Use of Lubricants in the NIF
There are two principal concerns that govern the use of lubricants in NIF: (1) Airborne molecular contaminants (AMCs)--AMCs are known to seriously degrade the performance of sol-gel coated optics. AMCs are produced by the slow outgassing of residues (non-volatile residues or ''NVRs'') of high molecular weight compounds left on surfaces. Lubricants, particularly hydrocarbon lubricants, are a primary source of such NVRs. (2) Particulates--Particulates that accumulate on optical surfaces can cause permanent physical damage when exposed to high energy density laser light. Lubricant residues exposed to high energy density light will pyrolyze or decompose and produce carbon particulates. The NIF Approved Materials Database lists several lubricants that have been tested for use in NIF environments. Many of these lubricants were tested according to MELs 99-006 (oven outgassing test) or 99-007 (vacuum outgassing test). In these tests, the change in percent transmission of light through a sol-gel coated optic placed next to the sample under evaluation is used as the diagnostic. Samples that cause less than 0.1% change in optical transmission are deemed suitable for use inside beam enclosures. This testing, however, addresses only the concern associated with AMCs. To assess the issue of particle generation, a flashlamp or ''aerosol'' test is used. In this test a sample with residues is subjected to intense light from the main amplifier flashlamps. The number density of particles per unit volume is measure after each flash. A measurement of an average of fewer than 1000 particles >0.5{micro}m in diameter produced per square foot of exposed surface per flash for each of the last ten flashes in a series of 60 flashes of light is deemed to be acceptable for polymers. A measurement of an average of fewer than 100 particles >0.5{micro}m in diameter produced per square foot of exposed surface per flash for each of the last ten flashes in a series of 60 flashes of light is deemed to be acceptable for metals.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 896602
- Report Number(s):
- UCRL-TR-222672; TRN: US200703%%856
- Country of Publication:
- United States
- Language:
- English
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