Investigation of the blistering and flecking effects materials of outer space factors on space optics

1Abraimov, VV, 2Lura, F, 2Bohne, L, 1Velichko, NI, 1Markus, AM, 1Agashkova, NN, 3Mirzoeva, LA
1B.Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, Kharkiv, Ukraine
2German Aerospace Research Establishment, Berlin, Germany
3Joint-stock company "State Optical Institute Name S. Vavilov ", St. Petersburg, Russia
Kosm. nauka tehnol. 1995, 1 ;(2):39–54
Publication Language: Russian
At present a variety of optical devices are being developed for monitoring the environmental conditions in the outer space. This requires investigation of the effects of space factors (SFs) on materials and scale models of optical devices. The authors have studied the effects of SFs on the scale model of an infrared telescope and its components (the lens and the baffle made of various materials). These studies were made on a simplified model of the infrared telescope. The scale model was irradiated under conditions quite similar to those of the outer space. Combined p+ + e~ irradiation was carried out with the energy E = 150—200 keV, a total fluence of 1016 cm~2 (equivalent to a year), as well as irradiation of the model with an artificial Sun and by VUV rays (/U 5—2500 nm).
          The structural and optical properties of the mirrors were investigated. The blistering effect was revealed, i. e., formation of a defect structure consisting of craters on the optics surface under bombardment by protons of the artificial and natural radiation belts of the Earth. Irradiation of the materials with 150—200 keV protons is absorbed by a 2 [im layer. Within this layer, protons recombine with electrons of the materials (p+ + e~ -» H) with formation of hydrogen atoms, e. g., the yearly dose of absorbed particles is D = = 1016 cm~2. As the irradiation dose increases, hydrogen is accumulated in spherical cavities. When the hydrogen pressure in the cavities becomes higher than the material strength, the material fails and hydrogen leaves the cavities, i. e., blistering takes place. The surface layer is thus eroded. A complicated structure appears on the surface as crater-like hemispherical defects 2—5 jum in diameter distributed uniformly. It has been shown experimentally that the proton fluence at which such defect structures form is 6-1015 cm~2, approximately equal to the annual equivalent dose. These defects, changing essentially the material surface properties, cause, in particular, decrease in the reflectivity both in the visible and the IR ranges.  
Keywords: blistering, flecking, space optics
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