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Summary form only given. A repetitive pulsed power modulator, which uses high voltage static induction thyristors as main switching devices, has been designed and constructed for application to discharge light source. The main components of the power modulator are a PFN and a semiconductor switch. The PFN consists of 100 ceramic capacitors (2000 pF, 30 kV) connected in parallel. The designed impedance and output pulse length of PFN are 1.2 ohm and 490 ns, respectively. The PFN is charged to 10 kV. The semiconductor switch is made of 3 high voltage static induction thyristors connected in series in order to withstand 10 kV. The thyristor used is RT103N made by NGK Insulators, Ltd., and its specification is as follows: The rated repetitive peak OFF-state voltage is 4000 V, rated direct OFF-state voltage is 3200 V, effective ON-state current is 400 A and surge ON-state current is larger than 10 kA. In particular the significant feature of the static induction thyristor is that they have very low ON-state voltage, which is shown by the fact that the ON-state voltage is only 15 V for short current pulse of 30 kA. This feature is especially suitable for high rep-rate operation of power modulators, since energy loss by switch can be remarkably reduced. Performance of the modulator will be presented.