The effects of nuclear radiation, moisture absorption, and temperature history on replica flat mirrors of filled epoxy have been investigated using the optical flat testing method. A radiation dose of the order of 1010 ergs per gram is required to produce changes in surface flatness. Residual activity after neutron irradiation is found to be somewhat less than that of Pyrex glass. Absorption of a fractional percent of water causes a loss of flatness, but flatness can be restored by removing the moisture with elevated temperature baking. Flats appear to survive temperature cycling from −200 to +125°C with little detectable changes. Upon being subjected to temperatures above 140°C, the flatness decreases and the reflecting surface deteriorates rapidly.
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For the approximate irradiation dose, in ergs/g, multiply the time in seconds by 2×105.
Due to an entanglement, the dose received is commensurate with a slightly longer time.
Epoxy refers to “Epon 828” (Shell Chemical Company), a Bisphenol-A based resin, catalyzed with m-phenylenediamine. Filler is powdered aluminum. Notation in parenthesis is parts of resin-catalyst-filler, i.e. (85-15-0F) corresponds to 85 parts resin-15 parts catalyst-zero parts filler by weight.
Table IV
Moisture absorption effects on filled expoy mirrors.
Time elapse (Days)
Optical flat test (fringes)
Remarks
0
1 concave
Pattern before mirror placed in water
2 concave
Pattern similar to irradiated samples
3–4 concave
6–7 concave
9 concave
10 concave
Little difference from the
-day reading. Fringes especially ragged in one 90° sector of the surface. Mirror subsequently placed in oven at 73° C after
days water soaking
Samples underwent coating adherence test successfully (cellulose tape test) at all temperature intervals. Time at each temperature was 2 hr. Original flatness was
fringe.
For the approximate irradiation dose, in ergs/g, multiply the time in seconds by 2×105.
Due to an entanglement, the dose received is commensurate with a slightly longer time.
Epoxy refers to “Epon 828” (Shell Chemical Company), a Bisphenol-A based resin, catalyzed with m-phenylenediamine. Filler is powdered aluminum. Notation in parenthesis is parts of resin-catalyst-filler, i.e. (85-15-0F) corresponds to 85 parts resin-15 parts catalyst-zero parts filler by weight.
Table IV
Moisture absorption effects on filled expoy mirrors.
Time elapse (Days)
Optical flat test (fringes)
Remarks
0
1 concave
Pattern before mirror placed in water
2 concave
Pattern similar to irradiated samples
3–4 concave
6–7 concave
9 concave
10 concave
Little difference from the
-day reading. Fringes especially ragged in one 90° sector of the surface. Mirror subsequently placed in oven at 73° C after
days water soaking
Samples underwent coating adherence test successfully (cellulose tape test) at all temperature intervals. Time at each temperature was 2 hr. Original flatness was
fringe.