A no. of diagnostics to measure all plasma properties in the vicinity of the hollow cathode are described. The momentum balance in the plasma and the source properties of the hollow cathode are detd. The main driving term in the momentum balance is the pressure gradient of ions and electrons. The deceleration of the ions is mainly caused by ion viscosity and to some extent by friction with neutrals. At high currents the ion flux almost equals the gas flux. At high gas flows the ion flux sats. [on SciFinder (R)
