Spatial Resolution Evaluation of ZnO Scintillator as an In-situ Imaging Device in EUV Region

We captured single shot images of ZnO emission patterns originating from excitation with the EUV laser at Japan Atomic Energy Agency (JAEA). The EUV laser was focused to a spot size of 1 μm on the ZnO crystal by a Fresnel Zone Plate (FZP). The FZP was shifted along the propagation direction of the EUV beam, essentially changing the spot size at the ZnO surface. The emission pattern was detected by a magnifier. The waist radii were determined from the fitting curve as 5.0 μm along the horizontal axis and 4.7 μm along the vertical axis. We also evaluated the spatial resolution of the magnifier, which consists of a Schwarzschild mirror, two lenses and a camera lens to be about 4 μm. These results suggest that the ZnO crystal has sub-micron spatial resolution when used as an in-situ imaging device for the diagnostics of EUV/X-ray sources.