Polyphase Resonant Converter-Modulators for the KAERI Proton Engineering Frontier Project Accelerator Klystron RF Amplifier System

The Korean Atomic Energy Research Institute (KAERI) is in the process of fabricating a long pulse, high average power, 100 MeV, 1.6 mA proton accelerator, called the "Proton Engineering Frontier Project" . For the power conditioning and RF systems operating above 20 MeV, this system will utilize 4 modulator systems driving 7 klystrons. The klystrons are a modified version of the Thales TH2089F, a 352 MHz horizontal tube that provides 1.6 MW RF output with a 105 kV, 25 A beam. The maximum expected pulse length is 1.5 ms with a 60 Hz repetition rate. The system average power, driving 2 klystrons at full duty, is about 500 kW. The converter-modulator design is based on those developed by Los Alamos for the Spallation Neutron Source (SNS) accelerator at Oak Ridge National Laboratory and the Stanford (SLAC) ILC L-band RF test stand . The KAERI design will benefit from the SNS and SLAC experiences as well as recent advancements that reduce IGBT switching losses and other dynamic parameters by a factor of 6. These topological changes also provide for pulse width modulation (PWM) regulation of the output pulse with adaptive controls at high average power. Other fabrication and design changes will provide subtle improvements to the overall system. In addition to the expected improvement in performance and reliability, the overall electrical efficiency is expected to improve from the SNS value of ~93% to ~96% conversion efficiency.