初级裂变产物电荷鉴别技术研究

正初级裂变产物电荷鉴别是实现初级裂变产物产额测量的关键技术。由于初级裂变产物每核子能量比较低(0.5～1.3 MeV),传统的ΔE-E组合探测器难以实现电荷鉴别。为突破初级裂变产物电荷鉴别的关键技术,本工作采用低气压屏栅电离室匹配电流灵敏前置放大器获取初级裂变产物在气体探测器中的电离过程信息,通过FADC采集并记录比电离曲线。数据处理时对采集到的比电离曲线进行上升过程积分可以得到裂变产物的总动能,对上升过程中部分电荷鉴别灵敏区域选择分段积分可得到电荷信息,对相同质量数的初级裂变产物电荷分段积分幅度谱统计分析就可以判别该质量数下的电荷分布几率。     

裂变室技术堆外中子探测器原理及与传统电离室的比较

所谓裂变室是指在腔内加涂了一层铀的电离室。裂变室技术的中子通量探头其基本原理也是与普通电离室相同。均为将腔室内的填充气体电离,从而生成电流脉冲。与普通电离室不同的是裂变室能够在应用于源量程的脉冲计数,因为由于裂变室产生的电流脉冲远大于普通电离室所产生的脉冲电压。在裂变室中,中子的撞击导致涂铀层的铀元素裂变,产生的铀元素裂片再去电离填充气体从而产生电流脉冲。在不同的阶段由于中子注量率水平的不同,我们采用两种方式对电流脉冲进行测量从而测得中子注量水平。当中子注量率越来越高时,所产生的电流脉冲也会越来越密集,这导致脉冲的堆积。这样的话就没办法区分单个的脉冲因此无法再采用脉冲计数法。但同时脉冲堆积情况的发生生成了一个波动的直流电流。     

裂变室技术堆外中子探测器原理及与传统电离室的比较

所谓裂变室是指在腔内加涂了一层铀的电离室.裂变室技术的中子通量探头其基本原理与普通电离室相同.均为将腔内的填充气体电离,从而生成电流脉冲.     

组织等效空腔电离室设计与饱和特性研究

MOS场效应管与空腔电离室两种技术结合,形成一种用于个人核辐射剂量监测的新型探测器一直接电荷存贮（Direct Ion Storage,简称DIS）探测器。本文在介绍该探测器原理基础上,从壁材料、气体成分、腔体形状和尺寸、壁厚度以及绝缘材料等角度,设计与研制组织等效空腔电离室。利用^60C07辐射源和中能X射线,测试了电离室饱和特性,很好的满足DIS探测器对电离室饱和特性的要求。     

高温裂变电离室气密性设计

正高温裂变电离室属于核反应堆安全级重要设备,反应堆的正常运行得益于其通过测量反应堆外孔道内中子注量率的大小及其变化速率,为反应堆保护系统提供实时有效的监控数据,进而判断得出反应堆功率水平和运行状态。在高温裂变电离室设计过程中,需要综合考虑工作模式、工作范围、气体工作压强等。电离室主要由圆筒,上、下盖板以及在上盖板的两个绝缘电极和抽气管组成。电离室长为254.8mm、外径     

曲线拟合在扩展电离室量程范围方面的应用

通过将曲线拟合扩展量程范围的技术应用于传统的电离室探测器,使电离室在低剂量率时工作在饱和收集区,高剂量率时工作在不饱和收集区,从而扩张电离室的量程范围。使得只采用一个电离室便可覆盖8个数量级的剂量率范围,从而实现对现有电离室测量方法补充和发展的目的。     

秦山第二核电厂RIC系统探测器校刻因子算法研究

秦山第二核电厂堆芯功率分布测量试验使用RIC系统的4个移动微型裂变电离室入堆进行测量。由于制造公差以及探测器辐照历史不同等原因,4个微型裂变电离室的探测效率各不相同。为了计算探测器之间探测效率的校刻因子,一般使用参考通道校刻法和交叉通道互校法。本文给出了几种校刻因子计算方法,并将所计算的校刻因子结果与法国CARIN程序...     

秦山第二核电厂RIC系统探测器校刻因子算法研究

秦山第二核电厂堆芯功率分布测量试验使用堆芯仪表系统(RIC系统)的4个移动微型裂变电离室入堆进行测量。由于制造公差以及探测器辐照历史不同等原因,4个微型裂变电离室的探测效率各不相同。为计算探测器之间探测效率的校刻因子,一般使用参考通道校刻法和交叉通道互校法。本文给出了几种校刻因子计算方法,并将所计算的校刻因子结果与法国CARIN程序校刻因子的计算结果进行了比对。     

^238U裂变电离室修正因子及探测响应的蒙特卡罗模拟计算

利用蒙特卡罗(MC)粒子输运程序MCNPX分别计算了用238U裂变电离室测量由加速器产生的14.8 MeV和25.5 MeV准单能中子注量率以及将其推广应用于测量散裂中子源和宇宙中子源的中子注量率时,由电离室结构、电离室气体、空气等引起的对探测器裂变计数率的修正因子,并给出了探测器在各种情况下的探测响应.为解决蒙特卡罗模拟中探测片太薄、统计误差过大的问题,计算中采用了Dxtran球和强迫碰撞两种方差减少技巧,以降低统计误差、提高计算效率.对于源中子谱覆盖范围较宽、抽样效率低的情况,采用了高能和低能两部分能谱分别计算的方法,以提高计算效率.将模拟计算得到的修正因子应用于探测响应的理论公式,得到相应的探测响应,并与MC模拟计算直接得到的探测响应进行了比较,对模拟计算进行自洽性验证.利用伴随α粒子测量装置和电离室同时测量14.8 MeV准单能中子注量率,得出238U裂变电离室对串列加速器上14.8 MeV准单能中子场的探测响应,与MC模拟计算结果进行比较,对模拟计算进行实验验证.     

射线能量对高压充气电离室探测器饱和特性的影响

通过实验测量一种高压充气电离室探测器在~(241)Am、~(137)Cs及X光机(管压200 kV)下的饱和特性,分析不同能量下饱和特性的规律,阐述探测器结构对饱和特性的影响。为充气电离室探测器设计以及探测器实际使用中工作电压的选择提供参考。     

Optimizing the performance of a neutron detector in the power monitoring channel of Tehran Research Reactor (TRR)

In this study, a general theoretical model is presented to calculate the current-voltage characteristics and associated sensitivity for a fission chamber. The chamber was used in a research nuclear reactor and a flux-mapping experiment was performed. The experimental current measurement in certain locations of the reactor was compared with the theoretical model results. The characteristic curves were obtained as a function of fission rate, chamber geometry, and chamber gas pressure. An important part of the calculation was related to the operation of the fission chamber in the ionization zone and the applied voltages affecting two phenomena, recombination and avalanche. In developing the theoretical model, we used the MCNP Monte Carlo code for fission rate and the SRIM program for ion-pairs computations. The theoretical model together with the above-mentioned codes was used to evaluate the effects of different applicable variations on the chamber's parameters.     

用于CSNS反角白光中子能谱及注量率测量的快裂变室

即将建成的中国散裂中子源(China Spallation Neutron Source,CSNS)反角白光中子束线可为核数据测量提供高注量率的脉冲白光中子束流,填补我国核数据测量用白光中子源的空白,提高我国核数据测量水平,满足核能、核技术及基础核物理研究对核数据的需求。该束线建成后,其中子能谱及注量率的精确测量将是开展其它物理实验的基础,快裂变电离室因其独特优点被选为中子能谱和注量率测量探测器。通过实验研究了快裂变电离室的粒子分辨性能、时间分辨性能;确定阴、阳极的合理间距为10 mm,据此测得电离室的时间分辨约15 ns;利用235U样品量计算的探测效率与利用伴随粒子法给出的探测效率在不确定度范围内符合,因此可以标定快裂变室的探测效率。通过这些工作,完成了满足反角白光中子束能谱及注量率测量需求的快裂变室的物理设计。     

Evaluation of Power History during Power Burst Experiments in TRACY by Combination of Gamma-Ray and Thermal Neutron Detectors

A combination method using γ-ray and thermal neutron detectors was newly applied to the accurate evaluation of power histories during reactivity-initiated power burst experiments in the Transient Experiment Critical Facility (TRACY). During an initial power burst, the power history was determined using a fast response γ-ray ionization chamber, which was used because of its ability to exactly trace the power history within a short duration of the initial burst. After the initial burst, a micro fission chamber containing highly enriched uranium was used for the determination of the power history because the γ-ray ionization chamber could not be applied due to the contribution of delayed γrays from fission products. By the present method, the power histories were evaluated for the experiments in the range of 1.50 to 2.93$ of the reactivity insertion. It was found that the peak power and integrated power as determined by the previous method using only the micro fission chamber were underestimated to be 40% and 30% in maximum, respectively, in comparison with the results from the present evaluation. The numerical simulation performed by using the Monte Carlo method indicated that the underestimation could be comprehended by considering the time delay of thermal neutron detection of the fission chamber, which arose from the flight-time of neutrons from the TRACY core to the fission chamber.     

基于微通道板的电离室及其在同步辐射中的应用

在同步辐射装置中,气体电离室是定标光束线能量和评估能量分辨率的一个重要实验装置。为了摆脱电极探针式电离室的气体展宽对束线能量分辨率测定的限制,本文将微通道板(Microchannel Plate,MCP)应用于同步辐射光束线中的电离室,研制成功了具有高能量分辨率的电离吸收谱的探测系统。利用此系统测量标准气体在X射线入射时的电离吸收谱,通过分析测量所得谱线中吸收峰的展宽,可获得光束线的仪器展宽,本文以Ar的吸收谱为例给出了测量结果。     

基于DCS改造最小验证平台的稳压器压力控制回路比对测试研究

通过试验研究了工作气体的压力和种类对涂硼电离室坪特性、中子灵敏度和γ感应度等性能的影响。试验结果表明,随着工作气体压力的增大,电离室坪区会向高电压方向移动,即电离室的工作电压会增大;工作气体为10%CH4+90%Ar（P10）时,当工作气体压力（从0.025 MPa 增加到0.15 MPa）增大,电离室中子灵敏度会迅速增大,继续增大工作气体压力,电离室中子灵敏度保持不变;电离室中子灵敏度会随着工作气体中高电离能气体成分增加而减小;P10气体压力在0.1~0.4 MPa范围内,电离室γ感应度与工作气体压力成正比。      

Time Delay of Thermal Neutron Detection during Power Burst in TRACY

Time delay of thermal neutron detection at a micro fission chamber has been experimentally confirmed during an initial power burst caused by reactivity addition in the Transient Experiment Critical Facility (TRACY). In the experiment, the power was measured by using a fast response γ-ray ionization chamber, which was newly designed exclusively for the TRACY experiment, in addition to the fission chamber. As results of the experiment, the transient power measured by the fission chamber was observed about 4 ms later than that by the γ-ray chamber during the power increasing, and then the delay time expanded after the power peak. The time delay must be taken into account to evaluate accurately the transient power. To comprehend the observed time delay in detail, time-dependent analyses were performed using the MCNP4B code. In the analyses, time response of neutron detection at the fission chamber was calculated and used for the simulation of the transient power measured by the fission chamber. From results of the analyses, it was confirmed that the simulated power well agreed with the measured power and the observed time delay was caused from the thermalization of neutrons emitted at the TRACY core and the following flight to the fission chamber.     

用于裂变研究的多参数测量系统

介绍了一种用于理解变研究的多参数测量系统。描述了裂变源、微型裂变室、中子探测器、实验安排以及降低测量本底的措施。系统适用于精确测量自发裂变中子能谱和裂变碎片特性,也可用于其他类型的测量。     

离线产氚实验中氚在线监测系统的研制

在增殖剂离线产氚实验中,如何准确实时测量回路中氚浓度和形态（HTO/HT）对于掌握产氚增殖剂氚释放行为,改进增殖剂的产氚性能非常重要。针对离线产氚回路中载气流量小、回路中气体量小以及载气为Ar等特点,基于流气式电离室原理研制了一套数字化氚浓度在线测量系统。该系统中电离室灵敏体积为50 mL,数字化仪表可自控获取、处理及显示回路中的氚浓度。测试结果表明,在Ar气氛下,在35 V左右,电离室即进入饱和区;该系统探测下限可达3.7×10 7 Bq/m 3,能满足离线产氚实验中氚在线监测的要求。     

Effects of the Discharge Parameters on the Efficiency and Stability of Ambient Metastable-Induced Desorption Ionization

Ionization efficiency is an important factor for ion sources in mass spectrometry and ion mobility spectrometry.Using helium as the discharge gas,acetone as the sample,and high-field asymmetric ion mobility spectrometry(FAIMS) as the ion detection method,this work investigates in detail the effects of discharge parameters on the efficiency of ambient metastableinduced desorption ionization(AMDI) at atmospheric pressure.The results indicate that the discharge power and gas flow rate are both significantly correlated with the ionization efficiency.Specifically,an increase in the applied discharge power leads to a rapid increase in the ionization efficiency,which gradually reaches equilibrium due to ion saturation.Moreover,when the discharge voltage is fixed at 2.1 kV,a maximum efficiency can be achieved at the flow rate of 9.0 m/s.This study provides a foundation for the design and application of AMDI for on-line detection with mass spectrometry and ion mobility spectrometry.     

Amplification process of a gas electron multiplier simulated by PIC-MCC model

The performance of a single gas electron multiplier(GEM) in pure Xe at an atmospheric pressure is investigated by Particle in Cell-Monte Carlo Collision(PIC-MCC) model.The micro development processes with electrons and ions distributions in space have been revealed.Based on the micro development processes,the macroscopic parameters such as GEM gain and the effective efficiency have also been obtained.The simulation results indicate that after tens of nanoseconds,electrons are collected by the readout electrode while the ions still exist in the gas space for several microseconds.The main signal current is formed by the electrons arriving at the readout electrode,but electrons and ions are also collected by the copper electrodes near the GEM hole and the thin Kapton film boundary.The simulated gain of GEM exponentially increases with the applied GEM voltage.With the PIC-MCC simulations,both the physical amplification and charging mechanisms in the GEM device can be well understood,which is beneficial to the device design.