氧化铒/环氧树脂辐射防护材料的制备及性能研究

用表面处理稀土氧化物Er2O3的方法制备了Er2O3/环氧树脂辐射防护材料。采用X射线衍射仪(XRD),扫描电镜(SEM),能量色散型X射线能谱仪(EDAX)等方法研究了材料的微观结构;对材料的力学性能进行了测试和分析;用多道γ谱仪和GammaVision软件测试并分析了材料的辐射防护能力;运用基于蒙特卡罗方法的EGSnrc程序模拟了射线在材料中的输运过程,讨论了射线通过材料前后注量的变化。结果表明,制得的材料致密无间隙,Er2O3粒子在材料中分布均匀,力学性能得到了改善,材料防护射线的效果明显,稀土元素Er防护低能射线的能力强于传统的屏蔽元素Pb。     

Fe_(78)Si_9B_(13)非晶薄带的力学性能与高能射线屏蔽性能研究

对Fe78Si9B13非晶薄带的微观结构、力学性能进行了初步研究,并测试了非晶薄带叠层板材对高能射线(热中子及60Co、137Cs 2种γ源射线)的屏蔽效果.Fe78Si9B13非晶薄带自由面与贴辊面的微观结构差异较大,自由面光洁平整,而贴辊面粗糙不平且有孔洞等缺陷.Fe78Si9B13非晶带材的常温抗拉强度可达1400MPa,延伸率为3.9%,而高温抗拉强度有所降低,但断裂延伸率明显提高.厚度为4.5mm、4.8mm的Fe78Si9B13非晶薄带叠层板材对0.5eV以下热中子的吸收率分别达到90.9%、94.9%;对60Co、137Cs2种γ源射线的线性减弱系数分别为0.28cm-1和0.46cm-1,说明这种非晶带材有极好的热中子吸收能力和较好的γ射线减弱效果,有望作为屏蔽材料应用在辐射防护系统中.     

氨化钡晶体闪烁特性与表征

氟化钡晶体是一种快速、耐辐照的新型闪烁材料，在高能物理、核医学、隐藏爆炸物检测、γ射线天文学、物理勘探等方面有着重要的应用前景．本文将对氟化钡晶体的特性、闪烁机理、表征及应用等作一概述．     

探测爆炸物和放射性材料的核技术方法

叙述了采用核技术方法探查隐藏爆炸物和放射性材料的优越性及其特点,重点介绍了8类主动式中子质询技术,对它们探查爆炸物的适用范围进行了剖析,对采用伽玛法的非中子质询技术作了一般性讨论.概括了各类已商用化工业中子源和伽玛射线探测器,论述了它们应用于安检系统的长处和不足.分析了两类典型的隐藏爆炸物安检问题,指出一个理想的爆炸物探查系统应具备的11项特性.介绍了国际上最受重视的伴随粒子成像和脉冲快中子系统的研制进展.简要描述了有别于主动式探查爆炸物的被动式放射性材料探查方法.指出隐藏爆炸物品和放射性物质的检查没有一种方法是万能的,不同场合不同目标需要用不同的技术或联合使用几种技术.     

基于非线性能量俘获机制的直驱浮子式波浪能发电装置研究

以直驱振荡浮子式波浪能发电装置为研究对象,探讨在应用线性和非线性能量俘获机制的情况下,装置在不规则波中的能量俘获情况。基于势流理论,针对垂荡运动,建立浮子与电机的耦合运动方程,应用四阶龙格库塔法数值求解,对非线性能量俘获机制中稳定平衡位置的影响进行研究,对线性和非线性装置在不同谱峰频率的不规则波中能量俘获功率的差异进行分析。结果表明:适当选取稳定平衡位置,非线性装置可以在低频时比线性装置俘获更多能量,且俘获能量频谱带宽更宽,更适应于实际海况中波浪能量俘获。     

巴氏噪声硬度检测方法研究

研究了一种新的硬度检测方法──巴氏噪声法．用自制的巴克豪森检测装置和洛氏硬度计对同一钢试样进行同位检测,建立了巴氏噪声综合参数γ与洛氏硬度值H的关系曲线,求出的函数关系式可作为巴氏噪声硬度检测的判定式．两种检测方法的检测结果很接近,绝对误差不大于1．5HRA研究结果表明：巴氏噪声法检测钢铁材料硬度是可行的,且具有一定的检测精度．     

用于~(60)Coγ射线照射量基准的石墨空腔电离室的研制

本文报告了一种用于γ射线照射量基准的石墨空腔电离室,采取球-圆柱形状,结构设计和材料选择保证了电离室良好的测量性能和稳定性。采用水称重法和几何尺寸测量相结合。精确测定了电离室体积。电离室内电场的合理分布,保证了可以得到良好的饱和特性。根据“等效壁厚”来考虑室壁的减弱效应,采用对“等效壁厚”外推的方法来得到室壁修正。用此电离室进行~(60)Co γ射线照射量测量的标准化,得到了满意的结果。测量照射量的合成不确定度为±0.25％。与BIPM的~(60)Co γ射线照射量测量比对,结果在0.16％以内一致,     

TiO_2膜的制备及其表面形貌对粘附力的影响

采用阳极氧化法制备出规整TiO_2纳米管阵列(TNA),溶胶-凝胶法制备致密TiO_2膜(Dense-TiO_2)。通过采用拉曼光谱(Raman)、X射线衍射(XRD)分析TNA、Dense-TiO_2表面,结果表明均为锐钛矿相,并采用场发射扫描电子显微镜(FE-SEM)、原子力显微镜(AFM)对Dense-TiO_2膜和TNA进行表征,结果表明TNA、Dense-TiO_2膜的粘附力分布呈非均一,粘附力随表面纳米形貌的变化而变化;孔径为9.9nm的TNA-V10的平均粘附力为1.65nN,孔径为35.3nm的TNA-V20的平均粘附力为2.39nN,Dense-TiO_2膜的平均粘附力为30.10nN。TNA的粘附力小于Dense-TiO_2膜的粘附力。     

测量不确定度实际应用讲座（九）：电离辐射计量中不确定度的评定

本文介绍电离辐射计量中的不确定度评定的三个具体例子，用液体闪烁计数器测定放射性核素的活度，用含氯正比计数管测量单能快中子注量和用自由空气电离室复现照射量和空气比释动能，给出了不确定度的各个分量以及合成标准不确定度的结果。一、液体闪烁计数器测量放射性活应1．基本原理液体闪烁计数器测量放射性活度是活度测量中最常用的方法之一，测量方法较多，本文只介绍用4π（LS）—γ了符合装置测量电子俘获核素的活度。孩装置采用“双死时间法”，它没有符合线路，不同于常规符合方法。当测量电子俘获核素时，液闪道卜十x）道记录核…     

巴氏噪声硬度检测方法研究

研究了一种新的硬度检测方法－巴氏噪声法,用自制的巴克豪森检测装置和洛氏硬度计对同一钢试样进行同位检测,建立了巴氏噪声综合参数γ与洛氏硬度值Ｈ的关系曲线,求出的函数关系式可作为巴氏噪声硬度检测的判定式。两种检测的检测结果很接近,绝对误差不大于１．５ＨＲＡ。研究结果表明：巴氏噪声法检测钢铁材料硬主是可行的。且具有一定的检测精度。     

Feasibility of fast neutron analysis for the detection of explosives buried in soil

A commercialized thermal neutron analysis (TNA) sensor has been developed to confirm the presence of buried bulk explosives as part of a multi-sensor anti-tank landmine detection system. Continuing improvements to the TNA system have included the use of an electronic pulsed neutron generator that offers the possibility of applying fast neutron analysis (FNA) methods to improve the system's detection capability. This paper describes an investigation into the use of FNA as a complementary component in such a TNA system. The results of a modeling study using simple geometries and a full model of the TNA sensor head are presented, as well as preliminary results from an experimental associated particle imaging (API) system that supports the modeling study results. The investigation has concluded that the pulsed beam FNA approach would not improve the detection performance of a TNA system for landmine or buried IED detection in a confirmation role, and could not be made into a practical stand-alone detection system for buried anti-tank landmines. Detection of buried landmines and IEDs by FNA remains a possibility, however, through the use of the API technique.     

A CdTe detector with a Gd converter for thermal neutron detection

A CdTe detector with a Gd converter has been developed and investigated as a neutron detector for neutron imaging. The fabricated Gd/CdTe detector with the 25 μm thick Gd was designed on the basis of simulation results of thermal neutron detection efficiency and spatial resolution. The energy resolution of the Gd/CdTe detector is less than 4 keV, which is enough to discriminate neutron capture gamma rays from background gamma emission. The Gd/CdTe detector shows the detection of neutron capture gamma ray emission in the ¹⁵⁵Gd(n, γ)¹⁵⁶Gd, ¹⁵⁷Gd(n, γ)¹⁵⁸Gd and ¹¹³Cd(n, γ)¹¹⁴Cd reactions and characteristic X-ray emissions due to conversion-electrons generated inside the Gd film. The observed efficient thermal neutron detection with the Gd/CdTe detector shows its promise in neutron radiography application.     

Thermal neutron cross-section and resonance integral for Dy(n,γ)Dy reaction

The thermal neutron cross-section (σ₀) and the resonance integral (I₀) of the reaction ¹⁶⁴Dy(n,γ)¹⁶⁵Dy were measured by the activation method, using ⁵⁵Mn(n,γ)⁵⁵Mn monitor reaction as a single comparator. The diluted MnO₂ and Dy₂O₃ powder samples within and without a cylindrical Cd shield case were irradiated in an isotropic neutron field obtained from the ²⁴¹Am–Be neutron sources, moderated with paraffin wax. The γ-ray spectra from the irradiated samples were measured by high-resolution γ-ray spectrometry with a calibrated n-type Ge detector. The necessary correction factors for γ-ray attenuation, thermal neutron and resonance neutron self-shielding effects and epithermal neutron spectrum shape factor () were taken into account in the determinations. The thermal neutron cross-section for ¹⁶⁴Dy(n,γ)¹⁶⁵Dy reaction studied has been determined to be 2672±104 b at 0.025 eV. This result has been obtained relative to the reference thermal neutron cross-section value of 13.3±0.1 b for the ⁵⁵Mn(n,γ)⁵⁶Mn reaction. For the thermal neutron cross-section, most of the experimental data and evaluated one in ENDF/B-VI, in general, are in good agreement with the present result. The resonance integral has also been measured relative to the reference value of 14.0±0.3 b for the ⁵⁵Mn(n,γ)⁵⁶Mn monitor reaction using a 1/E¹⁺ epithermal neutron spectrum of the ²⁴¹Am–Be neutron source. By defining Cd cut-off energy 0.55 eV, the resonance integral obtained was 527±89 b. The existing experimental and evaluated data for the resonance integral are distributed from 335 to 820 b. The present resonance integral value agrees with some previously reported values, 520 b by Holden, 505 b by Simonits et al. and 575±100 b by Heft, within the limits of error.     

In situ prompt gamma-ray activation analysis of water pollutants using a shallow 252Cf-HPGe probe

A shallow ²⁵²Cf-HPGe probe used for in situ prompt γ-ray activation of water pollutants is described. A 2.7 μg ²⁵²Cf neutron source and a 10% HPGe detector are inserted into a waterproof stainless steel probe, which is designed to be submerged and recovered in field operation. A laboratory test is performed to obtain the neutron flux distribution and prompt γ-ray contribution to the HPGe detector counts from around the submerged probe. The concentrations of toxic cadmium and chlorine in water are determined in the prompt γ-ray spectrum. The detection limit of industrial pollutants and some improvements of the current design are discussed.     

Ce~(3+)激活的锂-6玻璃闪烁体发光及核物理性能的研究

选取Ce~(3+)为激活剂离子,锂-6和硼-10为靶核核素分别研制了可用于热中子探测的玻璃闪烁体,并系统研究了其发光性能及部分核物理性能.研究结果表明,Ce~(3+)激活的锂-6玻璃闪烁体具有较长的发射波长(390nm),较短的衰减时间(46.9ns)以及良好的γ射线甄别性能和温度效应,是探测热中子优良的玻璃基质材料.靶核核素与激活剂离子在锂-6玻璃闪烁体中均有一较佳的浓度范围,浓度过大将产生不同程度的淬灭效应.     

Photon spectrometry in thermal neutron standard field

An NE213 liquid scintillation counter (5.08 cm in diameter and 5.08 cm long) with an LiF filter was used to measure the energy distribution of photons mixed in a thermal neutron field. The response function matrix of photons in an energy range up to 10 MeV was calculated by the EGS4/PRESTA code and properly folded with a resolution function. Pulse height spectra measured with a set of reference γ-ray sources were compared to the calculated response function and agreed very well for all reference γ-ray sources. The GRAVEL and MIEKE codes from the HEPRO program were used to unfold measured pulse height spectra. Energy distributions obtained by the unfolding were applied to evaluate the effective dose equivalent of photons mixed in a thermal neutron field.     

An airport cargo inspection system based on X-ray and thermal neutron analysis (TNA)

A cargo inspection system incorporating a high-resolution X-ray imaging system with a material-specific detection system based on Ancore Corporation's patented thermal neutron analysis (TNA) technology can detect bulk quantities of explosives and drugs concealed in trucks or cargo containers. The TNA process utilises a 252Cf neutron source surrounded by a moderator. The neutron interactions with the inspected object result in strong and unique gamma-ray signals from nitrogen, which is a key ingredient in modern high explosives, and from chlorinated drugs. The TNA computer analyses the gamma-ray signals and automatically determines the presence of explosives or drugs. The radiation source terms and shielding design of the facility are described. For the X-ray generator, the primary beam, leakage radiation, and scattered primary and leakage radiation were considered. For the TNA, the primary neutrons and tunnel scattered neutrons as well as the neutron-capture gamma rays were considered.     

Enhanced variant designs and characteristics of the microstructured solid-state neutron detector

Silicon diodes with large aspect ratio perforated microstructures backfilled with ⁶LiF show a dramatic increase in neutron detection efficiency beyond that of conventional thin-film coated planar devices. Described in this work are advancements in the technology with increased microstructure depths and detector stacking methods to increase thermal neutron detection efficiency. The highest efficiency devices thus far have delivered over 37% intrinsic thermal neutron detection efficiency by device-coupling stacking methods. The detectors operate as conformally diffused pn junction diodes with 1 cm² square-area. Two individual devices were mounted back-to-back with counting electronics coupling the detectors together into a single dual-detector device. The solid-state silicon device operated at 3 V and utilized simple signal amplification and counting electronic components. The intrinsic detection efficiency for normal-incident 0.0253 eV neutrons was found by calibrating against a ³He proportional counter and a ⁶LiF thin-film planar semiconductor device. This work is a part of on-going research to develop solid-state semiconductor neutron detectors with high detection efficiencies and uniform angular responses.     

基于Geant4模拟中子输运过程及建立中子监测模型

通过研究Geant4程序的中子输运模型与反应截面库,构建热中子至20 MeV中子的输运过程,为验证Geant4中子输运过程的正确性,通过建立中子监测模型,再根据监测模型设计试验装置,最后将试验装置放入中子参考辐射场中进行测试验证.模拟与实验结果表明:试验装置在241Am-Be中子源和252Cf源中子参考辐射场中测试结果最大误差为2.5％.     

爆炸物的探测技术综述

介绍了目前已经应用的和在研的各类爆炸物探测方法,并指出了每种方法的优缺点。其中,重点介绍了X射线成像技术及中子探测技术。目前,许多新的检测技术仍处在不成熟的阶段,漏报率与误报率始终存在,并且对于核检测技术而言,高灵敏度对应的高能量源与相应的屏蔽措施造成的设备体积过大是一对需要解决的矛盾。