LIGO Document E1300653-v1
- The RGA outgassing test results for a high temperature, low outgassing epoxy (Epo-Tek 353ND):
as part of the qualification for LIGO UHV service.
Greg Harry reports that EpoTek-353ND epoxy has been (preliminarily) measured to have a high mechanical Q. For Greg's Q tests, the epoxy was between a 3 inch diameter X 0.1 inch thick superpolished silica disk and a 0.5 inch diameter X 100 micron thick silica wafer. It was baked at 80 C for 30 minutes. He found Qs for two modes of ~350K in contrast to ~10K for other epoxies.
This adhesive is meant for use in "thin and thick film" bonds -- not for casting, molding or potting. Our intended application (the acoustic mode dampers for the test mass) will use bonds that are ~0.1 mm in thickness. However, rather than bond two items together and rely upon edge diffusion of outgassing products, we want to expose a large surface of epoxy. We will create samples by pressing them between two glass plates, or slides, and then shearing the two plates/slides apart.
We will test about ~600 sq. inches of surface area, for example 6 plates that are each 8 inches by 12 inches (or any other combination). If the bond is 0.004 inch thick (0.1 mm) then the total adhesive will be ~45 gm or about 1 kit of 10 packs (assuming 1.18 g/cc). The thickness should be no more than say ~0.010 inch (0.25 mm), which would require ~111 gm, or ~3 kits of 10-packs.
We will cure at the lowest recommended temperature and for the minimum time, i.e. 80C for 30 minutes (same cure cycle used by Greg Harry for his Q samples).
- The measured hydrocarbon flag AMU outgassing rate is 1e-15 torr-L/s/cm^2.
The optical (absorption and scatter) loss at 1064 nm due to exposure to this epoxy was found to be quite low (see E1300654).
This epoxy is approved for its intended use to bond Acoustic Mode Dampers (AMDs) to the barrel of Test Mass (TM) optics. This thin & thick film/bond adhesive may also be considered for other applications in the aLIGO vacuum system.
approved 6/4/2014 by Dennis Coyne
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