Contribution of low-energy protons to the degradation of shielded GaAs solar cells in space

The cumulative fraction of the displacement damage dose deposited in shielded GaAs solar cells in typical space proton environments is presented as a function of energy from the threshold for atomic displacement up to 400 MeV. Results are presented for silica coverglass thicknesses from 3–30 mils, and for both slowed down and incident proton energies. As an example, it is found that for cells shielded by 30 mils of coverglass in a circular 5000 km orbit, less than 15% of the degradation is caused by protons with slowed down energies <0.1 MeV, whereas ∽50% of the total degradation is produced by protons in the energy range 1<E<10 MeV.