闪烁光纤在快中子辐照下部分特性的蒙特卡罗模拟

采用蒙特卡罗方法对闪烁光纤在快中子辐照下的特性进行了研究。利用Geant4模拟计算得到了快中子照射下,闪烁光纤中的能量沉积效率与光纤长度、半径及入射中子能量的变化曲线,同时对量子效率随上述参数的变化关系进行了模拟分析。研究结果表明选择合适尺寸的闪烁光纤和入射中子能量对于快中子成像技术具有重要的意义,并为实际测量工作中的参数选择提供了的理论指导。     

形态滤波在快中子图像降噪处理中的应用

在基于CCD耦合闪烁光纤阵列的快中子照相系统中,快中子图像受噪声污染较为严重.针对快中子图像中的椒盐噪声和泊松噪声,研究了形态滤波技术在降噪方面的应用.结果表明在对快中子图像处理过程中,基于二维多方向结构元素的形态滤波在滤除噪声和保持图像细节等方面效果较佳.     

多探测器快中子飞行时间谱仪

描述了一台串列加速器HI-13上的多探测器快中子飞行时间谱仪,并与国际上同类谱仪进行了比较。本谱仪主要用于能量大于8 MeV的快中子散射实验、次级中子双微分截面及带电粒子引起的出射中子能谱的测量。简要介绍了谱仪各主要部分(包括零信号拾取筒、氘气体靶、探测器、电子学等)的结构和特性及其在快中子实验中的应用。     

DINROS程序在中国实验快堆事故分析中的应用

DINROS是应用于多环路、多回路快中子反应堆装置瞬态工况分析计算的系统程序,也可以用于快中子反应堆动态特性及安全性能的研究.给出了DINROS程序在中国实验快堆事故分析中的应用.     

快中子活化分析

快中子活化分析主要指的是利用粒子加速器产生的快中子对于元素进行定性和定量测定的一种核分析技术。本文简要叙述了快中子活化分析,主要是14MeV中子活化分析的基本原理、分析测量技术、方法特点和应用范围。特别就快中子活化分析在核材料和核燃料方面的应用作了较为全面的介绍。并且对于快中子活化分析的现状、今后的发展动向和应用前景也作了简要的评述。     

快中子活化分析

快中子活化分析主要指的是利用粒子加速器产生的快中子对于元素进行定性和定量测定的一种核分析技术。本文简要叙述了快中子活化分析,主要是14MeV中子活化分析的基本原理、分析测量技术、方法特点和应用范围。特别就快中子活化分析在核材料和核燃料方面的应用作了较为全面的介绍。并且对于快中子活化分析的现状、今后的发展动向和应用前景也作了简要的评述。     

用4.5MV静电加速器开展快中子照相的研究

用国产原材料研制了一种适用于快中子照相的关键部件——快中子转换屏。利用⁹Be(d，n)反应在北京大学4.5MV静电加速器上产生低于7MeV能区的快中子，采用胶片成像法进行了快中子照相的初步实验。借助带不同孔径的Fe等不同材料制作的不同厚度的试验样品，对快中子胶片成像法的基本性能进行了初步测试和研究。实验结果表明，研制的快中子转换屏能够满足快中子照相的需要。     

宽基硅二极管快中子剂量计

本文简要介绍所研制的宽基硅二极管快中子剂量计,它的测程宽,对快中子的能响好,适于在γ射线、热中子、快中子的混合场中测量快中子。     

隐藏爆炸物检测装置快中子辐照安全分析

为推广隐藏爆炸物检测装置在反恐领域的应用,对快中子辐照炸药、食品及药品的安全性进行了分析。通过蒙特卡罗方法建立了装置的快中子辐照炸药安全性评估模型。通过能量沉积计算及炸药起爆机理分析可知,快中子辐照炸药不会产生爆炸的危险。采用剂量分析法对快中子辐照食品及药品的安全性进行了分析,结果表明,在隐藏爆炸物检测装置的快中子辐照条件下,食品及药品的辐照剂量在国家和国际限定的标准内,快中子辐照食品及药品的安全性是可接受的。     

基于BM3D算法的快中子图像降噪方法

在快中子照相过程中,由于受到各种因素影响,快中子图像严重降质,呈现大量噪声,不利于无损检测和后续的定量分析。通过噪声分析得出了快中子图像的噪声统计分布符合高斯噪声模型,探讨了将BM3D算法应用到快中子图像降噪处理的方法。实验结果表明,BM3D算法不仅能够有效滤除快中子图像的噪声,而且保护了图像的细节和边缘信息,可为快中子图像的降噪处理提供参考。     

Parameter Optimization Studies for a Tandem Mirror Neutron Source

A basic plasma physics tandem mirror experiment is proposed to develop the potential uses of magnetic mirror confined plasmas for a neutron source. We consider parameter variations from the currently operating symmetric mirror plasma trap GDT in an attempt to optimize the neutron source intensity while minimizing the expense and complications of the system. The combined radial and axial plasma loss rates are analyzed and shown to yield an optimal operational point that minimizes the required auxiliary heating power.     

An evaluation of grazing-incidence optics for neutron imaging

The focusing capabilities of neutron imaging optics based on the Wolter-1 geometry have been successfully demonstrated with a beam of long wavelength neutrons with low angular divergence. A test mirror was fabricated using an electroformed nickel replication process at Marshall Space Flight Center. The neutron current density gain at the focal spot of the mirror is found to be at least 8 for neutron wavelengths in the range from 6 to 20 Å. Possible applications of the optics are briefly discussed.     

Measurement of Cold Neutron Spectrum with Liquid Mirror Reflection

Making use of the wavelength dependency of the critical angle for the total reflection of neutrons, the possibility of determining the energy spectrum of cold neutrons by means of a liquid mirror is examined. A carbon tetrachloride mirror, combined with a pair of fine slits, are used for the measurement of the angular distribution of the reflection intensity of beryllium filtered neutrons. For determining the correction required to account for non-reflected neutrons detected by the counter, the direct beam component is measured by disturbing the liquid mirror surface with small ripples generated by an ultrasonic vibrator submerged in the liquid, and the value obtained with this clouded mirror is subtracted from that determined with the clear undisturbed liquid mirror. The experimental results qualitatively show good agreement with those obtained with a helical-slot neutron velocity selector, and further reveal even better resolution than possible with the latter method, in the cold neutron energy region.     

Neutron Reflectivities of Ni-Mn and Ni-Ti Multilayers for Monochromators and Supermirrors

Multilayer films for neutron mirror were made by vacuum depositing thin films of Ni and Mn or Ni and Ti on a glass plate alternately. Their neutron reflectivities were measured as a function of neutron wavelength by the time-of-flight technique. For Ni-Mn multilayer monochromators, the numbers of layers necessary to give a nearly perfect reflection (≥90%) at the main Bragg peak, were found to be 7, 11 and 21 for layer thicknesses of 163, 112 and 83 Å, respectively. The reflectivities obtained experimentally were compared with those calculated with the method applying the conventional optics, and their agreements were quantitatively reasonable. Moreover, for supermirrors, the numbers of layers and the distributions of layer thicknesses were examined in order to get a reflectivity of near unity down to the wavelength much shorter than the critical wavelength of a totally reflecting mirror of Ni. The reflectivity of a supermirror consisting of 160 layers of Ni and Ti was observed to behave like that of a totally reflecting mirror with the critical wavelength of 1/2.5 time as long as that of the conventional Ni mirror. Such a supermirror can be used to improve much the characteristics of the neutron guide tube.     

Neutron and gamma ray heating in the grazing incident liquid metal mirrors for laser inertial fusion energy power plants

A thin film of liquid metal can serve as final optics of a laser inertial fusion energy (IFE) power plant. Calculations of pulsed neutron and gamma-ray heating are presented for a grazing incident liquid metal mirror (GILMM) used for robust final optics of a laser IFE power plant. Different liquid films (Li, Na, Mg, Al, Si, K, Ga, Ag, Au, Pb, Bi and Flibe “Li₂BeF₄”) are considered at a distance of 30 m from a nominal 1 GJ fusion source as well as different substrate materials (SS-304 and SiC). The effect of neutron heating both in the liquid metal film as well as in the subsrate material will be by around three to four orders of magnitude lower than the laser heating limit. Hence the nuclear heating will not be a limiting factor for grazing incident liquid metal mirror (GILMM) of a laser IFE power plant.     

High Beta Experiments in the GDT Axisymmetric Magnetic Mirror

This paper reports recent results from the Gas Dynamic Trap magnetic mirror device. Achieving plasma betas up to 60% provides a basis for extrapolating this concept to a fusion relevant 14 MeV neutron source for testing and validating materials applicable to fusion systems.     

Cusp-stabilized mirror-based neutron source

An optimally sized Fusion Engineering Test Facility should produce 10–20 MW of power at 2 MW/m² steady-state wall loading. Because mirror cells do not scale with size, one can choose the fusion power and wall loading free from minimum size constraints. A cusp stabilized axisymmetric mirror is seen to be ideally suited for this purpose due to excellent access, a simple coil set, and good MHD properties. We present parameters for a proof of principle experiment as well as for a neutron source facility.     

Some thoughts on the production of muons for fusion catalysis

For muon-catalyzed fusion to be of practical interest, a very efficient means of producing muons must be found. We describe here some schemes for producing muons that may be more energy efficient than any heretofore proposed. There are, in particular, some potential advantages of creating muons from collisions of high-energy tritons confined in a magnetic mirror configuration. If one could catalyze 200 fusions per muon and employ a uranium blanket that would multiply the neutron energy by a factor of ten, one might produce electricity with an overall plant efficiency (ratio of electric energy produced to nuclear energy released) approaching 30%.     

Stellarator-Mirror Based Fusion Driven Fission Reactor

The version of fusion driven system (FDS), a sub-critical fast fission assembly with a fusion plasma neutron source, theoretically investigated here is based on a stellarator with a small mirror part. In the magnetic well of the mirror part, fusion reactions occur from collision of an RF heated hot ion component (tritium), with high perpendicular energy with cold background plasma ions. The hot ions are assumed to be trapped in the magnetic mirror part. The stellarator part which connects to the mirror part provides confinement for the bulk (deuterium) plasma. Calculations based on a power balance analysis indicate the possibility to achieve a net electric power output with a compact FDS device. For representative thermal power output of a power plant (P _th ≈ P _fis = 0.5–2 GW) the computed electric Q-factor is in the range Q _el = 8–14, which indicates high efficiency of the FDS scheme.     

Three Game Changing Discoveries: A Simpler Fusion Concept?

This paper encourages exploration of a broad range of magnetic fusion concepts in parallel with mainline tokamak development. Such exploration will certainly lead to increased understanding of fusion science and possibly to an attractive fusion energy concept. As an example, this paper describes three discoveries which greatly increase the attractiveness of the magnetic mirror plasma confinement concept. The mirror concept is thought to have three unattractive characteristics. The magnets are complex, the plasma is plagued with micro-instabilities and the electron temperature would never approach required keV levels. Persistent research on the gas dynamic trap device at the Budker Institute of Nuclear Physics in Russia and elsewhere have overcome these three deficiencies. Stable high energy density plasma can be confined with simple circular magnets, micro-instabilities can be tamed, and electron temperatures reaching a keV have been measured. These three accomplishments provide a basis to reconsider the mirror concept as a neutron source for medical applications, fusion materials development, nuclear fuel production, and fusion energy production.