Deterministic figure correction of piezoelectrically adjustable slumped glass optics

McKinstry, "Thickness distribution of sputtered films on curved substrates for adjustable x-ray optics," J.Abstract. Piezoelectric adjustable x-ray optics use magnetron sputtered thin film coatings on both sides of a thin curved glass substrate. To produce an optic suitable for a mission requiring high-angular resolution like "Lynx," the integrated stresses (stress × thickness) of films on both sides of the optic must be approximately equal. Thus, understanding how sputtered film thickness distributions change for convex and concave curved substrates is necessary. To address this, thickness distributions of piezoelectric Pb 0.995 ðZr 0.52 Ti 0.48 Þ 0.99 Nb 0.01 O 3 films are studied on flat, convex, and concave cylindrical substrates with a 220-mm radius of curvature. A mathematical model of the film thickness distribution is derived based on the geometric properties of the sputter tool and the substrate, and film thicknesses deposited with a commercially available sputtering tool are measured with spectroscopic ellipsometry. Experiment and modeled results for flat and convex curved substrates demonstrate good agreement, with average relative thickness distribution difference of 0.19% and −0.10% respectively, and a higher average difference of 1.4% for concave substrates. The calculated relative thickness distributions are applied to the convex and concave sides of a finite-element analysis (FEA) model of an adjustable x-ray optic prototype. The FEA model shows that, left uncorrected, the relative film thickness variation will yield an optic with an optical performance of 2.6 arc sec half power diameter (HPD) at 1 keV. However, the mirror figure can be corrected to diffraction-limited performance (0.3 arc sec HPD) using the piezoelectric adjusters, suggesting that the tolerances for applying a balanced integrated stress on both sides of a mirror are alleviated for adjustable x-ray optics as compared to traditional static x-ray mirrors. Furthermore, the piezoelectric adjusters will also allow changes in mirror figure over the telescope lifetime due to drift in the stress states of the x-ray surfaces to be corrected on orbit.

Section: Experimental Methodsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Thickness distribution of sputtered films on curved substrates for adjustable x-ray optics

Bishop

Walker

DeRoo

et al. 2019

Lynx X-Ray Observatory: an overview

Gaskin

Swartz

Vikhlinin

et al. 2019

131

Lynx, one of the four strategic mission concepts under study for the 2020 Astrophysics Decadal Survey, provides leaps in capability over previous and planned x-ray missions and provides synergistic observations in the 2030s to a multitude of space-and ground-based observatories across all wavelengths. Lynx provides orders of magnitude improvement in sensitivity, on-axis subarcsecond imaging with arcsecond angular resolution over a large field of view, and high-resolution spectroscopy for point-like and extended sources in the 0.2-to 10-keV range. The Lynx architecture enables a broad range of unique and compelling science to be carried out mainly through a General Observer Program. This program is envisioned to include detecting the very first seed black holes, revealing the high-energy drivers of galaxy formation and evolution, and characterizing the mechanisms that govern stellar evolution and stellar ecosystems. The Lynx optics and science instruments are carefully designed to optimize the science capability and, when combined, form an exciting architecture that utilizes relatively mature technologies for a cost that is compatible with the projected NASA Astrophysics budget. © 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.

Lynx x-ray optics based on thin monolithic shells: design and development

Civitani

Parodi

Vecchi

et al. 2019

Lynx is the future x-ray observatory with superb imaging capabilities (<1 arc sec half-energy width) and large throughput (2 m 2 effective area @ 1 keV), which is being considered in the U.S. to take over Chandra. The implementation of the x-ray mirror module represents a very challenging aspect, and different approaches are being considered. Thin and low-weight substrates, working in grazing incidence configuration, are necessary to meet the severe mass constraints, but they have to also preserve the requirement of an excellent angular resolution. The use of monolithic glass (fused silica) shells is an attractive solution, provided that their thickness is kept very small [<4 mm for mirror shells up of 3-m diameter]. We present the optomechanical design of the Lynx mirror assembly based on this approach, together with the ongoing technological development process. In particular, we discuss the figuring process, which is based on direct polishing followed by an ion-beam figuring correction. A temporary structure is specifically devoted to support the shell during the figuring and polishing operations and to manage the handling of the shell through all phases up to integration into the final telescope supporting spoke wheel. The results achieved so far on a prototype shell will be discussed.