Speaker
Michael Barnes
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1076.pdf
Development of a Caesium Free Hydrogen Negative Ion Source Based on a
Pulsed ICP Discharge
M. J. Barnes and M. D. Bowden
Department of Electrical Engineering and Electronics, University of Liverpool, UK
The negative ion sources planned for use in ITER’s NBI system will utilise caesium to
enhance the surface production of H- and D- ions. However it has been suggested [1] that for
DEMO/commercial fusion reactors that a similar Cs injection rate to ITER is likely to lead to
NBI operational problems during the reactor’s lifetime. Fusion NBI ion sources of the future
will need to dramatically reduce their rate of Cs consumption, or will require alternatives to
Cs for H- surface production. The aim of this work is to evaluate the performance of a Cs free
RF inductively coupled ion source, operated in a pulsed regime to generate a high density of
volume produced negative ions. Such sources have been developed for use in damage free
plasma etching of future Ultra-Large Scale Integrated circuits [2]. Source performance has
been characterised by Langmuir probe measurements of plasma density and temperature at
the centre of the discharge and in proximity to the extraction grid, together with RFA
measurements of the extracted ion beam. The source will also be used for testing materials
which have shown promise as Cs alternatives for H- surface production, such as boron doped
diamond [3], for comparison with conventional magnetically filtered, caesiated fusion H- ion
sources.
References:
[1] R.S. Hemsworth, D. Boilson, ”Considerations for the development of neutral beam injection for fusion
reactors or DEMO,” AIP Conference Proceedings, 1869, 2017.
[2] S. Samukawa, ”Ultimate Top-Down Etching Processes for Future Nanoscale Devices: Advanced Neutral-
Beam Etching,” Japanese Journal of Applied Physics, 45, 4A, pp. 2395-2407, 2006.
[3] A. Ahmad, C. Pardanaud, M. Carr`ere, J.-M. Layet, G. Cartry et. al., ”Negative-ion production on carbon
materials in hydrogen plasma: Influence of the carbon hybridization state and the hydrogen content on H-
yield,” Journal of Physics D: Applied Physics. 47, 2014.
