Investigation of energy transfer in plane laser-irradiated targets with high X-ray conversion efficiency

Abstract

Results of experimental and computational investigations devoted to energy transfer mechanisms and X-ray conversion efficiency in laser-produced plasma are presented and discussed. The layers of different thicknesses and diameters deposited on the plane mylar substrate were irradiated by the focused beam of Nd:glass laser. Spectrally, temporally, and spatially resolved measurements of soft X-ray emission have been carried out at power densities of 1013-1014 W/cm2. The conditions of “re-emission” zone formation have been established. Radiative heat conductivity is shown to be the important energy transfer mechanism in the experimental conditions under investigation.

Development of comprehensive models for opacities and radiation transport for IFE systems.

“…19, one observes almost linear dependence of radiation on initial pressure in the energy region below 10 eV. At higher energies, the situation changes because strong absorption of the 6 5 p shells becomes important for the denser plasma.…”

“…Such low pressure as 0.05 torr may just partly absorb the initial spectrum of the X-ray radiation, while the higher-pressure 0.5 torr is sufficient for almost total absorption of the spectrum by the cold gas. The energies higher than 20 keV are practically transparent because the absorption coefficient of the 6 2 p , 2 2s , 2 1s shells is low enough. The intensity of the initial spectrum quickly decays when the wavelength grows, and one may observe not only weakening of the initial spectrum in its soft region, but also self emission, which is distinctly seen in the energy region lower than 10 eV.…”

“…The goal of the report is to demonstrate the dependence and sensitivity of plasma characteristics on the chosen atomic and plasma models. Theoretical analysis of physical processes inside the chamber is essential in choosing adequate physical models and in performing accurate numerical simulation [5,6].…”

HEIGHTS initial simulation of discharge-produced plamsa hydrodynamics and radiation transport for EUV lithography

“…The results of theoretical approximations of atomic data strongly depend on the chosen theoretical models [6][7][8], and, this is particularly true for high-Z materials. The atomic energy levels and radiative transition probabilities are usually calculated by modified simplifications of the Hartree-Fock (HF) method rather than by the pure H-F method.…”

“…It is known and has been thoroughly examined in several studies [7,8], that radiative emission and transport plays a key role in the dynamics and energy balance of laboratory plasma. In recent years, several studies [12,13] have shown that high-temperature, moderate-density plasma is not in local thermodynamic equilibrium and the radiative properties of plasmas that are optically thick to line radiation are not well-described by either "coronal" or Saha-Bolzmann models.…”