Mikhail Korepanov

The formation of a supersonic gas target for lasers that operate in the extreme ultraviolet wavelengths is considered. The gas target is generated in the interaction zone of two opposite supersonic gas jets. The emission properties of inert gas targets were investigated experimentally. The distributions of the emission radiation intensity for argon, krypton and carbon dioxide were obtained and the shapes of the emission zone were detected.
The experimental conditions were reproduced in numerical experiments. The mathematical model of viscous compressible gas was used to model the gas dynamics of supersonic gas jets. The problem was solved in a two-dimensional axisymmetric setting for argon. The obtained distributions of the main gasdynamic quantities made it possible to detail the flow features and estimate the size of the emission zone, as well as the density level corresponding to this zone. It was demonstrated that the results of calculations qualitatively agree with the experimental data. In addition, it was found that the density level of the emission region with the required extreme ultraviolet intensity factor can be obtained by monitoring the total pressure.

This paper considers krypton flow in a micronozzle with a cylindrical tube. A standardized conical nozzle elongated with cylindrical portion performs gas discharge into a vacuum chamber at a pressure of $10^{−2}$ Pa. Under such conditions, a low temperature area is formed in the central part of the jet with gas condensation. The particles are entrained by the gas flow. The portion with a constant section behind the nozzle should focus the supersonic flow part and the condensed particle flow and also decrease particle dispersion behind the nozzle throat.
The paper expresses a mathematical model of homogeneous gas motion with respect to formation processes and the growth of condensation nuclei. Since the condensed particles are small, the research is carried out with a single velocity motion model. The results obtained have shown that the application of the cylindrical tube leads to nonlinear flow effects. The flow responds to: the geometrical exposure related to flow transition from the conical diverging nozzle into the cylindrical tube, heat exposure and mass outflow due to particle formation and growth, and considerable friction force exposure due to the small sizes of the channel. The sum total ofthese factors leads to an insignificant deceleration of the supersonic flow part and highly impacts condensation.