Establishing of Accelerator Mass Spectromery at Kyushu University Tandem Accelerator and Measurement of Terrestrial Ages for Antarctic Meteorites

在南极陨石地球年龄的研究中，已知陨石中^<36>Cl的含量提供了决定性的信息。在九州大学串联加速器实验室建立了加速器质谱（AMS）系统，以方便^<36>Cl的测量。(1)提出了一种将传统双列加速器设备应用于AMS的新技术。在这种方法中，通过同步调制光束传输线（从离子源到探测器）上所有偏转磁体的场，以每秒几个周期的速率，对极弱的样品束（^<36>Cl）和参考束（^<35>Cl或^<37>Cl）进行加速和交替传输。对该方法进行了试验，验证了该方法具有足够的性能。(2)为了进一步识别探测器上的背景离子，指出在样品光束中加入时间结构及其在离子检测中的应用是重要的。为此，在串联注入口设计了一个束束装置，目前正在测试运行中。(3)构建了多收集器离子室（MCIC）作为粒子识别探测器，并对其进行了测试。实际应用于AMS测试实验中。(4)为了进一步提高AMS系统的性能，设计了先进的质量分析系统和用于串联加速器的汽提池。前者目前正在建设中，后者处于研发阶段。为了避免样品制备过程中对同位素<36>S的污染，并确保以合适的形式完美地收集到铯溅射离子源的同位素<36>Cl，开发了化学处理技术

In the study of terrestrial ages of the antarctic meteorites, it is known that the contents of ^<36>Cl in the meteorites give a decisive information. An accelerator mass spectrometry (AMS) system was constructed at Kyushu University tandem accelerator laboratory in order to facilitate the ^<36>Cl measurement.1. development of AMS techniques(1) We proposed a new technique for the application of a conventional tandem accelerator facility to AMS.In this method, an extremely weak sample beam (^<36>Cl) and a reference beam (^<35>Cl or ^<37>Cl) are accelerated and transported on the same orbit alternately at a rate of several cycles per second by modulating synchronously the fields of all the deflector magnets on the beam transport line (from the ion source to the detector). A test of the method was performed and an enough capability of this method was confirmed.(2) For further discrimination of the background ions on the detector, it was noted that the addition of a time structure to the sample beam and its use in the ion detection are important. For this purpose, a beam bunching device at the tandem injection port was designed and is now in test operation.(3) As a particle identification detector, a prototype multi-collector ion chamber (MCIC) was constructed and tested. It was practically used in the AMS test experiment.(4) To enhance the capability of the AMS system further, an advanced mass analyzer system and a gas-stripper cell for the tandem accelerator were designed. The former is now under construction and the latter is in R&D stage.2. To avoid contamination of the isobar nulide ^<36>S in the sample preparation, and to insure a perfect collection of the ^<36>Cl nuclide in an appropriate form for the Cs-sputtering ion source, the chemical treatment techniques were developed