We describe the fabrication of the two NuSTAR flight optics modules. The NuSTAR optics modules are glass-graphiteepoxy composite structures to be employed for the first time in space-based X-ray optics by NuSTAR, a NASA Small Explorer schedule for launch in February 2012. We discuss the optics manufacturing process, the qualification and environmental testing performed, and briefly discuss the results of X-ray performance testing of the two modules. The integration and alignment of the completed flight optics modules into the NuSTAR instrument is described as are the optics module thermal shields. OVERVIEW OF THE OPTICS MODULESThe Nuclear Spectroscopy Telescope Array (NuSTAR) is a NASA Small Explorer (SMEX) satellite mission scheduled for launch in February 2012. The NuSTAR experiment contains two telescopes each consisting of an optic and a CdZnTe focal plane detector separated from each other by a 10-meter deployable mast (figure 1). The experiment is an extension and improvement on the design successfully employed in the HEFT balloon experiment (Harrison et al. 2005 1 ). NuSTAR will operate in the 6-79 keV energy band. More details on the mission, the overall instrument design and performance requirements and scientific objectives can be found in Harrison et al. 2010 2 .A blowup of an individual optics module is also shown in figure 1. Each layer of the optic has an upper and lower conic shell (equivalent to the parabola-hyperbola sections of a Wolter-I optic). Each shell is composed of multiple thermally formed glass segments. Each piece of glass is coated with a depth-graded multilayer. The enhanced reflectivity provided by the multilayers, along with the shallow graze angles afforded by the focal length of the optics (10.15 meter) provide high effective area over the NuSTAR energy band of 6-79 keV, and a field of view of 12 arcminutes by 12 arcminutes. There are 133 concentric layers which together form each optic. The glass layers (a glass-epoxy-graphite composite structure) are built up on a Titanium mandrel. Titanium support spiders located on the top and bottom of each optic connect it to the optical bench. The compliant, radially-symmetric spiders accommodate thermal expansion effects as well as dynamic loading. Thin x-ray transparent thermal covers on the entrance and exit apertures of the optic reduce thermal gradients by blocking direct view of the sun and deep space. Two flight modules, FM1 and FM2, were fabricated. A third module, FM0, was fabricated earlier and has Pt/SiC multilayers on the inner 89 layers. FM0 is a potential flight spare and is available to provide for more extensive X-ray characterization than is permitted for either of the flight modules, given the compressed delivery schedule of the optics.
The Engineering Test Stand (ETS) is a developmental lithography tool designed to demonstrate full-field EUV imaging and provide data for commercial-tool development. In the first phase of integration, currently in progress, the ETS is configured using a developmental projection system, while fabrication of an improved projection system proceeds in parallel. The optics in the second projection system have been fabricated to tighter specifications for improved resolution and reduced flare. The projection system is a 4-mirror, 4x-reduction, ring-field design having a numeral aperture of 0.1, which supports 70 nm resolution at a k 1 of 0.52. The illuminator produces 13.4 nm radiation from a laser-produced plasma, directs the radiation onto an arc-shaped field of view, and provides an effective fill factor at the pupil plane of 0.7. The ETS is designed for fullfield images in step-and-scan mode using vacuum-compatible, magnetically levitated, scanning stages. This paper describes system performance observed during the first phase of integration, including static resist images of 100 nm isolated and dense features.
The extreme ultraviolet (EUV) Engineering Test Stand (ETS) is a step-and-scan lithography tool that operates at a wavelength of 13.4 nm. It has been developed to demonstrate full-field EUV imaging and acquire system learning for equipment manufacturers to develop commercial tools. The initial integration of the tool is being carried out using a developmental set of projection optics, while a second, higher-quality, projection optics is being assembled and characterized in a parallel effort. We present here the first lithographic results from the ETS, which include both static and scanned resist images of 100 nm dense and isolated features throughout the ring field of the projection optics. Accurate lithographic models have been developed and compared with the experimental results.
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