Gp. Fomenko et al., AZIMUTHALLY ASYMMETRIC OSCILLATIONS IN THE DIELECTRIC CHERENKOV MASER, Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 331(1-3), 1993, pp. 152-155
Theoretical and experimental evidences are presented showing that azim
uthally asymmetric modes of a dielectric-loaded circular waveguide can
also be generated due to the Cherenkov interaction mechanism with sym
metric TM modes. A Cherenkov maser configuration with a thin annular r
elativistic beam was analysed. Calculations for parameters of recent e
xperiments [W. Main et al., IEEE Trans. Plasma Sci. PS-18 (1990) 507]
and other experiments we carried out demonstrate the proximity of grow
th rates and radiation frequencies. In our experiments we investigated
the far field structure, the angular distribution and the spectrum of
the output radiation, and we observed qualitatively different far fie
ld patterns at various electron beam radii and, moreover, at various d
ielectric liner lengths. Also, the possibility of high-order modes gen
eration in the experiments of Main et al. is discussed.