Experimental measurements are performed in a Cs‐Ba diode to investigate the validity of the Maxwell‐Boltzman energy distribution for electrons and the homogeneity of the plasma parameters throughout the discharge volume. Results show that the energy distribution is Maxwellian at high discharge current, but deviates from a Maxwell distribution at lower currents. Also, the ion densities and electron temperatures near the emitter and the collector are significantly different. © 1995American Institute of Physics