Hydrogen Balmer beta: The separation between line peaks for plasma electron density diagnostics and self-absorption test

We propose a diagnostic technique for the measurement of plasma electron number density, N-e, based on the wavelength separation between peaks, Delta lambda(PS), of hydrogen Balmer beta line, H-beta. In favor of the proposed diagnostic technique we demonstrate high sensitivity of Delta lambda(PS) on N-e and low sensitivity on plasma elementary processes and plasma parameters that may distort the line profile. These properties of Delta lambda(PS) enable reliable N-e plasma diagnostics in the presence of considerable self-absorption. On the basis of available theoretical data tables for the H-beta line profiles, simple Ne=f(Delta lambda(PS)) formulas are proposed. Their validity is experimentally confirmed in a low initial pressure pulsed discharge for the Ne range of (0.2-7)*10(23) m(-3). The agreement of the proposed formulas with another diagnostic technique is well within 10%. In addition, the difference in N-e values obtained from peak separation and from the H-beta line width is successfully used as a self-absorption test for line profile. (C) 2014 Elsevier Ltd. All rights reserved.