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

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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