Rotation of a strongly magnetized hydrogen plasma column determined from an asymmetric Balmer-βspectral line with two radiating distributions

Abstract

A potential buildup in front of a magnetized cascaded arc hydrogen plasma source is explored via E x B rotation and plate potential measurements. Plasma rotation approaches thermal speeds with maximum velocities of 10 km/s. The diagnostic for plasma rotation is optical emission spectroscopy on the Balmer-beta line. Asymmetric spectra are observed. A detailed consideration is given on the interpretation of such spectra with a two distribution model. This consideration includes radial dependence of emission determined by Abel inversion of the lateral intensity profile. Spectrum analysis is performed considering Doppler shift, Doppler broadening, Stark broadening, and Stark splitting.

Optimization of the output and efficiency of a high power cascaded arc hydrogen plasma source

“…This effect, together with viscous ion heating, 17 molecular assisted recombination, 8,9 and not having velocity data for all experimental conditions introduces some uncertainties in the comparison between the estimated fluxes from the I -V measurements and the results in Figs. 12 and 13.…”

“…10 shows that the central electron temperature measured at z = 4 cm does not vary much, and that the width of the temperature profile increases with input power. We note that this is not a proof of these assumptions, because processes in the first 4 cm of the plasma beam might have influenced the temperature profile ͑such as plasma expansion, Ohmic heating, 11 and viscous ion heating 17 ͒. Figure 17 also explains the stable operation of the cascaded arc: If ͑e.g., due to a fluctuation͒ the dissipated power becomes larger than what is required to sustain the discharge, the current channel widens, which in turn immediately lowers P in .…”

“…We note that the measured Doppler shift represents an average over the full width of the plasma beam and over several centimeters in the axial direction. Furthermore, as the emissivity profile of the plasma beam in these conditions is hollow, 17 the slower edges of the beam contribute most to the measured signal.…”

Strongly Reduced Penetration of Atomic Deuterium in Radiation-Damaged Tungsten

“…The ion flux on the targets can be estimated by applying the Bohm criterion [13] and ranges from 2 Â 10 24 ions m À2 s À1 in the center of the target to 5 Â 10 23 ions m À2 s À1 at the edges. For our experimental conditions, the deuterium in the plasma predominantly consists of atomic ions [14,15]. The kinetic energy of the ions arriving at the surface can be estimated by considering a drifting Maxwellian velocity distribution for the ions in the plasma and an acceleration over the plasma sheath towards the surface.…”

“…The kinetic energy of the ions arriving at the surface can be estimated by considering a drifting Maxwellian velocity distribution for the ions in the plasma and an acceleration over the plasma sheath towards the surface. Assuming equal electron and ion temperatures in the plasma [15], this leads to an ion kinetic energy of roughly 5 eV. The temperature profile of the tungsten surface during exposure was measured with a fast infrared camera (FLIR SC7500-MB) and varies between 560 K in the center of the target to 470 K at the edges (the emissivity of the tungsten targets used was 0.07, a value verified ex situ with the help of a thermocouple measurement).…”