Measurement of the temperature and the resistivity of an impulse arc in variable-pressure CO2

The properties, as a function of pressure, of an arc produced by fast impulses in a carbon dioxide (CO2) atmosphere were investigated. A time-resolved spectroscopy technique consisting of a spectograph coupled to a fast camera was implemented to analyse the light emitted by the arc. Using this technique the arc's spectrum could be obtained at different moments of the development of the discharge. The use of a multi-element Saha-Boltzmann method allowed both the temperature T and the electron density ne of the arc to be obtained. These were found to have peak values of T = 28 000 K and ne ∼ 9 x 1017 cm-3 at the time of maximum current. The measured temperatures were incorporated into a variation of the Spitzer model to obtain the plasma resistivity. With it, the arc resistances were calculated and found to be consistent with the measured currents (∼1.85 kA). Mass spectroscopy sampling of the spent gas shows that CO2 degraded very little after several dozen kiloampere shots.