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Nishimori, Nobuyuki
Dai-14-Kai Kasokuki Kagaku Kenkyu Happyokai Hokokushu, p.108 - 110, 2003/11
The evolution of the field of an FEL oscillator at zero detuning length of an optical cavity (dL = 0) is studied analytically. The field on the leading edge at the first round trip is the same as that of a self-amplified spontaneous emission (SASE) FEL characterized by an FEL parameter. The field evolves with round trips by interaction with electrons. The field in the early stage of the evolution is found to scale with the FEL parameter and the round-trip number, and is similar to that of SASE with high electron beam density.
Nishimori, Nobuyuki; Nagai, Ryoji
Proceedings of 13th Symposium on Accelerator Science and Technology, p.95 - 99, 2001/00
We have observed sustained saturation in a Free-Electron Laser (FEL) oscillator at zero detuning of an optical cavity for the first time, and confirmed that the optical pulse length at zero detuning is 250 fs FWHM at wavelength of 22 um. The optical length corresponds to three optical cycles, which is the fewest cycles ever achieved at FELs in the world. The peak FEL power reaches 0.8 GW with the single optical pulse energy of 200 uJ. The sustained lasing at zero detuning is not allowed in conventional FEL oscillator theories and the physical mechanism is under investigation.