Paschen Tests at Cryogenic Conditions: Experimental Results

Superconducting devices are widely used in a variety of scientific fields, such as the International Thermonuclear Experiment Reactor (ITER), magnetic resonance imaging (MRI), and ultrahigh voltage power transmission (UVH). The insulation system plays a significant role in superconducting devices. Paschen discharge may cause insulation failure in superconducting devices, which affects the normal operation of superconducting magnets. However, there has been a lack of research on the dc breakdown of helium gas at cryogenic temperature with medium to high vacuum. In this article, the dc breakdown characteristics of helium gas under the condition of gas pressure ( $P$ ) from $1\times 10^{-2}$ to $1\times 10^{0}$ Pa are discussed, where the gap distance ( $d$ ) of the parallel plate electrodes are 1 and 2 mm. The gas pressure is regulated by a proportional-integral-differential (PID) system consisting of a pressure control instrument and a proportional valve. 77 K was realized by immersing the experimental setup in liquid nitrogen. The dc breakdown data of helium at room temperature (300 K) and liquid nitrogen temperature (77 K) were obtained under different vacuum conditions and different Pd. This data can be regarded as a supplement to the Paschen curve of helium under the special conditions of medium to high vacuum.