低强度脉冲中子束的数字式n/γ分辨测量

针对低强度脉冲中子束测量,使用高速数字示波器作为数据采集设备,配合BC501A液体闪烁体探测器组建了数字式脉冲形状甄别(Digital Pulse Shape Discrimination,DPSD)测量系统,实现了中子的n/γ分辨测量。系统工作时采集并存储探测器输出的中子与γ射线的脉冲波形及其记录时刻,利用DPSD方法甄别中子实现了中子脉冲高度谱统计;系统具有连续记录和具备时间戳的采集窗记录两种工作方式以适应不同的脉冲中子束强度,并通过分析数据记录中脉冲波形的位置或时间戳,实现了中子事件的时间信息统计。使用该系统在Am-Be中子源上使用采集窗工作模式开展了实验,成功获得中子脉冲幅度谱、中子时间谱以及n/γ甄别谱。     

基于FPGA的8通道脉冲波形分析器的研制

设计了一个8通道的脉冲波形分析器。此系统以双现场可编程门阵列(Field Programmable Gate Array,FPGA)为核心,板载大容量同步双端口随机存取存储器(Random-Access Memory,RAM),并行8通道96 MHz高速采样模数转换器(Analog-to-Digital Converter,ADC),能够同时对8路脉冲波形进行采样分析,得到脉冲时间间隔谱、脉冲幅度谱和脉冲宽度谱。该设备ADC以10.4 ns的采样间隔采集脉冲数据,通过通用串行总线(Universal Serial Bus,USB)2.0与电脑实现数据上传,并借助上位机进行数据的实时显示。该设备已成功运用于硬X射线调制望远镜(Hard X-ray Modulation Telescope,HXMT)卫星高能主探测器的电性测试,并能够广泛适用于核辐射研究领域。     

BaF2闪烁体探测器信号数字化方法研究

应用数字化方法对BaF₂闪烁体探测器脉冲信号进行了研究,信号的测量通过FADC和计算机系统实现,并对所采集的脉冲波形进行了离线分析。通过计算脉冲波形的面积提取了射线的能量信息,重建了能谱,并与传统电子学模拟信号测量方法得到的能谱进行了比较;应用过阈定时方法提取了脉冲的时间信息,测量并给出了4πBaF₂探测器系统的时间分布谱;应用脉冲形状甄别法对α粒子和γ射线进行了鉴别研究,根据脉冲信号快/慢成分比的差别清楚地将α粒子从γ射线中鉴别开来。本工作为在γ全吸收型4πBaF₂探测器系统中应用FADC进行多通道、多参数、大数据量数字化数据获取积累了经验。     

CLYC探测器n/γ甄别方法比较

为了实现中子和γ射线的分辨探测,搭建了基于Cs2Li YCl6:Ce3+(CLYC)闪烁体探测器、数字示波器和后端上位机的数字化核脉冲采集及分析系统,在239Pu-Be中子源产生的n/γ混合场中进行实验验证。分别采用电荷比较法、脉冲梯度法、离散傅里叶变换法和向量投影法完成了CLYC探测器的n/γ数字化脉冲波形甄别。结果表明:几种方法均可较为理想地实现CLYC探测器的n/γ甄别,在实时监测复杂辐射场时可根据需求进行算法选取。     

CLYC探测器n/γ聚类甄别方法研究

为了高性能分辨探测中子与γ射线,搭建了一套基于Cs₂LiYCl₆:Ce³⁺(CLYC)探测器和数字示波器的数字化核脉冲采集系统。通过Matlab编程,研究了系统聚类法和K-means聚类法两种n/γ脉冲波形甄别方法,并与传统的电荷比较法进行了对比。结果表明,两种聚类法均可准确分辨脉冲类别,K-means聚类法在计算时间和内存占用方面更具优势,有利于实时脉冲处理。该研究为研制基于CLYC探测器的n/γ双模式探测谱仪提供了一种有用的脉冲波形甄别技术解决方案。     

扫描成像用电子直线加速器完成现场验收

正2017年3月,6MeV电子直线加速器经过与探测器的出厂联合调试,即由外触发装置提供的同步脉冲分别触发加速器发出脉冲射线、阵列探测器光信号的采集与转换,通过图像获取软件得到某一时刻不同像素点的灰度值,从而可测量出加速器的单脉冲剂量稳定性、剂量场的初步分布等,为加速器、探测器的现场安装调试提供数据支撑。2017年5月,加速器成套设备,包括固态高压脉冲调制器、恒温水冷机组、X射线机箱等运抵用户现场并完成就位安装。加速器机头准直器为一     

热释光探测器在脉冲硬X射线能谱测量中的应用

介绍了TLD－3500热释光读出器和GR－100M型热释光剂量片构成的探测器在脉冲硬X射线辐射参数测量中的应用。详细论述了采用滤波荧光法与热释光探测器相结合测量10－10keV的硬X射线能谱的物理思想，在综合考虑了测量环境的具体情况下，设计研制了硬X射线测量系统，建立了热释光探测器对硬X射线绝对能量响应的标定方法。该方法已成功用于脉冲辐射装置“强光1号”的测量，并得到了实测数据。     

脉冲X射线参考辐射场研究与建立

脉冲辐射在新型探测器研制、工业探伤、X射线诊断、核事故应急和科学研究等领域中已得到了广泛应用,但其辐射剂量(率)测试难度极大。本文基于稳态X光机、脉冲X光机和便携式X光机研究建立了脉冲X射线参考辐射场,并基于脉冲X射线次级标准电离室和脉冲时间测量系统对辐射场的脉冲时间、脉冲剂量和瞬时剂量率等剂量学特性进行了研究。脉冲X射线参考辐射场的脉冲时间在50 ns～10 s之间可调,瞬时剂量率范围为2.5×10^-3～6.7×10⁵ Sv/h。本文所建立的脉冲X射线参考辐射场涵盖了环境水平、防护水平、诊断与治疗水平、核应急水平和核临界水平等剂量率水平范围,可用于主动式脉冲辐射剂量仪、个人剂量计和核临界事故探测与报警系统的脉冲响应特性研究,对于解决脉冲辐射剂量监测仪器的校准难题具有重要意义。     

有机闪烁体探测器数字化信号处理电路设计

介绍了基于FPGA的有机闪烁体探测器数字化信号处理电路的设计。电路设计由前置放大器、高速ADC、FPGA系统、MCU微控制系统、电源系统等组成,通过对粒子射线的模拟信号采集、后续分析处理和脉冲形状算法,实现中子和γ脉冲信号的甄别及对应剂量值的计算。主要性能测试结果表明:电路设计具有较好的中子和γ甄别效果,可实现准确有效的中子和γ剂量测量。     

脉冲X射线参考辐射场设计与研究

脉冲辐射在新型探测器研制、工业探伤、X射线诊断、核事故应急和科研等领域中已经得到了广泛应用,其辐射剂量(率)测试难度极大。为解决主动式辐射剂量仪的脉冲响应测试技术难题,基于多种X射线机建立了脉冲X射线参考辐射场,结合次级标准电离室及脉冲时间测量系统开展了脉冲辐射剂量(率)定值。实验结果表明,所建立的脉冲X射线参考辐射场的脉冲宽度在25 ns～10 s之间可调,瞬时剂量率范围为：5 mSv/h～6.7×10⁵ Sv/h,可广泛开展主动式辐射剂量仪的脉冲响应特性研究,对于解决脉冲辐射剂量监测仪器的校准难题具有重要意义。     

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.     

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.     

The role of AGFA high-energy CR in the calibration and quality control of multileaf collimators （MLC）

Linear accelerators equipped with multileaf collimators （MLC） are becoming more common and are widely used in the intensity-modulated radiotherapy （IMRT）. There is an imperative need to ensure the commissioning specification of the linear accelerators for the sake of quality assurance （QA） and quality control （QC）. This paper is aimed to investigate the role of AGFA high-energy CR （Computed Radiography） in calibrating dynamic multileaf collimators and evaluating the accuracy of the leaf position. The result shows that AGFA high-energy CR can easily and conveniently be used to calibrate MLC and verify its position. Hence, the application of AGFA high-energy CR is proved to be an accurate and time-saving method for routine MLC QC, especially when MLC calibration adjustments are required.