Aperture Size Effect on Extracted Negative Ion Current Density

de Esch, H. P. L.; Svensson, L.; Riz, D.
March 2009
AIP Conference Proceedings;3/12/2009, Vol. 1097 Issue 1, p309
Academic Journal
This paper discusses experimental results obtained at the 1 MV testbed at CEA Cadarache that appear to show a higher extracted D- current density from small apertures. Plasma grids with different shapes have been installed and tested. All grids had one single aperture. The tests were done in volume operation and in caesium operation. We tested four grids, two with O\14 mm, one with O\11 mm and one with O\8 mm apertures. No aperture size effect was observed in volume operation. In caesiated operation the extracted current density for the O\8 mm aperture appears to be significantly higher (∼50%) than for the O\14 mm aperture. Simulations with a 3D Monte Carlo Trajectory Following Code have shown an aperture size effect of about 20%. Finally, as byproducts of the experiments, data on backstreaming positive ions and the temperature of the plasma grid have been obtained.


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