Laser based beam diagnostic for the RAL Front End Test Stand (FETS)

For the diagnostic of high power particle beams, non-destructive measurement devices provide minimum influence on the beam and avoid various problems in connection with the high power density on surfaces. An H- ion beam offers the opportunity of non destructive beam diagnostics based on the effect of photo detachment. By the interaction of light with H- ions, the additional electron can be detached and a small number of neutrals will be produced. An additional magnetic dipole field can then be used to separate the detached electrons and neutrals from the ions. Using an integral detector the spatial distribution of the beam ion density can be derived, while the use of a spatial resolving detector enables to determine the phase space distribution. To investigate the measurement principle of the latter, a test stand was set up at the IAP in Frankfurt. This system will now be adopted to the requirements of the Front End Test Stand at CCLRC/ RAL. The aim of this FETS is to demonstrate a chopped H- beam of 60mA at 3MeV and 50pps with sufficiently high beam quality. The paper will present a detailed description of the proposed set up at RAL and discuss several results of simulations and experimental data gained in Frankfurt.