DIOCOTRON INSTABILITY OF A WARM ELECTRON-BEAM IN CROSSED FIELDS

The warm-fluid equation derived from the drift kinetic equation is sol ved numerically to investigate the electrostatic low-frequency stabili ty of an electron ribbon beam drifting in the crossed-fields of a plan ar magnetron. The temperature effect is manifested only for oblique pr opagation with respect to the drifting beam direction. The dispersion relation takes the form omega = omega(k(perpendicular to), k(parallel to)) = omega(k(parallel to)/k(perpendicular to)), where k(parallel to) and k(perpendicular to) are respectively the components of the surfac e wave vector k parallel and perpendicular to tile magnetic field. The obliqueness of the propagation direction and the non-zero temperature give rise to a resonant instability, in addition to the diocotron ins tability, and the wavenumber corresponding to the maximum diocotron gr owth rate shifts as the temperature changes.