Improved Materials and Structures for Large Area X-ray Windows

Large-area soft X-ray windows are needed for several emerging technologies, such as cryodetector arrays, semiconductor lithography tools, and pulsed light sources. New higher energy (2-20keV) applications also need as an alternative to beryllium foil windows. Beryllium is increasingly not useable due to foil defects, toxicity, and high cost. During Phase I, Luxel successfully demonstrated the feasibility of X-ray windows which meet these emerging needs. Phase II windows will feature large areas, high soft X-ray transparency, improved cryogenic shielding, and compatibility with overall ultrahigh vacuum system requirements, such as baking to 150C. Luxel will also adapt the Phase I innovations to soft X-ray sources, such as those to be used in semiconductor metrology. Anticipated benefits are consistent with the stated needs of the Department of Energy, as expressed in the Phase I request for proposal, the 2012 Basic Energy Sciences detector workshop, and by strategic plans for various DOE facilities. Improved windows will enable lower dose imaging of human soft tissue, higher detectivity of trace chemicals, better probing of the early universe, and new imaging spectroscopy methods. Instruments for studies of pulsed nuclear fusion at Sandia, the National Ignition Facility and Los Alamos will become feasible. The windows will improve capabilities for high harmonic generation and for pulsed energy studies, such as at free electron lasers beam lines. Higher source intensity will increase the capabilities of X-ray semiconductor manufacturing metrology in 2017 and beyond. Anticipated DOE benefits also include improved personnel safety, by providing a nontoxic window that has equivalent or better performance than beryllium for many applications. The DOE Chronic Beryllium Disease Prevention Program identifies reduced exposure as a primary path for improved beryllium safety. The Lawrence Livermore National Laboratory Safety Committee lists Elimination as the highest hierarchical element for improving beryllium safety. Phase I investigations focused primarily on the use of high precision lithography for producing large windows and cryoshields with high soft X-ray transparency. Associated membranes and high temperature bonding were developed to take advantage of the new structures, resulting in unparalleled window area, soft X-ray transparency, and thermal infrared blocking. Phase II will combine grids, meshes and membranes optimized for cryodetectors, general use X- ray windows, and soft X-ray lithography source windows. The Year 1 activities will focus on refining the Phase I innovations, and providing prototypes for user feedback. Cryoshields will be optimized by fabricating and testing numerically simulated designs. A light-element ceramic will be optimized as a soft X-ray window material. A high temperature bonding operation will be refined to minimize organic content and increase the membrane use power. Feedback will be solicited from users, such as those identified in the attached letters, and other users at National Institute of Standards and Technology and DOE facilities. Based on that feedback and further integration of the processes, a final round of prototypes will be fabricated in Year 2, which provide a final combination of the elements developed in Phase I