Ni. Karbushev et al., HIGHER HARMONIC-GENERATION IN A FEL WITH AN AXISYMMETRICAL UNDULATOR OF THE INDUCTION TYPE, Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 358(1-3), 1995, pp. 467-470
It is shown that the amplitudes of transverse components of velocities
of electrons in an axisymmetric undulator depend resonantly on the va
lue of an axial guiding magnetic field. They increase substantially wh
en the cyclotron frequency is approximately equal to the frequency of
the undulator oscillations of the electrons or its higher harmonic, wh
ich corresponds to resonance pumping of the undulator motion. Such an
effect was observed experimentally in a free electron laser with a hol
low kiloampere electron beam of microsecond duration and an axisymmetr
ic undulator consisting of alternating conducting and dielectric rings
in an axial magnetic field of a solenoid. The maximum generated micro
wave power in a FEL reached several megawatts in the centimeter and mi
llimeter ranges of wavelenghs.