Acceleration of microparticles in electrothermal launcher with multigap scheme of discharge unit

To obtain high quality coatings out of powder materials by means of an electrothermal launcher it is necessary to have a certain structure of the gas and plasma streams. It has been achieved by using two successively positioned discharge gaps in the launcher scheme. A launcher physical model was used for the analysis of dynamics of flows generated in the gaps and formation of a united shock-wave stream in which the acceleration and heating of powder material microparticles occurs. It was demonstrated that the capture of microparticles into acceleration is realized by the shock-compressed gas region that has specific shape and follows immediately behind the head shock-wave. Application of the laser probing of the flow, the shadow images of the flows and the radiation scattered from microparticles enabled us to study the shock-wave streams dynamics and microparticles acceleration. Experimental data have confirmed the microparticle acceleration mechanism and proved the differentiation of the bunch due to the nonuniformity of the particles dimensions. The strong influence of microparticle injection conditions on their acceleration dynamics is proved. The characteristics of obtained coatings, in particular, the porosity and adhesion indicate to a real possibility to get coatings with high qualities.