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Opening of the ELT secondary mirror ZERODUR® blank mould containing the glass at first annealing at the Schott AG 4-meter blank annealing facility in Mainz, Germany.[1]

Zerodur (notation of the manufacturer: ZERODUR®), a registered trademark of Schott AG,[2] is a lithium-aluminosilicate glass-ceramic[3] produced by Schott AG since 1968.[4] It has been used for a number of very large telescope mirrors including Keck I, Keck II,[5] and SOFIA, as well as some smaller telescopes (such as the GREGOR Solar Telescope or certain of the noteworthy Questar telescopes made by Questar Corporation). With its very low coefficient of thermal expansion it can be used to produce mirrors that retain acceptable figures in extremely cold environments such as deep space.[6] Although it has advantages for applications requiring a coefficient of thermal expansion less than that of borosilicate glass, it remains very expensive as compared to borosilicate. The tight tolerance on CTE, ±0.007×106 K−1, allows highly accurate applications that require high-precision.

Zerodur has both an amorphous (vitreous) component and a crystalline component. Its most important properties[7] are:

Contents

ApplicationsEdit

 
The Keck II Telescope showing the segmented primary mirror made of Zerodur
  1. Optics
  2. Microlithography
  3. Measurement technology[4]

Properties[7]Edit

See alsoEdit

ReferencesEdit

  1. ^ "Secondary Mirror of ELT Successfully Cast - Largest convex mirror blank ever created". www.eso.org. Retrieved 22 May 2017. 
  2. ^ "Archived copy". Archived from the original on July 24, 2011. Retrieved September 4, 2011. 
  3. ^ a b Viens, Michael J (April 1990). "Fracture Toughness and Crack Growth of Zerodur" (PDF). NASA Technical Memorandum 4185. NASA. Retrieved 28 August 2011. 
  4. ^ a b Schott AG Zerodur description Archived February 1, 2014, at the Wayback Machine.
  5. ^ Döhring, Thorsten; Peter Hartmann; Ralf Jedamzik; Armin Thomas; Frank-Thomas Lentes. "Properties of Zerodur Mirror Blanks for Extremely Large Telescopes" (PDF). Proc. SPIE. SPIE. Retrieved 26 August 2011. 
  6. ^ Baer, JW; WP Lotz. "Figure testing of 300 mm Zerodur mirrors at cryogenic temperatures" (PDF). Retrieved 26 August 2011. 
  7. ^ a b "ZERODUR® Extremely Low Expansion Glass Ceramic: SCHOTT Advanced Optics - SCHOTT AG". www.schott.com. Retrieved 15 April 2018. 
  8. ^ SCHOTT CTE Grades Archived October 4, 2013, at the Wayback Machine.
  9. ^ a b http://optomechanicalservices.com/Papers.html
  10. ^ Hartmann, P. (18 December 2012). "ZERODUR - Deterministic Approach for Strength Design" (PDF). NASA. Retrieved 11 September 2013. 
  11. ^ Senf, H; E Strassburger; H Rothenhausler (1997). "A study of Damage during Impact in Zerodur" (PDF). J Phys Iv France. 7 (Colloque C3, Suppltment au Journal de Physique I11 d'aotit 1997). Retrieved 31 August 2011. 

External linksEdit