SH23B-2447
Free-Standing Zone Plate Optimized for He II 30.4 nm Solar Irradiance Measurements Having High Accuracy and Stability in Space
Tuesday, 15 December 2015
Poster Hall (Moscone South)
John Francis Seely1, Donald R McMullin2, Robert Vest3, Anne Sakdinawat4, Chieh Chang4, Andrew R Jones5 and James Bremer2, (1)Space Systems Research Corporation, Alexandria, VA, United States, (2)Space Systems Research Corp, Alexandria, VA, United States, (3)National Institute of Standards and Technology Gaithersburg, Gaithersburg, MD, United States, (4)Stanford University, Stanford, CA, United States, (5)University of Colorado at Boulder, Boulder, CO, United States
Abstract:
A zone plate was designed to record the He II 30.4 nm solar irradiance, was fabricated using electron beam lithography, and was absolutely calibrated using the NIST SURF synchrotron. The zone plate has an open support grid identical to those used to successfully launch transmission gratings in previous solar radiometers and is otherwise free-standing with no support membrane that would absorb EUV radiation. The measured efficiency of 3.0 ± 0.1% at 30.4 nm is consistent with detailed modeling of the efficiency and accounting for the geometrical transmittance of the support grid. The binary nature of the zone plate, consisting of opaque gold bars and open spaces with no support membrane, results in excellent long-term stability in space against contamination, radiation damage, and other effects that could alter the efficiency and instrument throughput. The zone plate’s focusing property enables the rejection of out-of-band radiation by small apertures and high signal to background values that are superior to previous radiometers. The 4 mm outer diameter of the zone plate and the 25 mm focal length for 30.4 nm radiation enable a compact instrument that is attractive for small CubeSats and other space flight missions where resources are extremely limited.
