PROJECT TITLE :

Effects of space environmental exposure on photoemission yield of polyimide

ABSTRACT:

As photoemission plays a key role in surface potential of spacecraft materials in sunlight, the photoemission yield of spacecraft used polyimide film is required for surface potential analysis. To reveal the area environmental effects on the photoemission, the ground based degradations of polyimide film due to 500 keV electrons and fifty keV protons irradiation with 4 completely different fluences respectively, ultraviolet irradiation with five completely different doses, and atomic oxygen beam erosion with two different fluences were conducted separately. By using a developed measuring system, we tend to measured the photoemission yield of the virgin and also the 4 kinds of degraded polyimide films respectively and compared the results. It's inferred that, the variation of photoemission yield was obvious once electrons, protons and ultraviolet irradiation but slight for atomic oxygen erosion. The variation of photoemission yield has been explained from the perspective of surface reflectance, roughness, and also the free radical concentration of the exposed samples. Besides, the Monte-Carlo analysis software Casino and SRIM were used to analysis the distribution and stopping power of electron and proton respectively. It's thought of that, the degradation mechanism is that the multiple effects of reflectance, free radicals and therefore forth.