Collisional kinetics of non-uniform electric field, low-pressure, direct-current discharges in H$ {2}$ - Physics > Plasma PhysicsReport as inadecuate




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Abstract: A model of the collisional kinetics of energetic hydrogen atoms, molecules,and ions in pure H$ 2$ discharges is used to predict H$ \alpha$ emissionprofiles and spatial distributions of emission from the cathode regions oflow-pressure, weakly-ionized discharges for comparison with a wide variety ofexperiments. Positive and negative ion energy distributions are also predicted.The model developed for spatially uniform electric fields and current densitiesless than $10^{-3}$ A-m$^2$ is extended to non-uniform electric fields, currentdensities of $10^{3}$ A-m$^2$, and electric field to gas density ratios $E-N =1.3$ MTd at 0.002 to 5 Torr pressure. 1 Td = $10^{-21}$ V m$^2$ and 1 Torr =133 Pa The observed far-wing Doppler broadening and spatial distribution ofthe H$ \alpha$ emission is consistent with reactions among H$^+$, H$ 2^+$,H$ 3^+$, and H$^-H$ ions, fast H atoms, and fast H$ 2$ molecules, and withreflection, excitation, and attachment to fast H atoms at surfaces. TheH$ \alpha$ excitation and H$^-$ formation occur principally by collisions offast H, fast H$ 2$, and H$^+$ with H$ 2$. Simplifications include using aone-dimensional geometry, a multi-beam transport model, and the averagecathode-fall electric field. The H$ \alpha$ emission is linear with currentdensity over eight orders of magnitude. The calculated ion energy distributionsagree satisfactorily with experiment for H$ 2^+$ and H$ 3^+$, but are only inqualitative agreement for H$^+$ and H$^-$. The experiments successfully modeledrange from short-gap, parallel-plane glow discharges to beam-like,electrostatic-confinement discharges.



Author: A. V. Phelps

Source: https://arxiv.org/







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