硅半导体二重符合反冲质子望远镜

文章叙述半导体二重符合反冲质子望远镜的调试和在14MeV中子源上与伴随粒子法的比对测量。     

D-T中子源的反冲质子望远镜模拟研究

为了设计用于监测D-T中子产额的反冲质子望远镜系统,采用MCNP程序模拟了14MeV中子在不同厚度的聚乙烯膜上产生的反冲质子的产额、能谱及角分布,通过对反冲质子的产额、能谱和角分布数据的分析,给出了用于D-T中子产额监测的反冲质子望远镜系统的聚乙烯膜最佳厚度和探测器放置位置。建立了D-T中子源模型,模拟设计了反冲质子望远镜系统,并给出了系统的探测效率。     

快中子能谱在线测量的反冲质子望远镜响应模拟研究

快中子能谱是基于散裂中子源开展大气中子单粒子效应研究的关键输入参数,在线测量宽能区快中子能谱在近散裂靶位置面临飞行时间法不确定度大、中子通量高、本底干扰强等问题。设计了反冲质子望远镜(RPT)系统,利用Geant4模拟了20～200 MeV中子轰击不同厚度聚乙烯转换靶产生的反冲质子产额、角分布以及能谱,为优化探测系统设计提供了指导依据。通过模拟硅探测器与新型快响应CLLB闪烁体组成的二重符合RPT系统对入射中子的响应,分析了影响探测系统探测效率和能量分辨率的因素,确定了聚乙烯转换靶厚度为1 mm、符合质子探测器摆放角度为26.6°和探测器尺寸等重要参数,得到了RPT系统的中子响应函数矩阵,并计算了其探测效率达10-5,对高中子通量和复杂本底干扰环境下的快中子能谱在线测量具有指导意义和参考价值。     

反冲质子望远镜效率计算中的相对论修正

反冲质子望远镜和伴随粒子法是绝对测量14 MeV单能快中子通量的两种独立的方法,在高压倍加器上利用T(d,n)~4He反应可以获得14 McV单能快中子。反冲质子望远镜是通过中子入射在聚乙烯辐射体上产生反冲质子,用记录反冲质子数来确定中子通量的,而伴随粒子法则是通过记录α粒子数来测定中子通量。随着14 MeV单能快中子的应用越     

一个小型△E—E望远镜

一、引言 本望远镜是为在96MeV~(16)O+~(64)Ni系统上探测重离子而研制的。△E探测器是一个纵向电离室,它由阳极、阴极、栅极以及均压环构成。采用的工作气体为P10,使用流气式,气压稳定性为±100Pa。在气压为40kPa,栅极高压为350V,阳极高压400V时,~(241)Amα粒     

弹性反冲探测技术在材料分析中的应用

利用HI-13串列加速器提供的高品质的127I束,采用弹性反冲探测技术对材料表面成分和杂质的深度分布进行了分析.用△E-E望远镜探测器同时分析靶材料中从氢至中重的所有元素,其深度分辨为20～30 nm.用Q3D磁谱仪及其焦面探测器的高分辨动量分析,得到了纳米量级的深度分辨,此方法具有对纳米厚度的多层薄膜材料进行测试的能力.     

固体反冲质子辐射转换体THGEM快中子探测器特性模拟研究

使用Geant4模拟研究了基于聚乙烯辐射转换材料的THGEM快中子探测器的辐射转换特性。结果表明,探测器响应具有一定阈特性,其灵敏度、响应阈值随辐射体厚度、吸收层厚度、中子入射角度、辐射体面积变化而改变。中子垂直入射,聚乙烯辐射体厚度50μm、铝吸收层厚度10μm时,探测器阈上响应具有较好的坪特性,阈值为2.2 MeV,灵敏度为1.0×10-4cm2。     

静态真空度对PIN-反冲质子探测系统测量的影响

在用于脉冲中子辐射场测量的PIN-反冲质子探测系统中,静态真空的获得和保持是顺利开展测试、获取可信结果的重要保证。论文从真空度对测量产生影响的两个主要方面着手进行了研究:(1)计算了真空度对中子测量计数损失的影响;(2)分析了适于PIN探测器使用的真空条件。从两方面综合考虑,提出实际应用时将系统静态真空指标确定为百帕左右是合理和可行的。     

反冲质子磁分析技术的研究进展

反冲质子磁分析技术作为探测聚变中子能谱的新技术,具有能量分辨率和信噪比高的优点,适合混合干扰和宽量程中子注量率条件下的测量,已经成为聚变装置中子诊断的重要手段.介绍了国际上几个大科学装置研制的反冲质子磁分析谱仪和实验结果,磁质子反冲谱仪(MPR),磁分析系统使用两块分离的电磁铁,能量分辨率达2.5％;磁反冲谱仪(MRS...     

反冲靶中子探测系统DT灵敏度的实验研究

设计了实验标定用PIN-反冲质子靶室探测系统,利用加速器中子源对探测系统的DT中子灵敏度进行了实验研究,并与理论计算结果进行了比较,一致性较好.实验结果检验和验证了理论计算程序,可以为同种类型探测系统的参数设计提供实验依据.     

反冲质子探测系统中子灵敏度的Monte Carlo算法

在强流脉冲中子测量工作中,常利用PIN探测器测量中子与聚乙烯中的H核发生弹性散射产生的反冲质子.本文利用Monte Carlo技术进行快速计算的反冲质子探测系统中子灵敏度表达式,给出了算法和计算流程.     

Neutron Activation Analysis with Low Neutron Flux

Procedures are described for identifying and determining concentrations of trace impurities in minerals by means of neutron activation analysis with low neutron flux and standard gamma measurement equipment. Techniques developed in this work may be of use to those involved with the ever increasing need for mineral assays and for pollutant measurements, but who do not have the latest and most sophisticated equipment. This is especially true for institutions without formal nuclear programs and for developing countries desiring to be self-sustaining.     

In-Core Neutron Flux Instrumentation

A survey of the new work in the neutron monitoring of a nuclear power reactor is presented. The sensors have been moved into the reactor and the three modes of measurement necessary to cover the ten decades of the in-core neutron range from startup to rated power are described. The system specifications and life performance data are reviewed. Several innovative extensions of in-core monitoring such as the traversing probe and the Campbell method are covered in detail.     

Direct Measurement of Neutron Flux

An experimental study was carried out on steady-state boiling of sodium flowing in the annular channel formed around an electrically heated simulation of a fuel pin. In the present experiment, the inlet temperature and flow rate were held constant, and the heat flux was gradually increased up to the inception of boiling. Thereafter, the heat flux was further increased step by step until the surface temperature of the heater pin marked a sharp rise, indicating the occurrence of dry-out. Records were obtained of the changes brought by the increasing heat flux to boiling phenomena, with particular reference to the behavior of the two-phase flow pattern and to the characteristics of boiling noise, as well as of the frequency of bubble formation.

It was made clear that there exists a region in which steady-state boiling will be established, and under these conditions the two-phase flow pattern changes sequentially from bubbly flow to slug flow and then to annular flow. This behavior of sodium boiling in a narrow channel is quite similar to the case of water.

With rising heat flux, the level of noise intensity associated with boiling first increased sharply to attain a maximum point, then decreased somewhat and remained constant thereafter until dry-out.

The frequency of bubble formation depended on the size of the bubble. The product of bubble frequency and equivalent diameter was found to be constant.     

Optimization of Neutron Flux Distribution

A method of optimizing neutron flux distribution to obtain maximum power generation from a given core is presented. Constraining conditions governing maximum heat flux and control rod absorption are taken into consideration. It is shown that the problem is reduced to that of optimal control. In the case of one group model the phase plane technique is effective for an intuitive analysis of the problem. It is verified that the solution so obtained satisfies Pontry-agin's principle. The solution is one of “bang-pang type”. The result is extended to the case of two group model, assuming that the solution will again be of bang-pang type. A comparison is made between the one group and the two group models.     

用金活化法测定加速器中子源中子注量及MCNP4C修正

在四川大学720所2.5MeV静电质子加速器上,由核反应7Li(p,n)7Be,T(p,n)3He产生中子,对中国工程物理研究院研制的新型中子探测器进行效率刻度实验中,需要知道探测器位置处的中子绝对注量,为此我们测量了0.165、0.352、0.576、1.400MeV四个能点的中子注量。测量方法采用的是金活化法,在实验测量中,由靶头材料、冷却水层和样品的包层材料等引起的多次散射效应及中子在样品中的自屏蔽效应等均对实验结果产生影响。这些因素在实验中不可避免,也难以通过实验方法扣除,因此用Monte Carlo程序MCNP4C对上述效应进行了修正计算。     

High Efficiency Neutron Detector for Low Neutron Flux Measurement

A neutron flux detector composed of a bank of nine He³ detectors is developed. It is employed successfully to record neutron flux from a pulsed source as low as 5 × 10² neutrons per m², which is about 0.5 nrem per shot. It may find applications in recording low neutron flux at large distances from the source or in detecting leakage from the radiation shield, and hence may help to estimate health hazards.     

On Controllability of Neutron Flux Distribution

As a prerequisite to the optimal control of the neutron flux distribution of large reactors, the controllability of the flux distribution is invenstigated. The distributed parameter system is reduced to a lumped parameter system by means of truncated modal expansion. In a one dimensional reactor, any number of modes are controllable by a single control rod. To maintain the amplitude of each mode at a prescribed level however, it is necessary to have as many control rods as the number of the modes. Discussions are also presented on the decomposition of the optimal control of flux distribution into those of the individual modes, on the controllability of reactors with feedback, and on the controllability when there is constraint on the control rod speed.