INVESTIGATION OF THE CURRENT DENSITY LIMITATIONS IN A THERMIONIC CONVERTER.
Abstract
Transient measurements were made in a thermionic converter to ascertain which processes determine the ion loss rate for various operating conditions. A small pulsed increase in current was applied to the converter; just after the pulse an increase in output voltage was observed. The increased voltage then decayed back to the steady-state level. The analysis indicates that the voltage decay time was equal to one-half the average lifetime of ions in the interelectrode space. Since the current pulse was only a small perturbation of the steady-state current, the lifetime of ions after the pulse should be the same as the ion lifetime during steady-state operation. The data indicate that, over most of the experimental conditions, volume recombination was negligible; the ions were lost by migration to the electrodes, followed by surface recombination. The analysis shows that volume recombination is appreciable with large spacing and high current. At low cesium pressures and low current, the ion lifetime was proportional to the spacing, and increased when the cesium pressure was increased. The ion loss rate by diffusion to the collector was calculated for various spacings and cesium pressures; good agreement with the experimental data (at low output current) was obtained. At high current and/or high cesium pressure, very short lifetimes were observed, indicating a high ion flux to the emitter. The data and analysis indicate that very high ion generation and loss rates are present in the ignited-mode thermionic converter. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1966
- Accession Number
- AD0480068
Entities
People
- Coleman Kaplan