Second Coordinate Readout in Drift Chambers by Charge Division

The drift time measurement and the charge division can be performed simultaneously on the same electrode (resistive anode) without affecting the accuracy of either measurement. It is shown that for the shortest measurement time there is an optimum value for the anode wire resistance. The signal requirement for a position uncertainty ? ? 0.5% of the anode wire length is only 2.7 x 106 electron charges. The drift chamber can be operated in the linear mode and with negligible space charge effects, so that it can also be used for ?E/?X measurements. A simple preamplifier optimized for both the time and charge measurements using a monolithic transistor array is described.     

The Use of Nitrogen Laser for Observation of Space Charge Effects in Drift Chambers

A two-stage nitrogen laser has been built and is presently being used to investigate properties of drift chambers. In this paper we present the measured parameters of this laser, the results of a study of the double track separation in a drift chamber of jet design and a measurement of the saturation effects in this chamber as a function of total gain. An understanding of the saturation effects is important for drift chambers with multiple hit capability. The laser technique reported here represents a major improvement in the simplicity of investigation of the double track separation and saturation effects.     

Characteistics of Multiwire Proportional Chambers for Positron Imaging

We describe multivire proportional chambers (MWPC) designed for use in a positron camera for Nuclear Medicine applications. The coordinates of the two annihilation gamma rays are detected in the chamber by their interaction with thin lead converters placed on both faces of each chamber. In order to obtain reasonable efficiencies (10%) the lead converters have been made in a square honeycomb-like structure, which increases the effective surface area and also permits the application of a drift field to extract the electrons into the active area of the MWPC.     

大型丝室制作中的张力研究

研究了丝张力随时间的变化情况,比较了两种拉丝方式下丝张力的分布。介绍了一种新的丝张力测量法并给出了中心漂移室(模型)丝张力的测量结果。     

Readout of Drift Chambers with a 100 MHz Flash ADC System

An electronic read out system for drift chambers, based on a 100 MHz Flash ADC is described. Test results are reported which include a study of the reproduction of the shape of fast chamber signals and measurements of the time and double track resolution. Measurements and computer simulations were performed to study the charge resolution.     

Cylindrical Dritt Chambers with Two Dimsional Readout

We have built and used a set of three cylindrical drift chambers with delay line readout. The azimuthal coordinate is obtained in the conventional way; the resolution obtained is about 300 microns. The axial coordinate is obtained fran signals induced on printed circuit delay lines with a resolution of ±5 mn FWHM. The chambers are 120 cm long and have diamters of 29.3 cm, 70.1 cm and 118.5.     

基于GEM工艺的裂变时间投影室性能模拟研究

基于GEM工艺的裂变时间投影室具有探测效率高和空间分辨率高的特点,可实现裂变产物的多参量测量。本文主要研究基于GEM工艺的裂变时间投影室在不同条件下的测量精度,使用Garfield++软件计算得到裂变时间投影室中不同的裂变产物质量数测量误差约为4～6 u,并通过时间信息的径迹重建研究了裂变碎片在不同工作气体中的角度分辨。研究发现,电子漂移时间长的工作气体中,裂变产物具有更好的角度分辨,并可依此在实验中选择合适的工作气体、气压和漂移电场强度来进行裂变碎片的测量。     

Study of nonlinear relationship between position and drift time incylindrical-type drift chamber and use of backgammon-shaped cathode pads

A cylindrical-type drift chamber consists of an appropriate array of cylindrical single wire proportional counters and has a simple structure. It is shown that a quadratic function reproduced the space-time relationship in the cylindrical-type drift chamber filled with PR gas (Ar:methane=90:10). The difference in the drift times in pair-cells is simply converted into the incident position of charged particles perpendicular to the anode wire using the quadratic function of the space-time relationship. Furthermore, the quadratic function improves the position resolution. A backgammon pattern is employed for the cathode pad of the cylindrical drift chamber. The cylindrical drift cell with a backgammon-shaped cathode pad gives the position resolution along the anode wire. The position resolution in one sigma along the anode wire is obtained to be 1.7 mm on average. The cylindrical-type drift chamber with a backgammon-shaped cathode pad may be applied to a two-dimensional position sensitive detector with a compact structure and simple signal-processing electronics     

凸度仪电离室探测器时间响应特性研究

本文利用脉冲X射线机发射宽度很短的脉冲射线,通过分析数字示波器记录的电离室负载电阻上的电压信号,测量电离室内的离子漂移时间。利用该方法对凸度仪电离室探测器的时间响应特性进行了研究,给出了不同内部结构、不同电压及不同气压的电离室离子漂移时间的测量结果,并分析了误差产生的原因。实验结果表明,凸度仪电离室的时间响应满足在线测量热轧钢板的要求。     

Scintillating Drift Chambers?the Nature of the Emission Process in Ar/CH4

A mechanism involving optical emission from excited molecular fragments is proposed as the origin of the photon emission from scintillating drift chambers which contain Ar/CH4 mixtures. This explains a spectral feature observed at ~ 4300 ? and also the appearance of spurious photo-electric emission from the cathode wall material.     

Transfer Function Measurement of Ionization Chambers with the Use of Uncorrelated Reactor Noise

The frequency response of an ionization chamber was measured by utilizing the uncorrelated reactor noise, varying the voltages as parameters. The results obtained made it clear that the break frequency of the ionization chamber is determined by the transit time of positive ions and the applied voltage, and can further be represented by a simple first order time lag.     

固定式周围剂量当量率仪原位校准技术研究

固定式周围剂量当量率仪广泛分布于核电厂内部,用于常规连续监测或核事故后应急监测。由于采用固定安装,不便于拆卸送往计量实验室进行校准。为了确保固定式周围剂量当量率仪的量值准确,结合蒙特卡罗方法研制了周围剂量当量次级标准电离室和便携式γ射线辐照装置,并开展原位校准实验。将原位校准因子与实验室得到的校准因子进行比较分析,结果证明利用便携式γ射线照射装置配合周围剂量当量次级标准电离室能够较好的解决固定式周围剂量当量率仪的原位校准难题。      

Test Suite for the LHCb Muon Chambers Quality Control

This paper describes the apparatus and the procedures implemented to test the front-end (FE) electronics of the LHCb muon detector multi wire proportional chambers (MWPC). Aim of the test procedure is to diagnose every FE channel of a given chamber by performing an analysis of the noise rate versus threshold and of the performances at the operational thresholds. Measurements of the key noise parameters, obtained while performing quality tests on the MWPC chambers before the installation on the experiment, are presented. The test suite proved to be an automatic, fast and user-friendly system for mass production tests of chambers. It provided the electronic identification of every chamber and FE board, and the storage and bookkeeping of test results that will be made available to the experiment control system during data taking.     

低压多丝正比室的位置分辨研究

低压多丝正比室为放射性束核反应的靶前粒子提供位置和时间信号。本工作用²⁴¹Amα源研究电压、工作气体压强等因素对低压多丝正比室位置分辨的影响。实验结果表明：在不同的气体压强条件下，低压多丝正比室的位置分辨均可达到1mm，但考虑到时间、效率等因素，实验中需尽可能提高气压。     

Electronics for the CMS Muon Drift Tube Chambers: The Read-Out Minicrate

On the Compact Muon Solenoid (CMS) experiment for large hadron collider (LHC) at CERN laboratory, the drift tube chambers are responsible for muon detection and precise momentum measurement. In this paper the first level of the read out electronics for these drift tube chambers is described. These drift tube chambers will be located inside the muon barrel detector in the so-called minicrates (MCs), attached to the chambers. The read out boards (ROBs) are the main component of this first level data acquisition system, and they are responsible for the time digitalization related to Level 1 Accept (L1A) trigger of the incoming signals from the front-end electronics, followed by a consequent data merging to the next stages of the data acquisition system. ROBs' architecture and functionality have been exhaustively tested, as well as their capability of operation beyond the expected environmental conditions inside the CMS detector. Due to the satisfactory results obtained, final production of ROBs and their assembly in the MCs has already started. A total amount of 250 MCs and approximately 1500 ROBs are being produced and tested thoroughly at CIEMAT (Spain). One set of tests, the burn-in tests, will guarantee ten years of limited maintenance operation. An overview of the system and a summary of the different results of the tests performed on ROBs and MCs will be presented. They include acceptance tests for the production chain as well as several validation tests that insure proper operation of the ROBs beyond the CMS detector conditions.     

A New Preamplifier for Drift Chambers

We have developed a new preamplifier for drift chambers with a high gain (20mV/105 e), high speed (5 ns rise time) and low power consumption (28 mW). Some of its design considerations and performances are described. A monolithic version of the preamplifier is also developed.     

Operation of the ATLAS muon drift-tube chambers at high background rates and in magnetic fields

In the ATLAS muon spectrometer, large drift-tube chambers are used for precision tracking. The chambers will be operated at a high neutron and /spl gamma/ background resulting in count rates of up to 500 Hz cm/sup -2/ corresponding to 300 kHz per tube. The spatial resolution of the drift tubes is degraded from 82 /spl mu/m without background to 108 /spl mu/m at 500 Hz cm/sup -2/ background count rate. Due to afterpulsing in the Ar/CO/sub 2/ gas mixture used in the drift tubes, ionizing radiation causes more than one hit in a tube within the maximum drift time of about 800 ns which is expected for magnetic field strengths around 1.2 T. In order to limit the count rate, the drift tubes are read out with an artificial dead time of 790 ns which causes an efficiency loss of 23% at a rate of 300 kHz per tube. The space-to-drift-time relationship of the tubes varies with background rate, temperature, and magnetic field strength. The mean magnetic field strength in a muon chamber is 0.4 T on the average, but may vary by up to 0.4 T within a chamber. The space-to-drift-time relationship must therefore be determined in short time intervals with an accuracy better than 20 /spl mu/m using muon tracks and applying corrections for measured magnetic field variations.     

堆外核仪表系统(RPN)的预设效验系数理论计算

用蒙特卡罗方法及程序模拟给出了某核电厂堆内各组件(节块)对堆外探测器的响应矩阵。通过响应矩阵算出堆外探测器各节电流及堆外核仪表系统(RPN)刻度系数,进而得到堆芯热功率水平(Pr)及堆芯轴向功率偏差(△I)。过不同循环、不同氙振荡理论计算与实验对比,表明数值模拟是可行的,计算结果完全满足精度要求。     

High Resolution Cryogenic Spark Chambers

A cluster of four narrow gap (2.5 mm) spark chambers containing 8 wires per millimeter has been built and operated at low temperatures (as low as 118°K). Results obtained from these chambers indicate that the width of the spark column is reduced at lower temperatures due to the increased gas density. Electron diffusion and deviation of the spark column from the true particle trajectory are greatly reduced at lower temperatures with narrow gap spark chambers. Space resolutions less than ? = 70 microns (HWHM) has been achieved and even better resolutions are predicted from the observed temperature dependence.     

北京谱仪漂移室电子学系统电磁干扰问题的研究

介绍了北京仪漂移室电子学系统电磁干扰问题,阐述了如何根据造成电磁干扰的三要素分析与排除干扰的方法。