Spectrographic Measurements of a Pulsed Arc

摘要

A Kerr cell shutter has been used with a photographic spectrograph to do time‐resolved studies of an arc discharge in 2.5 Torr of helium with air impurity. The arc had a peak current of 40 kA and a period of 40 μsec. Temperatures were obtained from line intensity ratios of NII, NIII, OII, CII, CIII, and electron densities from Stark broadening measurements. Plasma temperatures were found to reach a peak in the first few μsec and decline thereafter. For an unconfined arc, Ne declined in time, whereas for a confined arc (tube diam 8–13 mm) the initial temperature was higher (as much as 3.8 eV), and its decline was accompanied by an increase in Ne (from 1017 to 1018 cm-3) due to wall erosion. The intensity of He I 5876 was anomalously low at first. This is interpreted as a temperature deficiency in neutral helium which decreases as time goes on, reaching equilibrium in some 30 μsec.