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| Paper IPM / P / 7124 |
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| Abstract: | |
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An analysis of the parametric instability which forms the basis
for operation of a free electron laser with a longitudinal
electrostatic wiggler is presented. A theory is developed that
allows for an arbitrary axial magnetic field and arbitrary ratio
of the electron beam radius a to the waveguide inner radius
R without imposing the electrostatic approximation on the
space-charge wave. Dispersion characteristic of the eigenmodes of
a magnetized electron beam inside a waveguide specially
EH01 electromagneric and SC01 space-charge
mode have been studied. A formula for the spatial growth rate of
parametrically excited eigenmodes is derived. variations of the
growth rate, efficiency, radiation wavelength, and required pump
wavelength as functions of the ratio a/R are
studied numerically. It is shown that excitation of the upper
branch or lower branch of an EH01 waveguide mode can
be achieved with suitable chosen values for the system parameters,
and a fully electromagnetic analysis can produce modest changes on
the operative quantities, as compared to the imposition of
electrostatic approximation on the space-charge wave.
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