Review of Recent Status of Coded Aperture X-ray Monitors for Beam Size Measurement

X-ray beam profile monitors based on coded aperture imaging use an array of pinholes or slits to achieve large open apertures, which provide improved photon collection efficiency over single pinholes or slits. The resulting improvement in photon statistics makes possible single-bunch, single-turn measurements at lower bunch currents than are possible with a single pinhole or slit. In addition, the coded aperture pattern provides extra information for beam profile reconstruction, which makes possible somewhat improved resolution, as compared to a single slit. The reconstruction algorithm for coded aperture imaging is more complicated and computing-intensive than that for a single slit, though with certain classes of coded pertures a faster reconstruction method is possible. This talk will provide a survey of efforts to use coded aperture imaging for beam profile diagnostics at accelerators to date, covering principles and practical experiences with the technique, as well as prospects for the future at SuperKEKB, where it forms the primary means of measuring vertical beam sizes.