Linac modulator solid state switch development for thyratron replacement at SLAC

Summary form only given. There are 243 line type modulators in Linac gallery to power klystrons at SLAC two-mile accelerator. High power thyratron is used as PFN switch in each modulator to produce pulses for Klystron operation through a step-up pulse transformer. About 83 modulators are used for LCLS operating at repetition rate of 120Hz. The thyratron average life time is about 16k hours, much shorter than state of the art solid state switches. Solid state switch will improve overall modulator performance by increasing switch life time and reliability, and decreasing maintenance intervention. In the paper, development of a solid state thyratron replacement switch for LCLS modulator will be presented, including switch specifications, electrical performance, timing jitter, pulse amplitude stability, thermal performance, and up to date long term reliability, etc.