Electron density and temperature measurements in a magnetized expanding hydrogen plasma

Abstract

Engeln, R. A. H. (2016). Electron density and temperature measurements in a magnetized expanding hydrogen plasma. Physical Review E, 94(2), [023201]. DOI: 10.1103/PhysRevE.94.023201 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. We report measurements of electron densities, n e , and temperatures, T e , in a magnetized expanding hydrogen plasma performed using Thomson scattering. The effects of applying an axial magnetic field and changing the background pressure in the plasma vessel on n e and T e along the expansion axis are reported. Magnetic field strengths (B field) up to 170 mT were applied, which are one order of magnitude larger than previously reported. The main effect of the applied B field is the plasma confinement, which leads to higher n e . At B fields larger than 88 mT the electron density along the expansion axis does not depend strongly on the magnetic field strength. However, T e is susceptible to the B field and reaches at 170 mT a maximum of 2.5 eV at a distance of 1.5 cm from the exit of the cascaded arc. To determine also the effect of the arc current through the arc, measurements were performed with arc currents of 45, 60, and 75 A at background pressures of 9.7 and 88.3 Pa. At constant magnetic field n e decreases from the exit of the arc along the expansion axis when the arc current is decreased. At 88.3 Pa n e shows a higher value close to the exit of the arc, but a faster decay along the expansion axis with respect to the 9.7 Pa case. T e is overall higher at lower pressure reaching a maximum of 3.2 eV at the lower arc current of 45 A. The results of this study complement our understanding and the characterization of expanding hydrogen plasmas.

Dynamic features of the electron drift and electron properties in a HiPIMS discharge

“…From a fit of the Raman lines, which are measured using a light transmission and collection setup identical to the Thomson measurements, a scaling factor is determined which allows the spectral area to be converted to an absolute electron density. The full procedure for such calibrations is described in reference [24], and by several other authors, for example, in references [26][27][28]; calibration using a Rayleigh spectrum is also a standard technique [29,30].…”