HI—13串列加速器质谱测量中的粒子鉴别技术

着重介绍中国原子能科学研究院的ＨＩ－１３串列加速器质谱计装置的粒子鉴别技术，该装置于１９８９年建成，到目前可以完成自然界中＾１０Ｂｅ，＾２６Ａｌ、＾３６Ｃｌ与＾１２９Ｉ的测定，测量灵敏度达到１０＾－１３－１０＾－１５，探测限度为１０＾５－１０＾７个原子。     

Bragg探测器在AMS测量中的应用

为提高Bragg探测器的总能量和Bragg峰的分辨等性能,对1台Bragg探测器进行改进,并利用其测量³⁶Cl、⁴¹Ca、⁷⁹Se系列标准样品,有效排除了相应同量异位素的干扰,为进一步提高AMS测量这些中重核的灵敏度提供有效试验手段。     

用于加速器质谱测量的Bragg探测器

文章涉及1台用于加速器质谱(AMS)测量的Bragg探测器的建立及其调试结果。该探测器是1台全阻止型的气体电离室,电场方向与入射粒子方向平行。用241Am源的α粒子对该探测器的主要性能进行了测试,并将该探测器用于AMS实验进行总能量测量和Z的鉴别。对于能量为49.7 MeV的26Mg离子,能量分辨达到1.4%,Bragg峰值的分辨好于4.1%。     

3 MV加速器质谱测量36Cl

在端电压为3 MV的AMS装置上实现³⁶Cl及其他中重核素的高灵敏测量是AMS技术发展的重要方向之一。为进一步提高充气飞行时间探测方法中³⁶S的压低能力,本文研究了³⁶S和³⁶Cl在P10、异丁烷和丙烷气体中的能量歧离和角度歧离。在32 MeV的入射能量下测量了几个地下水样品中³⁶Cl的[JP2]含量,测量结果与72 MeV能量下的测量结果相符。测量结果表明,采用充气飞行时间探测方法在3 MV的串列加速器上测量³⁶Cl时,探测限为³⁶Cl/Cl≈10^-14,当样品中³⁶Cl/Cl≈10^-13时测量不确定度为30%。     

一台用于加速器质谱测量的充气飞行时间探测器

研制了一种新型的气体探测器－充气飞行时间探测器。介绍了充气飞行时间谱仪的原理、结构和初步的在线调试结果。     

RIBLL中粒子鉴别探测器

描述了RIBLL上使用的飞行时间探测器、ΔE探测器和能量探测器。通过它们可以获得反应产物的飞行时间、ΔE和能量,从而达到粒子鉴别的目的。并对在RIBLL上实际调束得到的实验结果进行分析,验证了这些探测器的可靠性。     

回旋加速器质谱技术中氚和氦—3粒子的探测和鉴别

在利用回旋加速器质谱技术进行氚断代的测量中,工作气体是电解水样品时收集到的含氚氢气,并混入少许一定量的空气。空气中的微量~3He和样品中的~3H同时加速并被用作参考标准以监督加速器的束流变化。描述了利用金硅面垒探测器望远镜和铝吸收箔的组合来探测和鉴别~3H和~3He的实验方法和结果。     

超灵敏小型回旋加速器质谱计中单粒子微通道板探测器性能的改善和提高

叙述了为提高单粒子微通道板探测器的性能和稳定性所采取的措施，在采用本底同时交替扣除法以后，探测效率可以达到９５％以上，探测效率为５０％时，单粒子微通道板探测器探测＾１４Ｃ的丰度灵敏度达到２×１０＾－１５。     

超灵敏小型回旋加速器质谱计微通道板型低能单粒子探测器结构改进和性能提高

叙述了为提高SMCAMS单粒子微通道板探测器性能和稳定性所采取的措施。     

加速器质谱计在地球科学中的应用

本文介绍加速器质谱计用于测定天然物质中超微量同位素~(10)Be及其在地球科学中的应用。环绕样品~(10)Be的测定可用于研究大气和海洋中发生的各种传输作用过程;大陆沉积物~(10)Be分布及迁移直接与黄土(或土壤)的堆积和侵蚀有关。~(10)Be是一种反映各种地球化学作用过程的理想的示踪剂。     

利用静电加速器质谱技术测定氚

本工作描述基于2.5MV静电加速器建立的加速器质谱计的基本原理、实验装置以及重水样品中氚浓度(T/D)的测定。为了比较,还用放射性法进行了测量。实验结果表明,基于一台能量约1—2MeV加速器测定氚的灵敏度已达到10~(-14),而潜在灵敏度还可能高2—3个量级。本文还讨论了这种技术的前景和问题。     

Studies of Al metabolism in animal by accelerator mass spectrometry

The correlation between Al metabolism and senile dementia in animal has been studied by AMS(accelerator mass spectrometry).Three groups of laboratory rats were fed with normal food.food with high Al content,and with enriched Ca and Mg together with high Al,respectively for six to eight months.Mapping test was made to recored th degree of wisdom degeneration.Half of the rats were sacrificed and Al contents in various organs were measured by atomic absorption spectroscopy.The rest were injected with ^26Al,killed after 5,10,15,25,and 35d and ^26Al contents measured by AMS.The distribution of Al as well as the correlation among the accumulation of ^26Al,and the existed Al content and dementia was studied.     

用于粒子鉴别的布喇格曲线谱学探测器

在重离子反应中,气体电离室广泛地用于离子鉴别,这是由于它制造简单、成本低、便于维护,特别是可设计成不同长度,厚度均匀,相对于半导体探测器而言还有附加的优点,如无辐照损伤、无脉冲幅度亏损等。这类电离室通常有阳极、阴极和栅极三个电极,所施加的电场是平行于入射粒子轨迹的。     

Simulation of experimental spectra for medium-heavy nuclides in accelerator mass spectrometry

Some interferences are often encountered in accelerator mass spectrometry （AMS） measurements, especially for medium-heavy nuclide measurement, It is difficult for online discrimination of the nuclide of interest from the interfering ones. In order to solve this problem, we developed a method to simulate the experimental spectra of medium-heavy nuclides in AMS measurements. The results obtained from this method are in good agreement with experimental values.     

U measurement with accelerator mass spectrometry at CIAE

²³⁶U is a long-lived radioactive isotope which is produced principally by thermal neutron capture on ²³⁵U. ²³⁶U may be potentially applied in geological research and nuclear safeguards. Accelerator mass spectrometry is presently the most sensitive technique for the measurement of ²³⁶U and a measurement method for long-lived heavy ion ²³⁶U has been developed. The set-up uses a dedicated injector and the newly proposed ²⁰⁸Pb¹⁶ molecular ions for the simulation of ²³⁶U ion transport. A sensitivity of lower than 10⁻¹⁰ has been achieved for the isotopic ratio ²³⁶U/²³⁸U in present work.     

一台改进的充气飞行时间谱仪

在已有的基础上重新设计和研制了一台用于加速器质谱测量中进行同量异位素鉴别的充气飞行时间谱仪。介绍了该谱仪的原理、结构和调试结果。在入射能量分别为64．5和49MeV的情况下,用时间谱实现了^36S和^36Cl的鉴别。     

Investigation of metal matrix systems for cosmogenic Al analysis by accelerator mass spectrometry

We report experiments designed to help optimize accelerator mass spectrometry (AMS) of ²⁶Al (in the form of Al₂O₃) for geochronologic and geomorphologic applications. Analysis times are long and the precision of AMS are restricted by counting statistics for ²⁶Al, which are in turn limited by the intensity of Al⁻ beam currents. We show that ion beam currents are affected by the metal matrix in which Al₂O₃ is dispersed, by the matrix-to-Al₂O₃ mixing ratio, and for at least some matrices, such as Ag, by the depth to which the sample is packed in the AMS cathode. Typical instantaneous Al⁺⁷ currents (μA) produced by the LLNL CAMS Cs sputter ion source and measured in a Faraday cup after the accelerator are 2.26 for samples in Ag, 2.17 in Re, 2.00 in Nb, 1.92 in V and 1.73 in Mo. The AMS counting efficiency (Al⁻ ions detected per Al atom loaded in the target) for a constant analysis time (900 s) and for equimolar mixtures of Al₂O₃ and matrix is in the range of 6 × 10⁻⁵–9 × 10⁻⁵ in the order Ag > Re > Nb > V > Mo. Additionally, we observed a correlation between the ion detection efficiency (Al ions detected per Al atoms loaded) and the matrix work function and inverse vaporization enthalpy of the matrix and beam current. Typical currents (μA) obtained with elemental Al are 13.3 for samples in no matrix, 3.23 in V, 3.14 in Nb, 3.07 in Re, 2.85 in Mo, 1.46 in Ag. The ion detection efficiency for elemental Al correlates strongly with matrix electron affinity. Thus, our data indicate that the current practice of mixing Al₂O₃ with Ag is reasonable until a means is found to produce cathodes of elemental Al.