Modelling of the Soft X-Ray Spectrum Generated in Laser-Produced Tin Plasma

The paper presents a mathematical model of X-ray emission escape from tin plasma generated by irradiating a laser target with an Nd-laser pulse. The model enables calculations of soft X-ray spectra both in the local thermodynamic equilibrium approximation and with allowance for non-equilibrium kinetic effects. A series of calculations was performed for different Nd-laser intensities. As a result of the mathematical modeling, profiles of spatial distributions of temperature and average charge, as well as time- and energy-integrated spectra of the soft X-ray emission escaping the plasma, were obtained. The analysis showed that accounting for non-equilibrium kinetic effects leads to an increase in plasma temperature and an increase in the fraction of radiation in the useful spectral range near 13,5 nm. Furthermore, kinetics-based modeling allows more accurate reproduction of the experimental spectral profiles and the dependence of the conversion efficiency on the intensity of the Nd-laser compared to the local thermodynamic equilibrium approximation.

Keywords

mathematical modelling; laser-produced plasma; soft X-ray radiation; photolithography; kinetic plasma model.

References

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