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Sasaki, Akira
no journal, ,
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.
Sasaki, Akira
no journal, ,
Improvement of the efficiency and output power of the EUV source is essential for the realization of the next generation micro-lithography. Recently, a high efficiency is obtained using the double pulse technique, where the Sn droplet is broken up into particles by the irradiation of the relatively weak pre-pulse laser. For the optimization of the source, we study methods for the modeling of pre-plasma formation including the solid/liquid to gas phase transition of Sn and particle emission. We study the equation of state of Sn and phase transition theoretically, and also study methods to calculate distribution of solid/liquid and gas phase after the phase transition. Results of test calculation of the evaporation hot Sn droplet will be shown.