A 2D-FEL code without rotational symmetry

A 2D-FEL code with geometry infinitely extended in direction of electron wigging motion is established. Using this code, the evolution of optical field is calculated under the conditions of nonideal incidence of e-beam, which results in exponential degradation in output power and the excitation of transverse higher modes, as well as in displacement of the centroid of optical beam. It is pointed out that, beside the emittance of e-beam, the geometry of transverse phase space is also an important parameter having influence on FEL performance