Calibration and Performance Modeling of Free-Standing Zone Plates for Extreme Ultraviolet Solar Radiometry having High Accuracy and Stability in Space

Free-standing zone plates for use in EUV solar radiometers were fabricated using electron beam lithography and calibrated at the NIST SURF synchrotron facility. The measured efficiencies are compared to the calculated values. The free-standing zone plate, a binary zone plate consisting of open spaces and interconnected Au opaque bars, has the advantage that a support membrane is not required, resulting in excellent long-term stability in space against contamination, radiation damage, and other effects that could alter the efficiency and instrument throughput. The interconnections of the zones are designed as a robust open mesh of the same type that supports transmission gratings in current spaceflight instruments. The 4 mm outer diameter of the zone plate and compact size of the optical train make these zone plates attractive for small CubeSats and other space flight missions where resources are extremely limited.