Rare-earth Plasma Beyond Extreme Ultraviolet (BEUV) Sources at 6.x nm

Abstract

We have studied self-absorption effects of a laser-produced plasma (LPP) source at 6.xnm as a function of laser pulse duration and viewing angle. The spectral profiles are shown to have a strong dependence on viewing angle. Absorption effects are less pronounced when a 150-ps pulse duration is used due to reduced opacity resulting from plasma expansion. Conversion efficiencies and ion energies are also measured as a function of laser pulse duration and laser power density. A maximum conversion efficiency of 0.4% within a 0.6% bandwidth was measured, and lower ion kinetic energy was observed. It is concluded that in order to reduce self-absorption effects and ion yields, and increase conversion efficiencies, a short pulse duration should be used.