Laser Diagnostics of Laser-Produced Plasmas.
COLORADO STATE UNIV FORT COLLINS DEPT OF ELECTRICAL ENGINEERING
Pagination or Media Count:
Light scattering and holographic interferometry diagnostics using a ruby laser source have been applied to study a CO2 laser-induced argon breakdown with peak power density estimates at approximately 5 x 10 to the 9th power W per sq cm at subatmospheric pressures. Light scattering results indicate well-defined but asymmetric ion-acoustic peaks. Assuming Maxwellian velocity distributions for the ions and the electrons, the ion temperature is estimated to be 4.3 eV and the electron temperature 43 eV at 200 ns after spark initiation. However, there is indication that the scattered intensity is above thermal so that the Maxwellian velocity assumption may not be valid. The asymmetry of the ion peaks indicates a relative drift of the electrons with respect to the ions. In addition, a Doppler shift of the entire scattered spectrum is also observed. Holographic interferometry provides three-dimensional density profile of the laser peak spark at several gas pressures and different times after spark initiation. The pressure-dependence studies show that high electron densities are produced at high pressures due to larger absorption and smaller plasma dimensions. The temporal dependence indicates that at the peak of the CO2 pulse, the plasma produces a sharp shock front high density, low temperature followed by a period of minimum on-axis electron density, resulting from local laser heating of the plasma.
- Lasers and Masers
- Plasma Physics and Magnetohydrodynamics