Selective isobar suppression for accelerator mass spectrometry and radioactive ion-beam science

A new method of selective isobar suppression by photodetachment in a radio-frequency quadrupole ion cooler is being developed at HRIBF with a twofold purpose: (1) increasing the AMS sensitivity for certain isotopes of interest and (2) purifying radioactive ion beams for nuclear science. The potential of suppressing the S-36 contaminants in a Cl-36 beam using this method has been explored with stable S- and Cl- ions and a Nd:YLF laser. In the study, the laser beam was directed along the experiment's beam line and through a RF quadrupole ion cooler. Negative S-32 and Cl-35 ions produced by a Cs sputter ion source were focused into the ion cooler where they were slowed by collisions with He buffer gas; this increased the interaction time between the negative-ion beam and the laser beam. As a result, suppression of S- by a factor of 3000 was obtained with about 2.5W average laser power in the cooler while no reduction in Cl- current was observed. (C) 2009 Elsevier B.V. All rights reserved.