessary for the construction of the preamplifier was generated,as well as the printed circuit board was designed for its assembly.By simulating the preamplifier this worked in linear mode.This determines that the amplitude of the output signal is proportional to the amount of charge delivered by the detector.This card allows an automatic adjustment of the signals of the PMT as do the modern GC.

A versatile test bench for photomultiplier tube characterization and its application in the DAMPE-PSD

Performance characterization for massive photomultiplier tubes(PMTs) is a frequently encountered procedure in large nuclear and particle experiments.To facilitate this work,a dedicated test bench system has been developed at the Institute of Modern Physics,Chinese Academy of Sciences.The two-dimensional photocathode position scanning capability is an intrinsic function of the test bench,and up to 25 PMTs,with the diameter smaller than 2",can be tested simultaneously.The parameters of the light source pulses can be adjusted in a wide range,thus making it suitable for various characteristics measurements.The test bench system is highly automated with all the controlling operations integrated into a single software.Additionally,the hardware platform is extensible which allows complex testing schemes,and the modularity in the software design makes the migration from one testing configuration to another light-weight and efficient.All these features make the test bench versatile and reusable in different experiments.It has been first used in the construction of the Plastic Scintillator Detector(PSD) of DArk Matter Particle Explorer(DAMPE),and a total of 570 Hamamatsu R4443 tubes were tested successfully.The performance was verified and the testing results are also reported in this article.

Study of performance of small gamma camera consisting of crystal pixel array and position sensitive photomultiplier tube

The performance of gamma camera with NaI(Tl) array coupled with position sensitive photomultiplier tube (PSPMT) R2486 has been studied. The pixel size of NaI(Tl) crystal is 2mm×2mm and the overall dimension of the array is 48.2mm×48.2mm×5mm. There are 484 pixels in a 22×22 matrix. Because each pixel can produce a much focused light spot and restrict the spread of photons, position resolution of the gamma camera is mainly determined by pixel size. It is shown that crystal array pixel can reduce shrinkage effect and improve intrinsic position resolution greatly via restricting the spread of photons. Experimental results demonstrate that its position resolution and linearity are much improved comparing with the gamma camera using planar crystals coupled with PSPMT.

A method to measure transit time spread of photomultiplier tubes with Cherenkov light

With the technology of coincidence method, transit time spreads (TTSs) of PMTs are measured with Cherenkov light on the photocathode window of photomultiplier tube (PMT) produced by cascade γ radiation source, 60Co. TTSs with single and multi-photoelectron which are analyzed by convolution of Poisson and Gaussian are obtained. The study to XP2020 and XP2020Q PMTs shows that TTSs are consistent with data supplied by Philips. TTSs are inversely proportional to the square roots of number of photoelectrons. The method is feasible when single and multi-photoelectron can be distinguished.

An active base designed in high-counting-rate applications for Hamamatsu R1924A photomultiplier tube

Hamamatsu R1924A is one of the most widely used photomultiplier tubes(PMTs) in nuclear physics.Since the active base suitable for R1924A is still not available in market, an active base is designed for Hamamatsu R1924A PMT, and the test results at high counting rates are presented. The active bases with two different sets of resistor chains were tested and compared by a frequency-controlled green straw hat LED light. A stable signal output up to 100 kHz is achieved using frequency-controlled LED pulsed light. The temperature of bases, which reflects the power consumption and is crucial for applications in vacuum, is also monitored with the same LED pulsed light. The temperature of the active base with smaller resistances reaches about twice of that of the active base with larger resistances in the resistor chain. For the applications in vacuum, the active base with resistance between the two sets of resistor chains may be preferable.

共聚焦生物芯片扫描仪中PMT电流增益的自动控制

根据共聚焦生物芯片扫描仪获得的图像 ,设计了计算机控制下的PMT电流增益自动控制系统 根据计算生物芯片图像的灰度分布与期望灰度分布的差异 ,得到期望灰度分布时PMT的期望电流增益 ,进而获得PMT的期望控制电压 一个 1 2位数模转换器产生期望控制电压 ,自动控制PMT电流增益的调节 ,控制电压精度高达 2mV 实验结果表明 ,所设计的PMT电流增益自动控制系统可快速、准确地实现PMT电流增益调节 ,并具有稳定性高。

PMT水下内爆冲击波强度与传播特性研究

为研究光电倍增管(PMT)水下内爆后产生的冲击波强度及其传播特性,首先以气泡动力学、气泡破裂动力学理论为基础分析了球形气泡溃灭时长与气泡破裂回弹阶段冲击波传播特性,指出了真空容器水下内爆与气泡溃灭物理过程的相似性和特殊性。建立了水下气泡溃灭数值仿真计算模型,通过与文献实验结果和理论结果的对比验证了数值计算方法的可行性。最后以实际工作环境为基础对PMT水下内爆过程进行了数值模拟,分析了PMT外形尺寸对冲击波传播特性的影响,确定了PMT水下内爆的冲击波强度,为PMT防爆工作提供了针对性的参考。

PMT在测量超高速碰撞闪光趋势中的应用

为了研究超高速碰撞闪光强度和趋势,设计了超高速碰撞闪光光电倍增管测量系统.该测量系统由4通道组成,由光纤探头采集的不同波长的闪光信号经光纤输入光电倍增管,将光信号转换为电信号并放大后输入示波器.通过不同碰撞条件下的二级轻气炮加载实验测出给定位置、方位角和不同碰撞条件下的碰撞闪光趋势,根据测量系统的标定计算出碰撞闪光强度.实验结果表明,碰撞闪光的特点比较明显,强度峰值信号首先出现,其后伴随持续的黑体辐射衰减.

基于日盲PMT的绝缘子表面放电光信号检测系统

绝缘子是电力系统中使用量很大的绝缘设备,绝缘性能下降到一定程度的绝缘子表面可产生放电现象,检测放电辐射出的光信号可用于评估绝缘子的绝缘状况。由于绝缘子表面的放电一般为电晕式的弱放电,辐射出的光信号位于400 nm以下的紫外波段,检测日盲波段紫外光信号不仅有助于发现设备早期的放电现象还能实现白天放电检测。文章选择日盲型光电倍增管作为光信号传感器构建了一套放电紫外光信号检测系统,较详细地介绍了系统的硬件和软件的关键部分,硬件部分实现了光电转换和对信号的调理及采集功能,软件采用了虚拟仪器软件编写,可实现信号的采集控制和分析。测试结果表明,该系统具有线性度好和灵敏度高的特点,但室外较强太阳光对该系统有着一定的干扰作用。通过在实验室检测绝缘子的表面的放电,表明该系统能有效检测绝缘子的表面放电。

PMT电源纹波滤除电路设计

针对基于光电倍增管的计数型探测器易受高压电源纹波干扰的问题,探讨了一种抑制纹波的方法。该方法主要是在电源端增设电阻—电容滤波电路,对高压电源纹波进行事先滤波处理。通过光电倍增管的单光电子谱测试、计数率测试及渡越时间分布验证滤波效果,结果表明:利用该方法,电源的纹波得到有效抑制,减少了电源对光电倍增管单光电子测试信号的干扰,且输出电压稳定,提高了光电倍增管工作的稳定性。

基于模糊理论的PMT水下防爆试验故障树分析

为解决光电倍增管(photomultiplier tubes,简称PMT)水下防爆试验系统的故障诊断问题以及故障发生概率存在模糊不确定性的特点,应用模糊集数学方法和可能性理论,把模糊数学和故障树模型相结合,提出一种基于三角形模糊数算法的PMT试验系统失效模式分析方法。根据试验系统工作原理,采用下行法建立故障树并对其进行定量分析,获得了顶事件的结构函数及多种失效模式,进而利用专家语言评价法,计算顶事件发生的模糊概率和各底事件的模糊重要度,得到了PMT试验中故障发生率较高的环节,最后对故障分析结果进行改进测试。结果表明,该方法能够准确地诊断出存在的故障,为PMT防爆试验系统进行故障诊断以及提高PMT保护罩的水下防爆性能提供参考依据。

一种带纹波补偿的高精度PMT直流高压开关电源

采用一种纹波补偿电路使光电倍增管(PMT)直流高压开关电源的输出纹波幅度大大降低,同时对低频电压漂移也有很好的补偿效果。分析了基于信号交流分量反相叠加的纹波补偿工作原理,设计了纹波补偿电路。对不同频率、不同波形的纹波进行软件仿真,结果表明纹波衰减达40 dB以上,低频电压漂移降低了2个数量级。

能谱探测系统中PMT高压源

能谱探测是当今石油测井行业的一项新技术,文中主要讨论能谱探测系统中光电倍增管PhotoMultiplier Tube(PMT)高压源的设计和调试,该方法具有广泛的应用价值,达到并超过了规定的技术指标。

Database system for managing 20,00020-inch PMTs at JUNO

A database system,known as the large PMT characterization and instrumentation database system(LPMT-CIDS),was designed and implemented for the Jiangmen Underground Neutrino Observatory(JUNO).The system is based on a Linux+Apache+MySQL+PHP(LAMP)server and focuses on modularization and architecture separation.It covers all the testing stages for the 20-inch photomultiplier tubes(PMTs)at JUNO and provides its users with data storage,analysis,and visualization services.Based on the successful use of the system in the 20-inch PMT testing program,its design approach and construction elements can be extended to other projects.

基于Cockcroft-Walton电路的PMT高压电源

根据当前实验室资源的需要合理分配与利用的需求,设计与实现了一种高效率、低纹波的PMT高压电源。该电源主要有LM10CLN电压控制部分,基于Cockcroft-Walton升压电路部分,反馈和保护电路部分和I-V转换部分来实现。最后完成电路的PCB板制作,通过对样品的试验,验证了本方案是可行的。电路运行良好,电路的线性度、纹波大小均符合要求。

一种量能器中可连续调节的PMT高压源

本文主要讨论光电倍增管Photo Multiplier Tubes(PMT)的供电高压源设计和测试,利用数字和分压器两种方法调节,达到了规定指标。

光电倍增管计数温漂自适应补偿方法

光电倍增管是微光探测的重要器件,使用光子计数法对光强进行检测可以大幅降低噪声的干扰,但光电倍增管的阴极灵敏度、增益及暗噪声易受环境温度的影响,导致输出脉冲幅值的不稳定,影响系统对微光的检测性能。本文通过使用微控制单元、数字模拟转换器等模块对光电倍增管设计了高压增益补偿和阈值校正系统,通过对不同温度下光电倍增管的阴极饱和电流、灵敏度和暗噪声的综合分析,构建温度与高压补偿增量Vh及阈值补偿增量Vt混合函数模型,使用补偿增量混合模型对光电倍增管计数输出进行自适应温漂补偿。对滨松的端窗型光电倍增管CR135进行实验,证明了此系统在较大温度变化下仍具有良好的输出信噪比,在-20℃时计数率平均提升0.19,即使引入了少量暗噪声,仍大幅提升了探测性能。

可见光脉冲输入下微通道板光电倍增管的动态范围研究

结合理论分析与实验测试,研究了在可见光脉冲输入条件下频率以及第二片微通道板与阳极之间电势差对微通道板光电倍增管动态范围的影响。研究结果表明:随着信号光脉冲频率的增大,微通道板壁面电荷补充不充分致使阳极输出偏离线性,并逐渐趋于饱和。当输入可见光脉冲宽度为50 ns,频率为500 Hz时,阳极的最大线性输出达到2 V(即40 mA);当输入光频率增加到1000 Hz,阳极输出在1 V(即20 mA)时线性偏离程度达到10%以上;当输入光频率增加到5000 Hz,阳极输出在0.3 V(即6 mA)时线性偏离程度达到约15%。随着第二片微通道板与阳极之间电势差的增大,阳极最大线性输出电压呈现波动性变化而非与其呈线性关系。当第二片微通道板与阳极之间的电势差在200 V左右时,阳极线性输出电压达到峰值,随着电势差不断增大,阳极线性输出电压开始出现波动,在电势差为500 V左右时达到第二个峰值,这主要是由于极板间电场强度与空间电荷效应共同作用的结果。该研究可为提升微通道板光电倍增管的动态范围提供指导,便于其应用于强辐射脉冲测量、激光通信等领域。

Comparative studies of silicon photomultipliers and traditional vacuum photomultiplier tubes

Silicon photomultipliers （SiPMs） are a new generation of semiconductor-based photon counting devices with the merits of low weight, low power consumption and low voltage operation, promising to meet the needs of space particle physics experiments. In this paper, comparative studies of SiPMs and traditional vacuum photomultiplier tubes （PMTs） have been performed regarding the basic properties of dark currents, dark counts and excess noise factors. The intrinsic optical erosstalk effect of SiPMs was evaluated.

光电倍增管双电位聚焦系统设计研究

光电倍增管聚焦系统收集效率是影响光电倍增管性能的关键因素。本文提出了一种双电位聚焦技术,通过二次聚焦,将光电阴极产生的电子束进一步聚焦,通过COMSOL Multiphysics仿真软件对电位差、聚焦极直径、高度等参数进行了仿真优化,使得收集效率可达92.1%以上。通过装管验证,光电倍增管增益提高了14.76%。