1. Irradiation Effects on GIMM Lance L Snead

2. I need to know the fluence and irradiation temperatures for an accurate assessment of GIMM performance. However, I will assume the following. - fast neutron fluence of about 1E24 n/m2, - a thermal fluence of about 1E25 n/m2, - and a nominal temperature of 200°C - uniform gamma heating Given this input, my primary concern is swelling and thermal conductivity.

3. SiC as a Substrate SiC is now used as a highly polished substrate for mirror applications. Typically, CVD SiC material is used. The cost tends to be fairly high for the base material, especially for large pieces. The polishing is straightforward. For the application conditions assumes, SiC is one of the worst behaving materials as far as dimensional stability and conductivity reduction.

6. Assumption

7. Alternatives? An possible alternative material, which contains 4 protons, is also used in space mirror applications. - Al coating has been demonstrated for mirrors and an alloy with aluminum is commercially available. - 2/3 density than SiC - nominally the same cost as CVD SiC mirror - thermal conductivity will be unchanged - swelling will be less than 0.01%. Silicon nitride - should be easily polished and plated, though hasn’t been used as a mirror to my knowledge. - better performance under irradiation.