Fig. 3
From: Limitations in predicting the space radiation health risk for exploration astronauts
a The Bragg peak and depth dose characteristics of space radiation. The Bragg peak and relative dose deposition for ions at energies commonly used in space radiation studies compared to the X-ray and gamma sources used as surrogate radiations for Relative Biological Effectiveness (RBE) quantification. The Bragg peak refers to the point where a charged particle promptly loses kinetic energy before coming to rest in a medium. This effect is very pronounced for fast moving, charged particles. Shown are 60 MeV Protons (hydrogen, purple), 600 MeV 56Fe (iron, light blue), 290 MeV12C (carbon, green), 1 GeV 56Fe (iron, dark blue), X-ray (orange dotted line), and 60Co (cobalt, yellow dotted line). The shaded gray area, representing the average diameter of a mouse, demonstrates that the Bragg peak, and thus the majority of dose deposition, is outside the mouse body for SPE protons (energies ≥50 MeV) and GCR ions. b The proton and electron range, energy and dose distributions for the October 1989 solar particle event compared to a dose-equivalent 60Co exposure. Charged particles (electrons, protons, heavy-charged particles) typically deposit more energy towards the end of their range. In contrast, the current standard, 60Co radiation, loses the most energy at the tissue surface. These energy characteristics demonstrate the poor fidelity of 60Co as a surrogate for studying the complex SPE and GCR spectrums. Figure 3 (b) reprinted by permission from Conditions for RightsLink Permissions Springer Customer Service Center GmbH:Springer-Verlag32
