Rise time analysis of pulsed klystron-modulator for efficiency improvementof linear colliders

In linear accelerators, the periods during the rise and fall of a klystron- modulator pulse cannot be used to generate RF power. Thus, these periods ne ed to be minimized to get high efficiency, especially in large-scale machin es. In this paper, we present a simplified and generalized voltage rise tim e function of a pulsed modulator with a high-power klystron load using the equivalent circuit analysis method. The optimum pulse waveform is generated when this pulsed power system is tuned with a damping factor of similar to 0.85. The normalized rise time chart presented in this paper allows one to predict the rise time and pulse shape of the pulsed power system in genera l. The results can be summarized as follows: The large distributed capacita nce in the pulse tank and operating parameters, V-s x T-p, where V-s is loa d voltage and T-p is the pulse width, are the main factors determining the pulse rise time in the high-power RF system. With an RF pulse compression s cheme, up to +/- 3% ripple of the modulator voltage is allowed without seri ous loss of compressor efficiency, which allows the modulator efficiency to be improved as well. The wiring inductance should be minimized to get the fastest rise time. (C) 2000 Elsevier Science B.V. All rights reserved.