INVESTIGATION OF THE SPACE-CHARGE COMPENSATION PROCESS OF ION-BEAMS USING A TIME-RESOLVING ION ENERGY SPECTROMETER

For low-energy beam transport of pulsed high perveance ion beams under space charge compensated conditions the knowledge of the build up tim e of compensation is of main interest. An LEBT system consisting of tw o solenoids has been set up to measure the rise time of compensation. Therefore, the beam potential has been in a residual gas ion energy an alyser by time resolved measurements. The measured data has been used together with numerical simulation of different equilibrium states of the beam plasma to investigate the behavior of the compensation electr ons as a function of time. The data acquired shows that the theoretica l rise time of space-charge compensation is shorter by a factor of two than the build up time determined experimentally. An interpretation o f the results is given. (C) 1998 Elsevier Science B.V. All rights rese rved.