A 3 MV heavy element AMS system using a unique TOF set-up

Abstract

A heavy element AMS system, based on a 3 MV Tandetron, has been put into operation at JAERI, Mutsu, Japan. The system uses sequential injection, designed for cycle frequencies of up to 1000 Hz. The high-energy section is unique in that the identification of the isotopes of interest is done in two successive steps, each using a separate foil combined with energy discrimination. This method allows for the detection of elements that suffer from problematic isobar interference like 36Cl and 41Ca. In that case the foils are chosen to be relatively thick in order to achieve the required energy dispersion. In order to cope with the large scattering caused by the foils, the applied TOF has a unique design that features the acceptance of extremely high divergent beams of up to 80 mrad. During the acceptance tests the precision was shown to be ∼1.1% for 129I measurements. The background was found to be below 10−13.