The work is devoted to study of breakdown processes in a long discharge tube in argon with mercury vapors.. Its goal is determining reduced electric field strength in pre-breakdown ionization wave.. Optical diagnostics of ionization wave with a high time resolution is performed As compared with dc discharge, the spectral lines of not only mercury but also of argon atom and ion are found. The modeling has shown that the ratio of emission intensity of Ar+ and Ar depends on the electric field strength. So the field strength value could be found from comparison of model results with measured date. Two approaches were applied. В The first one was of steady-state approximation, in the second a model function for the electric field time dependence was used. The value obtained was by two orders of magnitude higher than that for a dc discharge, which corresponds to contemporary understanding on ionization wave. 	In a course of the work, the student learned the modern apparatus and operating with it. Together with PhD student S.Kalinin, she performed a large series of measurements of temporal behavior of ionization wave velocity for various points of the tube and for different wavelengths. Processing of all the bulk of the data she have done by herself. In this process, she showed good knowledge in plasma physics and atomic spectroscopy.. During all the work, she showed diligence and accuracy.   In conclusion, the work by M.Butris has been performed at high level, responses to conditions for the Master degree qualification, and may be marked as "excellent". The graduate student Maria Butris deserves the Master degree.  Supervisor,  Dr.Sci., professor   Y.Z.Ionikh