Electron temperature and electron density of copper vacuum arc in diffuse arc mode and anode spot arc mode

The objective of this paper is to compare the electron temperature and electron density in diffuse vacuum arc mode and anode spot mode. The experiment was based on the butt type copper electrodes, with contact diameter D=40mm, and gap distance g=10mm. The vacuum arc was ignited by a needle tungsten electrode, which was embedded in the cathode. A high-voltage pulse with a rise time of 8ns, and aptitude of 24kV was applied on the needle electrode. The arc current varied from 2.8kA to 7.5kA (rms). The arc current was measured by Hall sensor and the arc voltage was measured by Tektronix P6015A, respectively. The arcing process was recorded by a high-speed charge-coupled device (CCD) video camera. The emission intensities of the interelectrode plasma of the vacuum arc were collected by an optics spectrograph. The Bolzman plot method was used to calculate the electron temperature and the Saha equation was used to determine the electron density of diffuse vacuum arc mode and anode spot mode. The electron temperature was 1.09eV in diffuse arc mode and it was 1.22eV in anode spot mode. The electron density was increased from 7.6 × 10 15 /cm 3 to 2.1 × 10 15 /cm 3 when the arc mode changed from diffuse arc mode to anode spot mode.