Langmuir probe measurements of discharge parameters in a Cs–Ba tacitron

Abstract

Experimental measurements of steady-state discharge parameters are performed in a Cs–Ba tacitron equipped with Langmuir probes. Measured quantities include electron temperature, plasma density, and plasma potential, in both the emitter-grid and grid-collector regions. The effects of Cs pressure and electrode arrangements on the measured parameters are investigated. Measurements indicate that the electron energy distribution function in the emitter-grid gap is Maxwellian, and that there is an electron beam in the grid-collector gap, which relaxes to Maxwellian at high cesium pressure. Placing the grid closer to the collector not only increases the ion loss rate, but also makes ionization inefficient, lowering the plasma density in the grid-collector gap. The low plasma density makes it easier to extinguish the discharge during current modulation.