Numerical analysis of interferograms of asymmetric plasma objects

Interferometric studies of dense rapidly expanding plasmas require the use of lasers emitting pulses of ~10^–10–10^–11 sec duration. Since the emission lines are wide, it is necessary to analyze interferograms by methods which ensure the maximum precision for a small number N of experimental points. Moreover, it is important to know the error resulting from such analysis and the optimal number N_opt of points to be analyzed. The present paper reports the results of numerical calculations, carried out on an M-220 computer, of the values of N_opt and of the error in the Van Voorhis method for three typical profiles of electron density in a plasma focus. The values of N_opt and of the errors in the parabola and Van Voorhis methods arerefined for a plasma jet (these parameters have been estimated earlier analytically). A diagnostic method is suggested for asymmetric plasmas and typical electron density profiles are calculated for Rayleigh–Taylor instability modes, which develop in pinches.