Experimental determination of electron energy distribution functions in Townsend discharges in argon

A parallel-plate retarding-potential-difference technique has been used to measure electron energy distribution functions in non-self-sustaining Townsend discharges in argon. The experiments were performed for values of E/p 0 equal to 150 and 200 V cm -1 Torr -1 (where E is the electric field and p 0 the gas pressure reduced to 0 degrees C). The energy distribution functions were evaluated from the measured retarding characteristics using the analysis derived here for a parallel-plate energy analyser.