Radiation Transport

Dr. Aghara in Class

Primary Investigator – Sukesh Aghara

Radiation transport simulations play significant role in radiation knowledge

NASA identified radiation protection as one of five top priority issues that needs to be addressed for its proposed manned missions to moon and Mars. Any manned mission beyond Earth’s orbit will involve radiation threats to be more severe than the hazards faced by the astronauts on the International Space Station.

 

DE/DX mesh for a 55MeV Proton on a 1.7 g/cmsquaredIn many scenarios the delivered dose and the resulting damage to the astronauts and the electronics can increase substantially from the secondary radiation environment. NASA and its contractors need reliable and accurate shielding analysis tools for mission planning. Benchmarking computer codes is necessary to ensure confidence in the validity and reliability of simulated results.

 

The interactions of the incident radiation nuclides (primaries) with the target nuclei (shielding material or body organ materials) result in a modified radiation field downstream. A detailed and accurate radiation field at the dose/dose equivalent point is necessary to assess the short and long-term response of electronics and biological systems to the radiation exposure. The nuclear fragmentation processes resulting in a cascade of secondary products: Leptons, Baryons, Mesons, photons, electrons, positrons, light (A<=4) and heavy ions (A>4) have to be modeled explicitly for a comprehensive transport calculation. Differences in cross-section, transport methods and embedded assumptions result in differences between different radiation transport codes. Multiple layer shielding evaluation for neutron environment

Rigorous validation and verification (V&V) of these codes is necessary to reduce the uncertainty of the calculations, both for transport and physics. Specifically, research and design activities targeting collection of experimental data, code comparison and cross-section data measurements are required. The primary objective of the radiation simulations groups is to provide this expertise within CRESSE.

Some examples of the contributions of the simulation group are:

  1. (1)   Participation in experimental design of beam experiments (proton, heavy ions, neutrons)
  2. (2)   Perform Monte Carlo (MC) code simulations of the detector response to compare with   measurements
  3. (3)   Model complete space environment boundary conditions (example: Solar Particle Event (SPE) and Galactic Cosmic Ray (GCR) in free space and near a surface or in an atmosphere)
  4. (4)   Evaluate the effective attenuation from candidate-shielding materials for a given environment
  5. (5)   Determine secondary neutron environment (understand albedo neutrons), and
  6. (6)   Define dosimetry strategies, etc.

Multiple detector simulation to evaluate a thick carbon/water target. Schematics neutron, protons and photons tracks.

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