Date of Award

5-2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Nuclear Engineering

Major Professor

Lawrence H. Heilbronn

Committee Members

Robert M. Counce, Maik K. Lang, Lawrence W. Townsend

Abstract

Understanding the effects due to the space radiation environment is an important step as space missions become longer and more complex – there is a major risk to both astronauts and their equipment, and optimizing the shielding is the best way to ensure the safety and success of such long-term missions to the Moon or Mars. Galactic Cosmic Rays (GCR) and Solar Energetic Particles (SEP) are the two main sources that comprise the space radiation field. At Earth-based testing facilities, it is impossible to fully replicate the conditions astronauts will face, so the use of particle transport codes to model the physics associated with shielding strategies are necessary, and these transport codes (both stochastic and deterministic) are dependent on relevant experimental data. Thus, the models help better understand the radiation physics in outer space, and experimental results help improve the models. Most recent model predictions of the effective dose in an enclosed shielding design (looking at radiation dose within a front surface and a back surface) suggested an optimal shielding thickness for aluminium, and an experiment to test these simulation results was conducted at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL). It is believed that a secondary radiation field is produced via interactions of initial GCR and SEP radiation within the shielding material, and this secondary field is directed inwards (towards the human environment on a spacecraft or lunar habitat) and is responsible for the predicted optimal shielding thickness. This thesis contains the energy- and spatial-dependent (“double differential”) yield of Z = 1 and 2 light ions measured from the accelerator-based experiments at NSRL. Three nuclei (hydrogen, helium and iron) were accelerated to 400 and 800 MeV/n and fired at three thicknesses of aluminium shielding (20/40/60 g/cm2), and to detect the secondary light ions produced by beam interactions in the shielding, sodium iodide scintillation detector arrays were placed at 10 and 30 degrees off beam axis.

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