Diagnostics of pulsed vacuum arc discharges by optical emission spectroscopy and electrostatic double-probe measurements

Abstract

In this work the study of plasma characteristics by means of two of the most common techniques employed by the scientific community dedicated to the experimental plasma research is presented. The plasma was generated in a vacuum reaction chamber which was filled with hydrogen gas. Inside the chamber, two opposite electrodes were placed: the cathode, which was formed by a target of highly oriented pirolitic carbon and the anode. The electron temperature T e and the electron density n e were measured by using optical emission spectroscopy and electrostatic double probe, obtaining very close values for each case. T e was calculated as approximately 0.7 eV and n e of the order of 10 13 cm −3. The optical emission measurement allows one to identify the substances that are in the plasma like C I, C II, C III, H I and H 2 and some possible reactions. The double-probe technique showed the plasma potential of about 24 V. The characteristic curve of the double probe exhibited oscillational plasma instabilities which could be attributed to the charge density variation or other factors, such as the employed AC signal and the geometric probe.