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Proceedings Paper

Magnetorheological finishing (MRF) of potassium dihydrogen phosphate (KDP) crystals: nonaqueous fluids development, optical finish, and laser damage performance at 1064 nm and 532 nm
Author(s): J. A. Menapace; P. R. Ehrmann; R. C. Bickel
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Paper Abstract

Over the past year we have been working on specialized MR fluids for polishing KDP crystals. KDP is an extremely difficult material to conventionally polish due to its water solubility, low hardness, and temperature sensitivity. Today, KDP crystals are finished using single-point diamond turning (SPDT) tools and nonaqueous lubricants/coolants. KDP optics fabricated using SPDT, however, are limited to surface corrections due to tool/method characteristics with surface quality driven by microroughness from machine pitch, speed, force, and diamond tool character. MRF polishing offers a means to circumvent many of these issues since it is deterministic which makes the technique practical for surface and transmitted wavefront correction, is low force, and is temperature independent. What is lacking is a usable nonaqueous MR fluid that is chemically and physically compatible with KDP which can be used for polishing and subsequently cleaned from the optical surface. In this study, we will present the fluid parameters important in the design and development of nonaqueous MR fluid formulations capable of polishing KDP and how these parameters affect MRF polishing. We will also discuss requirements peculiar to successful KDP polishing and how they affect optical figure/finish and laser damage performance at 1064 nm and 532 nm.

Paper Details

Date Published: 31 December 2009
PDF: 12 pages
Proc. SPIE 7504, Laser-Induced Damage in Optical Materials: 2009, 750414 (31 December 2009); doi: 10.1117/12.836913
Show Author Affiliations
J. A. Menapace, Lawrence Livermore National Lab. (United States)
P. R. Ehrmann, Lawrence Livermore National Lab. (United States)
R. C. Bickel, Lawrence Livermore National Lab. (United States)


Published in SPIE Proceedings Vol. 7504:
Laser-Induced Damage in Optical Materials: 2009
Gregory J. Exarhos; Vitaly E. Gruzdev; Detlev Ristau; M. J. Soileau; Christopher J. Stolz, Editor(s)

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