EEDF measurements in plasma expansion region of a high-frequency driven hydrogen discharge

Abstract

The production of negative hydrogen ions by volume processes depends on the electron energy in the expansion region of a plasma source. The study presents experimental results for the electron energy distribution function (EEDF) obtained by probe diagnostics in this region. Measurements are performed in axial and radial directions at low gas pressures. The results for the EEDF show that its shape changes along the chamber axis because the plasma density and the electron temperature decrease to a nearly constant value in the main part of the expansion chamber. The EEDF is Maxwellian-like with tail up to 40 eV close to the driver. The nonlocal formation of the EEDF is experimentally obtained in expanded plasma. © 2007 IOP Publishing Ltd.