Fast Timing Methods for Semiconductor Detectors

This tutorial paper discusses the basic parameters which determine the accuracy of timing measurements and their effect in a practical application, specifically timing with thin-surface barrier detectors. The discussion focusses on properties of the detector, low-noise amplifiers, trigger circuits and time converters. New material presented in this paper includes bipolar transistor input stages with noise performance superior to currently available FETs, "noiseless" input terminations in sub-nanosecond preamplifiers and methods using transmission lines to couple the detector to remotely mounted preamplifiers. Trigger circuits are characterized in terms of effective rise time, equivalent input noise and residual jitter.     

新型快速的Blue—LED快时间探测器标定系统

为了能够连续有规律的监测宇宙线广延大气簇射（ＥＡＳ）阵列快时间探测器和电子学系统各部分的性能随时间的变化，羊八井宇宙线ＥＡＳ实验使用了一套由ＣＡＭＡＣ－ＤＡＣ，ＴＫＯ－Ｂｕｆｆｅｒ，Ｂｌｕｅ－ＬＥＤ和ＬＥＤ－ａｍｐ构成的快时间探测器标定系统，该标定系统的速度快，易于扩展，引起的数据采集系统的死时间少，对于３０ＴｅＶ以上的空气簇射事例，羊八井二期阵列的角分辨可达０．５°，此外它还能监测光电倍频管周围     

One Dimensional Scintillation Cameras for Positron Ect Ring Detectors

A one-dimensional scintillation camera configured as a continuous ring with coincidence-mode collimation avoids many of the problems associated with rings formed from an array of discrete detector elements. With the goal of achieving a stationary detector exhibiting high spatial resolution and sensitivity, several detector configurations have been designed. Both analytic and Monte-Carlo simulation techniques have been used to evaluate these designs. Results of the calculations and comparative measurements on the various detector designs are discussed.     

SG1402,SG1403大面积宇宙射线闪烁探测器

本文描述了500×500×50mm的大面积宇宙射线闪烁探测器的结构和性能,该探测器由于采用了塔式方圆型结构的空气光导箱和在光导箱内壁、闪烁体反射层用二氧化钛粉,使探测器对宇宙射线响应的全向谱单粒子分辨率达到53％,探测器响应的非均匀度达5.18％。     

Zero Cross-Over Timing with Coaxial Ge(Li) Detectors

The performance of zero cross-over timing systems of the constant fraction or amplitude rise time compensated type using coaxial Ge(Li) detectors is analyzed with special attention to conditions that compromise their energy-independence advantage. The outcome is verified against existing experimental results, and the parameters that lead to minimum dispersion, as well as the value of the dispersion to be expected, are given by a series of charts.     

Recent Developments in Scintillation Detectors for X-Ray CT and Positron CT Applications

The scintillation detectors considered in present and future instrumentation for XCT and PCT diagnostic imaging are Bi4Ge3O12 (BGO), CdWO4, Low Afterglow CsI(Tl) and CsF. These crystals with the exception of BGO have been known to scintillate as far back as NaI(Tl); their importance emphasized by their current use in CT application is relatively new. Recent improvements in purification, growth and performance characteristics present new and valuable data to the instrument designer. An evaluation and comparison of their properties vis à vis suitability for CT applications with particular emphasis on detector efficiency, light conversion, afterglow, timing, emission spectra, and general handling properties are examined and discussed. Future trends and possible replacement by other scintillators are commented on.     

Large-Field-of-View Image-Intensifier Gamma-Camera Detectors Using a Silicon X y Scintillation Localizer

Two years ago, a gamma camera detector, consisting of a 34 cm input field image intensifier coupled to a scintillator crystal at the input and to a silicon localizer at the output, was built and tested at Thomson-CSF. Snce that time the 34-cm model has been further developed, and a 40 cm model using an improved silicon localizer has been built and tested. This paper discusses the performances of the two cameras, and explains how the localizer output signal is processed to obtain gain uniformity and low geometrical distortion.     

圆柱体BGO探测器时间性能的研究

实验测得φ40mm×40mmBGO在GDB50L和GDB44D光电倍增管上的时间分辨率为1.9,3.4ns(对~(60)Co),φ76mm×100mmBGO在GDB76F上的时间分辨率为6.3ns。用蒙特卡罗方法研究了光电倍增管对探测器时间性能的影响,预计φ76mm×100mmBGO在3英寸快管上的时间分辨率可在2.5ns以下。     

Event Timing in High Purity Germanium Coaxial Detectors

The timing of gamma ray radiation in systems using high purity coaxial germanium detectors is analyzed and compared to that of systems using Ge(Li) detectors. The analysis takes into account the effect of the residual impurities on the electric field distribution, and hence on the rate of rise of the electrical pulses delivered to the timing module. Conditions under which the electric field distribution could lead to an improvement in timing performance, are identified. The results of the analysis confirm the experimental results published elsewhere and when compared with those for Ge(Li) detectors, which usually operate under conditions of charge carrier velocity saturation, confirm that high purity germanium detectors need not have inferior timing characteristics. A chart is given to provide a quantitative basis on which the trade-off between the radius of the detector and its time resolution may be made.     

Timing Performance of Ge(Li) Detectors

The influence of several parameters related to the detector,. such as depletion layer thickness, external radius of coaxial counters, applied electric field on the timing properties of planar and two open ended coaxial Ge(Li) detectors is investigated. Besides, the role of the electronical conditions is studied.     

快定时放大器

本文叙述了一种快定时放大器的结构，性能及实验结果以及在核物理实验中的应用，并对其工作原理进行了适当的分析。     

ICF中子探测器与前端电子学配接技术分析

ICF实验中,为避免中子辐射损伤电子学设备,电子学设备与探测器之间需有一定距离,因此必须考虑长距离传输对信号的影响。实验中X射线产生的信号高达50 V,次级中子产生的信号低于1V,而两者之间的时间间隔仅为百ns量级。因此由大幅度脉冲信号造成的信号反射、饱和、过冲,都可能会影响中子信号的测量。针对ICF实验中信号的长距离传输和接收问题,通过深入分析,确定了传输线和前端电子学各器件的选型。实验研究结果表明:该接收电路能对信号进行较好的接收,确保大幅度信号不会影响次级中子信号的测量。     

PET复合晶体甄别电子学及算法设计

设计并实现了一种高分辨率复合晶体探测器和电子学,并提出一种系统辨识的算法。复合晶体探测由LYSO(Lu2-xYxSiO5)和YSO(Y2SiO5)两种晶体交错排列而成,目的在于提高晶格的定位能力,改善空间分辨率。由甄别电路完成对PMT(photomultiplier tube)原始信号的处理,使用了高速ADC对信号连续采样,由FPGA完成波形采集,并能够完成实时基线恢复。甄别算法是分析了探测器响应和电子学采集模型之后提出的,是一种系统辨识算法。晶体甄别是基于提取与信号的衰减时间常数相关量来完成的。对LYSO和YSO的单晶体条实验,其甄别率超过98%;并绘制了甄别后两种晶体的二维直方图(2Dmap),有效地减少晶格间交叠,提高了空间分辨率。     

A Comparison of Various Filter and Discriminator Techniques on Timing with Ge(Li) Detectors

An experimental examination of the effect of several filters and two discriminator techniques on the time measurement of the signals from coaxial Ge(Li) detectors is presented in this paper. The signal to the filters and discriminators was obtained from the output of the charge-sensitive preamplifier in order not to degrade the energy resolution of the system. The discriminators used were a level discriminator for leading-edge discrimination and a fast zero-crossing discriminator. The filters examined for leading-edge discrimination were four RC time-invariant and four RC time-variant filters, and the filters for zero-crossing discrimination were three time-invariant RC filters. A comparison of time-invariant and time-variant filters reveals two advantages of the time-variant filter. These advantages are smaller timing errors and lower discrimination levels. The lower discrimination levels allow the reduction of energy dependent timing errors. Likewise, zero-crossing discrimination provides several improvements over leading-edge discrimination. By a compensation method, timing errors due to charge collection variations are reduced; and, due to the invariancy of the zero-crossing point as a function of amplitude, energy-dependent timing errors are also reduced.     

几种常用闪烁体受60Coγ源辐照前后探测器灵敏度比对

在闪烁体耐辐照特性研究中,通过比较闪烁体受辐照前后闪烁探测器系统灵敏度的变化,说明在大辐照剂量后闪烁探测器是否处于正常工作状态.利用三通道脉冲X射线源(平均能量800keV)、DPF脉冲中子源(D-T中子能量14.4MeV),通过实验标定几种常用闪烁探测器对脉冲中子、脉冲X射线的相对灵敏度值.所用闪烁体包括φ40mm,不同厚度的CeF3,NaI(T1)和BaF2等无机晶体及ST-401,ST-1422,NE111等塑料闪烁体.     

快脉冲二极管运行监测探头研制

研制了真空二极管电流电压参数监测用的电容分压器、微分环以及标定实验平台,对其工作原理及结构进行了描述,完成了探测器灵敏度实验标定和理论模拟,确定了探测器灵敏度的参数.从而解决了该探测器离线标定和在线使用之间的矛盾,并验证了设计的合理性.     

A Generalized Analysis of Zero Cross over Timing Systems for Semiconductor Detectors

A generalized analysis of zero cross-over timing systems is developed and applied to the case of germanium planar detectors to determine operating parameters which give smallest timing dispersion under the constraints of available charge-sensitive preamplifier risetimes. Charts are given using normalized values to indicate these parameters. The conclusions are verified by experimental results published elsewhere.     

Gain vs Temperature Effects in Nal(Tl) Photomultiplier Scintillation Detectors Using 10 and 14 Stage Tubes

The manner in which the gain of a radiation transducer comprised of a 2" × 2" NaI(Tl) crystal, and either a 5-inch 10-stage or 2-inch 14-stage photomultiplier tube viewing a Cs137 source, varies with ambient temperature changes over the range of 0° C to 50° C has been investigated. Gain vs temperature response curves are presented and operating temperatures which minimize gain variations are delineated. A method is given for evaluating the magnitude of gain variations encountered from the curves.     

Comparative Timing Performance of Large Volume Ge(Li) and HPGE Coaxial Detectors

The timing performance of several large (8% to 12% relative efficiency) Ge(Li) and HpGe coaxial detectors has been measured and compared. The Ge(Li) detectors are capable of timing resolution which is generally 10% to 30% better than that of the HpGe devices. This resolution capability can be attributed to the higher bias voltages which can be applied to the Ge(Li) detectors. However, in some applications that involve a wide dynamic range of energies, the HpGe devices can provide better timing resolution than their Ge(Li) counterparts. Advancements in the state of the art are expected to result in HpGe detectors that can provide timing performance equivalent to the performance of the best Ge(Li) devices.