Cumulation, collisions, and flow around fast gas jets in laser ablation of surfaces and in explosions of thin films of matter. Practical applications

Experiments were carried out on the cumulation, collisions, and flow around vapour jets at velocities of (1 — 2) × 10⁶ cm s^–1. The jets were formed by the action of high-power laser pulses incident on a concave or flat surface of a thin metallised film or a bulk target in vacuum. Strong cumulation was observed in explosions of a cylindrical surface: the jet cross section was reduced by a factor of 30 — 40. A study was made of the collisions of counterpropagating jets at a selected point and of the flow, around gas jets, of counterpropagating larger jets. Strong erosion tracks, formed by focused jets on solids, were observed. These results should be useful in the following applications: modelling of aerodynamic processes; filling of plasma traps; avoidance of plasma contamination by walls; interaction with matter; formation of strong welds and coatings; heating, compression, and acceleration of macroparticles of matter.