Thermal Conduction in Laser‐Driven Tin Plasmas and the Sensitivity of Plasma Properties to the Flux Limiter

ABSTRACT

We study the role of thermal conduction in laser‐produced tin plasma sources of extreme ultraviolet (EUV) light using radiation‐hydrodynamic simulations. Adopting the flux‐limited Spitzer–Härm approach, we investigate the sensitivity of the electron temperature, electron density, net in‐band emissivity, and conversion efficiency to the choice of flux limiter for plasmas driven by two laser wavelengths: = 10.6 and 2 μm. For plasmas driven by = 10.6 μm laser light, the plasma properties are highly sensitive to flux limiters in the range , which originates from the choice of heat flux (either Spitzer–Härm or free‐streaming) adopted in the simulations. The conversion efficiency is found to increase sharply from 2% to 5% with increasing in this range owing to the increased population of EUV‐emitting charge states in the plasma. By quantifying the Knudsen number, we find that SH theory is not valid in the underdense corona in these plasmas. Plasmas driven by 2 μm‐wavelength lasers are, on the contrary, largely insensitive to the choice of given the higher electron densities and dominance of the free‐streaming heat flux. We find that Spitzer–Härm theory is valid in these plasmas.