Laser Plasma Production and Expansion in a Supersonic Flow

Laser plasma was produced in a Af=2 flow, in a quiescent standard atmosphere, and in a quiescent air at reduced pressure. The efficiency in producing an explosion was estimated from the shadowgraph images. In the M=2 flow, the efficiency was found 0.4. This value was almost same with that in the quiescent standard atmosphere. However, it decreased in the air at reduced pressure below O.OSMPa. Electron density was measured by means of optical emission spectroscopy. It was found that the electron density increased with the ambient pressure, but was not influenced by the flow