Determination of the critical temperature of Nb–Al alloys from the plasma parameters of a vacuum arc cathode spot

Abstract

The plasma of pulsed-periodic splashes of explosive electron emission forms a vacuum arc cathode spot. The average parameters of the plasma can be evaluated from the parameters of the critical state of a metal for different materials. According to the measurements [Siegfried Zöhrer et al 2020 Plasma Sources Sci. Technol. 29 025022] of the average charge and the kinetic energy of plasma ions, the critical temperature and cohesive energy for Nb-Al alloys was evaluated within our model. It was close to the value corresponding to pure aluminum for all component ratios Nb/Al = ¼, ⅔, ¾. We have described the experimentally measured values of the cathode potential fall using the obtained magnitudes of critical temperature in the empirical “cohesive energy rule” and have reproduced the observed deviation from linearity in form of U or V shaped dependencies. The obtained results make possible to evaluate the critical temperature and cohesive energy from the parameters of the vacuum arc plasma.