Initial-beam-loading compensation system for high-intensity electron linacs

We developed an initial-beam-loading compensation system for electron linacs. This system consists of a ΔΦ–A (phase-to-amplitude) modulator and a fast-phase detector. The ΔΦ–A modulator can modulate the phase and the amplitude of a low-power RF simultaneously. Low-power and high-power tests were successfully carried out at KEK. The result of the high-power tests show that our system can reduce the energy spread from 27 to 0.3% for a 300-mA average current. The system that we developed can be a powerful tool for initial-beam-loading compensation. In addition, a numerical calculation method using the power-flow matrix was formulated to perform a fast beam-energy calculation with a simple algorithm. This method can be used to obtain the target RF waveform for energy-spread compensation.