A Transverse Schottky Noise Detector for Bunched Proton Beams
Transverse Schottky noise analysis is a powerful standard technique for continuous proton beam diagnosis. The extension to bunched proton beams of very low intensity, as will be used in pp¿ colliders, requires new technical features to enhance the detector sensitivity and to reduce the coherent signal of the parasitic common mode. During SPS pp¿ collider experiments, we met this requirement by using a resonating transverse pick-up three meters long, the two plates being movable to match the electrode gap to the beam width at high energy. The parasitic sum signal was drastically reduced by centering the plates around the beam and by filtering the output signal. Clean betatron and longitudinal Schottky bands have been observed for a 0.3 mA continuous beam and for a 0.01 mA single bunch beam. Betatron satellites have also been detected for a 6 mA multi-bunched beam. As a future development the coil inductance in parallel to the electrode plates will be varied by a movable ferrite core, to allow continuous modification of the pick-up transverse acceptance through a change of the gap distance without changing the resonant frequency, the band-width or the filtering device.