RF system for high-power industrial irradiators

The IMPELA family of industrial irradiators has electron beam energies ranging from 5 to 18 MeV at beam powers of 20 to 250 kW. Direct control of the RF fields during the beam pulses ensures constant output energy, independent of the beam current. These irradiators are designed for simple, push-button, reliable operation. The modular RF system supports the needs of either direct electron or photon conversion irradiations. The IMPELA I-10/50 prototype has a beam energy of 10 MeV and an average power of 50 kW. The RF system features a 1300-MHz, 2-MW peak, 150-kW average, modulated anode klystron amplifier with a maximum pulse length of 1 ms. A software-based control loop tracks the accelerator structure resonant frequency while a hardware loop controls the RF amplitude during the pulse. A circulator protects the klystron from reflected power and a crowbar protects the klystron from internal arcs. The design concepts of the system are described, and results from the characterization of the I-10/50 prototype RF system are presented