A 15-μm resolution imager for soft X-ray emitters

The design of a soft X-ray (3 to 10 keV) coded aperture microscope with 15 mu m resolution over a Field of View (FoV) of 8.5 mm x 8.5 mm with a sensitivity of 8 X 10(-4) at 1 Cut from the FoV is presented, along with a preliminary performance simulation. The microscope is based on a deep-depletion CCD detector with 20 mu m pixels. Efficiency peaks at 75% and is > 30% in the energy range considered. Liquid nitrogen cooling limits dark current to a value (0.03 e(-)/5min/p) compatible with the signal (1600 e(-)/5min/p). The aperture is an arrangement of 45600 10 mu m holes on a 604x604 NTHT MURA pattern. It is fabricated by electroforming as a 5 mu m deposition of Au on a 5 mu m NiCo substrate providing mechanical stability. The sensitivity of a single pinhole having the same resolution and FoV is about 8x10(-8). Due to multiplexing, the sensitivity increase does not always translate to a Signal-to-Noise Ratio increase, but the advantage is clear for activity distributions as may be encountered in studies of the biochemistry and diffusion mechanisms of biological electrolytes and metabolites, and of cell migration, signaling and trafficking. A tool capable of imaging directly not large molecules, but single atoms, in a relatively short time, has the exciting potential for transferring molecular imaging techniques to the space scale of human somatic cells, thus making a powerful modality available to investigators in fundamental life science problems.