laser-ifefinalopticsmini-workshop-資料下載頁
2025-07-17 15:16本頁面
【正文】 t in g t h ick n ess (h / l )0?60?85?l=532 nm 00. 250. 50. 751Reflectivity0 10 20 30 40 50 60 70 80 90an g le of in cid en ceAl2O3 r ef lec t i vit y at 53 2 n m00 . 20 . 40 . 60 . 810 0 . 0 5 0 . 1 0 . 1 5 0 . 2 0 . 2 5 0 . 3Effect of surface contaminants ? Surface contaminants (such as carbon) on mirror protective coatings can substantially alter reflectivity, depending on layer thickness and incident angle. ? Uniform film thickness is assumed. Carbon film thickness (nm) ?1 = 0o 20o 40o 60o 80o lo = 532 nm Al2O3 coating (10 nm) Al mirror d2=2 nm ?1 = 0o d2=2 nm ?1 = 80o d2=0 ?1 = 0o d2=0 ?1 = 80o lo = 532 nm Carbon film Al mirror reflectivity Al2O3 coating thickness, d3/lo Surface profile of undamaged Al1100 mirror SEM photos of damaged Al 50x 250x 1000x 4000x Nearterm experimental plans ? Install ShackHartmann sensor and ringdown reflectometer ? Examine source of grazingincidence profile distortions ? Test Al1100 mirrors to damage fluence at 8085? incidence。 pare damage threshold and surface morphology with normal incidence exposure ? Produce and test ultrapure Al and sputtercoated SiC mirrors ? Perform tests in vacuum (chamber available after Jan. 2022) Diffraction and Wavefront Distortions Diffractionlimited spot size: do = 4 l f M/pD l = 1/3 mm f = 30 m (distance to lens) do = 200 mm (zoomed) D = 1 m M 16 ? “There is no standard theoretical approach for bining random wavefront distortions of individual optics” (ref: Orth) ?Each l/3 of wavefront distortion translates into roughly a doubling of the minimum spot size (ref: Orth) Neutron and gamma effects ? Conductivity decrease due to point defects, transmutations, surface roughening – Estimated in Prometheus at ~% decrease in reflectivity (ref: private conversation) ? Differential swelling and creep – Swelling values of % per dpa in Al (ref. Prometheus) – The laser peration depth is d=l/4pk where k10, so the required thickness of Al is only ~10 nm. Swelling in Al can be controlled by keeping it thin. The substrate is the real concern. – Porous (1015%) SiC is expected to have very low neutron swelling. ? Absorption band at 215 nm in fused silica
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