Abstract
A space radiation application is developed based on Geant4 tool kit. Even though there are many space radiation applications like MULASSIS (MUlti-LAyered Shielding SImulation Software); the application developed here offers more flexibility in choosing the physical models. It can be used to analyze the spherical geometries directly in addition to the planar geometries. In this paper both planar and spherical geometries of aluminum (Al), polyethylene (CH2) and liquid hydrogen (lH2) materials are analyzed with the help of dose-depth curves. The hydrogen, helium and Fe particle spectra of Galactic Cosmic Radiation (GCR) radiation are used in the estimation of doses. The total equivalent doses for the periods of 1 Yr are evaluated for aluminum, polyethylene and liquid hydrogen materials respectively and the liquid hydrogen is found to be more effective shielding material. These doses are compared to NCRP 2000 (National Council on Radiation Protection and Measurements) career dose limits to analyze the radiation risk for astronauts. The doses in case of planar geometries are well below the career limits of male as well female astronauts of age 35Yrs but those that in case of spherical geometries are well above the career limits for female astronauts of the same age. Doses for spherical geometries are below the career limits of male astronauts of same age only when areal densities of shield materials reach 100g/<i>cm<sup>2</sup></i>. The dose in spherical geometry is found to be ~4.4 times to that of planar geometry when Al material of 10 g/<i>cm<sup>2</sup></i> is exposed to GCR hydrogen spectrum. This is in agreement with the estimations of previous studies. The effect of geometry on the dose levels received by astronauts is also analyzed. It is found that the reduction in dose is about 10% more in spherical geometry than in planar geometry of the Al material. This is observed when the Al material is exposed to GCR hydrogen spectrum and its thickness is varied from 10 g/<i>cm<sup>2</sup></i> to 120 g/<i>cm<sup>2</sup></i>.
Highlights
Geant4 (Geometry and tracking) is a toolkit developed and maintained by Geant4 international collaboration
The doses for respective ions are normalized in the present work according to the actual number of those ions calculated from their differential energy spectra as well as the source geometry and angular considerations
The real doses for respective ions are normalized here according to the actual number of those ions calculated from their differential energy spectra, source geometry and angular considerations
Summary
Geant (Geometry and tracking) is a toolkit developed and maintained by Geant international collaboration It is developed for the Monte Carlo simulation of particle transport across the materials. It is a modular software written in C++ It is capable of simulating interactions of various particles with various materials in wide energy range [1, 2, 3, 4]. This makes the usage of Geant toolkit in diversified areas like medical physics, detector simulations and space radiation transport etc. Galactic cosmic radiation includes 85% protons, 14% alpha particles and 1% heavy ions [5]
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