Soft X-ray microscopy at the NSLS

Abstract

The U15 beamline at the NSLS has been instrumented for various forms of soft X-ray imaging. A toroidal grating serves as the monochromator and as the optical element that images the source onto the exit slit. Thin contamination barriers separate the UHV region from an intermediate vacuum region and from the atmospheric environment. The scanning microscope uses a Fresnel zone plate to demagnify a 30 μm aperture located near the exit slit 100× to form a 0.3 μm focal spot through which the specimen is scanned under computer control. The electron-beam fabricated zone plate has 1500 Å wide outer zones and a 5 mm focal length at 32 Å. The focus is in the atmospheric environment. X-rays transmitted by the specimen are detected with a flow proportional counter, and the image is displayed on a television screen. Other forms of imaging take place in the intermediate vacuum environment. For contact microscopy an array of specimen-resist sandwiches are mounted on a manipulator and exposed in sequence. For tests of in-line Fresnel holography a camera is attached to the beamline which includes a collimator, the specimen and photographic film. Feasibility tests of soft X-ray diffraction are carried out using another camera, with particular attention to the detection of X-rays diffracted at large angles. We describe the performance of the apparatus, present some of the first results, and describe plans for the future.