Plasma dynamics of a laser breakdown in a gas flow

The paper presents the results of an experimental study of an optical discharge plasma obtained by absorbing radiation from a pulsed-periodic radiation of a CO2 laser with a pulse repetition rate of 40 kHz and an average power of 1.6 kW. In order to increase the length of the breakdown plasma the laser beam (diameter 25 mm) was focused in the in an argon subsonic flow by a lens with a focal length f = 254 mm. To visualize the process, we used a FASTCAM SA-Z video camera (Type 480K), exposure time (1.0 µs), and shooting speed of up to 200,000 fps. The conditions for registering an optical scheme varied by using a Foucault knife, diaphragms, and light filters in order to develop optimal methods for obtaining data. The experimental results showed that the plasma dynamics has two successive stages: from the high-speed optical discharge propagation with absorption of radiation behind the laser supported detonation (LSD) wave front to the next less speed stage.