Test of validity of Maxwellian statistics for electrons thermionically emitted from an oxide cathode

An experiment is described in which thermionically emitted electrons from the indirectly-heated cathode of an EB91 double diode valve move towards the anode against a retarding field. The observed dependence of anode current on retarding potential is in good agreement with that predicted assuming that the emission velocities have a Maxwellian distribution. The cathode temperature is indirectly determined from the characteristic temperature of this distribution and is then used to measure the work function of the cathode material (BaO/SrO).