Hydrodynamic proton beam-target interaction experiments using an improved line-imaging velocimeter

The hydrodynamic response of 10- to 100-μm-thick target foils exposed to a high-power proton beam is investigated by laser Doppler velocimetry of the rear surface. For the first time, the ablative acceleration and the ablation pressure have been measured spatially resolved by use of an improved line imaging velocimeter. The instrument was operated in both the VISAR and the ORVIS mode, and takes advantage of the spatial localization of the interference fringes in the mirror planes for an intermediate imaging. This allows us to obtain optimum contrast, high spatial resolution of ⩽10 μm, and to vary the magnification in a wide range.