COMPARISON OF COSMIC-RAY ENVIRONMENTS ON EARTH, MOON, MARS AND IN SPACECRAFT USING PHITS

Estimation of cosmic-ray doses is of great importance not only in aircrew and astronaut dosimetry but also in evaluation of background radiation exposure to public. We therefore calculated the cosmic-ray doses on Earth, Moon and Mars as well as inside spacecraft, using Particle and Heavy Ion Transport code System PHITS. The same cosmic-ray models and dose conversion coefficients were employed in the calculation to properly compare between the simulation results for different environments. It is quantitatively confirmed that the thickness of physical shielding including the atmosphere and soil of the planets is the most important parameter to determine the cosmic-ray doses and their dominant contributors. The comparison also suggests that higher solar activity significantly reduces the astronaut doses particularly for the interplanetary missions. The information obtained from this study is useful in the designs of the future space missions as well as accelerator-based experiments dedicated to cosmic-ray research.

[1]  Tatsuhiko Sato,et al.  Cosmic ray modulation and radiation dose of aircrews during the solar cycle 24/25 , 2017 .

[2]  Hiroshi Nakashima,et al.  Applicability of particle and heavy ion transport code PHITS to the shielding design of spacecrafts , 2006 .

[3]  Günther Reitz,et al.  The Martian surface radiation environment – a comparison of models and MSL/RAD measurements , 2016 .

[4]  Tatsuhiko Sato,et al.  Analytical Model for Estimating Terrestrial Cosmic Ray Fluxes Nearly Anytime and Anywhere in the World: Extension of PARMA/EXPACS , 2015, PloS one.

[5]  Tatsuhiko Sato,et al.  Analytical Model for Estimating the Zenith Angle Dependence of Terrestrial Cosmic Ray Fluxes , 2016, PloS one.

[6]  Tatsuhiko Sato.  Evaluation of World Population-Weighted Effective Dose due to Cosmic Ray Exposure , 2016, Scientific Reports.

[7]  L. Sihver,et al.  Dose estimation for astronauts using dose conversion coefficients calculated with the PHITS code and the ICRP/ICRU adult reference computational phantoms , 2011, Radiation and environmental biophysics.

[8]  Hiroshi Nakashima,et al.  Particle and Heavy Ion Transport code System, PHITS, version 2.52 , 2013 .

[9]  K. Niita,et al.  Comparison of the mean quality factors for astronauts calculated using the Q-functions proposed by ICRP, ICRU, and NASA , 2013 .

[10]  T. Slaba,et al.  A comparative study of space radiation organ doses and associated cancer risks using PHITS and HZETRN , 2013, Physics in medicine and biology.

[11]  R. Singleterry,et al.  Shielding evaluation for solar particle events using MCNPX, PHITS and OLTARIS codes. , 2015, Life sciences in space research.

[12]  T. Slaba,et al.  Variation in Lunar Neutron Dose Estimates , 2011, Radiation research.

[13]  Günther Reitz,et al.  A ready-to-use galactic cosmic ray model , 2013 .

[14]  N. Hasebe,et al.  Neutron production in the lunar subsurface from alpha particles in galactic cosmic rays , 2011 .

[15]  L. Pinsky,et al.  Benchmarking of calculated projectile fragmentation cross-sections using the 3-D, MC codes PHITS, FLUKA, HETC-HEDS, MCNPX_HI, and NUCFRG2 , 2008 .

[16]  Joseph Cugnon,et al.  New potentialities of the Liege intranuclear cascade (INCL) model for reactions induced by nucleons and light charged particles , 2012, 1210.3498.

[17]  T. Kuwabara,et al.  Radiation dose forecast of WASAVIES during ground‐level enhancement , 2014 .

[18]  G. P. Ginet,et al.  AE9, AP9 and SPM: New Models for Specifying the Trapped Energetic Particle and Space Plasma Environment , 2013 .

[19]  G. Reitz,et al.  An Adaptive Response to Uncertainty Generates Positive and Negative Contrast Effects , 2014 .