SpaceTRiP code for Space Radiation Research
Abstract
Understanding the health risk from space radiation is crucial for manned space exploration. Consisting mainly of particles with high-energy and charge (HZE), space radiation differs significantly from the natural radiation experienced on Earth [1]. On the other hand, HZE particles are also used in ion beam radiotherapy. Thus it seems natural to apply the knowledge gained in radiotherapy also to the issues of radioprotection in space. In this context we are extending TRiP98 (TReatment PlannIng for Particles) [2,3], a code originally developed for treatment planning in ion beam radiotherapy, in particular carbon ions. The extension, SpaceTRiP, is designed to match the additional requirements, i.e. projectiles up to iron, energies in the GeV/u range, and a multitude of different target materials, in particular the various shielding materials under discussion in order to achieve dose reduction. The radiation transport model relies on total nuclear reaction and nuclear fragmentation cross-sections, obtained from the Tripathi nuclear model [4], Sihver's parametrisation [5] and semi-empirical corrections where experimental data are available [6]. Each calculation step handles the energy spectra of all particles under consideration, primary beam as well as the produced secondaries, and thus allows the inclusion of risk models depending e.g. on LET rather than plain absorbed dose. Since the calculation is analytical-numerical, it should give a significant speed advantage compared to Monte Carlo (MC) codes. This offers the possibility for "fast prototyping" of habitat shielding configurations. The transport model has previously been shown to give results which compare well with experimental data [7]. The geometry handling follows the same logic as in radiotherapy planning, which is usually based on 3D CT or MRI patient images. Thus a space vessel or habitat is described by regular cubic voxels of different material composition, imported from a 3D model in GDML format. Moving from radiotherapeutic to space applications introduces a number of changes. A significantly larger number of projectile-target combinations have to be handled, as well as the larger dimensions of the geometrical model compared to a patient CT. These changes inevitably lead to an increase in calculation time, which can be counteracted by optimizing the resolution of the energy spectra and exploitation of multi-core CPUs. We present results for the dose reduction for different shielding materials, in comparison to available experimental data and MC approaches. The results comprise monoenergetic 12C beams in the radiotherapy energy range, representative Solar Particle Event (SPE) and Galactic Cosmic Ray (GCR) spectra. One conclusion of our study is that there is a strong need for more experimental cross-sections to consolidate our simulation inputs, especially for the GCR case with its multitude of projectile-target combinations. [1] M. Durante and F. A. Cucinotta, Rev. Mod. Phys. 83 (2011) p. 1245. [2] M. Krämer, O. Jäkel, T. Haberer, G. Kraft, D. Schardt, and U. Weber, Phys. Med. Biol. 60th Anniversary Collection, 37 (2016) [3] M. Krämer and M. Scholz, Phys. Med. Biol. 45, 3319 (2000) [4] R. K. Tripathi, F.A. Cucinotta, and J. W. Wilson, Nucl. Instrum. Meth. B 155, 349 (1999) [5] L. Sihver and D. Mancusi, Radiat. Meas. 44, 38 (2009) [6] E. Haettner, H. Iwase, M. Krämer, G. Kraft and D. Schardt, Phys. Med. Biol. 58, 8265 (2013) [7] M. Krämer, E. Scifoni, M. Giraudo, and M. Durante, GSI-FAIR Scientific report, p.189 (2017)
- Publication:
-
43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E1864T