Gas-cluster targets for femtosecond laser interaction: Modeling and optimization

A novel mathematical model for the investigations of a cluster formation process in a gas jet is presented, which enables us to obtain the detailed description of the spatial and temporal distributions of all cluster target parameters. In this model, a cluster target is considered as a two-phase medium, consisting of the continuous gas phase and the discrete condensed phase (clusters). The detailed nozzle geometry is also taken into account in this model. In order to confirm the advantage of the present model over a conventional model, a considerable amount of numerical computations has been carried out and the results are compared with the data obtained from Hagena’s theory [Rev. Sci. Instrum. 63, 2374 (1992)]. Based on the developed modeling, a three-staged nozzle, which cannot be modeled using the conventional model, is designed for the purpose of producing a sufficient amount of micron-sized clusters. The generation of unprecedented amount of keV x rays from the laser-cluster interaction experiments with this nozzle and their accurate intensity dependences on various experimental parameters support the adequateness of the nozzle design.