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Proceedings Paper

A new reactive atom plasma technology (RAPT) for precision machining: the etching of ULE optical surfaces
Author(s): Carlo Fanara; Paul Shore; John R. Nicholls; Nicholas Lyford; Phil Sommer; Peter Fiske
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Paper Abstract

The next generation of 30-100 metre diameter extremely large telescopes (ELTs) requires large numbers of hexagonal primary mirror segments. As part of the Basic Technology programme run jointly by UCL and Cranfield University, a reactive atomic plasma technology (RAP(tm)) emerged from the US Lawrence Livermore National Laboratory (LLNL), is employed for the finishing of these surfaces. Results are presented on this novel etching technology. The Inductively Coupled Plasma (ICP) operated at atmospheric pressure using argon, activates the chemical species injected through its centre and promotes the fluorine-based chemical reactions at the surface. Process assessment trials on Ultra Low Expansion (ULE(tm)) plates, previously ground at high material removal rates, have been conducted. The quality of the surfaces produced on these samples using the RAP process are discussed. Substantial volumetric material removal rates of up to 0.446(21) mm 3/s at the highest process speed (1,200 mm/min) were found to be possible without pre-heating the substrate. The influences of power transfer, process speed and gas concentration on the removal rates have been determined. The suitability of the RAP process for revealing and removing sub-surface damage induced by high removal rate grinding is discussed. The results on SiC samples are reported elsewhere in this conference.

Paper Details

Date Published: 6 July 2006
PDF: 12 pages
Proc. SPIE 6273, Optomechanical Technologies for Astronomy, 62730A (6 July 2006); doi: 10.1117/12.673080
Show Author Affiliations
Carlo Fanara, Cranfield Univ. (United Kingdom)
Paul Shore, Cranfield Univ. (United Kingdom)
John R. Nicholls, Cranfield Univ. (United Kingdom)
Nicholas Lyford, RAPT Industries (United States)
Phil Sommer, RAPT Industries (United States)
Peter Fiske, RAPT Industries (United States)

Published in SPIE Proceedings Vol. 6273:
Optomechanical Technologies for Astronomy
Eli Atad-Ettedgui; Joseph Antebi; Dietrich Lemke, Editor(s)

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