In FEL wavelength alteration manner and

摘要

PROBLEM TO BE SOLVED: To provide a means for varying an FEL wavelength capable of easily selecting any wavelength in an FEL apparatus which employs an unstable electron beam such, for example, as a linac. ;SOLUTION: A gap of an undulator 6 is first set to a reference value to position an electron beam at an inlet and an outlet to a predetermined location. Hereby, the intensities of correcting magnets 23, 24, 2, 5, 26 are adjusted for FEL oscillation. Thereafter, the gap of the undulator is changed so as to correspond to a deviation between it and a target FEL wavelength. The FEL wavelength is thus adjusted. Hereupon, the intensities of the correcting magnets 23, 24, 2, 5, 26 are set to values each obtained by adding a value adjusted to actually FEL oscillate to a reference adjusted value for every gap calculated previously.;COPYRIGHT: (C)2004,JPO