Development of mirrors made of chemically tempered glass foils for future X-ray telescopes

Abstract

Thin slumped glass foils are considered good candidates for the realization of future X-ray telescopes with large effective area and high spatial resolution. However, the hot slumping process affects the glass strength, and this can be an issue during the launch of the satellite because of the high kinematical and static loads occurring during that phase. In the present work we have investigated the possible use of Gorilla® glass (produced by Corning®), a chemical tempered glass that, thanks to its strength characteristics, would be ideal. The un-tempered glass foils were curved by means of an innovative hot slumping technique and subsequently chemically tempered. In this paper we show that the chemical tempering process applied to Gorilla® glass foils does not affect the surface micro-roughness of the mirrors. On the other end, the stress introduced by the tempering process causes a reduction in the amplitude of the longitudinal profile errors with a lateral size close to the mirror length. The effect of the overall shape changes in the final resolution performance of the glass mirrors was studied by simulating the glass foils integration with our innovative approach based on glass reinforcing ribs. The preliminary tests performed so far suggest that this approach has the potential to be applied to the X-ray telescopes of the next generation.

Lithium aluminosilicate (LAS) glass-ceramics: a review of recent progress

“…Surface strengthened alkali aluminosilicates were recommended for high-performance space solar cell application as they demonstrated outstanding durability and better transparency (only ∼0.2% degradation) even after radiation damage by ion beam bombardment [263]. The possibility of using chemically tempered glass foil as a mirror in future X-ray telescope was explored with Gorilla® glass (a Corning product) [264]. Low thermal expansion characteristics of LAS glass and glass-ceramics may offer more advantages in such a kind of application.…”

“…Such chemically strengthened LAS glass can find application as strike-face of layered transparent armour system [272]. Chemically tempered thin LAS glasses have the potential to become a substrate for future flexible electronic devices [273] and large x-ray telescopes [264].…”

Gradient scattered light method for non-destructive stress profile determination in chemically strengthened glass

“…The ion exchange process is started by immersing the glass substrate into a molten salt bath, where smaller ions are replaced with larger ones in the surface layer of glass. Consequently, a residual stress profile develops in the glass [2][3][4][5][6][7][8][9][10][11]. Reviews on chemical strengthening of glass in general have been published by many authors [15,52,55,[61][62][63][64][65].…”

“…Chemically strengthened aluminosilicate glass is used as protective cover glass due to its high scratch and impact resistance [3,4]. In a recent report, chemically strengthened aluminosilicate glass was proven suitable as mirror foil for future X-ray telescopes [5] and as protective coating of space solar cells [6]. The unique mechanical properties of lithium aluminosilicate glass-ultrahigh surface compression stress, deep compressive stress layer, and impact resistance-have made this glass type suitable as a layer of composite armor plate [2,3].…”