Radiation Transport Simulation

The radiation field experienced inside a spacecraft can be very complex, with a range of particle species and energies incident upon the sensitive components. Shielding serves to attenuate particles, but can also generate cascades of secondary particles, which in some cases are more damaging for microelectronics and sensors.

QinetiQ has almost twenty-five years of experience in developing and applying particle transport simulation tools to simulate radiation interactions in components and materials. These tools allow definition in 3-dimensions of geometries from parts of microelectronics structures to complete satellites, and then individually track millions of particles through these geometries, simulating the complex electromagnetic and nuclear interactions of particles. As well as shielding analyses, such radiation transport tools allow simulation of the detailed energy-deposition processes in microelectronics allowing, for example, component data collected using one type of incident particle to be translated into component susceptibility data for other particle species, thus avoiding the need for repeating costly irradiations.

Applications of particle transport codes by QinetiQ include the simulation of the radiation environment of the Space Shuttle, analyses of sensor backgrounds in the NASA Compton Gamma-Ray Observatory and ESA X-ray Multi-Mirror Mission (XMM) spacecraft. They are also being applied to assess the effects of shielding microelectronics on communications, and optimise shield performance (providing potentially x20 improvement for the same mass). Cosmic radiation effects are not just limited to space, and transport codes are being used in the QARM model to predict particle flux levels and radiobiological dose for avionic systems and flight crews.

QinetiQ in partnership with BIRA is also developing easy-to-use web-tools based on the Geant4 radiation transport toolkit. An example of such is the Multi-Layered Shielding Simulation Software (MULASSIS), allowing the user to perform complex 1-D shielding simulation using the detailed physics within Geant4 running at a remote web-site.