We observed the images of the vapor front directly in the confinement processes. A pulsed Nd:YAG laser (wave length 532nm, pulse duration 10ns, energy 50mJ/ pulse) is introduced via a plate set for shock waves reflected, and irradiates a silicon target mounted at 23mm far from the plate. We carefully poured the helium gas with no turbulent flow into the cluster generation cell along the spherical surface of the target holder. A bright image of photo-emission from the vapor front in the sufficient helium ambient was observed at the position of 6mm far from the target by using a high-speed image intensifier (Fig.5a). The image of the front edge is so much sharp as 0.4mm in boundary, compared to that in the condition of lower helium pressure (Fig.5b). This fact means that the density of vapor particles in the front edge is reduced with a steep gradient at the boundary, and the confinement of the mixed gas layer is achieved in a narrow space in 0.4mm.
展开▼
