Characterization of microwave discharge ion source for high protom beam production in cw and pulsed mode.

This thesis consist of an introduction to the plasma physics of Microwave Discharge Ion Source (MDIS) and a review of the result obtained including discussion of related work. This thesis begin with a theoretical discussion dealing with plasma physics relevant for the production of intense proton beam in MDIS. This is followed by an historical overview on the production of high current beams by the 2.45 GHz microwave ion sources. The experimental part of the work consist of the studies related to MDIS plasma physics. For each source the most important parameters are the maximum beam current and the intensity of the single ion species. So the total beam current and the proton beam was studied as a function of different experimental set-up. In order to make a meaningful analysis, further measurements are required, regarding the quality of the ion beam. The quality of the ion beam extracted from an ion source is characterized by the beam emittance; for high quality ion beams the emittance should be as small as possible. Emittance measurements were carried out for two source: the VIS source operating in cw mode and the SHILI source operating in pulsed mode. The main limitation of MDIS, in fact, consists of the so called electromagnetic cutoff, which naturally fixes the upper boundary of the plasma density which can be reached at a given frequency. Passive and active techniques can be used on the purpose to overcome this limit. Finally, another active mechanism was tested on a device very similar to the VIS source: we tried to employ an innovative mechanisms of plasma ignition based on electrostatic waves (ESW).