PURPOSE: To have frequently repeated operation by using a resonance power supply as a power supply for excitation of an electric magnet, and by using the positive and negative waveforms in resonance to acceleration of electron beam.

CONSTITUTION: An electron beam emitted by a linear accelerator 1 is deviated upward by a beam distributing magnet 4 and irradiated to a synchrotron 2. Electric magnets of this synchrotron 2 are excited in sinusoidally wave by a resonance power supply composed of a charging power supply 6, a capacitor 6, and a load for electric magnets. The electron beam irradiated at this time passes another beam distributing magnet 5 to be irradiated to an accumulator ring 3 and accumulated there. Then the electric magnets are demagnetized sinusoidally and vibrated in the opposite direction. Then the electron beam emitted by the accelerator 1 passes the magnet 4 and is deviated downward to be irradiated to the synchrotron 2. The electrons are accelerated while turned reversely with excitation of the electric magnets, and upon attaining the final energy, irradiated to the ring 3 to be accumulated. This process is repeated to provide accumulation of large current at the ring 3.