Modeling the Lunar Radiation Environment: A Comparison Among FLUKA, Geant4, HETC‐HEDS, MCNP6, and PHITS

• Published in: Space Weather 2022-08, Vol.20 (8), p.n/a
• Main Authors: Zaman, F. A., Townsend, L. W., Wet, W. C., Looper, M. D., Brittingham, J. M., Burahmah, N. T., Spence, H. E., Schwadron, N. A., Smith, S. S.
• Format: Article
• Language: English
• Subjects: Accuracy; Agreements; Albedo; Angles (geometry); Codes; Cosmic ray showers; Cosmic rays; Energetic particles; Energy transport; Environment models; Extraterrestrial radiation; FLUKA; Galactic cosmic rays; Geant4; Heavy ions; HETC‐HEDS; Ion transport; Laboratories; Lunar albedo; Lunar radiation; Lunar surface; MCNP6; Modelling; Moon; PHITS; Radiation; Radiation code; Radiation transport; Reliability analysis; Solar energetic particles; Space weather; Teams
• ISSN: 1542-7390; 1539-4964; 1542-7390
• DOI: 10.1029/2021SW002895

Radiation transport codes have been an increasingly important tool for studying the space radiation environment, which includes high‐energy and high‐nuclear‐charge particles. The unique advantage of transport models lies in covering a wider range of particles, energies, and angles than would be attainable in a laboratory or measurable by an instrument. However, since there are several transport codes developed by different teams that have contributed heavily to the literature, differences are expected between such codes. In this work, we use five such radiation transport codes (FLUctuating KAscade, GEometry ANd Tracking, High‐Energy Transport Code‐Human Exploration and Development in Space, Monte Carlo N‐Particle, and Particle and Heavy Ion Transport code System) to study the radiation environment near the Moon, specifically the lunar “albedo” radiation, which is the radiation emitted by the lunar surface through interactions with incident galactic cosmic rays and solar energetic particles. The primary goal of this paper is to provide a general characterization of the lunar albedo radiation and to find the areas where the modeled transport codes agree and disagree by using almost identical input parameters. The results of this work show overall good agreement between the codes. However, some areas of discrepancies exist that are reported herein. Thus, this paper equips the space weather and radiation biology communities with a comparison between popular radiation transport models applied to lunar albedo radiation. The overall agreement and, in some cases, discrepancies between these transport codes provide fundamental insight necessary for assessing code reliability and identifying where further study and improvements are needed to advance our understanding of lunar albedo radiation. Plain Language Summary Replicating the lunar radiation environment in a laboratory is extremely difficult for multiple reasons. One of the most effective alternatives is to use computer simulations equipped with the physical and mathematical tools to help us understand radiation in space. However, there are multiple radiation codes developed by different teams. Comparing the results from such codes and finding the areas of agreement and disagreement in their results help in improving the codes and in providing a better understanding of the space radiation environment. In this work, we studied the lunar radiation environment by comparing five different well‐known radiation code