The Development and Application of a Beta-Gamma-Gamma Multidimensional Spectrometer

A beta-gamma-gamma multidimensional spec trometer has been developed which employs two 12-inch diameter by 8-inch thick NaI(Tl) crystals with associated 4-inch thick NaI light pipes and two 5-inch diameter by 1/2-inch thick gas proportional counters as principal detectors and which utilizes two 40-inch diameter by 24-inch thick plastic phosphors as anticoincidence shields. The detector system is coupled to two 4096 word computer memories which record gamma-ray events in coincidence with either beta detector. The gamma-ray energies identify the radionuclide while the beta detectors can identify the relative position of the radioactivity in the specimen being analyzed. The background and efficiency of the system and its application to the identification of radionuclides in environmental, biological, and extraterrestrial materials are discussed.     

Bismuth Germanate: A High-Z Gamma-Ray and Charged Particle Detector

The room-temperature scintillation characteristics of single crystals of Bi4Ge3O2 under gamma-ray and alpha-particle excitation have been determined. The wavelength of maximum intensity in the scintillation spectrum is 480 nm. A decay constant of 0.30 microseconds was measured. Scintillation efficiency (pulse height) varied linearly with gamma-ray energy, E, and the resolution varied as E-1/2. 8% pulse height relative to NaI(Tl) with 15% resolution was measured for a 2.2 cm × 1.7 cm crystal under excitation by Cs137 0.662 Mev gamma-rays.     

采用基于标准谱的热中子俘获瞬发活化伽玛分析方法分析NaCl水溶液

使用ＮａＩ（Ｔｌ）等能量分辨率较低但探测效率高的探测器在复杂环境进行在线热中子瞬发活化伽玛分析时宜采用基于标准谱分析方法。该方法包括标准谱完全集的获得，加权最小二乘解谱，灵敏度及归一化参数刻度等关键环节。我们采用ＮａＩ（Ｔｌ）探测器，使用＾２５２Ｃｆ中子源，对ＮａＣｌ水溶液进行了分析，获得了较好的精度。     

X射线机重过滤X射线能谱的测量

本文报道了用 NaI(Tl)闪烁谱仪对国产 F34-Ⅰ型 X 射线机的重过滤 X 射线能谱的测量和解谱方法,给出一组测量结果,并对测量结果进行了比较和讨论。     

Automatic Analysis of Gamma-Ray Spectra on Small Computers

A program for the automatic analysis of Ge(Li) gamma-ray spectra is described. Owing to its reduced size it can be used on small (16 K memory words) computers. For the design of the program, the steps of manual methods of analysis have been followed as closely as possible. Most of the subroutines are written in Fortran II language.     

Resolution in large rectangular NaI(Tl) detectors: a study

Experiments were carried out for studying the resolution of 4-in (10-cm)×4-in (10-cm)×16-in (40-cm) NaI(Tl) detectors used in high-sensitivity airborne gamma-ray spectrometric surveys. Change of resolution with source-detector geometry emphasized the inadequacy of existing specifications for resolution in explaining the detector response. An additional specification for resolution measurement, namely, overall resolution, is proposed. Measurement and applications of overall resolution of the detector are discussed     

Hard X-Ray Images Created by a Series of Harmonically Related Modulation Collinators

A series of images of hard (30 - 300keV) X-ray sources have been created by use of a multi-pitch rotating modulation collimator (RMC) and a striped NaI(Tl)/CsI(Tl) scintillator detector arrangement. The performance of the system with respect to a series of point and extended objects has been analysed. The implications with respect to space instrumentation are discussed.     

SPAS-G:高分辨率γ谱定量分析程序

本文叙述了一个高能量分辨率γ谱定量分析程序。由于程序中包含了几种不同的峰分析方法,对不同的谱数据和不同的计算机系统都有良好的适应能力。文中对于适应于微型计算机的线性函数拟合计算峰净面积方法的精度也进行了讨论。     

The Characteristics of an Ultra-High Resolution Ge(Li) Spectrometer for Singles and Coincidence X-Ray and Gamma-Ray Studies

The use of an ultra-high resolution Ge(Li) photon spectrometer in low and high energy X-ray and gamma-ray measurements has been evaluated. Studies were made of the resolution, low energy cutoff, the full energy and K X-ray escape efficiencies, tha effective detector dead layer and the detector linearity. The detector was used simultaneously with a high resolution Si(Li) detector to measure fast coincidences between Ka1 , Ka2 and L X-rays, as well as coincidences between K, L conversion electrons and L X-rays. A detailed discussion is presented of the electronic problems associated with making these kind of measurements. Measurements were also made of X-ray beams produced by clinical X-ray machines at 40, 78 and 220 kV.     

惰性气体β-γ符合测量系统探测器能量及分辨率刻度

β-γ符合法是全面禁止核试验条约(CTBT)放射性核素核查中惰性气体氙测量的一种重要方法,探测器能量及分辨率刻度是其首要解决的关键技术。本工作详细介绍了β-γ符合测量系统NaI(Tl)闪烁体和塑料闪烁体探测器能量及分辨率刻度的方法和结果,采用γ放射性核素点源刻度NaI(Tl)γ射线能量及分辨率,利用137Cs661.66keVγ射线康普顿散射电子刻度塑料闪烁体β射线能量及分辨率,并与131Xem内转换电子刻度的β射线能量分辨率结果进行了比较。结果表明:用137Cs康普顿散射电子刻度塑料闪烁体β射线能量是一种简便可行的方法,但用其刻度的β射线分辨率比实际的大。     

野外γ谱仪刻度的蒙特卡罗模拟

用蒙特卡罗方法对NaI(Tl)野外γ谱仪刻度进行模拟,计算谱仪的响应系数.通过与实验的比较,研究利用蒙特卡罗方法对NaI(Tl)野外γ谱仪进行刻度的可行性.结果表明,当模拟探测器对137Cs的能量分辨率从8%～14%变化时,模拟结果与实验结果的差别在12%以内.     

Measurements of keV-neutron capture cross sections and capture gamma-ray spectra of 105Pd

The neutron capture cross sections and capture gamma-ray spectra of ¹⁰⁵Pd were measured in the region from 15 to 100 keV and at 585 keV. A neutron time-of-flight method was utilised with an anti-Compton NaI(Tl) spectrometer and a 1.5-ns pulsed neutron source by the ⁷Li(p,n)⁷Be reaction. The capture yields were obtained by applying a pulse-height weighting technique to the observed net capture gamma-ray pulse-height spectra. The capture cross sections of ¹⁰⁵Pd were derived with errors less than 5%, using the standard capture cross sections of ¹⁹⁷Au. The evaluated capture cross sections of JENDL-4.0 and ENDF/B-VII.1 were compared with the present results. The evaluations of JENDL-4.0 and ENDF/B-VII.1 were larger than the present results by 3%–15% in the region from 15 to 100 keV and at 585 keV. The capture gamma-ray spectra of ¹⁰⁵Pd were also derived by unfolding the observed net capture gamma-ray pulse-height spectra. The multiplicities of capture gamma rays of ¹⁰⁵Pd were obtained from the capture gamma-ray spectra.     

Recent Developments in Scintillation Detectors for X-Ray CT and Positron CT Applications

The scintillation detectors considered in present and future instrumentation for XCT and PCT diagnostic imaging are Bi4Ge3O12 (BGO), CdWO4, Low Afterglow CsI(Tl) and CsF. These crystals with the exception of BGO have been known to scintillate as far back as NaI(Tl); their importance emphasized by their current use in CT application is relatively new. Recent improvements in purification, growth and performance characteristics present new and valuable data to the instrument designer. An evaluation and comparison of their properties vis à vis suitability for CT applications with particular emphasis on detector efficiency, light conversion, afterglow, timing, emission spectra, and general handling properties are examined and discussed. Future trends and possible replacement by other scintillators are commented on.     

Cerium-doped lutetium oxyorthosilicate: a fast, efficient newscintillator

The authors discuss a single-crystal inorganic scintillator, cerium-doped lutetium oxyorthosilicate (Lu_2(1-x)Ce_2x (SiO₄) or LSO). It has a scintillation emission intensity which is ~75% of NaI(Tl) with a decay time of ~40 ns. The peak emission wavelength is 420 nm. It has a very high gamma-ray detection efficiency due to its density of 7.4 g/cm³ and its effective atomic number of 66. Its radiation length of 1.14 cm is only slightly longer than bismuth germanate (BGO). The scintillation properties of Ce-doped LSO are compared to NaI(Tl), BGO, and cerium-doped gadolinium oxyorthosilicate (GSO). In addition to desirable physical properties such as high density and high atomic number, LSO also processes a combination of high emission intensity and fast decay which together are superior to any other known single crystal scintillator     

Low-Background Measurements of 22Na in Natural Waters of Krasnodar Krai

Gamma spectrometers with 100 × 100 mm NaI(Tl) and 200 × 100 mm CsI(Tl) crystals for detecting annihilation radiation of ⁺ radionuclides are described. Two spectrometers are located in a surface laboratory and one underground, at a depth of 500 m of water equivalent, in Novorossiisk. The background characteristics and the detection efficiency are presented for different operating modes of the coincidence system and for samples with different mass. A coincidence scheme in which all events with coincidences of pulses in both crystals and energy released in each detector are detected, making it possible to raise the ²²Na detection efficiency by approximately 30%, was tested. The results of measurements of the ²²Na content in some natural waters in Krasnodar krai, including in mud volcanoes, are presented. They show large seasonal variations.     

Radioactivity measurement of Sr/Y-90 mixed with Cs-134 and Cs-137 using large solid angle detectors without chemical separation

We proposed a method to measure the radioactivity of Sr/Y-90 in the mixture of Cs-134 and Cs-137 without chemical pretreatment. It was realized by subtracting the electrons produced in Cs-134 and Cs-137 from entire electron emission rate that can be determined by the efficiency tracer technique in the 4πβ–γ coincidence counting method. The radioactivity of Cs-134 and Cs-137 can be determined by gamma ray spectrometry. The measurements were conducted using plastic and NaI(Tl) scintillation detector with a large solid angle. The validity of the measurement method was shown by agreement of the results with the known radioactivities.     

A DSP-based multichannel analyzer for simultaneous acquisition of coincidence and anticoincidence spectra

A digital signal processor (DSP) based multichannel analyzer (MCA) has been developed for simultaneous acquisition of coincidence and anticoincidence γ-ray spectra. The shaped pulse from the spectroscopy amplifier is digitized by a flash analog-to-digital converter and then processed by a DSP. The coincidence mode operation is implemented by an external gate signal from a coincidence module. Fundamental performance was tested using NaI(Tl) detectors and compared with that of a standard NIM module. The new MCA is currently used for in vivo neutron activation analysis. Further development is in preparation toward full digital processing, which is free from the remaining analog component, that is the spectroscopy amplifier.     

Development of a direction finding gamma-ray detector

This paper describes a direction finding gamma-ray detector, which consists of three different scintillators; NaI (Tl), CsI (Tl) and BGO. The detector positively increases directional sensitivity to incident gamma-rays, and can measure direction, energy and number of gamma-rays. This detector will be useful to carry out monitoring of nuclear power plants or radiation facilities in emergencies. It will be also effective in searching for radiation sources such as radioisotopes and radioactive contaminations. Experimental results have shown the proposed directional detector has a potential for practical use in real fields and will contribute to radiation emergency preparedness.     

G(E)法与Gravel法处理能谱-剂量转换效果研究

为准确地得到γ射线的辐射剂量,对G(E)函数法和Gravel算法处理能谱-剂量的转换效果进行了研究。根据实际应用需求,采取蒙特卡罗方法模拟获取了?50 mm×50 mm NaI(Tl)探测器的Gravel法响应矩阵,并使用Matlab得到探测器的G(E)函数。使用NaI(Tl)探测器和多道谱仪系统测量标准源的能谱,分别使用G(E)法和Gravel法计算剂量值并与理论值进行比较,同时在计算过程中总结对比了两种方法的特点。