CARR堆冷中子瞬发伽玛活化分析系统及实验研究  

Experimental Research on Cold Neutron Prompt Gamma-ray Activation Analysis System at CARR

作　　者：姚永刚[1] 肖才锦[1] 金象春[1] 运威旭 刘旭东 唐婵娟 石丛 杨俊凯 王平生[1] 倪邦发[1] YAO Yonggang;XIAO Caijin;JIN Xiangchun;YUN Weixu;LIU Xudong;TANG Chanjuan;SHI Cong;YANG Junkai;WANG Pingsheng;NI Bangfa(China Institute of Atomic Energy,Beijing 102413,China;Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]中国原子能科学研究院,北京102413 [2]成都理工大学,四川成都610059

出　　处：《同位素》2018年第6期362-369,共8页Journal of Isotopes

基　　金：国家自然科学基金项目(11475266);CARR基地建设项目(17ZYGC201401)

摘　　要：利用中国先进研究堆(CARR)在国内首次开展了冷中子瞬发伽玛活化分析(CNPGAA)实验,采用定制加长的电制冷高纯锗(HPGe)探测器和先进的数字多道谱仪DSPEC~? -502进行测量,获得了NH_4Cl样品中元素冷中子瞬发伽玛谱和本底谱等数据,同时利用伽玛放射源^(152)Eu、^(137)Cs、^(60)Co以及NH_4Cl产生的瞬发伽玛射线对探测器在宽能区0.1~8MeV进行能量刻度。为降低环境辐射本底,HPGe探测器外围采用环形锗酸铋(BGO)康普顿谱仪,10cm铅以及含~6Li和^(10)B材料对中子束流准直屏蔽。此外,利用金片活化法测量了CARR堆运行功率为15 MW时有无冷源情况下冷中子导管B(CNGB)末端1m处的中子注量率,结果显示有冷源时中子注量率可提高一个量级。Prompt gamma-ray activation analysis(PGAA)is a neutron beam technique in which the gamma rays are measured during sample irradiation,which is used for the analysis of light elements such as H,B,C,N,as well as for the heavy elements Cd,Sm,Gd.PGAA can be performed using either a cold or thermal beam of neutrons.Due to the advantages of minimizing gamma-ray background and maximizing neutron flux by cold neutron guide,the cold neutron prompt gamma-ray activation analysis(CNPGAA)is used primarily for certification of inorganic standard reference materials(SRMs)and measurement of trace hydrogen and boron in materials.The CNPGAA experiment was firstly carried out at China Institute of Atomic Energy(CIAE)using the China Advanced Research Reactor(CARR)with cold neutron source(CNS).In the experiment,a customized and extended electro-mechanical cooler for high purity germanium(HPGe)detector and advanced digital multichannel spectrometer DSPEC-502 were used to measure the cold neutron prompt gamma-ray spectrums of system background and NH 4Cl sample.The energy calibration was constructed for HPGe detector in the energy range from 0.1 MeV to 8 MeV using decay gamma rays produced by 152 Eu,137 Cs,60 Co and prompt gamma rays produced by NH 4Cl sample with neutron capture.In order to reduce the background of ambient radiation,the HPGe detector was surrounded successively by an annual bismuth germinate compton(BGO)suppressed spectrometer,10 cm lead and materials for neutron beam collimator including elements of 6Li and 10 B.In addition,the neutron flux was measured with and without CNS using the gold activation method at one meter far from cold neutron beam guide B(CNGB)exit of CARR under operating power of 15 MW.The results show that the neutron flux can be increased more than one order of magnitude by adding the CNS.

关 键 词：冷中子活化分析 中国先进研究堆(CARR) 瞬发伽玛谱 中子注量率 

分 类 号：TL816.3[核科学技术—核技术及应用]