Abstract: An RF accelerating cavity includes an accelerating cavity unit and an inductance varying device having a magnetic member connected parallel to an acceleration electrode gap. The RF accelerating cavity is tuned in such a fashion that a charged particle beam acceleration frequency matches a resonant frequency of the RF accelerating cavity by regulating inductance of the inductance varying device in accordance with a changing pattern of the charged particle beam acceleration frequency. Alternatively, impedance of the RF accelerating cavity is increased with the provision of a fixed inductance connected parallel to the acceleration electrode gap when the RF accelerating cavity has a narrow acceleration frequency range.

Abstract: An RF accelerating cavity includes an accelerating cavity unit and an inductance varying device having a magnetic member connected parallel to an acceleration electrode gap. The RF accelerating cavity is tuned in such a fashion that a charged particle beam acceleration frequency matches a resonant frequency of the RF accelerating cavity by regulating inductance of the inductance varying device in accordance with a changing pattern of the charged particle beam acceleration frequency. Alternatively, impedance of the RF accelerating cavity is increased with the provision of a fixed inductance connected parallel to the acceleration electrode gap when the RF accelerating cavity has a narrow acceleration frequency range.

Abstract: A high performance beam accelerator in which accelerating voltage may be increased by applying a high excitation frequency to the accelerator core and controlling heat generation. The beam accelerator includes an annular hollow vessel with an annular passage, fixed magnetic field generators generating magnetic fields for deflecting and guiding a charged particle beam into an orbit, an accelerating gap for inducing an accelerating electric field, and an accelerator core for generating the accelerating electric field via the accelerating gap by changing magnetic state in accordance with electromagnetic induction. Injection to ejection of charged particles is completed within one cycle of the excitation frequency applied to the accelerator core. The accelerator core includes wound multiple layers of a ribbon-shaped soft magnetic alloy, 50 &mgr;m or less in thickness, and having a saturation magnetic flux density of 1 Tesla or more.