| Zugriffsnummer | 39508 |
| Dokumenttyp | Konferenzartikel |
| Sprache | Englisch |
| Titel | Ion beam assisted sphericity error correction of Si spheres as new kg artefacts |
| Autor(in); Institution |
Arnold, Thomas; Leibniz-Institut für Oberflächenmodifizierung (IOM), Leipzig, GERMANY
Pietag, Fred; Leibniz-Institut für Oberflächenmodifizierung (IOM), Leipzig, GERMANY
Bartl, Guido; 5.4, Interferometrie an Maßverkörperungen, PTB-Braunschweig
Mai, Torsten; 5.4, Interferometrie an Maßverkörperungen, PTB-Braunschweig
Nicolaus, Arnold; 5.4, Interferometrie an Maßverkörperungen, PTB-Braunschweig
|
| Quelle/Jahr | Proceedings of the 17th International Conference of the European Society for Precision Engineering and Nanotechnology:(2017), 323 - 324 |
| Herausgeber(in) |
Billington, D.
|
| ISBN | 978-0-9957751-0-7 |
| Verlag | Bedford: Euspen |
| Konferenzangaben | 17th International Conference of the European Society for Precision Engineering and Nanotechnology, Hannover, 29, May - 02, June, 2017, Germany |
| Freie Schlagworte | Avogadro project ; silicon spheres ; ion beam figuring |
| Zusammenfassung | Full spheres made of silicon exhibiting a very high degree of roundness and a mass of 1 kg are utilized as artefacts for the accurate determination of the Avogadro number NA in the framework of the International Avogadro Coordination project. The knowledge of an accurate value of NA with low relative uncertainty is required for a redefinition of the SI unit mole. It may also contribute to the redefinition of the SI unit kilogram which is awaited to take place in 2018. Furthermore, silicon spheres of 1 kg can be used as artefacts for dissemination of the new kg. Since the sphericity error of such spheres significantly contributes to the measurement uncertainty in interferometric sphere volume determination it is desirable to further reduce the surface error of such spheres. Further improvement of the form error aiming at values of < 10 nm PV has been investigated by deterministic ion beam figuring. The ion beam figuring utilizing low energy ions of 500-1000 eV is an established process for optical surface correction. One of its key features is its assumed insensitivity of the material removal mechanism with respect to crystalline orientation. The process has been adopted for the figuring of silicon spheres. A multi-axis CNC motion system equipped with ion beam source as well as with sensors for sphere alignment has been set up to treat the full sphere. Based on the surface topography measurement provided by PTB a bespoke dwell time calculation algorithm and process simulation combined with a spiral tool path has been developed and applied to a sphere correction process. As a result a partial improvement of the sphere surface could be achieved. The interferometric measurement and the machining process will be presented and discussed. |
Zitierung
Arnold, T., Pietag, F., Bartl, G., Mai, T., & Nicolaus, A. (2017). Ion beam assisted sphericity error correction of Si spheres as new kg artefacts. 17th International Conference of the European Society for Precision Engineering and Nanotechnology, Hannover, 29, May - 02, June, 2017, Germany.