Pressure and temperature dependence of breakdown characteristics of sub-cooled liquid nitrogen

We investigated breakdown (BD) characteristics of sub-cooled liquid nitrogen (SLN₂) using a sphere-to-plane electrode configuration for different pressures (0.1-0.3 MPa) and temperatures (65-77 K) of SLN₂. BD voltage of SLN₂ was measured repeatedly under ac voltage application. Experimental results quantitatively revealed that how much BD voltage increased with the increase in gap length and pressure, and with the decrease in temperature of SLN₂. The gap length dependence of BD strength in SLN₂ was analyzed and discussed in terms of number and size of bubbles in SLN₂. In addition, we found that the decisive electric field factor (a) for BD was enhanced to 87-93 % of the maximum electric field strength in SLN₂ against 82-83 % in LN₂ under atmospheric boiling condition.