The Transverse Feedback System in Desy

To overcome single bunch instabilities at high intensities, a transverse feedback in DESY was necessary. A position-monitor detecting the coherent betatron oscillations delivers a signal which is amplified, matched in phase and used to power a kicker magnet. The latter consists of a two turn air coil which - with additional capacitors - has been made resonant in the betatron frequency range. Fine tuning of the system is effected by a ferrite loaded inductance in series with the kicker coil and biased by a variable magnetic field. The frequency range can be changed by switching capacitors. Appropriate triggering of the amplifiers and phase shifters allows the use of the same system for both electrons and positrons which are accelerated in different cycles.