PHITS simulations of the Matroshka experiment K. Gustafsson a, * , L. Sihver a,b , D. Mancusi c , T. Sato d , G. Reitz e , T. Berger e a Nuclear Engineering, Chalmers University of Technology, SE-41296 Gothenburg, Sweden b Department of Mathematics, Computer Science and Physics, Roanoke College, 221 College Lane, Salem, VA 24153, USA c Fundamental Interactions in Physics and Astrophysics, University of Lie `ge, 4000 Lie `ge, Belgium d Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency (JAEA), Shirakata-Shirane 2-4, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan e Institute of Aerospace Medicine, DLR-German Aerospace Center, Linder Ho ¨ he, D-51147 Cologne, Germany Received 17 May 2009; received in revised form 19 May 2010; accepted 29 May 2010 Abstract The radiation environment in space is very different from the one encountered on Earth. In addition to the sparsely ionizing radiation, there are particles of different Z with energies ranging from keV up to hundreds of GeV which can cause severe damage to both elec- tronics and humans. It is therefore important to understand the interactions of these highly ionizing particles with different materials such as the hull of space vehicles, human organs and electronics. We have used the Particle and Heavy-Ion Transport code System (PHITS), which is a three-dimensional Monte Carlo code able to calculate interactions and transport of particles and heavy ions with energies up to 100 GeV/nucleon in most matter. PHITS is developed and maintained by a collaboration between RIST (Research Orga- nization for Information Science & Technology), JAEA (Japan Atomic Energy Agency), KEK (High Energy Accelerator Research Orga- nization), Japan and Chalmers University of Technology, Sweden. For the purpose of examining the applicability of PHITS to the shielding design we have simulated the ESA facility Matroshka (MTR) designed and lead by the German Aerospace Center (DLR). Pre- liminary results are presented and discussed in this paper. Ó 2010 Published by Elsevier Ltd. on behalf of COSPAR. Keywords: PHITS; Simulation; Matroshka; Space radiation; Dose estimation 1. Introduction When aiming for longer and more advanced space mis- sions, such as to the Moon or to Mars, several issues must be taken into consideration. One problem is the radiation environment. Different types of radiation with a large range in charge and energy such as Galactic Cosmic Rays (GCRs), Solar Particle Events (SPE) and Trapped Protons create a very complex radiation environment which is a threat to humans as well as for electronic equipment. Due to this, several experiments have been launched in space, including on the International Space Station (ISS), in order to measure the radiation environment, and its characterizing parameters. Examples of such experiments are Matroshka (Reitz and Berger, 2006; Reitz et al., 2009) and Matroshka-R (Semkova et al., 2005) which focus on depth dose determination outside and inside the ISS, and Altea (Narici et al., 2001) which focus on light flashes phenomena. There are also ground based experiments, e.g. measurements of projectile fragmentation (Webber et al., 1998; Zeitlin et al., 1997, 2001, 2007; La Tessa et al., 2005, 2007; Mancusi et al., 2007), which are of importance for benchmarking and validating the particles and heavy- ion transport codes needed for the estimation of the radia- tion environment inside and outside the space vehicles. Sev- eral transport codes are available, such as the one- dimensional deterministic codes HZETRN (Wilson et al., 1995) and HIBRAC (Sihver et al., 1998; Sihver and Mancusi, 2009), and the three-dimensional Monte Carlo codes FLUKA (Fasso et al., 2005; Battistoni et al., 2007), GEANT4 (Agostinelli et al., 2003; Allison et al., 0273-1177/$36.00 Ó 2010 Published by Elsevier Ltd. on behalf of COSPAR. doi:10.1016/j.asr.2010.05.028 * Corresponding author. Fax: +46 31 772 2931. E-mail address: katarina@nephy.chalmers.se (K. Gustafsson). www.elsevier.com/locate/asr Available online at www.sciencedirect.com Advances in Space Research 46 (2010) 1266–1272