AMS FOR M-GREATER-THAN-36 WITH A GAS-FILLED MAGNETIC SPECTROGRAPH

Small concentrations of long-lived radioisotopes such as Ni-59 are not necessarily easy to determine by AMS because of the background of sta ble isobars, in this case Co-59. The gas-filled Q3D magnetic spectrogr aph has been successfully used for isobaric separation. Additional sup pression of non-isobaric background is accomplished by means of a Wien filter directly after the tandem and a highly sensitive time-of-fligh t measurement just before the spectrograph. Until now we have used the se techniques for the radioisotopes Ca-41, Ni-59, Sr-90 and Pd-107. Th e limits in sensitivity am at present between approximately 3 x 10(-15 ) for Ca-41/Ca and approximately 1 x 10(-8) for Pd-107/Pd-106. Measure ments have been performed on environmental, extraterrestial and nuclea r waste samples. Because of the insufficient sensitivity for measureme nts of very low concentrations with the existing Q3D, a dedicated gas- filled magnet with a deflection angle of 135-degrees is now under cons truction.