Measurements with a Novel Non-Intercepting Bunch Shape Monitor at the High Current GSI-LINAC

For bunch length determination in the range of 0.3 to 5 ns at the GSI heavy ion LINAC a novel, non-intercepting device has been realized. It uses the time spectrum of secondary electrons created by atomic collisions between beam ions and residual gas molecules. These electrons are accelerated by an electric field of 400 V/mm toward an electro-static energy analyzer, which is used to restrict the effective source region. Then the electrons are deflected by an rf-resonator running in phase with the acceleration frequency (36 or 108 MHz) to transform the time spectrum into spatial separation. The detection is done with a multi-channel plate equipped with a phosphor screen and observed by a CCD camera. The achieved time resolution is about 60 ps, corresponding to 2 degree of 108 MHz. The general layout of the device and first results will be presented.