高温下4H-SIC α探测器的性能研究

制成了基于4H碳化硅(4H-SiC)二极管的4H-SiC探测器,研究了室温～200℃下该探测器的IV特性,同时研究了该温度范围内4H-SiC探测器对α粒子的探测性能,获得了该探测器测得的α能谱及其半高宽和能量分辨率随温度变化的规律。探测器的正向电流值随着温度上升而逐渐增大,开启电压逐渐减小;当反向偏压一定时,在温度大于100℃时探测器的漏电流随温度迅速增加。但在温度为200℃和反向偏压为70 V的条件下,探测器的漏电流仅为190 nA。在室温～200℃范围内,4H-SiC探测器均具备α粒子探测能力。所得能谱的峰值随温度增加而增大,变化幅度相对于峰值小于1%;环境温度为200℃时,探测器的能量分辨率可达1.86%。本研究结果表明,4H-SiCα探测器具有良好的耐高温能力。     

辐照后4H-SiC带电粒子探测器的特性研究

碳化硅材料因其禁带宽度大、晶体原子离位能高等物理特性,被视为制作耐高温、抗辐射器件极具代表性的宽带隙半导体材料。为观察辐照对4H-SiC肖特基二极管带电粒子探测器的电学特性及对α粒子响应的能量分辨率的影响。利用60Co源的γ射线对4H-SiC肖特基二极管探测器进行辐照实验。经过总剂量为1 000 kGy的γ射线辐照后,探测器的正向电流相较于辐照前减小了三个数量级;反向电流值在0～120 V偏压下没有明显变化,当反向偏压高于120 V时,反向电流值变化明显。同时,辐照前后对α粒子的能量分辨率没有明显变化。     

单球中子谱仪n-γ混合辐射场中子甄别技术研究

正单球中子谱仪利用单慢化球、位置灵敏探测器的组合实现了多球谱仪的功能。采用~6Li、~7Li玻璃闪烁体实现了n-γ混合辐射场的中子甄别,探测器组件结构如图1所示。~6Li闪烁体对热中子和γ射线均有响应,而~7Li闪烁体对热中子无响应。通过前者与后者探测信号的扣除得到热中子信号,实现n-γ混合辐射场内中子甄别。在n-γ场中对单球中子谱仪使用的探测器组件开展了相应研究,探测器组件测试电路如图2所示,其中主放大器增益为10倍,ADC采集时间为300s,ROI设置为200～1 023道,并通过ADC     

夹层式中子-γ射线联合探测器设计原理

针对可能存在的单次脉冲高γ射线与中子比、10ns级γ射线和10ms级聚变中子辐射场,根据射线与物质的相互作用原理,初步提出了综合利用电流和计数模式的方法对辐射场中的γ射线和聚变中子进行探测。该辐射场中的γ射线脉冲比聚变中子提前到达,从而降低了辐射探测背景,更有利于信号的提取。     

新型超快光电辐射探测器研制

针对超快脉冲辐射测量的需求,开发了一种具有超快时间响应、大线性电流输出的新型光电探测器件——超快大电流光电管。利用脉冲氙灯、飞秒激光器对该光电探测器件的最大线性电流输出、时间响应等特性参数进行了实验测量。同时,利用该探测器件与超快闪烁体耦合构成的超快脉冲辐射探测器对亚纳秒脉冲X射线源时间谱进行了测量。结果表明,该光电探测器件对脉冲的响应前沿为251ps、半高宽小于500ps,在其典型电压下具有3A以上线性电流输出,对于亚纳秒脉冲X射线束等脉冲辐射场的测量是一较为理想的探测器件。     

用于卫星探测X、γ射线的大灵敏面积CdZnTe探测器的研发

本工作研制用于卫星探测X、γ射线的大面积CdZnTe探测器，可用于卫星与载人航天器对空间环境下的X、γ辐射场的探测。     

高压~4He气体闪烁体中子探测器的物理设计

高压4He气体闪烁体中子探测器是一种具有快响应、高n-γ甄别比和较高探测效率等特点的新型快中子探测器。本工作采用了蒙特卡罗方法研究了4He气体压强和几何尺寸对高压4He气体闪烁体中子探测器的性能影响规律,并开展了探测器结构的优化设计。研究结果表明,气压增大可线性增加中子本征探测效率;探测器长度增加会降低中子的探测效率;探测器管径增加会使中子探测效率提高。当气压取120 atm,长度和管径分别取200 mm和44 mm时,探测器对近裂变谱中子(平均能量1.05 Me V)的探测效率为4.28%,为后续探测器制备提供理论指导。     

基于固体径迹探测的中子个人剂量计性能研究

CR-39固体径迹探测器作为一款被动式的中子个人剂量计,具有方便携带、价格低廉、抗干扰能力强、对γ、β射线不敏感、对快中子响应好等优点。针对新开发的一款中子个人剂量计,根据国际标准ISO 21909-1,对新型中子个人剂量计的CR-39固体径迹探测单元的相关性能开展了实验研究。实验结果表明,CR-39固体径迹探测器具备良好的测读重复性、批次均匀性、剂量线性、稳定性、参考辐射场响应以及对光子不敏感的属性,同时给出了CR-39测量中子剂量的剂量探测下限和不确定度,为国际标准引进提供了实验数据参考。     

环境γ闪烁照射量率仪

引言在环境γ辐射监测中,要求监测仪器具有足够高的灵敏度、良好的能量响应与角响应,及抗干扰能力强、统计起伏小、功耗低、携带方便等要求。我们对闪烁探测器在环境γ辐射照射量率测量中的应用开展了研制工作,本文对其工作原理、样机性能、及实际应用结果予以介绍。原理简述测量γ辐射场照射量率的基本方法是测量自由空气电离室的电离电流。对低水平环境γ辐射照射量率测量、大都采用高气压电离室以提高探测灵敏度。     

新型硅酸镥电流型闪烁探测器性能研究

硅酸镥是一种新型的高发光强度、快响应的无机闪烁体.本工作采用硅酸镥与光电倍增管构成新型电流型探测器,并对其性能进行了实验研究.采用多种方法测量得到了该探测器的γ灵敏度能谱响应曲线,检验获得探测器的γ与中子的分辨本领至少在28以上.该探测器极其适于在脉冲中子、γ混合场中探测脉冲γ射线束.     

Preparation of Zn/TiO2 powder and its photocatalytic performance for oxidation of P-nitrophenol

Zn-doped TiO2 catalysts were prepared using a sol-gel method and characterized by XPS,UV-Vis, BET, XRD in this study. Under the irradiation of simulant sunlight, the photocatalytic activity for the degradation of p-nitrophenol was studied too. After irradiation for 2.5 h, the degradation percentage of p-nitrophenol could rise to more than 80 %. The results showed that the spectrum absorption band edge of Zn/TiO2 powder does not broaden obviously comparing with pure TiO2 powder. Zinc exists as Zn （11）. When calcined at 973 K, there is a new phase as ZnTiO3 in Zn/TiO2 catalyst. The order of photocatalytic activity of Zn/TiO2 catalysts calcined at different temperatures for p-nitrophenol is 773 K 〉 673 K 〉 873 K 〉 573 K 〉 973 K and the photocatalytic activity of Zn/TiO2 catalyst calcined at 773 K is better than TiO2 catalysts heated at the same temperature, and outclasses that of commercial TiO2 catalyst. It also showed that the photocatalytic degradation of p-nitrophenol follows first-order kinetics under the irradiation of simulant sunlight.     

Current status of radiation therapy for prostate cancer

Radiotherapy for the treatment of prostate cancer has been extensively explored in the past. Along with the comprehensive understanding of the biology of prostate cancer and rapid advances in terms of technology, the out- come of treatment for the patients with prostate cancer has improved. The authors review radiotherapy as the primary treatment for the disease, with particular emphasis on the technological advances from both the radiobiological and radiophysics aspects. Nonconventional fractionated irradiation like hyper- or hypo-fractionation has been imple- mented in the clinic, the final results still need to be confirmed in the future. Technological advances like IMRT, IGRT, in the last two decades have significantly improved the delivery of external radiotherapy to the prostate. This has re- sulted in an overall increase in the total dose that can be safely delivered to the prostate, which has led to modest im- provements in the biochemical outcome. However, establishing the standard therapy for prostate cancer remains con- troversial. It is hoped that the next decades will bring continued advances in the development of biologicals that will further improve current clinical outcomes.     

The control system for SSRF injection and extraction

This paper introduces the injection and extraction control system design for SSRF,which is a distributed control system aimed at stability and reliability of the pulse power supplies,PPS(Personnel Protection System)and MPS(Machine Protection System).The hardware environment is mainly based on PLC(Programmable Logic Con- troller),and ARM(Advanced RISC Machine)is also applied for studying stability of the power supplies.WinCC and EPICS(Experimental Physics and Industrial Control System)have been selected as the platforms of SCADA(Super- visory Control and Data Acquisition).For unifying the interfacing to the control computer,all front-end equipments are connected via Industrial Ethemet.     

水平管内含空气蒸汽强制对流冷凝换热模型研究

为研究含空气蒸汽在水平管内强制对流冷凝换热特性,基于对传热传质过程的分析,建立了管内为环状流与波状流条件下的流动冷凝换热模型。从潜热、显热和液膜3个环节对整个换热过程进行建模,最终得到计算局部冷凝换热系数的理论关系式。模型预测结果与实验数据的对比表明,二者相对偏差在±20%以内,验证了该换热模型的准确性与适用性。通过进一步的研究发现：从换热管入口至出口,随着冷凝的进行,管内换热主要热阻由液膜热阻向气液界面的凝结热阻转变;主流气体对流换热过程基本可忽略。     

Investigations on landmine detection by BF3 detector

Experiments were carried out to investigate the possible use of neutron backscattering for the detection of polyethylene (PE) sample buried in the soil. In detection of landmine by neutrons, the neutron detector and its shield play an important role. In this paper, the effects of graphite, heavy water, polyethylene and boric acid moderators on the flux of back scattered neutrons were investigated. We have also experimentally verified the effect of BF3 detector shield and obtained good agreement with theory.     

Web Services interface of SSRF archive data analysis system

Accelerator database stores various static parameters and real-time data of accelerator. SSRF (Shanghai Synchrotron Radiation Facility) adopts relational database to save the data. We developed a data retrieval system based on XML Web Services for accessing the archive data. It includes a bottom layer interface and an interface applicable for accelerator physics. Client samples exemplifying how to consume the interface are given. The users can browse, retrieve and plot data by the client samples. Also, we give a method to test its stability. The test result and performance are described.     

有效探测面积大于1000 cm2的正比计数器测量系统性能测试

为对自制的活性面积高达1 000 cm²的大面积源进行表面发射率定值,同时作为现有2πα、2πβ表面发射率标准装置能力的扩充,研制了一套内置式大面积2π多丝正比计数器测量系统,并利用活性区直径为8 mm的²⁴¹Am点源及活性区面积为10 cm×15 cm的大面积²⁴¹Am和⁹⁰Sr-⁹⁰Y源对其进行计量学性能测试。结果表明：计数器内计数响应均匀性优于±0.4%,有效探测面积达1 400 cm²;所得²⁴¹Am源高压坪曲线的坪长为1 400 V,坪斜为0.27%/100 V,坪区内计数变化为0.87%;⁹⁰Sr-⁹⁰Y源高压坪曲线的坪长为300 V,坪斜为0.75%/100 V,坪区内计数变化为0.80%;10次测量重复性好于0.4%,8 h内短期稳定性好于0.3%,1 a内长期稳定性好于0.8%。     

Assessment of radioactivity levels in some oil samples from the western desert, Egypt

Distributions of natural gamma-emitting radionuclides were determined in 93 oil samples collected from some petroleum fields in the western desert of Egypt. The radioisotope activities in the area under investigation lay in the range of (21 ± 4) to (38 ± 13) Bq?L-1 for 226Ra, (9 ± 2) to (15 ± 5) Bq?L-1 for 232Th, and (154 ± 28) to (303 ± 54) Bq?L-1 for 40K. The mean values were 27, 12, and 201 Bq?L-1, respectively. Among oils, variations in radionuclide ac- tivities could be on account of differences in TDS, HCO3, and Ba, with high or low pH. In this environment, oil prop- erties differently affected the mobilization of natural radionuclides. The range of 226Ra variation had been compared with available data from other countries. The calculated absorbed dose rate ranged from 22.33 to 32.66 nGy?h-1 in lo- cation (B) and (E) respectively, which was less than the accepted value.     

Preparation and properties of 117m Sn(IV)-TTHMP in in-vitro and in small animals

In this work,TTHMP was synthesized and labelled with 117m Sn.The preparation conditions,stability and lipophilicity of 117m Sn(IV)-TTHMP were investigated.Biodistribution of the complex in rabbits and mice was studied.It was found that the quantity of TTHMP and pH value of the prepararion solution had vital effects on the labeling yield of 117m Sn(IV)-TTHMP.It was also found that 117m Sn(IV)-TTHMP was hydrophilic and stable at room temperature and 37℃ in open air 117m Sn(IV)-TTHMP showed unexpectedly high bone uptake and bone-to-blood ratio in the animals.This made it potentially useful as an reagent for skeletal scintigraphy and radiotherapy of bone tumors.     

Gamma radiation levels in the ambient environment of the QNPP Base

Monitoring results of gamma dose rate level in 1992～2004 in the ambient environment of the Qinshan Nuclear Power Plants(QNPP)Base,the northeast of Zhejiang Province,are reported in this paper.It is shown that the gamma dose rate of five monitoring sites of 2.5 km to QNPP Base is 84～113 nGy/h,with an average of 96 nGy/h in the 13 years.The average value is close to the background level of 93 nGy/h prior to operation of the QNPP Base,and is lower than the monitoring result of 101 nGy/h at the reference site in Hangzhou City.Within 50 km from the QNPP Base,the cumulative dose rate of the thermoluminescent dosimeter(TLD)is 90 nGy/h,which is lower than the back- ground level of 111 nGy/h.