Full-shell x-ray optics development at NASA Marshall Space Flight Center

Abstract

NASA's Marshall Space Flight Center (MSFC) maintains an active research program toward the development of high-resolution, lightweight, grazing-incidence x-ray optics to serve the needs of future x-ray astronomy missions such as Lynx. MSFC development efforts include both direct fabrication (diamond turning and deterministic computer-controlled polishing) of mirror shells and replication of mirror shells (from figured, polished mandrels). Both techniques produce full-circumference monolithic (primary + secondary) shells that share the advantages of inherent stability, ease of assembly, and low production cost. However, to achieve high-angular resolution, MSFC is exploring significant technology advances needed to control sources of figure error including fabrication-and coating-induced stresses and mounting-induced distortions. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Technologies for advanced X-ray mirror fabrication

“…In this study robotic polishing has been used in two roles, first to improve the roughness of the ground surface to allow for interferometry, and second, to provide a high frequency oscillation smoothing operation of the mid-spatial frequencies (waviness) -Figure 8 left. Regarding the latter, it has been implemented to process mandrels for electroforming [31] -Figure 8 right. Mandrels for electroforming, discussed later in this chapter, are solid, metallic, have the inverse form, and are easier to process than thin fused silica full shells.…”

“…Looking beyond, Fig. 8 Left -the use of robotic polishing applied directly to remove mid-spatial frequency errors from a thin fused silica full shell, image credit: Civitani, M., et al 2019 [14] (CC BY 4.0); rightrobotic polishing applied indirectly to a mandrel for electroforming, image credit: Kilaru, K., et al 2019 [31] (CC BY 4.0). robotic polishing and in-situ metrology provide a foundation for an Industry 4.0 approach, where 'smart manufacturing', enabled in-part by artificial intelligence, allows for generic machines to deliver a more streamlined and consumer driven product/process -discussed further in the final section of this chapter.…”

Lynx X-Ray Observatory: an overview

“…Multiple candidate technologies for the mirrors and the science instruments are described in detail in this paper. X-ray mirror technologies that were studied in detail by the Lynx team included silicon meta-shell optics developed by GSFC, 4 fullshell optics developed by Brera (INAF/Brera) and Marshall Spaceflight Center (MSFC), 5,6 and adjustable segmented optics developed by the SAO. 7,8 Similarly, multiple technologies were studied for the large-scale active sensor pixel array, dubbed the high-definition x-ray imager (HDXI) [9][10][11][12] and for the XGS.…”

“…5 Replicated full-shell optics are made by an entirely different process and have a different set of benefits and challenges. 6,41,42 The best performance to date is individual replicated mirror shells that have around 8 arc sec HPD and larger (>1 m) diameter replicated optics have yet to be proven. 6 Surface treatments such as differential deposition and ion milling can further improve performance.…”

“…6,41,42 The best performance to date is individual replicated mirror shells that have around 8 arc sec HPD and larger (>1 m) diameter replicated optics have yet to be proven. 6 Surface treatments such as differential deposition and ion milling can further improve performance. 43,44 Adjustable optics.…”