α能谱法测定241Am(n,γ)242Amg,m的反应分支比

研究建立了1种利用α能谱测定²⁴¹Am(n,γ)²⁴²Am^g,m的反应分支比K₁和K₂的方法。利用²⁴²Am^m与²⁴²Am^g半衰期差别很大的特点，分两次测量²⁴¹Am辐照样品中的²⁴²Cm含量，分别推算²⁴²Am^g与²⁴²Am^m的生成量，从而得到K₁和K₂。实际分析了某反应堆辐照的样品，测得了该反应堆中子能谱对应的K₁和K₂值。     

电荷耦合器件质子辐照效应研究

利用2×6 MV串列静电加速器提供的1~10 MeV质子,开展了线阵电荷耦合器件辐射损伤效应的模拟试验和测量,研制了加速器质子扩束扫描装置及电荷耦合器件辐射敏感参数测量系统,建立了电荷耦合器件质子辐射效应的模拟试验方法,分析了质子注量、质子能量、器件偏置等对器件电荷转移效率和暗电流的影响。模拟试验结果表明,电荷转移效率随辐照质子注量的增加而下降,暗电流随辐照质子注量的增加而增大,在1~10 MeV质子能量范围内,质子能量越低,电荷转移效率的降低与暗电流的增加越显著。     

光敏晶体管的中子位移损伤效应研究

通过开展光敏晶体管的反应堆中子辐照实验,获得位移效应实验结果,并分析位移损伤机理。研究发现,在3×10¹¹~5×10¹²cm^-2中子注量范围内,光敏晶体管增益和光响应度的下降导致集电极输出电流下降。增益的倒数与注量的增加呈线性关系,注入电流越大,线性关系的斜率越小。理论分析表明,通过提高基区掺杂水平或减小基区宽度,可提高增益的抗辐射水平;不同反向偏置电压下的初级光电流辐照前基本相同,随着辐照注量的增大,差异逐渐增大,反向偏置电压越大,初级光电流的退化越小;通过采用PIN结构或加大反向偏置电压来展宽耗尽区以减少受位移效应严重影响的扩散电流份额,可提高初级光电流的抗辐射水平。与PIN光电二极管不同,本实验注量范围内,光敏晶体管的暗电流随注量的增大而减小。     

镝活化法测量低产额脉冲中子

设计一个快中子聚乙烯慢化体，用来慢化加速器的d-T和d-D中子，利用¹⁶⁴Dy(n,γ)¹⁶⁵Dy^m在热中子区极高的反应截面，得到半衰期为75s的¹⁶⁵Dy^m，使用HPGe探测器测量¹⁶⁵Dy^m放出的γ射线。由于测得的γ射线与加速器的中子产额成一定比例，故通过这种方法可测量脉冲中子源的中子产额。     

Am-Be中子源辐射场周围剂量当量与吸收剂量的计算

根据最近更新的微观中子核反应截面数据（ENDF/B-Ⅶ库）计算了热中子到20MeV中子能区,H、C、N、O、Ar5种元素以及干燥空气和ICRU四元素组织的中子比释动能系数（kerma因子）。在此基础上,结合MCNP程序对Am-Be源外中子能谱的模拟,计算了Am-Be源中子场的周围剂量当量,单位中子注量下为373.0pSv•cm²。利用本实验室计算国产Am-Be源的中子能谱,算得相应中子场的周围剂量当量为374.0pSv•cm²,距离该源1m处空气对中子和γ射线的吸收剂量率分别为1.457×10^－2和1.580×10^-1μGy/(GBq•h)。     

位移损伤效应对AlGaN/GaN HEMT器件的影响

对AlGaN/GaN高电子迁移率晶体管(HEMT)分别进行3 MeV质子辐照和14 MeV中子辐照实验。3 MeV质子辐照下累积注量达到1×10¹⁵ cm^-2或14 MeV中子辐照下累积注量达到2×10¹³ cm^-2时，AlGaN/GaN HEMTs饱和漏电流下降，阈值电压正向漂移，峰值跨导降低。分别对3 MeV质子辐照和14 MeV中子辐照后的AlGaN/GaN HEMTs进行深能级瞬态谱(DLTS)测试。3 MeV质子辐照后缺陷浓度下降降低了反向栅极漏电流，而14 MeV中子辐照会导致缺陷浓度增加，使得反向栅极漏电流增加。根据质子和中子辐照后的缺陷能级均为(0.850±0.020) eV,推断缺陷类型均为氮间隙缺陷，质子辐照和中子辐照后氮间隙缺陷的位移导致的位移损伤效应是AlGaN/GaN HEMT器件电学性能退化的主要原因。     

g玻色子对100Pd核高自旋态能谱的影响

以新近的实验单粒子能量为输入，应用唯象sdgIBM理论的两种微观实现——微观sdgIBM-2方案和sdgIBM-F_max方案，仔细研究¹⁰⁰Pd的核能谱和B(E2)跃迁。计算结果表明:sdgIBM-2方案成功地再现了¹⁰⁰Pd核的较复杂的基态带和γ带的高角动量态能谱以及已知的B(E2)跃迁，其再现角动量达J^π=16⁺、E_x≈700MeV，比通常IBM理论再现的J^π=6⁺~8⁺、E_x≈200MeV高出很多;指认直到16⁺的yrast态都是基态，很可能目前观测到的yrast带中根本就不存在玻色子破对后的准粒子态。理论分析和数值计算进一步表明，为了能在IBM理论框架下描述好核的高角动量基态，需要平权地引入g玻色子，以便提供较强的十六极对相互作用，抵抗住高速转动下玻色子的破对趋势。用g玻色子数为0~3的弱耦合sdgIBM-F_max方案的计算结果对此作了进一步说明。按照微观sdgIBM 2方案，解释了实验上3个14⁺态的异常:14⁺₁态是由于1个中子g玻色子在转变为中子d玻色子的量子相变中辐射出1对光子的结果，14⁺₂是16⁺₁态退耦的中间态，而14⁺₃是真正的基态。     

0.144~1.2MeV单能中子参考辐射场的建立

本工作利用2×1.7MV串列加速器建立了0.144、0.250、0.565和1.2MeV单能中子参考辐射场。所需能量的中子通过⁷Li(p,n)⁷Be和³H(p,n)³He反应产生。利用TARGET程序计算了中子注量谱，利用自行设计的反复充气式反冲质子正比计数器绝对测量了上述能量点的中子注量，合成标准不确定度≤2.0%。2001年参加了由国际电离辐射咨询委员会第三分部组织的单能快中子注量测量国际比对，取得了较为满意的结果。     

基于硅光电倍增管的Cs2LiYCl6(CLYC)探测器快中子辐照效应研究

实验通过将硅光电倍增管(silicon photomultiplier, SiPM)器件和Cs₂LiYCl₆(CLYC)闪烁体探测器暴露于14 MeV的快中子场中,最高累积注量达到1.53×10¹¹ cm^-2,分析了中子辐照对SiPM器件参数和CLYC探测器性能的影响。重点研究了不同注量辐照前后,SiPM的增益、暗计数率、暗电流、击穿电压和淬灭电阻等参数,以及CLYC探测器探测性能的变化情况和原因,其中暗计数率最高上升了3个数量级,暗电流最高上升了2个数量级,CLYC探测器的能量分辨率去除本底后下降了1.4%。辐照实验后,在室温条件下对SiPM和CLYC探测器进行退火,研究SiPM器件参数和探测器性能恢复情况。SiPM和CLYC探测器的性能会随着中子注量的增加而逐渐变差。对于SiPM,主要表现为暗计数率和暗电流的提高。对于CLYC探测器,主要表现为能量分辨率的降低。退火过程有助于减轻中子辐照的影响,恢复SiPM和CLYC探测器的部分性能。     

Ru3+和［RuNO］3+的速差动力学分析方法

建立了用速差动力学分光光度法分析同一体系中Ru³⁺和［RuNO］³⁺的方法。在盐酸羟胺存在下，测定了Ru³⁺和［RuNO］³⁺与bipy的反应表观速率常数、浓度级次及反应平衡常数。通过测量反应产物Ru(bipy)²⁺₃的起始反应速率和平衡时的浓度，由建立的相关线性方程组计算出Ru³⁺和［RuNO］³⁺的浓度。Ru³⁺和［RuNO］³⁺的回收率分别为96%~105%和95%~106%。加入EDTA能较好地掩蔽常见金属离子的干扰。     

Radiation Effects on GaAs Charge Coupled Devices with High Resistivity Gate Structures

The results of a study on the effects of 1 MeV electrons and 1 MeV neutrons on the operation of high speed GaAs Charge Coupled Devices (CCDs) are presented. Radiation-induced trapping levels are characterized using a linear array CCD structure and the periodic pulse technique. 1 MeV electron irradiation introduced traps at 0.1 eV and 0.39 eV with bulk trap introduction rates of 1 cm-1 and 0.33 cm-1, respectively. The devices were irradiated to a maximum fluence of 9×1014 electrons/cm2. 1 MeV neutron irradiation introduced an electron trap level at 0.64 eV with a bulk trap introduction rate of 0.5 cm-1. Catastrophic device failure occurred at neutron fluences of 6×1013 neutrons/cm2. Device charge transfer efficiency was characterized pre- and post-irradiation over the temperature range of 80°K to 300°K.     

Charge collection and noise analysis of heavily irradiated silicondetectors

Measurements performed on high-resistivity silicon detectors irradiated with proton and neutron fluences, up to 3.5×10¹⁴ p/cm², and 4.0×10¹⁵ n/cm² respectively, are presented. The charge collection efficiency (CCE) and the output noise of the devices have been measured to carry out a detector performance study after irradiation. The CCE is found to slowly decrease for fluences increasing up to approximately 1.8×10¹⁴ p/cm². For higher particle fluences, the device inefficiency increases rapidly because full depletion could not be reached (up to 75% for the highest fluence: 4×10¹⁵ n/cm ²). A complete analysis of the noise of the irradiated devices has been carried out assuming a simple model which correlates the main noise sources to the fluence and the leakage current. A linear dependence of the square of the noise amplitude on the fluence has been observed: a value of the leakage current damage constant has been found to be in good agreement with the values reported in literature, obtained with current-voltage (IV) analysis. An extension of the noise analysis is carried out considering the detectors irradiated with very high fluences, up to 4×10¹⁵ n/cm²     

CCD在不同注量率电子辐照下的辐射效应研究

对TCD1209线阵CCD进行能量为11MeV的电子辐照试验,采用两种不同的注量率辐照后,对器件进行常温退火试验,在辐照与退火过程中考察CCD的光响应灵敏度、暗电流、参考电平、功耗电流等特性参数的变化规律。结果表明,CCD受电子辐照后主要产生电离总剂量损伤,在不同注量率电子辐照下的辐射损伤效应类似于MOS器件的时间相关效应。     

Neutron Damage Mechanisms in Charge Transfer Devices

A study of neutron damage mechanisms in charge transfer devices has been performed with emphasis placed on investigation of dark current increases. MOS capacitors were used to determine damage coefficients that are applicable to the radiation response of CCDs. Measurements of dark current density in CCDs were made following neutron bombardment. A unique value for generation-lifetime damage coefficient was determined (Kg = 7.0 × 106 n-sec/cm2) using MOS capacitors on both n- and p-type silicon substrates and this value was then used to calculate the expected change in dark current density with neutron fluence in a charge transfer device. The calculated value is in good agreement with the present experimental value of ~4×l0-11 nanoamps per neutron. A qualitative explanation is given to account for the nearly two-orders-of-magnitude difference between Kg and recombination-lifetime damage coefficients which is based in part on the nature of neutron damage in a depletion region. An explanation is also given to account for the more than six-orders-of-magnitude difference between Kg and storage-time damage coefficient. It is demonstrated that a moderate reduction in the operating temperature of a charge transfer device should result in substantial radiation tolerance in terms of neutron-induced increases in dark current.     

Neutron-induced radiation damage in silicon detectors

Ion-implanted silicon pad detectors fabricated on different n-type and p-type silicon wafers with initial resistivities between 2.6 and 12.9 kΩcm were irradiated with neutrons of ~1 MeV energy, up to a fluence of 5×10¹³ n cm^-2. The evolution of diode leakage current and capacitance characteristics is presented as a function of the neutron fluence. The reverse diode current increases proportionally to the neutron fluence. There is evidence that the doping of the initial n-type material evolves towards intrinsic and inverts to an apparent p-type at fluences between 1×10¹³ and 3×10¹³ n cm^-2, depending on the initial silicon resistivity. There is also evidence that p-type material remains of the same conduction type with a slight increase of the acceptor doping with fluence. The signal shape and the charge collection efficiency for incident β particles were measured     

线型聚能切割器热中子照相检测技术研究

研究使用热中子照相技术检测线型聚能切割器装药线密度,确定其分布均匀性,并判别装药是否存在缺陷。对多个样品进行了热中子照相,得到清晰样品图像,并通过图像处理得到样品内部装药相对线密度分布,准确呈现出装药稀疏、断续、空穴等缺陷。该方法检测结果直观、可靠、精确,弥补了线型聚能切割器现有质量检测手段的不足,对切割器质量的精确检测及其在精确爆破中的应用具有重要意义,可广泛应用于索类火工品的质量检测。     

Degradation of a COTS linear CCD induced by proton irradiation

A Commercial Off-The-Shelf (COTS) linear CCD irradiated by protons is examined experimentally in this study. A dummy output voltage, the charge transfer efficiency (CTE) and a dark signal were degraded by 2-, 5-, and 10-MeV proton irradiation for comparison. The CCDs irradiated by 2-MeV protons were damaged most seriously, and the CCDs irradiated by 5-MeV protons were damaged more than those irradiated by 10-MeV protons. Biased CCDs were damaged more seriously than unbiased CCDs with the same proton irradiation conditions. The vacancy density and distribution induced by proton displacement damage and the ionizing energy loss induced by proton ionization damage were calculated using TRIM software. The correlation between CTE degradation and nonionizing energy loss is analyzed.     

Charge transfer efficiency in proton damaged CCD's

We have performed detailed measurements of the charge transfer efficiency (CTE) in a thinned, backside-illuminated imaging charge-coupled device (CCD). The device had been damaged in three separate sections by proton radiation typical of that which a CCD would receive in space-borne experiments, nuclear imaging, or particle detection. We examined CTE as a function of signal level, temperature, and radiation dose. The dominant factor affecting the CTE in radiation-damaged CCD's is seen to be trapping by bulk states. We present a simple physical model for trapping as a function of transfer rate, trap concentration, and temperature. We have made calculations using this model and arrived at predictions which closely match the measured results. The CTE was also observed to have a nonlinear dependence on signal level. Using two-dimensional device simulations to examine the distribution of the charge packets in the CCD channel over a range of signal levels, we were able to explain the observed variation     

可逆比热容法测量反应堆中子注量率的可行性及应用前景

热分析仪器和测量技术的迅速发展为通过测量受辐照材料热性质的变化测量中子注量提供了可能。本文提出采用调制差示扫描量热（MDSC）法测量反应堆辐照的含硼材料可逆比热容的变化,进而得到反应堆的中子注量率。从理论和实验两方面讨论了利用该方法测量反应堆中子注量率的可行性。介绍了可逆比热容法测量反应堆中子注量率的原理和实验方法。展望了这种测量方法在测量高注量反应堆中子注量率的应用前景。     

Fracture toughness of irradiated and recovered vessel steels

This paper presents the fracture toughness measurements carried out on three vessel steels in an irradiated condition and after a post-irradiation recovery treatment. A statistical approach and the fracture parameters corresponding to two theoretical models of the fracture tests are used for evaluating toughness. Test results show that the neutron fluence gradually transforms the fracture behaviour of the vessel steels from ductile to brittle and seriously reduces their fracture toughness. The effectiveness of the recovery treatment, as evaluated from the toughness measurements, is confirmed, although the efficiency is not the same for the steels and depends on the evaluation parameter except in the case of almost complete recovery. The recovery effect increases with the received neutron fluence if the toughness values after treatment are compared with those in the irradiated condition rather than those in the as received condition.