Electrode conditioning effects in liquid helium

A theoretical model explaining the anomalous conditioning/ deconditioning effects observed in liquid helium1 is presented and preliminary experimental results supporting this theory are given. The hypothesis of the formation and breakdown of bubbles initiating complete breakdown of liquids has been extended by assuming that pulses (partial discharges) of constant energy (Wb?10?8J, see ref. 6) occur, which lead to a calculable bubble size and hence make prediction of breakdown strength possible. Theoretical results are compared to experimental data obtained in liquid helium and liquid nitrogen; good qualitative agreement is found.