Transport calculations and accelerator experiments needed for radiation risk assessment in space

Book chapter, 2010

It is well known that one of the largest obstacles to be solved to enable safe future humanactivities on the lunar surface, building of a lunar base, and performing interplanetary spacemissions, is how to protect the personnel from cosmic and solar radiation. To do so, theradiobiological effects of the radiation inside and outside a spacecraft must be well understoodand countermeasures developed. The major uncertainties on space radiation risk estimates inhumans are associated to the poor knowledge of the biological effects of low and high LETradiation, with a smaller contribution coming from the characterization of space radiation fieldand its primary interactions with the shielding and the human body. However, to decrease theuncertainties on the biological effects and increase the accuracy of the risk coefficients forcharged particles radiation, the initial charged-particle spectra from the Galactic Cosmic Rays(GCRs) and the Solar Particle Events (SPEs), and the radiation transport through the shieldingmaterial of the space vehicle and the human body, must be well characterized. Since it ispractically impossible to measure all primary and secondary particles from all possibleposition-projectile-target-energy combinations needed for a correct risk assessment in space,accurate particle and heavy ion transport codes must be used. These codes are also neededwhen estimating the risk for radiation induced failures in advanced microelectronics, such assingle-event effects, etc., and the efficiency of different shielding materials. It is thereforeimportant that the models and transport codes will be carefully benchmarked and validated tomake sure they fulfill preset accuracy criteria, e.g. to be able to predict particle fluence, doseand energy distributions within a certain accuracy. When validating the accuracy of thetransport codes, well defined ground based accelerator as well as space experiments areneeded. In this paper, accelerator experiments needed for testing and validating particle andheavy ion transport codes, and shielding materials, are presented. Advantages anddisadvantages with deterministic one dimensional and stochastic three dimensional transport codes are discussed, together with different concepts of shielding and protection from cosmicradiation.