An exploration of the production of negative ions from neutral gases using a negative hydrogen ion source driver
Date
2024-01-04
Authors
Paul, Andrew
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Abstract
Negative ion beams have wide-ranging applications from acceleration in cyclotrons for
medical radioisotope production to areas where tandem accelerators are leveraged. The
fields in which tandem accelerators are used include nuclear structure research, environ-
mental studies, materials characterization, medical treatments and ion implantation in
semiconductor devices. A commercially important case where negative helium ions are
utilized is in the semiconductor industry where they are conventionally created by double-
charge exchange ion sources using metallic vapours (typically Alkali’s). These metallic
vapours lead to challenges such as contamination, electrical shorts, and maintenance difficulties. In an effort to overcome the significant disadvantage of metallic vapour charge
exchange, this thesis will firstly investigate the production of negative helium ions using a
non-metallic charge exchange method in which negative hydrogen ions will be impinged
upon neutral helium gas. A charge exchange cell is developed for this project which includes an electrostatic accelerator to accelerate newly produced negative ions from the
target gas. The main objective focuses on negative helium ion production but the method
is applied to different gas targets including H2, CO2, and O2 with the goal of accelerating
and measuring negative ions that are the products of these targets. This approach aims
to avoid the significant contamination issues from the metallic vapour double-charge ex-
change method and explore novel methods for negative ion production via charge transfer.
Description
Keywords
Ion source, Negative ion beam, Electrostatic accelerator, Charge exchange