两种位置灵敏平行板雪崩探测器

为兰州重离子加速器放射性次级束流线 (RIBLL)设计研制了两种结构双维位置灵敏低压气体平行板雪崩探测器 (PPAC)。用 3组分α粒子辐照 ,传统结构的PPAC ,对于 70 0Pa异丁烷和C3F8工作气体 ,分别得到 0 76mm(FWHM )和 0 64mm(FWHM)的位置分辨 ,探测效率为 99 1 %。新的多级位置灵敏平行板雪崩探测器 (MPPAC) ,对 65 0Pa异丁烷工作气体 ,测得 0 5 8mm (FWHM )的位置分辨、99 2 %探测效率和色散远好于± 0 2mm的位置线性。MPPAC增益较传统PPAC高 ,C3F8较异丁烷阻止本领强 ,适合探测较轻粒子。     

17F+p共振态弹性散射实验中PPAC性能测试

在兰州放射性次级束流线（RIBLL）上进行的¹⁷F+p共振态弹性散射实验中,用到的位置灵敏平行板雪崩探测器（PPAC）使用延迟线读出法,使得PPAC有着很干净的本底噪声和较好的信噪比。对实验所用的PPAC进行了性能测试,经分析,位置分辨好于1mm、时间分辨为0.29ns、探测效率为97%以上,达到了实验要求。     

一种高性能双维位置灵敏平行板雪崩探测器

本文描述了为兰州放射性离子束流线（RIBLL）研制的一种高性能平行板雪崩计数器（PPAC）。它由中心阳极和X、Y位置阴极构成，阳极间距3mm。阳极为1.5mm厚Mylar膜，双面镀金。阴极为φ25μm镀金钨丝，丝距1mm，位置读出采用电荷分除法。工作气体异丁烷。当工作气压为700Pa，阳极电压为500V时，对3组分α粒子位置分辨0.76mm(FWHM)，探测效率约99.1％。     

快时间分辨平行板雪崩计数器性能测试

用²⁴¹Amα源对裂变多参数实验中使用的平行板雪崩计数器(PPAC)进行了各探测单元时间分辨和位置分辨的系统测试。PPAC的工作气体为异丁烷,流气气压为600Pa,阴极工作电压为-600V。使用飞行时间法测得探测单元的时间分辨好于400ps,使用延迟线法得出位置分辨为6mm。结果表明,PPAC的性能满足实验需求。     

掠入射涂硼多丝正比室中子探测器设计及其性能模拟

针对国内中子散射谱仪对高效率高位置分辨的热中子探测器需求,对基于多层掠入射涂硼多丝室的新型位置灵敏中子探测器进行了模拟研究。利用蒙特卡洛模拟软件Geant4对探测器的中子探测效率、位置分辨率以及基材对中子的散射进行了模拟仿真。结果表明,采用掠入射多层结构可以实现较高的中子探测效率和位置分辨率。当掠入射角度为5°时,采用3层结构可以对波长2.5 A的热中子实现62%的探测效率;对于2 mm的阳极丝间距,掠入射结构下探测器的位置分辨(FWHM)可达0.286 mm。     

基于波形采样的PPAC数据处理

数字化波形采样技术在实验核物理中得到了广泛的应用,选取合适的采样频率非常重要。本文使用脉冲幅度甄别定时方法和恒比定时方法对采样频率为100 MHz~5 GHz的平行板雪崩计数器(PPAC)信号进行了模拟分析,采样频率为250~500 MHz时,使用脉冲幅度甄别定时方法可得到比较精确的位置信息,与传统获取系统定位的位置分辨的差别Sigma小于0.15 mm,采样频率低于100 MHz时信号定位误差较大。使用高速采样数字化仪可对信号幅度小于20 mV的信号进行定时分析,与传统的PPAC获取系统相比,探测效率提升了4.3%。     

基于波形采样的PPAC数据处理

数字化波形采样技术在实验核物理中得到了广泛的应用,选取合适的采样频率非常重要。本文使用脉冲幅度甄别定时方法和恒比定时方法对采样频率为100 MHz～5 GHz的平行板雪崩计数器(PPAC)信号进行了模拟分析,采样频率为250～500 MHz时,使用脉冲幅度甄别定时方法可得到比较精确的位置信息,与传统获取系统定位的位置分辨的差别Sigma小于0.15 mm,采样频率低于100 MHz时信号定位误差较大。使用高速采样数字化仪可对信号幅度小于20 mV的信号进行定时分析,与传统的PPAC获取系统相比,探测效率提升了4.3%。     

微小角中子散射谱仪的高分辨中子闪烁体探测器研究

微小角中子散射谱仪是中国散裂中子源(China spallation neutron source,CSNS)工程目前在建的谱仪之一,为了实现微小角散射模式下中子衍射的精确测量,要求中子探测器的位置分辨≤2 mm、探测效率≥60%@0.4 nm。在此物理精度需求下,研制了基于⁶LiF/ZnS(Ag)闪烁屏、波移光纤阵列和硅光电倍增管(Silicon Photomultiplier,SiPM)结构的位置灵敏型闪烁体探测器,以实现热中子的高效率和高分辨实时探测。探测效率测试以标准3He管的入射中子数归一化计算得到,位置分辨通过含有“CSNS”字样的含硼铝板验证。本文详细研究了0.5 mm直径波移光纤的光传输性能,对比了不同硅光电倍增管的增益和热噪声特性,并以此设计了有效面积为300 mm×300 mm的探测器工程样机。经测试,该探测器的位置分辨为1.2 mm×1.2 mm,探测效率为(61.8±0.2)%@0.4 nm,达到了工程设计指标,满足了CSNS工程微小角谱仪的中子衍射测量需求。     

一种多极平行板雪崩探测器

描述了一种为RIBLL研制的在线束流监测用双维位置灵敏多极平行板雪崩探测器(Multi-platePPAC)。它主要由中心阳极、两个位置灵敏栅极和两个阴极平面组成。灵敏面积为100mm×100mm。使用异丁烷工作气体,气压稳定在650Pa,阳极在+400V,阴极在-350V时,对三组分α源测得探测器的位置分辨约0.58mm(FWHM),位置非线性±50μm,探测效率好于99.2%。由于该探测器明显的高增益,它适合探测较高能量的较轻粒子。     

用于次级束物理实验的低气压多丝室

阐述了位置灵敏探测器在核物理实验中的作用，同时详细叙述了低气压多丝室(LP—MWPC)的工作机理及时间、位置特性．描述了用于较高能量轻粒子的次级束实验的LP—MWPC的结构和测试结果，得到△X＝△Y＝0．7mm的位置分辨。     

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.