Effects of plasma-facing materials on the negative ion (H-/D-) current extracted from an ECR plasma source
Résumé
The possibility of enhancing the extracted negative ion (H-/D-) current due to plasma-surface
interactions on selected materials (potential alternatives of Cs in NBI for tokamak), is herein
demonstrated. Current results, from plasmas sustained at a few mTorr by ECR dipolar plasma
sources, as obtained with laser photodetachment at 1064 nm, demonstrate that, when tungsten
material faces plasma it induces an obvious enhancement of the negative ion density. An
extracting system using magnetic cores and three cooled electrodes are used to evaluate effects of
the material itself and its relative position in the plasma, on the extracted current. The influence of
the dimensions and geometry of the extracting aperture on the beam intensity, are also studied.