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Self-fields in a free-electron laser with helical wiggler and axial magnetic field

Published online by Cambridge University Press:  25 November 2005

MAHDI ESMAEILZADEH
Affiliation:
Department of Physics, Iran University of Science and Technology, Tehran, Iran
JOSEPH E. WILLETT
Affiliation:
Department of Physics and Astronomy, University of Missouri-Columbia, Columbia, MO 65211, USA ([email protected])
LORI JO WILLETT
Affiliation:
Department of Mathematics, University of New Orleans, New Orleans, LA 70148, USA

Abstract

An analysis of self-fields associated with charge and current densities of the electron beam in a free-electron laser with helical wiggler and axial magnetic field is presented. The self-electric field is derived from Poisson's equation. A more detailed analytical model for the self-magnetic field is determined from Ampere's law. Mutual influence of the electron velocity and self-magnetic field is considered to account for the total self-magnetic field. It is shown that for group I orbits, the self-magnetic field acts as a diamagnetic correction to the wiggler magnetic field; for group II orbits, it acts as a paramagnetic correction. Both diamagnetic and paramagnetic effects become stronger near the transverse velocity resonance. An important effect of the self-fields on the electron trajectories is the creation of unstable orbits for group II, which are not found in the absence of self-fields.

Type
Papers
Copyright
2005 Cambridge University Press

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