Abstract

The experimental comparison of laser-produced, plasmas characteristics under the influence of radiation of wavelength λ=1.06 μ and 0.265 μ(laser intensity I ~ (10⁹ – 10¹³) W/cm², pulse duration 10 ns, focusing spot diameter d ~ (0.1 -3)mm) on the Al metal target Is carried out. The dependence of dense plasma ablation pressure P and Its electron temperature T_e (which is measured by the double charge layer potential) versus I are found out to have various behavior at different λ. Whereas the pressure depends only on the Intensity of the radiation P(kBar)=0.1*(I(MW/cm²))^1/2, the electron temperature value T_e and the character of the T_e(I) increase depend not only on I and λ, but also on d. It is obtained, that, when d is constant T_e(λ = 1.06μ) > T_e(λ = 0.265μ). The saturation of the dependence T_e(I) with the increase of I at the largest value of d = 3 mm is found out. And at the smallest d = 0.1mm the relation T_e(I) ~ I^1/2 takes place, If λ = 1.06 μ. The study of X-ray emission from plasma enabled to evaluate T_e ~ 300 eV at the experimental conditions I ~ 10¹³ W/cm², λ = 1.06 μ and double charge layer potential ≈ I keV. The possible explanation of the phenomena under Investigation is suggested.

© 1992 Optical Society of America