How Galactic Cosmic Ray models affect the estimation of radiation exposure in space

Mrigakshi, Alankrita Isha; Matthiä, Daniel; Berger, Thomas; Reitz, Günther; Wimmer‐Schweingruber, R. F.

doi:10.1016/j.asr.2012.10.017

Cited by 19 publications

(13 citation statements)

References 20 publications

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“…Consequently, when the models are evaluated over a common epoch and propagated through a transport code, it has been found that differences on integrated quantities like dose, dose equivalent, or effective dose can exceed 50% [ Mrigakshi et al ., ]. This is also shown below in Figure , where relative differences between the BON2010 and BON2011 models reach 50% near 1991 and 2001 and exceed 30% for several epochs.…”

Section: Introductionsupporting

confidence: 65%

“…The proton effective dose behind shielding has the broadest distribution of any ion, ranging from 100 MeV/n to 10 GeV/n—consistent with similar results from Mrigakshi et al . []. The heavy ion distributions narrow because secondary ions produced in nuclear interactions are typically less biologically damaging than the original ion.…”

Section: Sensitivity Analysismentioning

confidence: 99%

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GCR environmental models I: Sensitivity analysis for GCR environments

Slaba

Blattnig

2014

Space Weather

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Accurate galactic cosmic ray (GCR) models are required to assess crew exposure during long-duration missions to the Moon or Mars. Many of these models have been developed and compared to available measurements, with uncertainty estimates usually stated to be less than 15%. However, when the models are evaluated over a common epoch and propagated through to effective dose, relative differences exceeding 50% are observed. This indicates that the metrics used to communicate GCR model uncertainty can be better tied to exposure quantities of interest for shielding applications. This is the first of three papers focused on addressing this need. In this work, the focus is on quantifying the extent to which each GCR ion and energy group, prior to entering any shielding material or body tissue, contributes to effective dose behind shielding. Results can be used to more accurately calibrate model-free parameters and provide a mechanism for refocusing validation efforts on measurements taken over important energy regions. Results can also be used as references to guide future nuclear cross-section measurements and radiobiology experiments. It is found that GCR with Z > 2 and boundary energies below 500 MeV/n induce less than 5% of the total effective dose behind shielding. This finding is important given that most of the GCR models are developed and validated against Advanced Composition Explorer/Cosmic Ray Isotope Spectrometer (ACE/CRIS) measurements taken below 500 MeV/n. It is therefore possible for two models to very accurately reproduce the ACE/CRIS data while inducing very different effective dose values behind shielding.

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Section: Introductionsupporting

confidence: 65%

Section: Sensitivity Analysismentioning

confidence: 99%

GCR environmental models I: Sensitivity analysis for GCR environments

Slaba

Blattnig

2014

Space Weather

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“…Various other assets have measured light ions and higher energy heavy ions but for only short time periods. The limited measurements were shown to lead to a calibration bias, in which the models are found to be reasonably accurate (less than 15% model error) [ NCRP , ] when compared to the available data, but larger differences (>50%) in radiation exposure calculations behind shielding using the GCR models were found [ Mrigakshi et al , ; Slaba and Blattnig , ]. The discovery of the calibration bias has led to more rigorous sensitivity analysis and validation [ Slaba and Blattnig , ; Slaba et al , ].…”

Section: Galactic Cosmic Ray Modelsmentioning

confidence: 99%

Evaluating galactic cosmic ray environment models using RaD-X flight data

2016

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Galactic cosmic rays enter Earth's atmosphere after interacting with the geomagnetic field. The primary galactic cosmic rays spectrum is fundamentally changed as it interacts with Earth's atmosphere through nuclear and atomic interactions. At points deeper in the atmosphere, such as at airline altitudes, the radiation environment is a combination of the primary galactic cosmic rays and the secondary particles produced through nuclear interactions. The RaD‐X balloon experiment measured the atmospheric radiation environment above 20 km during 2 days in September 2015. These experimental measurements were used to validate and quantify uncertainty in physics‐based models used to calculate exposure levels for commercial aviation. In this paper, the Badhwar‐O'Neill 2014, the International Organization for Standardization 15390, and the German Aerospace Company galactic cosmic ray environment models are used as input into the same radiation transport code to predict and compare dosimetric quantities to RaD‐X measurements. In general, the various model results match the measured tissue equivalent dose well, with results generated by the German Aerospace Center galactic cosmic ray environment model providing the best comparison. For dose equivalent and dose measured in silicon, however, the models were compared less favorably to the measurements.

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“…Mrigakshi et al (2012Mrigakshi et al ( , 2013aMrigakshi et al ( , 2013b and have investigated several models suitable as input for the calculation of radiation exposure in space and found that the most suitable models currently available are BO-10 model (O'Neill 2010) and the DLR model (Matthiä et al 2013). GCR consists mainly of fully ionized atomic nuclei of which about 87% are hydrogen, 12% helium, and about 1% heavier nuclei (Simpson 1983).…”

Section: Galactic Cosmic Ray Modelmentioning

confidence: 99%

“…These transport models, which are discussed in more detail below, have to be combined with models of the primary GCR spectra taking into account the solar modulation. Following recent studies evaluating different GCR models concerning their applicability for the calculation of radiation exposure (Mrigakshi et al 2012(Mrigakshi et al , 2013b the Badhwar-O'Neill 2010model (O'Neill 2010, named BO-10 hereafter, and the model by Matthiä et al (2013), named DLR model hereafter (Deutsches Zentrum für Luft-und Raumfahrt, DLR), are used in this work.…”

Section: Introductionmentioning

confidence: 99%

The Martian surface radiation environment – a comparison of models and MSL/RAD measurements

Matthiä

Ehresmann

Lohf

et al. 2016

J. Space Weather Space Clim.

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Context: The Radiation Assessment Detector (RAD) on the Mars Science Laboratory (MSL) has been measuring the radiation environment on the surface of Mars since August 6th 2012. MSL-RAD is the first instrument to provide detailed information about charged and neutral particle spectra and dose rates on the Martian surface, and one of the primary objectives of the RAD investigation is to help improve and validate current radiation transport models. Aims: Applying different numerical transport models with boundary conditions derived from the MSL-RAD environment the goal of this work was to both provide predictions for the particle spectra and the radiation exposure on the Martian surface complementing the RAD sensitive range and, at the same time, validate the results with the experimental data, where applicable. Such validated models can be used to predict dose rates for future manned missions as well as for performing shield optimization studies. Methods: Several particle transport models (GEANT4, PHITS, HZETRN/OLTARIS) were used to predict the particle flux and the corresponding radiation environment caused by galactic cosmic radiation on Mars. From the calculated particle spectra the dose rates on the surface are estimated. Results: Calculations of particle spectra and dose rates induced by galactic cosmic radiation on the Martian surface are presented. Although good agreement is found in many cases for the different transport codes, GEANT4, PHITS, and HZETRN/OLTARIS, some models still show large, sometimes order of magnitude discrepancies in certain particle spectra. We have found that RAD data is helping to make better choices of input parameters and physical models. Elements of these validated models can be applied to more detailed studies on how the radiation environment is influenced by solar modulation, Martian atmosphere and soil, and changes due to the Martian seasonal pressure cycle. By extending the range of the calculated particle spectra with respect to the experimental data additional information about the radiation environment is gained, and the contribution of different particle species to the dose is estimated.

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How Galactic Cosmic Ray models affect the estimation of radiation exposure in space

Cited by 19 publications

References 20 publications

GCR environmental models I: Sensitivity analysis for GCR environments

GCR environmental models I: Sensitivity analysis for GCR environments

Evaluating galactic cosmic ray environment models using RaD-X flight data

The Martian surface radiation environment – a comparison of models and MSL/RAD measurements

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