A fast extraction instrument of a 1-GeV electron synchrotron

Abstract

A kicker magnet and a modulator were developed as a fast extraction instrument of a 1-GeV electron synchrotron. A 1-kG pulsed magnetic field was generated by the kicker magnet with the rise time of 40 ns. The ripple of the flattop of the current wave form was less than ±1%, and the shot-to-shot fluctuation of the peak current was no more than 0.1%. The modulator consists of two Blumleins in series which operate at a quarter of the charging voltage as compared to a pulse forming network (PFN) type modulator. The damped oscillating wave form of the current could decrease the residual field to be less than 0.5 G. The effect of the residual field of the kicker magnet on the dynamic aperture of the low-energy electron beam was estimated by the tracking calculation. The result shows the dynamic aperture decreases as the residual field increases. To obtain enough accelerated current, the residual field must be less than 1 G. This restriction could be satisfied by the developed kicker magnet and the modulator. Successful extraction of eight bunches out of 15 bunches in the synchrotron were measured by a wall current monitor located in the extraction transport line.