Single-shot Resolution of X-ray Monitor Using Coded Aperture Imaging

We report on tests of an x-ray beam size monitor based on coded aperture imaging[1]. This technique uses a mask pattern to modulate incoming photons, with the resulting image being deconvolved through the mask and detector responses, including the effects of diffraction and attenuation materials in the path, over the spectral and angular distribution of the synchrotron radiation generated by the beam. We have tested mask patterns called URA masks[2], which have relatively flat spatial frequency response, and an open aperture of 50% for high-flux throughput, enabling single-shot (bunch-bybunch, turn-by-turn) measurements without the need for heat-sensitive mirrors. Bunch size measurements of ~10 micron bunches with single-shot (statistics-dominated) resolutions of ~2.5 microns have been demonstrated at CesrTA, and single-shot measurements with similar or better resolution of beams in the ~5 micron range are being aimed for at the ATF2. A beam-size monitor based on these principles is also being designed for the SuperKEKB low-emittance rings. We present estimated single-shot resolutions, along with a comparison to single-shot resolution measurements made at CesrTA.