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Influence of diamond turning and surface cleaning processes on the degradation of KDP crystal surfaces

Conference · · Proceedings of SPIE - The International Society for Optical Engineering
DOI:https://doi.org/10.1117/12.50764· OSTI ID:5487203
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  1. Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
  2. Cleveland Crystals, OH (United States)
One factor influencing the efficiency of KDP (potassium dihydrogen phosphate) frequency conversion arrays on the Nova laser system at LLNL has been environmental degradation, or 'fogging', of the crystal surfaces. Decreases in array transmission by as much as 20% have been attributed to crystal fogging. The surfaces of the 27-cm square Nova array crystals are prepared by a wet diamond-turning process. The rate of surface fogging has been associated with several parameters of the diamond turning and subsequent cleaning processes. High humidity during diamond turning, storage, and use on the laser tends to accelerate the fogging. We suspect that some of the additives present in the diamond turning oil increase the fogging rate and have found a machining oil which minimizes this surface degradation. Efficient removal of the machining oils from the crystal surface also minimizes the fogging problem. Care must be taken to use cleaning solvents which do not cause additional surface degradation. The fogging rate is sensitive to the crystallographic orientation of the material as well as to surface roughness related to the diamond turning process. Accelerated fogging at diamond turning artifacts may increase crystal surface roughness causing increased beam modulation and scattering losses.
Research Organization:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Organization:
USDOE
DOE Contract Number:
W-7405-ENG-48
OSTI ID:
5487203
Report Number(s):
UCRL-JC--105835; CONF-9107115--7; ON: DE91015300
Conference Information:
Journal Name: Proceedings of SPIE - The International Society for Optical Engineering Journal Volume: 1561
Country of Publication:
United States
Language:
English