Application of a dual-thermopile radical probe to expanding hydrogen plasmas

Abstract

We compare the performance of a hydrogen radical probe to historic data determined via Two-Photon Absorption Laser Induced Fluorescence (TALIF) using a comparable cascaded arc source under similar operating conditions. This probe has dual heat flux sensors (DHFS) each coated with materials with different catalytic properties for hydrogen atoms. In the ideal situation, the hydrogen radical flux can be deduced based on the difference between the heat loads measured by these two sensors. The influence of DHFS temperature on the performance was also assessed. The experimental results showed measurement errors of <10% could be obtained regardless of the probe temperature during plasma exposures. To convert heat fluxes into atomic fluxes, we calibrated the difference of the recombination coefficients using a vacuum ultraviolet (VUV) absorption technique, which is more reliable than modeled values based on assumptions or scattered values reported in literature. As a result, we measured the hydrogen plasma and radical parameters at various settings using both a double Langmuir probe and the DHFS. The typical atom flux in the 1022 m-2s-1 range was in good agreement with those obtained using optical techniques. We also observed that the ion and atom fluxes are both sensitive to the background gas pressure. These findings validate application of the DHFS to the cascaded arc source, and could pave the way for optimization of the source performance in the plasma material processing experiments.

Promotion of Plasma-Induced Deuterium Uptake in Ruthenium Films by Monolayer-Thick Tin Layers

“…Plasmas in nano-PSI are generated by a cascaded arc source. , During operation of the plasma source, the gas flow into the source was 1.5 slm, the vessel pressure was 45 Pa, the cathode current was set to 40 A, and the characteristic cathode voltage was 130 V for deuterium plasmas. At this setting, the electron temperature was 0.21 ± 0.024 eV, the ion flux (4.2 ± 0.47) × 10 19 m –2 s –1 , the radical flux (2.3 ± 0.32) × 10 22 m –2 s –1 , and the fwhm of the plasma beam was 67.2 ± 2.6 mm, according to measurement results using a double Langmuir probe described in ref . A target was mounted on a water-cooled target holder, and the target surface was 100 mm away from the nozzle of the plasma source.…”

“…The work on deuterium plasmas was performed using the nano-PSI device at DIFFER. The details of nano-PSI can be found in refs and , but a short description is given here. Nano-PSI is an experimental setup at DIFFER to study plasma surface interactions (PSIs) .…”