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Terahertz sources based on the free-electron laser (FEL-THz) is one of the most effective methods to produce high-power THz sources , it has other THz sources can not match advantage is that its wavelength is continuously adjustable , Therefore , the frequency can cover the entire terahertz band , even broader . The optical cavity is the core component of the free-electron laser , it is not only to make the light field and the free-electron fully functioning so that the light field to obtain sufficient gain , but it also bears the important task of the laser output , so the light cavity and the design is very necessary. First, we study the FEL of one-dimensional theory , including the lateral movement of the free electrons in the swing field , free electrons and the interaction of the light field , the resonance relations , FEL gain . Secondly , according to the one-dimensional theory of FEL , summed up the three equations : the electron energy change equation , the phase change of the electron equation , and the radiation field field strength change equation . Finally, based on the above three equations written MATLAB simulation program , and to do the numerical calculation . The main research work , including endoscopic study on the stability of the optical cavity structure , material , and coupled output mode ; numerical calculation , respectively, to the cold electron beam and Gaussian pulse input, analog optical cavity of the start-up conditions , the light field small signal gain and index gain analog power saturation phenomenon of the light field , rocking the number of cycles and the relationship of the gain of the light field , the relationship between the number of cycles reached saturation needs transit times , the number of different electronic and electron beam energy divergence FEL parameters .
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