Stabilization of liquified-inert-gas jets for laser-plasma generation

We investigate the hydrodynamic properties of liquified-inert-gas jets in a vacuum with a special emphasis on their stability. Such jets have applications as targets for laser–plasma generation of soft-x-ray and extreme-ultraviolet (EUV) radiation. An important example is the liquid-xenon-jet laser-plasma source, one of the source candidates for EUV lithography. A simple hydrodynamic model in not sufficient to explain experimental observations of jet stability. Evaporation-induced cooling explains observed in-flight freezing of the jet and may be a key factor influencing jet stability. It is shown how the jet stability, and, thus, the stability of the laser–plasma x-ray and EUV emission, are improved by applying localized heating to the tip of the jet-generating nozzle.