Langdon effect in the realm of extreme ultraviolet source plasmas

Already some years ago, Langdon [Phys. Rev. Lett. 44, 575 (1980)10.1103/PhysRevLett.44.575] proposed that inverse bremsstrahlung absorption in plasmas drives free electrons into non-Maxwellian distributions. Radiation-hydrodynamic simulations of plasma-based light sources, however, often (implicitly) assume Maxwellian-distributed electrons. In this paper, we quantify the effect of non-Maxwellian distributions on laser absorption and thermal conduction in laser-driven plasma light sources. For irradiation conditions I_{las}λ_{las}^{2}∈[10^{11},10^{13}]Wcm^{-2}µm^{2} and plasma parameters Z_{eff}/T_{e}∈[0.2,0.6]eV^{-1}, the electron distributions are predicted to be super-Gaussian of order m≃2.2-2.4. As a result, laser absorption is calculated to be 10-20% lower than plasmas with Maxwellian-distributed electrons. A ∼10-30% reduction of the Spitzer-Härm thermal conduction coefficient is also predicted.