Design of High Power FELS and the Effects of Diffraction on Detuning in an FEL Oscillator
Naval Postgraduate School Monterey United States
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In experiments going back to the first free electron laser FEL oscillator at Stanford, the measured width of the desynchronismcurve is often significantly greater than predicted by theory and two-dimensional 2D simulations in z t. The results of new four dimensional4D simulations in x,y,z,t show that this difference can be explained by the effects of diffraction. When the light isartificially constrained to remain in the cavity fundamental mode, 2D and 4D simulations give similar results, but when the light isallowed to self-consistently develop higher-order modes, the 4D simulations give different results that agree better with experiments.The results of new 4D simulations also show the effects of emittance versus electron beam energy and mirror shift versus mirror tilton extraction. Analysis of these results examine the robustness of FEL designs.