Modeling of fragmentation of laser irradiated tin droplet target for extreme ultraviolet (EUV) light sources

Sasaki, Akira

In the study of extreme ultraviolet (EUV) light sources, high conversion efficiency is achieved using the double pulse technique; a small tin droplet target is irradiated by the prepulse laser to cause fragmentation of the target to form a cloud small particles or mist, which is heated by the main CO laser pulse to produce the uniform plasma from which efficient EUV emission is obtained. The fragmentation may be caused due to shock heating driven by the prepulse laser irradiation, which also may bring the target to the warm dense state. In this paper, a new hydrodynamics simulation, which will be used to calculate the temporal and spatial development of tin particles, is proposed. The simulation is based on the two dimensional self-adapting Lagrangian grid. The theory of liquid and gas phase transition in thermodynamic equilibrium, allows one to determine the ratio between gas and liquid phase at given temperature and density.