Thursday, 8 September 2005

This presentation is part of: Poster Session II

A ¹²⁹I-AMS by a ⁹⁷Mo¹⁶O molecular pilot beam method

A ¹²⁹I-AMS system has been developed on a 12UD tandem accelerator at the Tandem Accelerator Complex, University of Tsukuba. A ⁹⁷Mo¹⁶O molecular pilot beam method, which is developed in the Tandem Accelerator Complex, is applied to the ¹²⁹I-AMS. The acceleration voltage of the tandem is precisely controlled and is kept within 0.1% accuracy for several days of AMS measurement. This stability is enough to keep a stable transmission of ¹²⁹I ions through the tandem accelerator. The ¹²⁷I ions are measured simultaneously with the ¹²⁹I ions. Because of enough number of ¹²⁷I ion, amount of ¹²⁷I is measured as a current of negative ¹²⁷I ions with a Faraday cup installed just after a bending magnet of an ion source. Both ¹²⁹I⁻ and ⁹⁷Mo¹⁶O⁻ ions are accelerated concurrently and ¹²⁹I¹²⁺ and ⁹⁷Mo⁹⁺ can pass through a 90° analyzing magnet. Once the analyzing magnet is adjusted for ¹²⁹I¹²⁺, the ⁹⁷Mo⁹⁺ ions pass through about 5 mm down at an image point of the magnet and produce so called slit current for a slit current feedback terminal potential stabilizer. A magnetic rigidity of ⁹⁷Mo⁹⁺ is almost the same as that of ¹²⁹I¹²⁺, so, ⁹⁷Mo⁹⁺ ions can easily reached to a detector for ¹²⁹I detection and are strong enough to destroy the detector. In order to sweep out the ⁹⁷Mo⁹⁺ ions, a second stripper foil is prepared in an AMS beam line. After passing through the second stripper foil, if ¹²⁹I²⁶⁺ is selected as a particle which can enter the detector, no ⁹⁷Mo particles can enter the detector because the magnetic rigidity of ⁹⁷Moⁿ⁺ is different from that of ¹²⁹I²⁶⁺. Finally, ¹²⁹I²⁶⁺ ions are clearly detected by a SSD detector with no strong background. The acceleration voltage is set to 9.68 MV in order to get most efficient yields of both ¹²⁹I¹²⁺ and ¹²⁹I²⁶⁺. A detail of the ¹²⁹I-AMS system and results of test experiment are reported as well as discussion of usefulness of ¹²⁹I-AMS in the environmental studies.

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See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)