Mapping the 3-Dimensional Dose Distribution from Space Radiation

Solar particle events and galactic cosmic rays are major concerns for astronauts in space or on a planet’s surface. Calculating the full 3-dimensional dose map is essential for the radiation risk analysis and optimal... [ view full abstract ]

Solar particle events and galactic cosmic rays are major concerns for astronauts in space or on a planet’s surface. Calculating the full 3-dimensional dose map is essential for the radiation risk analysis and optimal mitigation. In this presentation, I will use a dome structure on the lunar surface as an example for the 3-dimensional dose distribution.

I will first review our results from the 1-dimensional HZETRN code with ray tracing. In that study [1], we find that the center of the hemispherical dome on the lunar surface has the largest radiation exposure to blood-forming organs while locations on the inner surface of the dome have the lowest exposure. This reduction in the radiation exposure from the center to the inner edge of the dome can be as large as a factor of 3 or more for the radiation from solar particle events while being smaller for the radiation from galactic cosmic rays. Then I will show our Monte Carlo results [2] using the 3-dimensional Geant4 code on how the radiation effective dose, especially that from albedo particles such as neutrons, in the dome depend on the dome thickness in a galactic cosmic-ray environment. Finally, I will discuss our ongoing Geant4 work [3] that aims to fully map out the 3-dimensional dose distribution inside and outside the dome on the lunar surface.

[1] Lin, Z.W., Baalla, Y., and Townsend, L.W. (2009). Variation of Space Radiation Exposure Inside Spherical and Hemispherical Geometries. Radiation Measurements 44, 369-373. [2] Jia, Y. and Lin, Z.W. (2010). The Radiation Environment on the Moon from Galactic Cosmic Rays in a Lunar Habitat. Radiation Research 173, 238-244. [3] Smith, J.D. and Lin, Z.W. (2017). In preparation.