Diagnostics of an optical discharge plasma sustained in atmospheric air by neodymium laser radiation

Measurements of the temperature distribution and electron density were made in an optical discharge, sustained in atmospheric air by 1.06-μ laser radiation of ~1 MW/cm² intensity. The plasma temperature within the beam was ~20 kK and the electron density was 2×10¹⁷ cm^–3. The measured temperature distribution was used to show that about 90% of the energy absorbed by the discharge was carried away by the characteristic plasma radiation, and less than 10% by heat conduction. The method of schlieren photography was used to determine the shape and dimensions of the discharge as a whole, including a region of heated gas surrounding the ionized core. The energy distribution in the various discharge zones was determined.