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Ultrasensitive methods of measuring isotope ratios of heavy elements using accelerator mass spectrometry

使用加速器质谱测量重元素同位素比的超灵敏方法

基本信息

批准号：
02554003
负责人：
NAKAMURA Masanobu
金额：
$ 11.58万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1992
项目状态：
已结题

项目摘要

An accelerator mass spectrometry (AMS) system based on an 8UDH Pelletron at Kyoto University was developed. Long-lived radioisotopes of ^<36>Cl, ^<41>Ca and ^<129>I were interesting to study for dating and environment measurements. We were starting the AMS program with ^<14>C measurements in order to test and improve the reliability of our AMS system. We introduced a sputter ion source with 59 samples and operated the sample manipulation mechanism manually by monitoring its position with television and linear potentiometers. With x-y slits at the ion source, the beam transmission through the tandem accelerator was stable. The terminal voltage was controlled using ^<13>C_<4+> ions whic were dissociated at the terminal from molecular ions of ^<13>CH^-. ^<14>C ions were counted by a silicon detector. The background peaks of ^<14>N^<4+> and (^7Li_2) ^<4+> ions were separated using a 3 mum thick Al foil in front of the detector. We used sequential injection with slow cycling by varying the magnetic field of the bending magnet. The transmission was measured for ^<12>C and ^<13>C ions and we estimate the transimission for ^<14>C using the stripping efficiency. Sample materials of NBS oxalic acid standard were oxidized and the resulting CO_2 was purified cryogenically in a vacuum preparation system. It was converted to graphite by reducing the CO_2 on Fe catalyst with H_2 gas.For the ^<36>Cl measurements, we tested the gas ionization chamber as the DELTAE counter in order to separate the isobar (^<36>S) and also tested the electrostatic deflector to reduced the backgroud ions of different charge states.The graphitized sample of NBS was measured using sequential injection of ^<12>C,^<13>C and ^<14>C ions. Measured ^<14>C/^<12>C ratios show the reproducibility of our AMS system. We will start the research program of ^<14>C measurements and optimize the detector system for heavy elements.

本文介绍了一种基于京都大学8 UDH Pelletron的加速器质谱分析系统。长寿命放射性同位素^<36>Cl、^<41>Ca和^<129>I在测年和环境测量中具有重要意义。为了<14>测试和提高AMS系统的可靠性，我们开始了AMS计划，并进行了^ C测量。我们介绍了一个溅射离子源与59个样品和操作样品操纵机构手动监测其位置与电视和线性电位器。在离子源处具有x-y狭缝时，通过串列加速器的束传输是稳定的。端电压由^<13>C_<4+>离子控制，^C_<4+>离子在端部与^ CH^-分子离子解离<13>。通过<14>硅检测器计数13 C离子。在<14>检测器前使用3 μ m厚的铝箔分离^ N^<4+>和（^7Li_2）^<4+>离子的背景峰。我们使用顺序注射与缓慢的循环，通过改变磁场的偏转磁铁。测量^<12>C和^<13>C离子的透射率，并且我们使用剥离效率估计^ C的透射率<14>。采用NBS草酸标准样品，在真空制备系统中进行氧化，并对氧化后的CO_2进行低温净化。在NBS石墨化样品的测量中<36>，我们采用了气体电离室作为DELTAE计数器来分离同量异位素（^<36>S），并采用静电偏转器来减少不同电荷态的背景离子<12><13><14>。测量的^<14>C/^<12>C比率显示了我们的AMS系统的可重复性。我们将启动^ C测量的研究计划<14>，并优化重元素的探测器系统。