KISTI 2013 달 토양에서 지하 깊이에 따른 고에너지 우주선 환경 영향 분석 Jongdae Sohn, Yu Yi Dept. of Astronomy & Space Science, Chungnam National University

Motivation Introduction – Geant 4 (for Geometry And Tracking) – Geant 4 for Space Science – Lunar Surface Structure Simulation and Analysis Summary Contents

Many countries of the world including the United States, China, Japan and India explore the moon and Mars. We have to prepare the moon exploration here and now. When the human being explores and lives on the Moon, the Human being is influenced by a lot of the high-energy particles in lunar environment ; galactic cosmic ray (GCR), solar energetic proton (SEP). Thus, we must consider the environmental impact of high-energy cosmic radiation. Motivation

A toolkit for the simulation of the passage of particles through matter Developed by a world-wide Collaboration of approximately 100 scientists Its areas of application  High Energy Physics  Astrophysics and nuclear physics  Experiments, Medical, Accelerator and Space Science Introduction: Geant 4 (for Geometry And Tracking)

Space electronics and Space Science detector systems Simulations of astronaut radiation hazards Planetary exploration applications Interfaces and tools to space environment analysis tools such as SPENVIS Cosmic ray magnetospheric propagation analyses Micro-dosimetry Large-scale simulations requiring event biasing and GRID capabilities General shielding optimization applications Introduction: Geant 4 for Space Science 5º5º 5º 5º

Introduction: Lunar Surface Structure Geological structure of the Lunar soil [cited by Lunar Sourcebook: a user’s guide to the moon]

Introduction: The energy spectrum for cosmic rays Composition of cosmic rays (1 ~ 20 GeV) [cited by : protons (89%), helium nuclei (10%), the nuclei of heavier elements (1%)

Introduction: Composition of Lunar Soil Chemical compositions of average Apollo 15 soils samples used in the radiation experiments. Mean soil density: 3.39g/cm 3 [Wieczorek et al. (2006)] [Soil in Mare][Soil in Highland]

Introduction: Linear Energy Transfer Linear energy transfer (LET)  A measure of the energy transferred to material as an ionizing particle travels through it.  This measure is used to quantify the effects of ionizing radiation on biological specimens or electronic devices.  An average energy for a given path length traveled.  An average path length for a given deposited energy. t: an thickness of material (-dE/dx): Energy imparted to matter

Simulation: Deposited energy of protons Deposited energy of proton beam (1 ~ 6500 MeV) after passing through the Lunar soil of 10m depth

Simulation: Residual LET for Lunar Soil (Linear Scale) Residual energy deposition in Soil for 1, 5, 10, 15, 20 GeV/nucleon Proton beam after passing through Lunar Soil (Linear Scale)

Simulation: Residual LET for Lunar Soil (Log Scale) Residual energy deposition in Soil for 1, 5, 10, 15, 20 GeV/nucleon Proton beam after passing through Lunar Soil (Log Scale)

Analysis: Effective Dose Effective Dose (H E ) :

Analysis: Effective Dose for Lunar Soil (Linear Scale) Effective Dose for the depth [0 ~ 10 m] of the Lunar soil. Natural Background is based on the Atlantic Seaboard value [0.6 mSv/year]. [National Council on Radiation Protection and Measurements, NCRP Report 116]

Analysis: Effective Dose for Lunar Soil (Log Scale) Effective Dose for the depth [0 ~ 40 m] of the Lunar soil. Natural Background is based on the Atlantic Seaboard value [0.6 mSv/year].

Analysis: Effective Dose for Lunar Soil (Log Scale) Effective Dose for the depth [0 ~ 10 m] of the Lunar soil. Natural Background is based on the Atlantic Seaboard value [0.6 mSv/year].

Summary Using Geant4, we examine the environmental impact of high-energy cosmic radiation for the range of 1, 5, 10, 15, and 20 GeV for Lunar soil depth [1 ~ 40 m] of Lunar soil chemical compositions (3.39 g/cm 3 ). At the result, under the Lunar soil of 4.5 m depth, there is less impact of high-energy environment in Lunar radiation environment compared with the natural background radiation on the Earth [0.6 mSv/year]. We will also examine the environmental impact of high-energy cosmic radiation on the Martian and Lunar surface using other composition of cosmic rays.