反符合屏蔽低本底Ge(Li)γ谱仪

本文报道了一台由Ge(Li)主探测器和环形NaI(Tl)反符合探测器组成的高灵敏度γ谱仪的结构、性能和应用。谱仪用交替的物质屏蔽和井形NaI(Tl)反符合屏蔽降低本底。Ge(Li)探测器的体积为78cm~3,对~(60)Co 的1332keVγ射线的分辨率为2.42keV,不加任何屏蔽时峰康比为36.4,相对效率为16%,对~(187)Cs 点源γ射线全能峰的探测效率为1.6%。本谱仪在不加和加反符合屏蔽时,对~(137)Cs 点源的峰康比分别为79和333;康普顿区积分抑制因子为3.67,康普顿端抑制因子为5.2;在50—2700keV 能量范围内,本底抑制因子为3.2。在物质屏蔽和反符合屏蔽条件下,在上面的能量范围内,谱仪本底为24cpm。对~(137)Cs 点源,当测量时间为1000min、置信水平为95%时,谱仪的最小探测限(判断限)为2.2×10~(-2)Bq(0.59pCi)。本谱仪主要用于分析测量环境样品和其他低水平放射性样品中发射γ射线的核素的含量。     

塑料闪烁体环探测器作反符合屏蔽的NaI(Tl)γ能谱仪

本文报告了一个用塑料闪烁体环探测器作反符合屏蔽的NaI(T_1)γ能谱仪的结构及主要性能。它采用Φ76×76mmNaI(Tl)晶体作为主探测器和符合探测器,以自制的Φ500×520mm塑料闪烁体作环探测器。在有无井型反符合屏蔽条件下,能量范围0.1—2MeV时,谱仪的积分本底比为2.8,对~(137)Csγ源的康普顿减弱因子(积分比)为2.5。当源位于晶体表面中心时,谱仪对~(137)Cs源的能量分辨率和全能峰效率分别为9.5％和8.4％。     

BGO六棱柱探测元性能的研究

用~(54)Mn,~(57)Co,~(60)Co,~(22)Na和~(137)Cs源测量了BGO六棱柱探测元的能量线性,对662keV的γ射线能量分辨率为18％。两个BGO探测器间的符合时间分辨半宽度为6.9ns,BGO六棱柱与HPGe探器测间的时间分辨半宽度为8.3ns。     

锗γ谱仪110mAg 657.8 keVγ射线符合相加修正因子与137Cs效率的相关性

本文主要介绍获得HPGe γ谱仪对110mAg 657.8 keV γ射线符合相加修正因子c与137Cs全能峰效率ε的拟合直线回归方程的方法、结果及其验证.用标准110mAg 和标准137Cs水溶液,各分别制成70 mm 10个不同高度(5～55 mm)并保持相同活度的掺标源;根据137Cs γ射线能量与110mAg的657.8 keV十分接近,利用在HPGe γ谱仪表面测量10个110mAg掺标源657.8 keV γ射线的净计数率n和10个137Cs掺标源的探测效率ε的实验数据,计算不同源高度的c和ε,经拟合计算得到c=1.111 7.454ε(R2=0.9915).在与其他方法获得的c的比较和在比对(灰样)测量的应用中均获得较满意的结果;本拟合方程在一定的误差范围内,可以用到其他基质样品和其他HPGe γ谱仪上.     

FH1906型低本底 γ 闪烁谱仪

本文介绍了 FH1906型低本底γ闪烁谱仪的结构及性能。该谱仪可实现低本底γ分析测量,γ-γ符合测量,β-γ符合测量和低本底β测量等功能。在井形反符合屏蔽条件下,谱仪在0.05—2.0兆电子伏能量范围内的本底约37计数/分,对~(137)Cs点源的能量分辨率为10.6%,对~(137)Cs薄膜源的康普顿减弱因子(面积比)约为3.9,对~(137)Cs 小体积样品的最小可探测下限约为4.8×10~(-13)居里。     

锗γ谱仪~(110m)Ag657.8 keVγ射线符合相加修正因子与~(137)Cs效率的相关性

本文主要介绍获得HPGeγ谱仪对110mAg 65 7.8keVγ射线符合相加修正因子c与137Cs全能峰效率ε的拟合直线回归方程的方法、结果及其验证。用标准110mAg和标准137Cs水溶液 ,各分别制成70mm 1 0个不同高度 ( 5～ 5 5mm)并保持相同活度的掺标源 ;根据137Csγ射线能量与110mAg的 65 7.8keV十分接近 ,利用在HPGeγ谱仪表面测量 1 0个110mAg掺标源 65 7.8keVγ射线的净计数率n和 1 0个137Cs掺标源的探测效率ε的实验数据 ,计算不同源高度的c和ε,经拟合计算得到c =1 .1 1 1 +7.45 4ε(R2 =0 991 5 )。在与其他方法获得的c的比较和在比对 (灰样 )测量的应用中均获得较满意的结果 ;本拟合方程在一定的误差范围内 ,可以用到其他基质样品和其他HPGeγ谱仪上     

用反符合和热中子屏蔽降低γ谱仪本底

新建的一台反宇宙射线低本底HPGeγ谱仪,在物质屏蔽的基础上采用反符合和热中子屏蔽联合方法,实验研究次级宇宙射线μ子和中子产生的本底。结果表明,反符合屏蔽(塑料闪烁探测器)能大幅度降低μ子产生的本底,还能有效抑制快中子与锗晶体和屏蔽材料非弹性散射引起的本底,100-2000keV能区反符合积分本底抑制系数可达8倍。热中子屏蔽(镉吸收片)的加入可明显降低锗晶体和屏蔽材料热中子俘获产生的本底,使511keV正电子湮灭峰本底的抑制系数由5.8倍提高到20.7倍,100-2000keV反符合积分本底抑制系提高到13.2倍。     

锗γ谱仪110mAg 657.8 keVγ射线符合相加修正因子与137Cs效率的相关性

本文主要介绍获得HPGe γ谱仪对^110mAg 657．8keV γ射线符合相加修正因子c与^137Cs全能峰效率ε的拟合直线回归方程的方法、结果及其验证。用标准^110mAg和标准^137Cs水溶液,各分别制成φ70mm10个不同高度(5～55mm)并保持相同活度的掺标源;根据^137Cs γ射线能量与^110mAg的657．8keV十分接近,利用在HPGe γ谱仪表面测量10个^110mAg掺标源657．8keV γ射线的净计数率n和10个^137Cs掺标源的探测效率ε的实验数据,计算不同源高度的c和ε,经拟合计算得到c=1．111 7．454ε(R^2=0．9915)。在与其他方法获得的c的比较和在比对(灰样)测量的应用中均获得较满意的结果;本拟合方程在一定的误差范围内,可以用到其他基质样品和其他HPGe γ谱仪上。     

环境测量用NaI(Tl)γ谱仪

本文报道以φ100×100mm的低钾NaI(T1)晶体和GDB-76F型光电倍增管组合探头为探测器的室内外通用γ谱仪。在铅屏蔽室内,γ光子能量从0.05—2MeV范围本底计数率为1053计数/min。对~(137)Cs面源(φ5mm)的γ射线能量分辨率<10％,全能峰效率为16.3％,测量1000min,置信水平为95％,最小可探测下限为0.06Bq。环境就地测量20min可分析出10m半径范围内土壤中U系,Th系、~(40)K和~(137)Cs等核素的比放活度,并可给出距地面1m高处它们各自的γ吸收剂量率及总吸收剂量率值。     

低本底反康普顿γ谱仪分析谷物中放射性核素

通过比较低本底反康普顿HPGeγ谱仪两种操作模式(有反康和无反康)测量4种谷物样品中放射性活度的异同,讨论反康普顿抑制的优越性.结果显示,有反康时能谱中的康普顿基线本底有显著抑制,从低能区的2倍至高能区的5倍(60keV～1.46MeV)不等.但对特定核素的分析探测限不仅与康普顿本底有关,还与系统自身可能存在的特定能峰的本底净计数率有关.由于无~(137)Cs系统本底且反康抑制达4～5倍,测到4个样品中~(137)Cs比活度在0.03～0.06Bq/kg,而如没有反康则都低于探测限.由于系统中本底几乎可以忽略,~(234)Th探测限(0.2～0.4Bq/kg,对63keV)和~(228)Ac探测限(～0.1Bq/kg,对911keV)有反康时下降了20%～30%.由于测量期间的高氡环境本底,~(226)Ra(测~(214)Pb352keV峰)探测限有点高(0.7～1Bq/kg),反康未起作用.样品中的~(40)K高达22～144Bq/kg.     

FJ422型BGO反康普顿屏蔽探测器

本文介绍了FJ422型BGO反康普顿屏蔽探测器的主要性能,它与ORTEC的高纯锗探测器相配合,在无物质屏蔽的条件下,对~(60)Coγ源在50—1100keV范围内的康普顿减弱系数为4—5.5,与同样效果的NaI(T1)屏蔽探测器相比较,其体积减小了80％。     

Intrinsic Efficiency of Germanium ? A Basis for Calculating Expected Detector Efficiency

A method is presented whereby the intrinsic efficiency of Ge is utilized to calculate the expected peak efficiency of detectors having a wide range of sizes. The intrinsic efficiency of Ge, which is the probability for total absorption, was measured at 122 and 136 keV in Ge(Li) coaxial detectors and HPGe planar detectors having an effective thickness ranging from 5 to 50 mm. At 136 keV it is 64% for a thickness of 10 mm and 82% for 20 mm, after which it levels off reaching 89% at 50 mm. It is shown that the peak efficiency of a detector is a product of only the intrinsic efficiency and the solid angle, once losses due to edge escape and detector imperfections (surface channels and high dislocation densities) are determined. The absolute and relative [to NaI(T1)] peak efficiency of a sample detector, calculated on the basis of intrinsic efficiency, are in good agreement with measured values. This method should find applications in the design of new detector systems particularly those for diagnostic imaging with 99Tc (140 keV).     

基于低能特征峰的自然伽玛能谱测井方法探讨及实践

提出了一种新的自然伽玛能谱测井的方法,该方法仅探测低能伽玛射线,选定~(214)Bi的609.3keV和~(208)Tl的583.2keV特征峰分别作为铀道和钍道的计数窗口.采用HPGe伽玛谱仪对测井模型进行实验测量,获得的铀道、钍道测井曲线效果很好,验证了该方法的可行性,表明基于HPGe探头的铀矿伽玛测井研究前景诱人.     

Improved Timing with NaI(Tl)

By timing on the earliest component of the anode current pulse of the photomultiplier, the time resolution obtained with NaI(TI) at 300°K can be made somewhat superior to that reported for pure NaI at 77°K. For example, the time distribution for x rays (31. 6 keV) relative to the conversion electrons from a Cs137 source, shows a full width at half maximum of 1.6 nsec and a slope corresponding to a half life T? = 0.63 nsec. This implies that ? /R is much smaller than commonly believed, where ? is the mean life of the scintillation and R is the average number of photoelectrons per event. This small value is not due to a small ? because only the usual slow component is observed when the shape of the scintillation is measured by a probability technique. Therefore R must be larger than expected; the observed time resolution requires at least 8.7 photoelectrons/ keV. This is consistent with the value 9.3 p.e./ keV inferred from the pulse-height resolution obtained with artificial light pulses which are equivalent in amplitude to a 662-keV event in NaI(Tl). It is also consistent with the value (9. 1 p.e./keV) obtained by combining the absolute efficiency of NaI(Tl) measured by Van Sciver and Bogart with the quantum efficiency that RCA lists for the bi-alkali photocathode.     

基于数字脉冲成形技术的HPGeγ谱仪系统研究

为满足高能量分辨率γ能谱测量要求,设计了基于数字脉冲成形技术的HPGe γ谱仪系统。该系统由前端电路、数字信号处理模块和上位机软件3部分组成,实现了8192道能谱测量。本文对前端电路的设计及数字脉冲成形参数的选择进行了介绍,并用⁶⁰Co、¹³⁴Cs、¹³⁷Cs和¹⁵²Eu源对该系统进行了初步测试。测试结果表明,基于数字脉冲成形技术的HPGe γ谱仪系统对1 332 keV能量峰的能量分辨率为1.8 keV;¹⁵²Eu特征能量峰与相应道址的线性拟合参数R²=0.999 993。该系统可满足高能量分辨率γ能谱测量要求。     

低杂波电流驱动下HT-7超导托卡马克等离子体硬X射线辐射研究

用７个ＮａＩ（Ｔｌ）闪烁探测器组成的阵列观测能量范围在２０－５００ｋｅＶ,来自ＨＴ－７托卡马克等离子体的硬Ｘ射线轫致辐射。实验结果显示,硬Ｘ射线的径向辐射强度分布与低杂波的功率谱和等离子体的密度及磁志强度等放电参数密切相关。通过测量不同放电参数下硬Ｘ射线的径向强度分布,研究低杂波在等离子体中传播和吸收机制。     

On the scintillation response of NaI(TI)-crystals

Several articles have been reviewed on the scintillation response of NaI(Tl). Those publications which report results obtained with radioactive sources either dispersed throughout the NaI(Tl)-lattice or located inside the wells of NaI(Tl)-crystals match within a ±0.9% standard deviation of a linear scintillation response between 3 MeV and 3 keV. Several authors who plated their sources outside the crystals measured nonlinear responses of NaT(TI) with up to ±7% of standard deviations between 700 and 4.5 keV. The presented analysis suggests that the observed nonlinearity is not an intrinsic effect of NaI(TI) but could be caused, at least partly, by effects occurring at the radiation entrance surfaces of the crystals     

低空气比释动能率和窄谱系列过滤X射线参考辐射能谱测量和分析

利用HPGe探测器能谱仪对已经建立的低空气比释动能率和窄谱两个系列的过滤X射线参考辐射进行了实验测定,通过蒙卡模拟方法建立了探测系统的模型,模拟计算能量6 keV～305 keV间隔1 keV的响应矩阵,利用反卷能谱法得到参考辐射场的注量谱,进而计算了各参考辐射的平均能量、能量分辨率、半值层、同质系数、从空气比释动能到...     

参数法测量放射性活度

用HPGe探测器替代传统4πβ-γ符合装置中的NaI（Tl）探测器,对γ射线进行精细测量。选取一组适当的γ射线进行符合或反符合测量,计算出较为准确的β效率,从而简单地得到待测核素的放射性活度。¹³³Ba和131I活度的实验测量结果表明,4πβ-γ（HPGe）参数法是1种准确、可靠的放射性活度测量方法。     

A Well-Type Ge(Li) Detector

The feasibility and usefulness of a coaxial Ge(Li) spectrometer as a well-type detector for sum spectra of coincident gamma rays is demonstrated. The value of the welltype geometry has previously been established in nuclear gamma spectroscopy with the use of (NaI(Tl) detectors. In this work a 16 cm3 hollow cylindrical germaniun detector has been made and mounted in such a way that access to the center of the detector is achieved from outside the cryostat. The detector is a fully depleted structure in which a hole of 1 cm diameter was ultrasonically cut, and a non-injecting contact applied to the inside surface. The measured resolution of the detector for a 1173 keV gamma ray sum peak from 144Pm was 2.6 keV f.w.h.m, which was mainly limited by statistics and preamplifier noise. The detection of sum lines arising from 2 or more coincident gamma rays is demonstrated by using the radioactive source of 144pm. With the source inside the well, for which the counting solid angle is nearly 4?, the sum peak of three lines at 1791 keV (696 + 618 + 477) was observed with an energy resolution of 3.5 keV f.w.h.m, and a peak to background ratio greater than 15:1. For the source outside the detector at a distance of 10 cm, this sum line was not observed above background for comparable counting statistics. Comparison is also made to results obtained from a 3" well-type NaI(Tl) crystal.