Laser beam-profile monitor development at BNL for SNS

A beam profile monitor for H- beams based on laser photoneutralization is being developed at Brookhaven National Laboratory (BNL) for use on the Spallation Neutron Source (SNS) [1]. An H- ion has a first ionization potential of 0.75eV and can be neutralized by light from a Nd:YAG laser (lambda=1064nm). To measure beam profiles, a narrow laser beam is passed through the ion beam neutralizing a portion of the H- beam struck by the laser. The laser trajectory is stepped across the ion beam. At each laser position, the reduction of the beam current caused by the laser is measured. A proof-of-principle experiment was done earlier at 750keV. This paper reports on measurements made on 200MeV beam at BNL and with a compact scanner prototype at Lawrence Berkeley National Lab on beam from the SNS RFQ.