Paper 
Title 
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MOP068 
First Simulation Results on Free Electron Laser Radiation in Displaced Phasecombined Undulators 
196 

 N.S. Mirian
UVSOR, Okazaki, Japan
 E. Salehi
AUT, Tehran, Iran



This report deals with self amplified spontaneous emission free electron laser (FEL) amplifier where the FEL emission is obtained from displaced phase combined undulators. Magnetic field of this adjustment methods in three dimensions is presented. The electron dynamics is investigated. The simulation method and results are explained. The radiation properties of the fundamental resonance and third harmonic through the phase combined undulators are compared with the normal undulator with the same undulator deflection parameter


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MOP074 
Efficiency Enhancement of a Harmonic Lasing FreeElectron Laser 
209 

 N.S. Mirian
UVSOR, Okazaki, Japan
 B. Maraghechi, E. Salehi
AUT, Tehran, Iran



The harmonic lasing freeelectron laser amplifier, in which two wigglers is employed in order for the fundamental resonance of the second wiggler to coincide with the third harmonic of the first wiggler to generate ultraviolet radiation, is studied. A set of coupled nonlinear firstorder differential equations describing the nonlinear evolution of the system, for a long electron bunch, is solved numerically by CYRUS code. Thermal effects in the form of longitudinal velocity spread are also investigated. The second wiggler field decreases linearly and nonlinearly at the point where the radiation of the third harmonic saturates to enhance the efficiency. The optimum starting point and the slope of the tapering of the amplitude of the wiggler are found by a successive run of the code. It is found that tapering can increase the saturated power of the third harmonic considerably.


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MOP075 
Threedimensional Simulation of a Harmonic Lasing FreeElectron Laser Amplifier 
213 

 E. Salehi, B. Maraghechi
AUT, Tehran, Iran
 N.S. Mirian
UVSOR, Okazaki, Japan



Threedimensional simulation of harmonic lasing Freeelectron laser is represented in the steadystate regime. Here, the third harmonic of the first wiggler is adjusted at the fundamental resonance of the second wiggler by reducing the magnetic field strength of the second wiggler. The hyperbolic wave equations can be transformed into parabolic diffusion equations by using the slowly varying envelope approximation. A set of coupled nonlinear firstorder differential equations describing the nonlinear evolution of the system is solved numerically by CYRUS3D code. This set of equations describes selfconsistently the longitudinal spatial dependence of the radiation waists, curvatures, and amplitudes together with the evaluation of the electron beam. Thermal effects in the form of longitudinal velocity spread are also investigated. In order to reduce the length of the wiggler, the prebunched electron beam is considered.


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