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Sasaki, Akira; Nishihara, Katsunobu*; Sunahara, Atsushi*; Nishikawa, Takeshi*
Proceedings of SPIE, Vol.9776, p.97762C_1 - 97762C_6, 2016/03
Times Cited Count：1 Percentile：52.91(Optics)For the improvement of efficiency and output of the laser pumped plasma (LPP) extreme ultra-violet (EUV) light source, we present a hydrodynamics model of laser irradiated Sn targets. The model takes liquid/solid to gas transition and mixed phase condition of the flow into account for the calculation of the distribution of the particles produced by the pre-pulse laser irradiation and optimization of the EUV source. Firstly, we investigate the mechanisms of the fragmentation of the target and particle emission, including the effect of the equation of state of Sn, and secondly, an applicable model is proposed based on the analysis.
Sasaki, Akira
no journal, ,
EUV source at 
=13.5nm has been studied toward the realization of next generation microlithography to achive high output (
200W) with high efficiency (5%). A noble pumping scheme using double pulse irradiation has been proposed. We investigate methods of modeling hydrodynamics, especially interaction of the low intensity prepulse laser with the solid Sn target taking the phase transition into account to reproduce fragmentation of the droplet target through the processes of heating, melting evaporation as well as generation of shock wave by prepulse laser.
Sasaki, Akira; Torii, Tatsuo; Kato, Susumu*; Takahashi, Eiichi*; Kanazawa, Seiji*; Fujii, Takashi*; Kishimoto, Yasuaki*
no journal, ,
no abstracts in English
Sasaki, Akira; Sunahara, Atsushi*; Nishihara, Katsunobu*
no journal, ,
no abstracts in English
based on percolation modelSasaki, Akira; Torii, Tatsuo; Kato, Susumu*; Takahashi, Eiichi*; Fujii, Takashi*; Kanazawa, Seiji*
no journal, ,
no abstracts in English
Sasaki, Akira; Sunahara, Atsushi*; Nishihara, Katsunobu*
no journal, ,
no abstracts in English
Sasaki, Akira; Murakami, Izumi*; Kato, Daiji*; Morita, Shigeru*
no journal, ,
The non-local thermodynamic equilibrium (nLTE) atomic kinetics in high-Z plasmas is investigated for Ag, Sn through W, which are used for X-ray lasers, EUV sources and fusion devices. We develop the atomic model based on nl configuration averaged levels structure, with atomic energy levels, radiative rates and autoionization rates calculated using the HULLAC code. The dielectronic recombination processes are included into the model by including autoionizing levels explicitly. We investigate the mean charge and radiative power loss with respect to the size of the model; by defining the groups of the levels, which consist of core a configuration and one excited electron, and by performing calculations increasing the number of groups. It is found that as a general trend, the mean charge decreases and the radiative power loss increases, until convergence is obtained when sufficiently large number of dielectronic recombination channels is included. The model is validated at code comparison workshops and also comparison with spectroscopic measurements, which are carried out using magnetic fusion devices.
Sasaki, Akira
no journal, ,
no abstracts in English
Sasaki, Akira; Nishihara, Katsunobu*; Sunahara, Atsushi*
no journal, ,
no abstracts in English
Sasaki, Akira
no journal, ,
no abstracts in English
Sasaki, Akira; Sunahara, Atsushi*; Nishihara, Katsunobu*
no journal, ,
no abstracts in English
Sasaki, Akira; Sunahara, Atsushi*; Nishihara, Katsunobu*
no journal, ,
no abstracts in English
Sasaki, Akira; Sunahara, Atsushi*; Nishihara, Katsunobu*
no journal, ,
no abstracts in English
Sasaki, Akira
no journal, ,
no abstracts in English
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.
Sasaki, Akira
no journal, ,
Modeling of the fragmentation and particle emission from Sn droplet target, which is irradiated by the pre-pulse laser is developed for the optimization of the output and efficiency of the EUV source. Methods of reconstruction of the Lagrangian mesh to represent the shape and arrangement of particles for the hydrodynamics simulation are developed. The ratio of liquid and gas as well as the latent heat are determined by evaluating the Gibbs free energy in the material based on the Van-der-waals theory. Results of test calculation for the evaporating hot Sn droplet are presented.
Sasaki, Akira; Sunahara, Atsushi*; Nishihara, Katsunobu*
no journal, ,
For the development of laser plasma pumped (LPP) extreme ultraviolet light (EUV) source, we develop a new hydrodynamics model, which is applicable to the fragmentation of liquid Sn by the pre-pulse laser irradiation. A 2-dimensional Lagrange simulation code with mesh reorganization algorithms as well as phase transition dynamics is developed and initial application to an analysis of the particle formation during the evaporation of a hot Sn droplet is presented.
