Plasma Transport in a Magnetic Multicusp Negative Hydrogen Ion Source
Abstract
An analysis of plasma transport through the magnetic filter in tandem magnetic multicusp negative hydrogen ion sources was conducted to determine the mechanism of thermal electron diffusion, explain thermal electron cooling, describe the transport of primary electrons through the filter, and model positive ion species transport. The thermal electron flux was shown to exceed its classical value by one to three orders of magnitude. The flux variation with temperature was best described using a Coulomb-like temperature gradient drag term, consistent with diffusion due to ion-sound-like turbulence. Thermal electron energy flux loss was shown to be dominated by inelastic collisions at low values of the particle flux. Consequently, an equation was derived which correctly reproduces the observed variation in the ratio of source to extraction chamber densities as a function of the ratio of source to extraction chamber electron temperatures. The primary electron flux was found to be one order of magnitude higher than the classical collisional rate. Positive ion species transport was modelled assuming ballistic flow. Ion production and loss mechanisms were used in conjunction with transport to calculate extracted positive ion species percentages. Results were found to be in reasonable agreement with experiment.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1991
- Accession Number
- ADA243876
Entities
People
- Ricky G. Jones
Organizations
- Air Force Institute of Technology