Very Low Temperature Rise Laser Annealing of Radiation-damaged Solar Cells in Orbit V. POULEK Summary Solar cells of all space objects are damaged by radiation in orbit. This damage, however, can be removed by laser annealing. A new in-orbit laser regeneration system for both body- and spin-stabilized space objects is proposed. An in-orbit laser regeneration system was originally proposed only for spin-stabilized geostationary communication satellites. The results of the research on very low temperature rise laser annealing show that a laser regeneration system could be used also in body-stabilized space objects such as an international space station or geostationary communication satellites. For successful annealing of solar cells damaged by 10 years' radiation dose in orbit it is necessary for the temperature rise in the incidence point of the laser beam to reach about 400°C. By continuous regeneration, however, between two annealing cycles the solar cells are hit by about two orders of magnitude lower radiation dose. This makes it possible to carry out the regeneration at a temperature rise well under 1°C! If an optimal laser regeneration system is used, such low temperature rise laser annealing of radiation-damaged solar cells is possible. A semiconductor GaAlAs diode laser with output power up to 10 mW CW was used for annealing. Some results of the very low temperature rise annealing experiment are given in this paper. Introduction In the second half of the 1970s research work was begun with the aim of regenerating radiation-damaged solar cells by means of a laser beam. In the course of research work it has been found that solar arrays can be regenerated by a laser beam which heats up the cell to a temperature of about 400°C. There are some problems, however, caused by these high temperatures. For example, a very important problem of the in-orbit laser regeneration of radiation-damaged solar arrays is to ensure that the repeated laser annealing will neither damage the solar cells nor the complete solar panel [1]. It is also difficult to find a suitable laser for in-orbit application. Experiments with the very low temperature rise laser annealing of radiationdamaged solar cells were begun with the aim of overcoming these problems. Low Temperature Rise Laser Annealing Experiment Continuous annealing has been selected for the in-orbit laser regeneration system because between two annealing cycles the solar cells are hit by a low radiation dose. V. Poulek, Czechoslovak Academy of Sciences, Institute of Physics, 180 40 Prague, Czechoslovakia.
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