CSNS束流损失监控(BLM)系统电离室的改进

报道了中国散裂中子源工程(CSNS)和强流质子加速器(PA)柬流损失监控(BLM)系统的电离室的改进.对改进后的电离室测量得到,电离室有良好的坪特性(坪长≥2 000 V),测量的辐照剂量范围到3.6×10 5rad/h,高压加到3500 V仍能稳定工作.测量的结果表明电离室探头性能已能满足CSNS和PA对束流损失监控...     

重离子径迹影像探测器研制及初步实验测试

研制了一套基于气体雪崩电离室和CCD(charge-coupled device)影像获取系统的重离子径迹影像探测器。利用239Pu放出的α粒子,对所研制的重离子径迹影像探测器系统进行了初步的实验测试。测试结果显示,所研制的重离子径迹影像探测器系统能够成功地抓拍到α粒子的径迹,其径迹形貌与气体雪崩电离室中工作气体的气压、CCD相机的曝光时间等参数密切相关。对工作气体气压为15 hPa、曝光时间10 s的α粒子径迹影像数据分析表明,径迹分布呈轴对称,径迹宽度沿轴向逐渐减小,径迹影像的像点密度沿轴向逐渐增加。     

横向场气体电离室信号模拟

本文利用Geant4、Garfield和Magboltz程序模拟了横向场气体电离室的输出信号。通过比较模拟与实验结果,检验了模拟的可靠性。同时,通过模拟得出了不同工作气体对信号输出幅度的影响,其中,产生的信号幅度最大的气体为C4H10,这为以后改进此类电离室提供了理论依据。     

IMP质子治癌3D剂量探测系统

文章描述了中国科学院近代物理研究所(IMP)正在研制的IMP质子治癌装置3D剂量测量系统.该系统主要由2D剖面探测器、辐照深度和剂量探测器、射程调整器等组成.其中,多级双维位置灵敏平行板雪崩探测器(MPPAC)使用C3F8作为工作气体,工作气压为700 Pa,阳极电压为+700 V.对3组分α粒子测得位置分辨为0.54 mm(FWHM).     

用于CSNS反角白光中子源的双屏栅电离室设计及性能研究

为测量中国散裂中子源（China Spallation Neutron Source, CSNS）反角白光中子源150 keV以下能区飞行时间法中子能谱,研制基于¹⁰B(n, α)⁷Li和⁶Li(n, t)α核反应的双屏栅电离室,采用薄窗和薄底衬的结构设计。通过Garfield++、SRIM和Simcenter Magnet Electric程序对屏栅电离室的工作气体、极间距和电场分布等工作参数进行模拟设计,并采用α源及CF₄、P10、90%Ar-10%CO₂三种气体对电离室进行性能参数测试。结果表明,选定电子漂移速度快、扩散系数小,以及阻止本领大的CF4作为CSNS/Back-n束上测试工作气体,阴极-栅极和栅极-阳极间距分别为20 mm和5 mm。屏栅电离室收集区74 mm范围内是电场均匀区,场强的相对偏差≤0.03%;性能测试结果表明,工作气体为CF₄时,电离室对²³⁹Pu/²⁴¹Am/²⁴⁴Cm混合α面源具有很好的能量分辨,最佳能量分辨率为2.4%@5.48 MeV。对比平板型电离室和硅微条探测器的测量结果,验证了本工作研制的屏栅型电离室的能量分辨优势。     

300Cm~2平行板α屏栅电离室的研制

本文介绍了阴极面积为300cm~2的流气式平行板α屏栅电离室的结构和性能。电离室工作气体为 P-10(90%Ar+10%CH_4)气体,充气压约1.8×10~5Pa。在流气量小于25mL/min 时可连续工作48h。该装置的主要性能是:能量分辨率为36keV(对φ<10mm的~(239)Pu 电沉积源),4—6MeV 能区本底为12.6cph,最小可探测活度为2×10~(-4)Bq(按本底计数率标准差的3倍及27小时测量时间估计),探测效率为44%(对φ=190mm 大面积~(232)Th 源)。     

一台用于AMS的鉴别同量异位素的气体电离室

文章描述一台用于加速器质谱计(AMS)的鉴别同量异位素的气体电离室,它由三个分离的阳极、一个栅极和阴极组成。利用这台电离室,在加速器上进行了~(36)Cl的测定。它有效地排除了~(36)S等本底的干扰。     

一种束流强度监测电路设计

介绍了一种新型的电流频率(I-F)转换电路,该电路用于测量平行板气体电离室的电流信号,配合实现了中国科学院近代物理研究所重离子治癌中束流强度的监测.治癌终端的临床试验表明该束流强度监测电路具有较高的灵敏度,能很好地应用在束流强度监测系统中.该电路也可以用于条形电离室信号的读出.     

基于DCS改造最小验证平台的稳压器压力控制回路比对测试研究

通过试验研究了工作气体的压力和种类对涂硼电离室坪特性、中子灵敏度和γ感应度等性能的影响。试验结果表明,随着工作气体压力的增大,电离室坪区会向高电压方向移动,即电离室的工作电压会增大;工作气体为10%CH4+90%Ar（P10）时,当工作气体压力（从0.025 MPa 增加到0.15 MPa）增大,电离室中子灵敏度会迅速增大,继续增大工作气体压力,电离室中子灵敏度保持不变;电离室中子灵敏度会随着工作气体中高电离能气体成分增加而减小;P10气体压力在0.1~0.4 MPa范围内,电离室γ感应度与工作气体压力成正比。      

用于CSNS和PA束流损失监控(BLM)系统的电离室设计参数的优化

运用GEANT4蒙特卡洛模拟程序包,对用于中国散裂中子源(CSNS)和质子加速器(PA)束流损失监控系统(BLM)的γ电离室探头进行模拟研究,由模拟计算给出优化的电离室设计参数。工作气体选用1个大气压的氩气;内、外电极用无缝不锈钢管代替镍管,它们的分别为0.1和0.15 mm;屏蔽外壳亦选用1 mm厚度的不锈钢。按照以上参数制成的电离室模型用放射源测试,性能良好。     

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.     

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%。     

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.     

Interaction between uranium and humic acid (Ⅰ): Adsorption behaviors of U(Ⅵ) in soil humic acids

The adsorption behaviors of uranium on three soil humic acids (HAs), which were extracted from soils of different depths at the same site, were investigated under various experimental conditions. The adsorption results showed that U(Ⅵ) in solutions can be adsorbed by the three soil HAs, with the order of FHA (HA from 5 m depth of soil) ＞SHA (HA from the surface) ＞THA (HA from 10 m depth of soil) for adsorption efficiency in each desirable condition, and the adsorption reached equilibrium in about 240 min. Although the maximum adsorption efficiency was adsorption could be described with Langmiur isotherm or Freundlich isotherm equation. The L/S (liquid/solid, mL/g)ratio and pH were important factors influencing the adsorption in our adsorption system besides uranium concentration. The adsorption efficiency decreased with the increase of the L/S ratio and pH at the pH range of 2.0-3.0 for SHA and THA or 2.5 - 6.0 for FHA. However, no significant difference in adsorption of U(Ⅵ) was observed at the experimental temperature. All the results implied that humic substances have different characteristics in samples even collected at the same site.     

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。     

Information for authors

<正>1.NUCLEAR SCIENCE AND TECHNIQUES(NST),a bimonthly journal,is devoted to all aspects of nuclear science and technology,theoretical or experimental.Its special interest lies in the subjects of synchrotron radiation science and technology;low energy accelerators,radiation technology and applications;radiochemistry,radiopharmaceuticals and nuclear medicine;nuclear electronics and instrumen-     

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

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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.