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Proceedings Paper

High-precision large-diameter single-crystal silicon spheres: their fabrication and measurements of sphericity
Author(s): Achim J. Leistner; Walter J. Giardini
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Paper Abstract

We describe the optical grinding and polishing, and the measurement of sphericity by multiple roundness profiles, of large single crystal silicon spheres (balls) (93.6 mm diameter and 1 kg mass). The balls are used in direct measurements of volume and density in the determination of the Avogadro constant. A typical peak to valley error of sphericity achieved was < 60 nm. The arithmetic mean deviation of the error surface relative to a least square sphere was around 16 nm. The microroughness was < 0.2 nm rms when measured with a WYKO TOPO 3D noncontact surface profiler. Defects in the optical finish were negligible when compared to the total allowable uncertainty specified for the volume of the balls of 0.1 ppm.

Paper Details

Date Published: 8 September 1995
PDF: 15 pages
Proc. SPIE 2536, Optical Manufacturing and Testing, (8 September 1995); doi: 10.1117/12.218436
Show Author Affiliations
Achim J. Leistner, CSIRO (Australia)
Walter J. Giardini, CSIRO (Australia)


Published in SPIE Proceedings Vol. 2536:
Optical Manufacturing and Testing
Victor J. Doherty; H. Philip Stahl, Editor(s)

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