The current of an annular electron beam with virtual cathode in a drift tube

An analysis based on the laws of conservation of energy and the z components of the field and particle momentum shows that a thin magnetized annular electron beam in a homogeneous drift tube behind a virtual cathode under stationary conditions occurs in a "squeezed" state corresponding to a slow left-hand branch of the current characteristic with a relativistic factor in the interval 1 less than or equal to gamma less than or equal to Gamma(1/3). The beam current I-1 behind the virtual cathode in a homogeneous drift tube can vary from zero up to a limiting value I-lim , while the injection currents (I-2) and the current of electrons reflected from the virtual cathode (I-3) for every stationary state are single-valued functions of I-1 and fall within the intervals I-F /2 less than or equal to I-2 less than or equal to I-lim and 0 less than or equal to I-3 less than or equal to I-F/2, respectively, where I-F is the Fedosov current. (C) 2003 MAIK "Nauka / Interperiodica".