Simulation of Shielding Materials against Galactic Cosmic Rays
Master of Science
Radiation is one of the most critical hazards for deep space missions. Among the sources of deep space radiation, the Galactic Cosmic Rays, which are composed of high energy ions travelling at relativistic speeds from outside the solar system, are especially difficult to shield. As spacefaring nations have progressed in their exploration activities, there has been increasing interest in longer and deeper space voyages. However, beyond Low Earth Orbit, without the protection afforded by the Earth's magnetic field, long space voyages have increased risks from radiation exposure. Hence more efficient shielding materials are necessary for solving this radiation issue. Space radiation shielding can be examined by either ground-based experiments or simulations. Deterministic or Monte Carlo approaches are the two computational methods to simulate the radiation transport problem. MULASSIS, a Monte Carlo code developed by QinetiQ, BIRA and ESA is based on Geant4 and is used in this thesis. A convergence study is first performed with aluminum as a shielding material in order to determine the number of primary particles to use in the MULASSIS simulations. Dose equivalent analysis is then performed for single shielding materials with updated radiation weighting factors recommended in ICRP 103, including aluminum, polyethylene, boron nitride infused with hydrogen and liquid hydrogen. Dose equivalent depth curves are plotted for each shielding material, and in addition for various multilayer combinations of aluminum and the other materials. Because the biological impact from secondary produced neutrons can be so harmful, a fluence analysis is performed for various elemental components of the GCR radiation spectrum for different shielding materials.