Extreme Ultraviolet (EUV) Radiation from Punched-Out Target

Abstract

Extreme ultraviolet (EUV) emissions from a laser-irradiated, low-density flying target were thoroughly investigated. The target was produced by irradiating a 1-μm-thick solid tin layer with a weak laser pulse that passes through an optically transparent substrate. This irradiation causes the tin overcoat layer todisintegrate into a mixture of plasmas, gases, clusters, and fine particles. The center-of-mass velocity and angular spread of the target were observed to be 0.93km/s and 6-8 degrees, respectively. EUV emission spectra, at around 13.5nm, from the target driven with a CO2 laser pulse were narrower than those from a solid tin irradiated with a Nd: YAG laser beam, and the conversion efficiency at 13.5nm in a 2% bandwidth became as high as 2.8% at a laser intensity of 1010W/cm2.