Ultralow-background photon-detection system for collinear laser spectroscopy of high-energy highly charged ion beams

An ultralow-background fluorescence-photon detection system has been succes sfully developed for the collinear laser spectroscopy of highly charged ion beams having a relativistic velocity. We applied the technology of a cryop ump to a photon-detection system. A charcoal panel, optical filters and fou r movable collimators strongly reduced the background due to scattered phot ons of the incident laser beam. The background due to collisions between th e ion beam and residual gas was also suppressed by improving the vacuum usi ng a cryopump technique. With this system, we clearly observed the laser-in duced fluorescence spectra of the 2S(1/2)-2P(1/2,3/2) transitions in an Li- like B-11(2+) ion beam with a signal-to-noise ratio of 200. The ion-beam en ergy was 11.25A MeV and the intensity was 10(4) ions/bunch. We also demonst rated that the system has the capability of measuring the lifetimes of exci ted states. (C) 1998 Elsevier Science B.V. All rights reserved.