快响应无机闪烁体CeF3的时间特性研究

CeF3是一种新型的适合脉冲γ测量的快响应无机闪烁体。本工作采用上升时间约为0．8ns、半高宽为1．5～2．2ns的脉冲辐射源，对CeF3与光电管构成探测器的时间响应进行了测量。多组实验测量结果表明：CeF3的脉冲响应前沿时间小于2ns，半高宽约10ns，波形响应后沿约60ns，平均发光衰减常数为20～30ns。     

快响应无机闪烁体CeF_3的时间特性研究

CeF3是一种新型的适合脉冲γ测量的快响应无机闪烁体。本工作采用上升时间约为0 8ns、半高宽为1 5～2 2ns的脉冲辐射源,对CeF3与光电管构成探测器的时间响应进行了测量。多组实验测量结果表明:CeF3的脉冲响应前沿时间小于2ns,半高宽约10ns,波形响应后沿约60ns,平均发光衰减常数为20～30ns。     

无机闪烁体CeF3的时间特性

本文用脉冲γ源方法实验测量了北京玻璃研究院生产的新型无机闪烁体CeF3的发光衰减常数，得出了该种闪烁体的两种发光成分：对于直径为45mm，厚度分别为14．5，10，4．5和3mm的4个闪烁体，其发光衰减时间的快成分在12．1－9．9ns，慢成分在34．0－30．7ns，等效衰减时间常数在26．2－20．8ns，随着闪烁体厚度的增加发光时间变慢。     

改善CeF_3闪烁探测器输出特性的方法研究

常用的CeF3闪烁探测器,由于闪烁体发光与光电器件光谱响应不完全匹配,使得探测器的主要输出特性——输出幅度和脉冲波形形状发生明显变化,较难依据相似性通过探测器输出复原得到辐射源的真实特征。本工作针对这种不完全匹配情况,分析比较了几种改善闪烁探测器输出的方法,提出了在CeF3无机闪烁体与光电器件光阴极之间加移波膜片耦合的方法。原理分析和实验测量结果表明:采取移波膜片耦合方法可使传统CeF3闪烁探测器输出特性得到明显改善,输出幅度增加50%以上,脉冲时间响应前沿由传统方式的12ns变化到移波方式的约3ns。     

ZnO(In)闪烁体在α粒子辐照下的发光特性

采用241Am-α源研究了ZnO(In)样品(购自美国Cermet Inc.公司)的发光和表面光输出特性、α粒子能谱响应和单脉冲时间响应,同时对EJ212、BC418、ST401、CeF3等闪烁体进行了比较测量。实验发现,ZnO(In)样品在α粒子轰击下,两表面的光输出相差3～5倍,显示出表面不同的光学性质。测试结果表明,ZnO(In)晶体对α粒子的能谱响应波形光滑,发光效率仅次于有机闪烁体,对单粒子脉冲时间响应快,是超快脉冲射线束探测较理想的闪烁元件。     

几种常用闪烁体受^30Coγ源辐照前后探测器灵敏度比对

在闪烁体耐辐照特性研究中，通过比较闪烁体受辐照前后闪烁探测器系统灵敏度的变化，说明在大辐照剂量后闪烁探测器是否处于正常工作状态。利用三通道脉冲X射线源（平均能量800keV）、DPF脉冲中子源（D-T中子能量14．4MeV），通过实验标定几种常用闪烁探测器对脉冲中子、脉冲X射线的相对灵敏度值。所用闪烁体包括Ф40mm，不同厚度的CeF3，NaI（T1）和BaF2等无机晶体及ST-401，ST-142Z，NE111等塑料闪烁体。     

几种闪烁体γ/n分辨能力的MC模拟计算及比较

本文利用蒙特卡罗通用程序MCNP4B对脉冲γ射线束测量中可能用到的几种闪烁体的有关性能进行了模拟计算和比较,给出了三种比较感兴趣的无机闪烁体CeF3、LSO和CsF对γ射线的能量响应曲线。并利用有关能谱数据对八种无机闪烁体BaF2、NaI、CsF、CsI、GSO、PbWO4、YAP：Ce、YAG：Ce的γ/n分辨能力进行了计算,估算了分辨能力的最大、最小值,并与有机闪烁体ST401进行了比较。     

几种常用闪烁体受60Coγ源辐照前后探测器灵敏度比对

在闪烁体耐辐照特性研究中,通过比较闪烁体受辐照前后闪烁探测器系统灵敏度的变化,说明在大辐照剂量后闪烁探测器是否处于正常工作状态.利用三通道脉冲X射线源(平均能量800keV)、DPF脉冲中子源(D-T中子能量14.4MeV),通过实验标定几种常用闪烁探测器对脉冲中子、脉冲X射线的相对灵敏度值.所用闪烁体包括φ40mm,不同厚度的CeF3,NaI(T1)和BaF2等无机晶体及ST-401,ST-1422,NE111等塑料闪烁体.     

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.     

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。     

Identification of radiation treatment of wheat （Triticum aestivum. L）and rice （Oryza sativa. L） samples using thermoluminescence of contaminating minerals

Food irradiation is gaining popularity worldwide and this technology is important to improve quality and reduce the post harvest losses of food. Because of the rapid commercialization of irradiated foods throughout the world, compliance of different regulations relating to use of technology in different countries and demand of consumers for clear labelling of irradiated foods, there is need for the development of analytical methods to detect radiation treatment of food. Among several methods studied so far, thermoluminescence （TL） is an important method that can be used to find out the irradiation history of food that contain even a very minute amount of dust particles. In this study, the irradiated and unirradiated wheat and rice samples were analyzed using the TL method. The samples were purchased from the local market of Peshawar and irradiated to radiation doses of 0.5 and 1.0 kGy using Co-60 gamma irradiator at the Nuclear Institute for Food and Agriculture （NIFA）, Peshawar. The mineral contaminants were isolated by jet water, ultrasonic treatment, and density gradient. TL glow curves of the isolated minerals from irradiated and unirradiated samples were recorded between the temperature ranges of 50-500℃ using a TL reader. Generally, the glow curves for irradiated samples showed much higher TL intensities （TL1） than the unirradiated samples. The results were normalized by rerradiation of mineral samples to gamma-ray dose of 1.0 kGy followed by determination of the second glow curves （TL2）. The ratio of the area of first glow curve to that of second glow curve （TL1/TL2） was calculated for selected temperature intervals and compared with the recommended values for unirradiated and irradiated samples. Finally, the shapes of the glow curves for irradiated and unirradiated samples were also analyzed. On the basis of these results （comparison of TL-intensities, TL1/TL2 ratios and shapes of the glow curves）, all the irradiated and unirradiated samples of wheat and rice were unequivocally identified.     

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。     

The preclinical pharmacological study of dopamine transporter imaging agent 18F-FP-β-CIT

The paper is to study pharmacologic characteristics of 18F-FP-β-CIT (18F-N-(3-fluoropropyl)-2β- carbomethoxy-3β- (4-iodophenyl)nortropane) as an imaging agent for dopamine transporter. The radiochemical purity of 18F-FP-β-CIT in aqueous solution was over 95% after standing at room temperature for 4h. Biodistribution displayed rapid uptake in rat brain (1.375 %ID/organ at 5min and 0.100 %ID/organ at 180 min) and the striatal uptake was 1.444,0.731, 0.397, 0.230 and 0.146 %ID/g at 5, 30, 60, 120 and 180 min, respectively. The values of striatum/cerebellum,striatum/frontal cortex and striatum / hippocampus in rat's brain at 30 min were 3.38, 2.17 and 2.40 respectively. The uptake in striatum can be blocked by β-CFT, suggesting that 18F-FP-β-CIT binds to DAT peculiarly. The compound was rapidly cleared from monkey's blood. The striatal uptake was bilaterally decreased in the left-sided lesioned PD rats, compared with normal control. Brain PET imaging studies in normal monkey showed that 18F-FP-β-CIT was concentrated in striatum. The test of undue toxicity showed that the dose received by mice was 1250 times as by human, which indicates that 18F-FP-β-CIT is very safe. So 18F-FP-β-CIT is a promising PET imaging agent for DAT with safety and validity.     

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.     

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.     

PLASMA SCIENCE AND TECHNOLOGY AUTHOR INDEX TO VOLUME 16(2014)

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Radioactivity levels in soil of salt field area,Kelambakkam,Tamilnadu,India

Soil samples in and around salt field area have been analyzed for natural radioactivity concentration using gamma ray spectrometer.The activity concentration for ~(232)Th,~(238)U and ~(40)K are ranged from 27.88 to 45.27 Bq/kg, from BDL to 13.30 Bq/kg,and from 135.54 to 381.28 Bq/kg,respectively.The measured activity concentrations for these radionuclides were compared with world average activity of soil.The average activity concentration of ~(232)Th in the present study is 1.19 times higher than world median value while the activity of ~(238)U and ~(40)K is found to be lower. The absorbed dose rates due to these radionuclides were calculated.The average absorbed gamma dose rate due to the presence of ~(232)Th,~(238)U and ~(40)K in soil samples is 36.99 nGy·h~(-1).These results indicate no radiological anomaly. The data presented in this study will serve as a base line survey for primordial radionuclides concentration in the study area.