Parameters of accelerated multi-species pulsed ion beam propagating through a drift gap

By means of an electrostatic ion analyzer we have experimentally studied energy spectrum of an accelerated ion beam moving in a drift space upon separation by a grid electrode system from a metal plasma jet of a pulsed high-current vacuum arc discharge. It is established that the average energy per unit ion charge in the beam is below the value corresponding to the accelerating voltage. The width of the energy spectrum of accelerated ions is close to their average energy and significantly exceeds the width of the energy spectrum of the initial beam. The results of model calculations show that the observed phenomena can be explained by the action of a nonstationary electric field of the space charge of the ion beam transported via the drift space. Measurements performed with a heated and Langmuir probes show that the separated ion beam consists also a significant electron component, which, nevertheless, do not compensate the space ion charge formed in the drift gap. Dependence on the accelerating voltage of positive potential that is due to influence of the space ion charge is studied, as well.