The polarity effect of the dielectric breakdown voltage in liquid He is studied. The breakdown voltage for a positive needle is higher than that for a negative needle and even than that for uniform field. The field strength on the cathode surface at breakdown threshold for a positive needle is calculated with a simple hyperboloid approximation of field distribution, and agrees approximately with the breakdown field in the uniform field condition. The breakdown strength also depends on the work function of the cathode metal but not that of the anode metal. Therefore, breakdown threshold in liquid He seems to be determined by the field strength at the cathode.
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Fujii et al. (1979) studied this question.