中国光学期刊网

利用CFBR-Ⅱ快中子反应堆（中国第二座快中子脉冲堆）和⁶⁰Co装置开展不同顺序的中子/γ辐照双极晶体管的实验。在集电极-发射极电压恒定条件下，测量了双极晶体管电流增益随集电极电流的变化曲线，研究不同顺序中子/γ辐照对双极晶体管电流增益的影响。分析实验结果发现，集电极-发射极电压一定时，集电极电流极低情况下电流增益退化比较大，随集电极电流增加电流增益逐渐减小；就实验选中的两类晶体管而言，先中子后γ辐照造成双极晶体管电流增益的退化程度大于先γ后中子辐照，而且PNP型晶体管比NPN型晶体管差异更明显。本文进行了双极晶体管电离/位移协同辐照效应相关机理的初步探讨。

Stable neutron generation with a yield of ~1.2×10⁴ neutrons per pulse was obtained during d(d,n)³He reaction initiated by the high-voltage nanosecond discharge in a gap with a potential tungsten cylinder (anode) and a grounded deuterated zirconium plate (cathode) filled with deuterium at a pressure of ~10² Pa. Estimated duration of the neutron pulse was ~1.5 ns. Less intensive neutron emission was registered without deuterated plate. Splashing of material of the tungsten electrode was observed during the high-voltage nanosecond discharge in the deuterium, hydrogen, helium and argon at pressures of 10²-10⁴ Pa.

This paper describes an overview of our recent discovery – clear demonstration that LiF crystals can be efficiently used as a high-performance neutron imaging detector based on optically stimulated luminescence of color centers generated by neutron irradiation. It is shown that the neutron images we have obtained are almost free from granular noise, have a spatial resolution of and a linear response with a dynamic range of at least . The high contrast and good sensitivity of LiF crystals allow us to distinguish two holes with less than 2% transmittance difference. We propose to use such detectors in areas where high spatial resolution with high image gradation resolution is needed, including diagnostics of different plasma sources such as laser and z-pinch produced plasmas.

根据辐射屏蔽后5.5 m测点处的辐射场情况,分别设计了电流型探测器系统和成像型探测器系统.通过Geant4数值模拟分析可得:在面密度达到10 mg/cm2、初级中子产额为1012时,电流型探测器系统满足测量的信噪比,信噪比达到40∶1;在面密度达到10 mg/cm2、初级中子产额为1011时,成像型探测器系统满足测量的信噪比,信噪比好于10∶1;面密度增大时,信噪比有所改善;但是当初级中子产额达到1012时,出现中子信号重叠现象,可通过缩短曝光时间或者减小塑料闪烁体厚度来降低中子重叠率.

在惯性约束聚变实验中,用下散射法诊断燃料面密度对本底的屏蔽要求较高.分析了神光Ⅲ主机纯氘燃料靶在实际诊断环境中产生的本底辐射场,通过蒙特卡罗方法得知测量点处散射本底主要来源于初级中子与真空腔室、周围诊断平台、天花板和地板的作用.据此分析选取合适的材料和屏蔽方案.通过模拟计算,得到尺寸优化后的准直器设计方案,该方案达到了实验要求.

The laser system PALS, as a driver of a broad-beam ion source, delivered deuterons which generated neutrons with energies higher than 14 MeV through the reaction. Deuterons with sub-MeV energy were accelerated from the front surface of a massive target in the backward direction with respect to the laser beam vector. Simultaneously, neutrons were emitted from the primary target and a secondary LiF catcher. The total maximum measured neutron yield from , , reactions was .

将经验模态分解方法应用于光电探测的裂变中子事件的分析与处理中,通过引入基于二次平滑度检测的自适应的分量处理机制和基于小波阈值技术的分量去噪方法,构建了一种基于光电探测的中子裂变事件信号去噪处理新方法。模拟实验和实测数据的分析结果研究表明,在同等条件下,此方法适应性好,通过去噪处理后,信号的信噪比高,且信号的平滑度也较好,避免了因采取过度的去噪处理而将一些有用信息损失掉的不足。同时,去噪程度指标可进行量化设置。

研究了中子辐照下钛宝石单晶体缺陷的形成及光学性能的变化。对温度梯度法(TGT)生长的钛宝石晶体进行中子辐照,中子能量为1.5 MeV,剂量为4.32×1016 neutrons/cm2。辐照后194 nm吸收峰强度增加,268 nm吸收峰强度则降低。荧光谱检测中发现辐照使得420 nm荧光峰强度明显降低,荧光峰位置也蓝移至414 nm处。分析表明辐照使得钛宝石晶体内形成F+缺陷,同时Ti4+离子则转化成Ti3+离子。辐照后的钛宝石在247 ℃处有热释光TL出现,通过初始上升法计算出其陷阱深度为0.63 eV。该热释光的产生与辐照形成的色心有关,但由于钛离子的猝灭效应使得钛宝石的热释光强度较低。

通常采用概率方法来评定不确定度,但该类方法不太适用于非精确性测量数据.集中讨论了利用证据理论对非精确性中子测量数据的不确定度进行了评估,提出一个公式并对来自不精确传感器和专家估计的一些非精确性中子测量数据的不确定度进行了测度和计算.该公式可同时适用于精确性和非精确性中子测量数据,两方面的例证佐证了其应用有效性.

针对由于样本数量、测量误差和动态特性等因素,致使采用概率统计方法来对中子发生器的中子测试数据进行统计存在许多局限性和不合理性,讨论了D-S理论中的基本分配、信任函数、上下概率等概念,利用该理论对中子发生器的中子测量数据进行处理统计,最终得到中子产额在一定置信区间内概率分布上、下限值和平均中子产额.与传统的概率统计方法相比,该统计方法能适用于非精确性数据,且不受样本大小的限制.