Efficiency Enhancement in a Tapered Free Electron Laser by Varying the Electron Beam Radius

Jiao, Yi ; Wu, J. ; Cai, Y. ; Chao, A.W. ; Fawley, W.M. ; Frisch, J. ; Huang, Z. ; Nuhn, H.-D. ; /SLAC ; Pellegrini, C. ; /SLAC /UCLA ; Reiche, S. ; /PSI, Villigen

关键词: APPROXIMATIONS;    EFFICIENCY;    ELECTRON BEAMS;    FREE ELECTRON LASERS;    RADIATIONS;    SATURATION;    SIMULATION;    WIGGLER MAGNETS Accelerators;    XFEL;   

DOI  :  10.2172/1035087
RP-ID  :  SLAC-PUB-14756
PID  :  OSTI ID: 1035087
Others  :  TRN: US1201124

学科分类：核物理和高能物理

美国|英语

来源: SciTech Connect

【 摘 要 】

Energy extraction efficiency of a free electron laser (FEL) can be increased when the undulator is tapered after the FEL saturation. By use of ray equation approximation to combine the one-dimensional FEL theory and optical guiding approach, an explicit physical model is built to provide insight to the mechanism of the electron-radiation coherent interaction with variable undulator parameters as well as electron beam radius. The contribution of variation in electron beam radius and related transverse effects are studied based on the presented model and numerical simulation. Taking a recent studied terawatt, 120 m long tapered FEL as an example, we demonstrate that a reasonably varied, instead of a constant, electron beam radius along the undulator helps to improve the optical guiding and thus the radiation output.