Momentum spread determination of Linac beams using incoherent components of the bunch signals

Measurements of the momentum spread of the particles in a beam are of great importance when optimizing Linac setup for high current operation concerning controlled longitudinal phase space occupation. A new method of the momentum spread determination was tested at GSI heavy ion linear accelerator. It is based on the analysis of incoherent components of the bunch signal. A significant enhancement of signal to noise ratio was achieved by means of resonant cavity pick-up of pile-box shape. Spectra were analyzed on 36th harmonic of the rf-frequency i.e. at 1.3 GHz. This reduced contribution of the coherent components in the frequency spectrum of the bunched beam. Fast digital processing and gating synchronized to the bunch train allowed a drastic reduction of the measuring time and additionally suppressed a noise in the frequency spectrum, respectively. This contribution describes the measurement setup and discusses the first results obtained with heavy ion beams. Since measurements were taken just two days before conference started the results presented here are to be treated as a very preliminary.