A rapid sample changer system for studying fission shape isomers through the electron-capture-delayed fission process

A new sample changer system has been designed to rapidly transport activity from a heavy element production target chamber at the Lawrence Berkeley Na tional Laboratory 88-Inch Cyclotron to a fission, alpha-particle, X-ray, an d gamma-ray detection site. This changer was specifically designed to help study the nuclear structure of isotopes involved in electron-capture-delaye d fission decay with half-lives greater than 30s. The system integrates a r otating wheel and a cycling piston to transport samples from the end of a g as transport capillary line to the detection site. The overall efficiency o f the sample changer system was determined by running off-line experiments to determine the activity collection site efficiency and the detector effic iencies. Under the most favorable conditions, we calculated a relative He-E ;CI gas transport and collection efficiency of around 70%. Efficiencies wer e calculated by comparing the yield of Fr-221 (half-life = 4.8 min) at the sample changer collection site to the activity collected directly on a piec e of glass filter paper. (C) 2000 Elsevier Science B.V. All rights reserved .