Investigations of the performance of gas-discharge counters with a controlled pulsed power supply

With a pulsed power supply for gas-discharge counters, counting errors, determined by the dead time, are eliminated. Because of this, the possibility arises of using hodoscope systems of counters with a controlled pulsed power supply in experiments carried out with accelerators having a large background of extraneous radiation. In the present work the counting characteristics were investigated, and also measurements were carried out of the efficiency and the resolving power of self-quenching factory-produced counters with a controlled pulsed power supply. It is found that in the case of short-duration pulses (pulse length ～ 10^?6 sec) the counters can work under over-voltages of up to 2 kv. At the same time there is no necessity to amplify the pulses in the hodoscope channel or to use a discriminator to obtain their coincidences with the control pulse. Each channel, in this case, in addition to the counter contains a load resistance and a neon lamp. The considerable simplification of the system, by comparison with the usual type of hodoscope, and also the reliable performance of counters with pulsed power supplies, make such systems also useful for the study of cosmic radiation.     

GM计数管脉冲供电电压对计数率的影响

本文重点介绍了ＧＭ计数管脉冲供电电压对计数率的影响。经测试分析研究，结果表明脉冲供电比固定电压供电电压变化对ＧＭ管计数率的影响较大，应对脉冲电源提出更高的要求，     

Photoneutron interrogation of low-enriched uranium induced by bremsstrahlung from a 4 MeV linac

Revealing smuggled nuclear material by passive γ-detection is hindered, because the weak radiation can easily be shielded. Neutrons, as penetrate shielding, represent a detection potential, by inducing fission in the nuclear material. A 4 MeV linear accelerator was used as a pulsed neutron source for active interrogation of U-bearing material. Produced in heavy water by bremsstrahlung, neutrons subsequently induced fissions in UO₂ samples. Delayed fission neutrons were detected in a neutron collar built up by ³He counters in a polyamide container. The counters were gated to be detached from high voltage during the electron pulse. Irradiation-measurement cycles were carried out with a 25 Hz pulse repetition rate as optimum setting. The time analyser start-up was externally triggered and synchronised by the electron beam pulse. The response of the system was studied as a function of the intensity of the electron current, the amount of heavy water, U enrichment, and total U content. Sensitivity limit was achieved as 0.5 g ²³⁵U and/or 30 g ²³⁸U in a 20 s measurement time (500 cycles) with the amount of heavy water of 100 g and a mean electron current of 2 μA. Because of the long decay time of the prompt (interrogating and fission) neutron pulse, about a half of the time interval (40 ms) between pulses is only available for counting delayed neutrons.     

Optimal Parameter Ratios Guaranteeing Safety During Reactor Startup

A method and relations are proposed for determining the optimal ratio of the parameters for putting a reactor into a critical state safely: the initial subcriticality before reactor startup, the reactivity variation step, the initial pulse frequency, the initial counting rate of the number of pulses, the frequency of the spurious signal pulse, and the sensitivity of the pulsed startup channel, the neutron-flux density at the detector site, the neutron source strength, and the frequency of the pulses in the startup channel that gives the required speed of formation of the emergency signal according to the time interval as the reactor is put into a critical state. The methods and formulas for determining the optimal parameters are obtained taking into account the statistical nature of the frequency of the detector pulses and of the spurious output signal.     

A pulsed ion source with low gas flowrate

This paper describes the development of a high-intensity pulsed ion source with a low flowrate for the working gas. Various designs were elaborated, and studies were made of two variants of a titanium source with deuterium-loaded electrodes (washers). The deuteron beam current at the 10 mm diameter collector spaced 120 cm from the source was 10 mA. The gas flowrate per pulse was 10^–3 cm³. The duration of a current pulse was 500 sec. The pulse repetition rate was several pulses per minute.In conclusion, the authors would like to express their gratitude to L. M. Nemenov for his constant interest in the work and discussing the results; to Yu. V. Korshunov, E. A. Meleshko, S. N. Rybin, and O. V. Lavrov for working out the supply circuitry and source designs; and to E. G. Ladutin and V. V. Gavrilin for their kind aid in conducting the investigations.     

Measurement of the Beam Position in the Extraction System of the ILU-10 Linear Electron Accelerator

A system for measuring beam position for a ILU-10 pulsed linear electron accelerator is described. The accelerator generates an electron beam with energy up to 5 MeV. The rf generator operates at 115 MHz in the pulsed mode with pulse duration of about 500 sec and pulse repetition frequency up to 50 Hz. The average beam power can reach 60 kW. Two electrostatic sensors (pickups) are used to measure the position of the beam. The principle of operation of the measurement apparatus is based on homodyne detection of the signals from the pickups. The second harmonic of the frequency of the accelerating voltage of the accelerator power supply (230 MHz) is chosen as the working frequency. The detected signal is fed from each pickup plate into an integrator and then a ADC. The beam position is calculated on a computer. The resulting error in the beam coordinates is about 0.5 mm with a 110 mm in diameter position sensor.     

X-ray energy separation method using a CdTe semiconductor X-rayimaging sensor and photon counting method

A multichannel X-ray imaging sensor using a CdTe compound semiconductor radiation detector in photon counting mode was developed and tested for digital X-ray imaging and an X-ray energy separation capability. The X-ray imaging sensor was constructed of CdTe detector elements at a pitch of 0.25 mm. High band amplifiers, discriminators, and counters attached to each element formed the pulse counting circuit. Charge pulses generated by absorbed X-ray photons were directly counted and separated into two energy regions. Digitized X-ray images containing energy information were thus obtained. Using this sensor two separate X-ray images of different energy can be obtained simultaneously. A 256-channel X-ray imaging sensor was prepared and used to provide spatial resolution measurement for an X-ray charge. Low and high energy images of a hand phantom were thus obtained and both a soft tissue image and a bone image were produced using an energy subtraction method     

脉冲电流相位检测与反馈系统设计

大多数环型加速器引出束流方向受冲击磁铁的磁场控制,引出冲击磁铁脉冲电源输出的脉冲励磁电流抖动和漂移过大会降低束流引出效率,主要来源于触发系统、闸流管、环境温度变化等[1]。国内抑制引出脉冲电源输出电流相位偏移的相位检测及反馈系统尚属空白。针对中国散裂中子源(CSNS)快循环同步加速器(RCS)引出脉冲电源的需求,设计一种TDC芯片+FPGA结构的输出脉冲电流相位检测及反馈系统,通过研究TDC芯片和FPGA间的数据传输方式、基于FPGA的串口通信及反馈控制算法,实现电源输出电流相位ps级精度实时检测及偏移量反馈,反馈调整步长5 ns,为脉冲电流高精度相位检测与锁定提供了新方法。     

Measurement of Electromagnetic Shower Position and Size with a Saturated Avalanche Tube Hodoscope and a Fine Grained Scintillation Hodoscope

A hodoscope has been constructed from 100 ?m diameter wires and brass tubes (1.2 × 0.7 cm2 cross section) filled with a mixture of argon, ethane and ethyl alchohol. It has been tested in the saturated avalanche mode in an SCG1-C electromagnetic shower detector to determine its properties for the measurement of the position and size of electromagnetic showers. Two of these tube hodoscopes were positioned 3.5 radiation lengths deep in the detector and the profiles of 1-25 GeV electromagnetic showers were measured. Simultaneous measurements were performed using a plane of twenty, 0.5 cm wide scintillation counters positioned immediately behind the gas tube hodoscope. In addition the transition between saturated avalanche and limited streamer modes has been measured for the tube hodoscopes.     

Silicon counters for nuclear spectrometry

Laboratory models of surface-barrier and diffusion-type silicon n-p counters were developed which were suitable for nuclear spectrometry. The counters have linear pulse height-energy dependence for particles with 60 paths (in particular, for -particles with energies up to 10 Mev), and 0.5 % resolution for an E of 5.5 Mev (with units of small area).The authors consider it a pleasure to thank engineer G. V. Khozov, technicians I. A. Lebedeva and G. D. Gusarina, and machinist P. I. Gorshkov for helping greatly in this work.     

某压水堆首次装料次临界监督结果分析

某压水堆使用已活化的二次中子源（ASNS）完成首次装料。在首次装料期间,堆内临时中子探测器（TND）发生响应试验结果远高于仿真结果问题和计数率大幅度下降问题。为了查明上述问题的原因,监督工作组对二次中子源特性和由ASNS建立的辐射场进行了分析,对核燃料次临界增殖中子对TND计数率的影响进行了分析和验证,对使用ASNS进行反应堆首次装料的次临界监督数据进行了分析。结果表明：TND周围的辐射场为γ射线和中子形成的混合辐射场;在中子源组件与TND之间安装核燃料组件后,核燃料次临界增殖中子对TND计数率的影响是使其升高;ASNS衰变产生了大量γ射线,TND输出的γ脉冲在主放大器内发生峰堆积导致脉冲幅度畸变,TND响应试验结果远高于仿真结果的原因是脉冲幅度甄别器无法有效甄别畸变后的γ脉冲和中子脉冲;TND计数率大幅度下降的原因为核燃料中的铀屏蔽掉了由ASNS射向TND的大部分γ射线。源量程通道和TND的运行状态满足首次装料程序对次临界监督设备的要求。     

Calibration of scintillation counters with allowance for scattered radiation

A method is described for calibrating scintillation counters which takes scattered radiation into consideration. Buildup factors for the reflection of radiation from a radium source, and analytic approximations to them, were determined. The formula obtained for the total intensity of direct and scattered -rays gives a calibration curve unperturbed by scattered radiation when used for the calibration of scintillation counters.Translated from Atomnaya Énergiya, Vol. 21, No. 2, pp. 121–125, August, 1966.     

ns级快脉冲电源研制

高重复频率ns级快脉冲电源是粒子加速器超快kicker注入引出技术中有待攻克的关键技术难题。本工作利用计算机仿真和桌面实验等手段从理论上研究了感应叠加技术、射频MOSFET开关及驱动电路技术,并在此基础上设计研制了1台10级感应叠加的快脉冲电源性能样机。经初步测试,10级叠加性能样机在500 Hz低频工作条件下,输出脉冲幅度>4.3 kV,脉冲前沿<2.8 ns,脉冲宽度<9 ns,基本达到了预期目标。     

Experimental Study of the X-Ray Radiation Source at Approximately Constant Radiation Temperature

An X-ray radiation source with approximately constant radiation temperature is realized by irradiating golden hohlraum with a shaped laser pulse. A simple theoretical model based on power balance is used to design the shape of the drive laser pulse. Experiments are carried out on the Shenguang III prototype laser facility, and the experimentM results are presented for radiation sources with the flat-top lasting about 2.5 ns at two different peak temperatures of about 150 eV and 170 eV, respectively, including the the drive laser pulses and the time integrated possible improvements are discussed. time histories of the temperatures, the shapes of radiation spectra. The validity of the model and     

基于Si-PIN探测器的电流型计数式α粒子测量

为解决基于Si-PIN探测器的传统计数型粒子测量系统在测量低强度脉冲辐射场时存在的计数率低和不能直接测量粒子时间信息的问题,提出了电流型计数测量方法。其原理是对电流型Si-PIN探测器在粒子入射时输出的脉冲信号进行线性放大和高速数字化,并使用数字信号处理算法进行数据分析以获得粒子测量信息。利用电流型Si-PIN探测器、电流型前置放大器和高带宽数字示波器组建了电流型计数测量系统,并在241 Am-244 Cm和239 Pu源上开展了α粒子测量实验。实现了脉冲幅度谱和粒子入射时间的联合测量,同时利用FIR及IIR型数字滤波器改善了能谱测量的能量分辨率。系统的最大计数率达2×106 s-1,适用于低强度脉冲辐射场测量。     

Linear Parallel to Serial Conversion

The system accepts up to 21 simultaneous pulses in parallel and forms a train of pulses for the display on a single channel scope. Representative pulses have the following characteristics: ~15 nsec wide at the base line, ~5 nsec rise time, ~1 ma peak current. Each channel contains a linear gate, controlled by the same event pulse. Upon arrival of the event pulse, the 21 channels open simultaneously for ~25 nsec and allow transmission of the signal pulses into a system of 20 cable delay sections, connected in series. Each joint is a feedpoint for one signal pulse as passed by its corresponding linear gate. The 21 roughly simultaneously occurring pulses can now be displayed as a train of pulses on a single channel scope. Circuit design and performance data are given in the report.     

Low level gas multicounter for 14C dating of small samples

A compact gas multicounter has been constructed and is undergoing tests. Up to 14 methane samples can be counted simultaneously in an array of 10 ml (at NTP) copper counters at a pressure of 1–8 bar. The gas filling, application of high voltage and decay energy monitoring are microprocessor controlled. Multichannel analyses (256 ch. sample and cosmic detector energy data), sample identity, counting time and critical validity parameters are stored on disc. Numerical discrimination and manipulations of counting parameters can be performed without destroying the original data set. Statistical quality control is based on chi-square and Poisson distribution of countrates around their mean in user defined energy regions as well as “ time of arrival” (TA) of pulses mode. TA analysis offers the user an early means of recognition of some types of system malfunction that otherwise might remain undetected for long periods of time. Pulse shape analysis is used to discriminate sample beta from environmental radiation pulses resulting in a low background with compact and relatively inexpensive shielding.     

A Nuclear Radiation Sensitive Switch

High intensity pulsed nuclear radiation tends to make back biased semi-conductor junctions conduct. Arma undertook the design and development of a circuit which would provide a switch opening in response to nuclear radiation pulses. The design objectives for the Radiation Sensitive Switch were that switch response should be fast, triggering should be adjustable, operation should not be impaired at high pulse intensities, reset, or switch closure, should be auto matic and at a preset time after trigge ring and switch status should be indicated. A prototype switch was designed and constructed. A number of tests were conducted in a high energy linear accelerator (LINAC) to investigate circuit performance under irradiation. The results of the tests proved that the Radiation Sensitive Switch met or exceeded all design objectives. Switch opening was sustained to pulse intensities as high as 4.8 x 1010 rad/ sec. Switch response timnes were less than 0.2 micro seconds. Reset times were constant throughout the test series. A control range of over 4 to 1 in radiation triggering threshold was achieved without changing components. A radiation sensitive switch, to provide a controlled switch opening in response to a nuclear radiation pulse has been shown to be feasible and practical.     

On the possibility of accelerating heavy pulsed currents in linear electron accelerators

The applicability of various linear electron accelerators for the acceleration of heavy pulsed currents is estimated. It is shown that linear standing-wave electron accelerators, which use the high-frequency power stored in resonant cavities, for the acceleration of particles offer greater possibilities in comparison with ordinary linear traveling-wave electron accelerators. The possibility of accelerating currents of the order of 100 amp in pulses with a duration of approximately 1 sec is demonstrated.In conclusion, we hereby express our deep gratitude to K. D. Sinel'nikov and Ya. B. Fainberg for the valuable discussions.