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- G. Isoyama, M. Fujimoto, S. Funakoshi, K. Furukawa, A. Irizawa, R. Kato, K. Kawase, K. Miyazaki, A. Tokuchi, R. Tsutsumi, M. Yaguchi
ISIR, Osaka, Japan
- F. Kamitsukasa
Osaka University, Graduate School of Science, Osaka, Japan
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We have been conducting studies on upgrade of the THz-FEL and its applications, using the L-band electron linac at ISIR, Osaka University. The stability of the FEL is crucial for these studies and the operation of the FEL depends on characteristics of the electron beam, especially on stability of the electron energy, which is strongly affected by the RF power and its phase provided to the linac. We uses a klystron modulator with the a highly stable charging system to the PFN with a fractional variation of 8×10-5 (peak-to-peak), but the klystron voltage varies by one order of magnitude larger due probably to the thyratron used as a high voltage and high current switch in the klystron modulator. In order to make the stability of the FEL higher, we have developed a solid-state switch using static induction thyristors. The performance of the switch is as follows; the maximum holding voltage is 25 kV, the maximum current is 6 kA for the pulse duration of 10 us, the switching time is 270 ns, and the maximum repetition frequency is 10 Hz. The intensity fluctuation of the FEL macropulse is reduced to a few percents using the solid state switch.
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