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。     

用于个人剂量测量的硅探测器信号处理电路的设计

介绍了一种用于个人γ剂量测量的微型硅探测器的信号处理电路的设计,讨论了PCB(印制电路板)设计中应注意的问题。该信号处理电路主要包括前置放大电路、滤波成形电路和极-零相消电路,前置放大电路采用了电荷灵敏前置放大器,滤波成形电路采用了CR-RC滤波成形网络。设计的信号处理电路PCB面积仅有10 cm2,对于0.662 Me V的γ射线,信号处理电路的输出信号的信噪比达到了50:1,输出脉冲幅度达到了1.5 V左右,输出信号之后没有明显的下冲现象,其性能可以满足用于个人剂量测量的要求。     

γ射线连续液位仪中BGO闪烁体探测器设计

介绍了一种在钢铁连铸结晶器连续液位仪上使用的BGO闪烁体探测器电路的设计,并给出了信号处理电路的测试结果。     

用于复合闪烁体的α、β脉冲甄别电路设计

设计了一种用于复合闪烁体,能够甄别区分α、β脉冲信号的甄别电路,并给出了测试结果。结果表明该电路能很好地甄别α、β脉冲信号,满足了α、β复合闪烁体探测器的要求。     

SiPM核辐射探测器电路设计

本文研究基于硅光电倍增管(SiPM)和塑料闪烁体的核辐射探测器电路,设计了适用于SiPM电压偏置电路和信号放大电路,并测试了电路的相关参数:电压偏置电路噪声在5m V以下,放大电路输出信号幅度可达伏级,带宽约为80MHz,最大信噪比在50db左右,四路探测器总功率为0.84W,符合项目设计要求。     

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.     

DAMPE-PSD读出电子学研制

暗物质粒子探测卫星(dark matter particle explorer, DAMPE)是我国空间科学卫星系列的首发星,用于找出可能的暗物质粒子信号。塑料闪烁体阵列探测器(plastic scintillator detector, PSD)分系统作为卫星有效载荷的主体部件之一,参与承担高能粒子电荷测量和电子/γ射线鉴别任务。PSD由82根塑料闪烁体条和164个光电倍增管（photomultiplier tube, PMT)组成,有328个输出通道,每根塑料闪烁体条的动态范围为2×103,需配备1套完备的读出电子学系统。该电子学系统由4块前端电子学（front-end electronics, FEE）板构成,共具有360个信号处理通道,总功耗6 W。电路主要包括电荷测量电路、模拟调理电路、模数变换电路、刻度电路、环境监测电路、FPGA电路、电源管理电路以及接口电路等,其主要功能是基于32路模拟信号将PMT的电荷信号输入VA160 ASIC芯片,考虑了抗辐照加固、温度设计等一系列关键问题,以确保在严酷的太空中具有长期的可靠性。测试结果表明,该FEE系统工作稳定、性能良好,具有较好的技术指标,每个电子学通道实现了0～12.5 pC的动态范围,通道的随机噪声水平好于2 fC,积分非线性好于0.6%。FEE能适应恶劣的空间环境,具有很高的可靠性。FEE配合PSD样机还分别于2014年和2015年在欧洲核子中心（CERN）的PS和SPS终端成功完成了2次束流试验,验证了PSD的探测能力完全满足任务书中提出的功能和指标要求,能很好实现实际科学任务需求。     

手持式单板500MHz采样率数字化多道设计

针对Cs2LiYC16:CE(CLYC)闪烁晶体、掺硼塑料闪烁体等中子/γ探测器的电流脉冲波形的甄别,需要高速数字化多道脉冲幅度分析器。采用直接耦合方式设计高速模拟前端电路,将高速模数转换器(Analog-to-Digital Converter,ADC)配合现场可编程逻辑门阵列(Field-Programmable Gate Array,FPGA)芯片实现数字化设计,在FPGA内部实现了高速数字滤波、脉冲幅度提取、基线扣除、谱线存储与传输等功能。通过嵌入式的Power PC内核,实现替代外部控制器的复杂时序功能,并挂接通用串行总线(Universal Serial Bus,USB)外设芯片实现与外部计算机的高速双向数据传输。本文还设计了低噪声、大电流的开关电源,最终实现了可脱机独立运行的手持式单板高速数字多道。通过实测数字多道的模拟前端电路大信号带宽达110 MHz,小信号带宽达200 MHz,实时采样率为500 MHz,脉冲计数通过率大于107 s-1,线性度达0.999 8,连接NaI(Tl)、掺硼塑料闪烁体、LaBr_3(Ce)等闪烁体探测器实测谱线合理,满足实际使用要求。     

IEC 60412:2007《核仪器 闪烁探测器的命名(标识)和闪烁体的标准尺寸》

IEC412:1973《闪烁体标准尺寸》(Standard dimensions of scintillators)是国际电工委员会核仪器技术委员会(IEC/TC45)早年发布的关于闪烁体尺寸的国际标准。我国于1983年等效采用该标准制定了GB4077?1983《闪烁体尺寸》,曾在我国闪烁体的设计、制造、销售和使用中发挥了重要作用。由于国际电工委员会多年未提供IEC412的修订版,加之闪烁体生产技术的日益发展,产品的种类和型号迅速增加,其尺寸已突破GB/T4077的规范,所以,在2005年被废止。国际电工委员会于2007年出版了IEC412的第2版——IEC60412:2007《Nuclear instrumentation-Scintillation detectors-Nomenclature(identification)-Standard dimensions of scintillators》。该版本与第1版的最大不同是增加了闪烁探测器的命名(标识)指南;另外,闪烁体的直径增加了203.2mm(8inch)一档,闪烁体的高度增加了0.5mm(0.020inch)和400mm(16inch)两档。为使核仪器工作者了解IEC60412:2007的内容,以便用于对外贸易,并使我国闪烁探测器的命名和闪烁体的尺寸尽可能与国际接轨,特将其翻译以飨读者。     

基于核探测器信号波形特征的故障诊断研究

核探测器是一种特殊的随机信号转换器,发生故障时,采用传统的人工方法很难及时有效地对故障进行诊断。本文提出了一种针对闪烁体探测器信号波形特征的在线智能故障检测与分类方法,通过分析闪烁体探测器不同故障时的输出信号变化特征,建立了相应的故障模型。使用小波包算法与支持向量机理论分解并提取特征向量,即可判断故障类型。以ST401闪烁体探测器为例,进行了模拟仿真实验。实验结果表明,基于信号波形特征的数字化方法能快速有效地对闪烁体探测器进行故障自动诊断。     

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.