Abstract
Droop in rectangular pulses is a problem in crystron power supplies for linear particle accelerators. Reduction methods by superposing auxiliary pulses have been discussed. Though feedback control of the auxiliary pulse waveforms and of the switching times for synchronizing the supplies seems to be useful, any analog or real-time digital control does not seem applicable because of pulse widths at several micro seconds or less. This paper presents a control scheme that the waveform is observed during a pulse generation and control calculations are done based on the stored waveform during the following interval to manipulate the time and waveform in the next pulse generated. The scheme is well suited for many pulsed power applications, in which the repetiton rate is so low as lk pps or less. The representation of the control becomes extremely simple, as the pulse decays rapidly not affecting the pulses that follow and the samples of waveform can be reduced to a small number of feedback variables representing waveform and time parameters to be controlled.
The feasibility and performance are tested in a experimental study on switching time control of micro-second pulses with a 12 bit 20MS/s A/D converter and a PC compatible. A delay time control based on correlation maximization is introduced, which proved to be effective for removing low-frequency components in jitter and keeping steady-state deviation as low as 0.6ns.
