High field dielectric loss measurements of liquid nitrogen

Dielectric loss measurements have been made in liquid nitrogen under different conditions to analyze the influence of flow speed during injection of liquid into the cryostat, level of air above test liquid, and waiting period before the application of voltage. The results indicate that the losses in commercial pure liquid nitrogen are in well under acceptable range for practical applications (<5/spl times/10/sup -4/). Dry air with 1% equivalent concentration of condensed oxygen in liquid nitrogen did not have any significant effect on measured losses. Some high values of tan/spl delta/ that have been measured are thought to be resulting from moisture condensation or deposition of other particulate contamination on electrode surfaces, and their effect on high field conduction.