甄别级CdZnTe探测器在康普顿散射成像系统中的应用研究

通过分析康普顿散射成像系统及CdZnTe探测器性能,并考虑到相应核电子学电路的噪声特性,设计了用于康普顿散射成像系统的甄别级CdZnTe探测器,并设计了与探测器相适应的低噪声小尺寸电荷灵敏前置放大器和主放大器。在常温下,5 mm×5 mm×5 mm的甄别级CdZnTe探测器与小尺寸核电子学电路系统对于662 keV的~(137)Cs源,其能量分辨率小于4%。     

背散射成像系统的甄别级CZT探测器特性研究与应用

为设计适用于康普顿背散射成像系统,通过分析成像系统及CdZnTe探测器性能,并考虑到相应核电子学电路的噪声特性,设计了甄别级CdZnTe探测器,并设计了相应的低噪声电荷灵敏前置放大器和主放大器.在常温下,5mm×5mm×5mm的甄别级CdZnTe探测器与核电子学电路系统对于662 keV的137Cs源,其能量分辨率小于4%.     

像素CdZnTe探测器的研制

介绍了研究的像素CdZnTe探测器的研发情况,包括探测器的制作和性能检测.4×4面阵CdZnTe的尺寸为11 mm×11 mm×6.3 mm,像素为2 mm×2mm.性能最好的一个像素对137Cs 662keV伽玛射线的能量分辨率达到了1.4%,在加保护环并进行各像素峰位归一修正后,整个CdZnTe探测器对 137Cs 662keVγ射线的能量分辨率为2.08%.     

空间X射线测量用电荷灵敏前置放大器和主放大器的研制

为配合我室与高能物理研究所合作的星载“多路Si—PIN探测器系统”地面原理样机项目的需要,开发研制空间X射线测量用多路电荷灵敏前置放大器和主放大器。把电荷灵敏前置放大器和主放大器共同安放在1个90mm×60mm的电路板上,有单独的3路输入和输出,相当于常规的3个电荷灵敏前置放大器和主放大器。整个电路采用低功耗的表面贴元器件,具有低噪声、低功耗、电路简单、体积小等特点,并可应用于多路探测器测量系统中。     

一个二维位置灵敏X射线探测器的研制

本文报道-个二维位置灵敏X射线探测器的研制.探测器采用多丝正比室(MWPC)结构,有效面积200×200mm2,采用阴极感应读出,由电荷重心法确定入射X射线位置.经测试,探测器的位置分辨(fwhm)好于0.4mm.     

基于DMOS管的电荷灵敏前置放大器设计

提出了一种由DMOS场效应管构成的电荷灵敏前置放大器,可用于硅,Si(Li),CdZnTe及CsI探测器。该前置放大器采用不同于传统的阻容反馈式的电路结构,完全使用MOS管搭建,该前放的设计完成为设计实现ASIC电路准备了技术基础。由Multisi m仿真结果看出该电荷灵敏前置放大器输出信号上升时间小于15ns,并且具有很好的稳定性。     

半球型CdZnTe核辐射探测器的制备与性能

CdZnTe半导体核辐射探测器具有较高的探测效率和较好的能量分辨率,可方便地应用于X、γ射线的探测,在环境监测、工业无损检测等领域具有很好的应用前景.CdZnTe探测器有多种电极结构,其中半球型结构在国内鲜有研究.该工作制备了体积为8 mm×8 m×4mm的半球型CdZnTe探测器,经测试,在室温条件下,其漏电流为nA级,对未经准直的241Am(59.5 keV)、57Co(122 keV)、137Cs( 662keV)γ射线的分辨率(FWHM)分别为6.96％、5.66％、3.92％,在连续使用的条件下具有较好的稳定性.     

小尺寸电荷灵敏前置放大器

介绍了一种应用于半导体探测器的小尺寸电荷灵敏前置放大器的实例，并分析了测量其噪声的方法，给出了降低前放噪声的几种手段。     

使用Geant4模拟CAPture电极CdZnTe探测器对γ射线的响应

采用CAPture电极CdZnTe探测器获取X射线注量谱,为建立ISO 4037-1：1996标准以外的参考辐射和计算辐射场特殊剂量物理量的约定真值提供基础。CdZnTe探测器的主要缺点是由于空穴迁移率寿命积过小,导致电荷收集不完全,全能峰左侧出现低能尾。CAPture电极CdZnTe探测器采用扩展阴极降低阴极附近区域的电场强度,弱化空穴输运对电荷收集效率的影响,实现对低能尾的抑制。但由于探测器内的电场不再均匀,电荷收集效率无法用Hecht方程计算。本文根据Shockley-Ramo原理建立了CAPture电极CdZnTe探测器电荷收集效率计算公式,用有限元分析软件模拟了探测器内的电场分布。进而用Geant4软件开展了蒙特卡罗仿真计算,确定了载流子迁移率寿命积,并取得了与实测结果基本一致的脉冲幅度谱,为建立探测器的响应矩阵奠定了基础。     

基于CdZnTe探测器的核素探针探头的研制

为了解决在核医学手术中使用放射性核素进行病灶定位的难题,设计了一种基于碲锌镉(CdZnTe)探测器的核素探针探头。该核素探针探头主要包含CdZnTe探测器、低噪声电荷灵敏前置放大器和快驱动电路。考虑到环境本底和外界电磁干扰,对探针探头的结构作了特殊设计,该特殊设计能够提高核素探针探头的探测能力。探头中的放大器和快驱动电路能明显的放大核脉冲信号的幅度和提高核脉冲信号的信噪比,便于后端信号处理分析系统对信号的进一步处理。     

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.     

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.