CERN Accelerating science

Article
Title	Harmonic Amplifier Free Electron Laser
Author(s)	Jia, Qika
Affiliation	(USTC/NSRL, Hefei, Anhui)
Publication	2004
In:	26th International Free Electron Laser Conference and 11th FEL User Workshop 2004, Trieste, Italy, 29 Aug - 3 Sep 2004, pp.e-proc. MOPOS41
Subject category	Accelerators and Storage Rings
Abstract	The evolution of the optical field for an optical klystron(OK) free electron laser is described analytically for both low gain case and high gain case. The harmonic optical klystron (HOK) in which the second undulator is resonant on the higher harmonic of the first undulator is analysed as a harmonic amplifier. The optical field evolution equation of the HOK is derived analytically for both CHG mode (Coherent Harmonic Generation, the quadratic gain regime) and HGHG mode (High Gain Harmonic Generation, the exponential gain regime), the effects of energy spread, energy modulation and dispersion in the whole process are considered. For the quadratic gain regime, the analytical formula of CHG mode is given and compared with that of OK case. For the exponential gain regime, the linear theory of HGHG mode is given and discussed.