A Liquid Film Stripper for High Intensity Heavy Ion Beams

Abstract

Electron strippers are widely used in heavy ion accelerators such as tandem Van de Graaff generators and heavy ion linacs. The SuperHILAC at Lawrence Berkeley Laboratory, employs a fluorocarbon oil vapor stripper at 113 keV/A for its high intensity injector ABEL, while after acceleration to 1.199 MeV/A a 35 ..mu..g/cm/sup 2/ carbon foil stripper is used. At present, the lifetime of these foils is about 1 hour for an /sup 40/Ar beam of approx. 1 ..mu..A average particle current. With higher intensity high mass (100 less than or equal to A less than or equal to 238) beams available from ABEL injector the lifetime is expected to drop drastically and might be as low as one minute. A different approach to solve the stripper foil lifetime problem uses a thin free standing oil film spun from the edge of a sharp-edged rotating disc touching the surface of an oil reservoir. Areas of about 10 cm/sup 2/ with areal densities down to 20 ..mu..g/cm/sup 2/ have been reported. The work described here is based on the same concept, and produces a constantly regenerated, stable, free standing oil film of appropriate thickness for use at the SuperHILAC.