PhD ceremony: Mr. S. Saminathan, 12.45 uur, Aula Academiegebouw, Broerstraat 5, Groningen
Dissertation: Extraction and transport of ion beams from an ECR ion source
Promotor(s): prof. S. Brandenburg
Faculty: Mathematics and Natural Sciences
Ion beams extracted from an Electron Cyclotron Resonance (ECR) ion sources have, compared to other types of ion sources, a relatively large and correlated emittance and therefore transport of these beams is a challenging task. In this thesis an extensive simulation study based on ion trajectory calculations of the beam formation, extraction and transport of highly charged ions from an ECR source is presented. This study concentrates on the full three dimensional (3D) simulation of beam extraction and transport. Both higher order aberrations and space-charge effects have been investigated by analyzing the 4D phase-space distributions of the ions at various positions along the beamline. The simulations and measurements show good agreement which indicates that the important physical processes are properly incorporated in the codes. The simulations demonstrate that non-paraxiality is a very important aspect for low energy ion beams extracted from ECR sources and that the fringe fields of the magnets cause significant second-order aberrations leading to a strong increase of the effective emittance. Furthermore it has been demonstrated that by suitably modifying the pole faces of the magnets the effective emittance growth can be significantly reduced. The simulations also clearly show that full space-charge compensation of the extracted ion beam is important to minimize the emittance degradation. To ensure satisfactory transmission of the high intensity beams from the new generation of superconducting ECR ion sources beam optics and space-charge compensation will definitely require more attention than they have got up to now.
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