Mass and magnetic dipole shielding against electrons of the artificial radiation belt

Computations of magnetic shielding system masses required for protection against electrons of various energies have been performed. We have also obtained a comparison of the required shielding masses for a space vehicle traversing circular orbits through the anomaly in the artificial radiation belt (ARB) at altitudes of 200, 400, 600, and 800 km and inclined at 30° to the earth's equatorial plane: first with a magnetic superconducting solenoidal shielding system approximated by a point dipole and then with a two-layer composite material shielding system consisting of an outer layer of aluminum and an inner layer of lead. The aluminum thickness equaled the practical range of 10-Mev electrons, and the lead was used to attenuate the bremsstrahlung to specified skin dose rates. The averaged electron flux in ARB, used in estimating dose, was computed to be sufficiently accurate for missions not shorter than 100 hr and more accurate for longer missions. The material shielding mass, primarily designed for protection when appreciable bremsstrahlung occur, was at best (no lead) an order of magnitude larger than that of the magnetic shielding system. The mass of the cryogenic system was neglected, being a fraction of the combined mass of the solenoid and support structure.