Comparison of EUV spectral and ion emission features from laser-produced Sn and Li plasmas

Abstract

Planar slabs of pure Sn and Li were irradiated with 1064 nm, 9 ns Nd:YAG laser pulses. The resulting plasmas were evaluated with an absolutely calibrated extreme ultraviolet (EUV) power tool, a transmission grating spectrograph, a pinhole camera, and a Faraday cup. These diagnostic tools have allowed us to determine EUV conversion efficiency (CE), EUV spectral emission features, EUV-emitting plasma size, and the kinetic energies and fluxes of ions at various laser intensities for both Sn and Li plasmas. The maximum estimated CE values for Li and Sn plasmas are 1 ± 0.1 % and 2 ± 0.2 %, respectively. The Li2+ Lyman-α line and Sn8-13+ lines generate the in-band emissions of Li and Sn. The intensity of Li2+ lines was found to increase with laser intensity. However, the Sn unresolved transmission array (UTA) showed remarkable changes with at higher laser intensities, including the appearance of a spectral dip. EUV plasma images showed that Sn plasmas take on a conical shape, as opposed to the hemispherical shape of Li plasmas. Ion debris analysis showed the kinetic energies for Li ions are less than that of Sn ions under similar conditions. Moreover, the kinetic spread of Li ions has been found to be narrower compared to the kinetic energy distribution of the Sn ions. We also compared the ion flux emitted by Sn and Li plasmas.