temperature is 125°C, which produces an 18.2% cell efficiency. At 125°C, self-annealing of radiation-induced damage occurs in the GaAlAs cells. As indicated in figure 8, the solar cell blanket material is Kapton (25 ^m thick). The 20 yum synthetic sapphire (AI2O3) substrate, used in an inverse orientation, also acts as the cell cover. The blanket weight is 0.252 kg/nA The projected cost of the GaAs solar cell blanket is $71/m^. Solar reflectors for the GaAlAs CR2 concept consist of thin reflective membranes aluminized Kapton mounted in a 60° Vee trough configuration. The reflector membrane has a reflectivity of 0.9 BOL and 0.83 EOL. The effective end-of- 1ife efficiency is 0.915 as previously stated. The membrane mass is 0.018 kg/m^. The silicon solar blanket consists of 50 jqm thick single crystal silicon solar cells with borosilicate cover glass electrostatically bonded to the cells front and back. The cells are designed with both P and N terminals brought to the back of the cells. This feature makes it possible to use 12.5 jL|m silver- plated copper interconnections which are formed on the substrate glass. Complete panels are assembled electrically by welding together the module-to-module interconnections. The cell efficiency is 17.3% (AMO, 28°C) at beginning of life. At design operating temperature of 36.5°C, the efficiency is 16.5%. A key feature of the blanket design is the ability to perform in-situ annealing of the solar cells using a laser annealing concept. The laser annealing concept utilizes gimbal-mounted CO2 lasers. The gimbals would be mounted on an overhead gantry structure to permit transversing of the entire solar array by several lasers as illustrated in figure 9. The laser beam heats the solar cells to annealing temperature (500°C) without damaging cell interconnect and substrate materials. Annealing is required to recover radiation induced degradation of the cells. The o projected cost of the silicon solar blankets is $35/m . D. Solar Array and Structure The solar array consists of the deployed solar cell blankets attached to solar array structure. In the case of the CR2 GaAlAs option, the array includes the solar reflectors mounted on each side of the solar cell blankets. The solar cell blankets would be transported to orbit in modular packages in
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