A study on the extraction of negative ions from a multicusp ion source

A beam of charged particles can perform wonders in the field of science and technology. Oneof the methods of producing charged particle beams is its extraction from gaseous plasmacreated inside ion sources. The thesis deals with a collection of studies on the extractionof negative ion beams from a multicusp ion source, where multicusp refers to the type ofmagnetic field used for plasma confinement inside the ion source. The study revolves aroundimproving the H− and D− beam extraction from the ion source.Two kinds of ion sources are considered in the study. One of them, the filament ionsource, generates plasma through thermionic emission, while the other, the RF ion source,generates plasma through RF energy coupling. The characteristics of the extracted ion beamdepend on a multitude of factors in the ion source and extraction system, and some of themare analysed in the thesis. Both ion sources produce negative ions in the plasma primarilythrough volume production methods. The thesis presents evidence for the negative ionproduction through plasma-wall surface interactions also. Results indicate that an optimummagnetic filter field is needed to increase the efficiency of volume production and a lowersurface temperature is needed to enhance the surface interactions. Design upgrades of theRF ion source were also performed and improvements in H− and D− beam currents wereachieved. The thesis also presents the results of an experimental campaign for analysing thevalidity of IBSimu, an ion beam extraction simulation code. Results indicate that IBSimu iscapable of reproducing the ion beam emittance trends obtained in the experiments. Resultsof plasma analysis performed using Langmuir probe and laser photodetachment tools, andthermal analysis conducted using Solidworks simulations, are also presented in the thesis.