Studies of the cathode region of the dc glow discharge

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:6054189

Den Hartog, E A

Laser-based spectroscopic diagnostics are employed to gain an increased understanding of the cathode region of a dc helium glow discharge. A pair of diagnostics are used to determine the density (n{sub e}) and temperature (T{sub e}) of low energy electrons confined in the negative glow. The first diagnostic is based on the observed suppression of 2{sup 1}S metastables in the negative glow due to electron collisions. The reaction primarily responsible for the suppression is the metastable spin conversion reaction which converts 2{sup 1}S metastables to 2{sup 3}S metastables. 2{sup 1}S and 2{sup 3}S metastable densities and 2{sup 1}P resonant atom densities are mapped as a function of position, and the maps are analyzed to determine a relation between n{sub e} and T{sub e}. A second relation between n{sub e} and T{sub e} is determined by measuring the electron impact transfer rate between Rydberg levels. The intersection of the two relations yields n{sub e} and T{sub e} for the low energy electrons in the negative glow. Empirical determinations of the current balance at the cathode surface and metastable production are compared to results of Monte Carlo simulations. The current balance comparison leads to the prediction of a field reversal at the cathode fall-negative glow boundary. As a consequence of this field reversal a simple model of the negative glow is suggested, in which the plasma in the negative glow diffuses toward the anode in an ambipolar-like process. Ion production in the negative glow is determined from Monte Carlo simulations. An equation is written balancing production and diffusion losses. This equation is written balancing production and diffusion losses. This equation leads to a third relation between n{sub e} and T{sub e} which is compared to the earlier results.

• Research Organization: Wisconsin Univ., Madison, WI (USA)
• OSTI ID: 6054189
• Country of Publication: United States
• Language: English

Related Subjects

640410* -- Fluid Physics-- General Fluid Dynamics
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CATHODES
COLLISIONS
COMPARATIVE EVALUATIONS
DIFFUSION
ELECTRIC DISCHARGES
ELECTRODES
ELECTRON COLLISIONS
ELECTRON DENSITY
ELECTRON TEMPERATURE
ELEMENTS
ENERGY LEVELS
EXCITED STATES
FLUIDS
GASES
GLOW DISCHARGES
HELIUM
MATHEMATICAL MODELS
METASTABLE STATES
MONTE CARLO METHOD
NONMETALS
PLASMA
RARE GASES
RYDBERG STATES
SPECTROSCOPY