Recombination of Alkali Plasma Ions on Hot Tungsten Surfaces

The rate of surface recombination of cesium and potassium plasma ions on the hot tungsten end plates of a $Q$ machine has been measured with a Langmuir-Taylor detector. Good agreement of the measurements with the equilibrium theory of electrostatic confinement is found under conditions in which the plasma potential is not highly negative or positive ($\mathrm{}\left|V\right|<\frac{2kT}{e}$). Corrections to the equilibrium theory for ion heating (highly negative plasma) and ion drifts (highly positive plasma) bring theory into good agreement with experiment over a range in density of 2 × ${10}^9$ to 2 × ${10}^{12}$ ${\mathrm{cm}}^{-3\mathrm{}}$.