RF accelerating system for a compact ion synchrotron

We have developed an RF accelerating system for a compact ion synchrotron. The RF cavity is an untuned type loaded with FINEMET cores, which have high complex permeability, high saturation flux density, and high Curie temperature properties. A new power feeding method, "multi-feed coupling," was developed to match the cavity impedance with output impedance of a solid-state RF amplifier. We have installed the RF accelerating system for a multi-purpose synchrotron at the Wakasawan Energy Research Centre in Japan. Ion beams were successfully accelerated by adjusting the RF control system using a direct digital synthesiser. For proton beam acceleration, dual-harmonics operation was effective to enhance the beam intensity due to reduction of the space-charge effect.