Reconstructing Solar Particle Event Spectra from Absorbed Dose Measurements

Journal Article · Sat Jul 01 04:00:00 EDT 2017 · Transactions of the American Nuclear Society

OSTI ID:23050282

Bahadori, Amir A.; Roberts, Jeremy A. ^[1]; Kroupa, Martin ^[2]; Fry, Dan J. ^[3]

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1. Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States)
2. Leidos, Houston, TX 77058 (United States)
3. Space Radiation Analysis Group, NASA Johnson Space Center, Houston, TX 77058 (United States)

The space radiation environment is unlike anything encountered on Earth. It is dominated by heavy charged particles consisting of highly charged nuclei with atomic numbers ranging from 1 to 94 with a broad spectrum of kinetic energies. The three primary sources of radiation in space are trapped belts, galactic cosmic rays (GCRs), and solar particle events (SPEs). The trapped belts are only of concern near bodies with significant magnetic fields and GCR flux spectra are relatively well-predicted using models that account for solar modulation of the local interstellar spectrum. SPEs, which consist primarily of protons, are difficult to predict in terms of occurrence, duration, intensity, and energy spectrum. SPE intensity and energy spectrum are critical for understanding radiation exposure-related health effects for astronauts in space. The National Aeronautics and Space Administration (NASA) relies on data from the Geostationary Operational Environmental Satellite series to characterize intensities and energy spectra of SPEs near Earth. However, these data are not applicable for spacecraft in other regions of the solar system. To understand the radiation environment for astronauts embarking on travel beyond Earth orbit, NASA is developing the Hybrid Electronic Radiation Assessor (HERA), a distributed dosimetry system that employs a solid-state silicon sensor coupled with the Timepix readout chip. The pixelated nature of the detector permits detailed analyses of charged particle tracks which can then be used to characterize the fluence spectrum at the location of the detector. Despite the unprecedented level of detail regarding the radiation environment provided by these detectors, knowledge of the fluence spectrum at all locations within the vehicle, specifically inside of astronauts, is desired to fully characterize the associated risk of harmful health effects. Radiation transport of the external radiation environment, considering the shielding provided by the vehicle, other objects, and even astronauts, is performed to obtain this information. Thus, there is clearly a need to define the external radiation environment using measurements performed within the vehicle. The number of detectors that may be flown as a part of HERA is limited by logistics, including data, power, and mass restrictions. The current configuration for crewed flight consists of six detectors at various locations with in the Orion Multi-Purpose Crew Vehicle (MPCV). It follows that an external proton fluence spectrum can be characterized with at most six energy bins with traditional matrix inversion techniques. The purpose of the present study is to determine whether it is possible to reconstruct SPE spectra with greater resolution from absorbed dose measurements and knowledge of the response of individual detectors using linear programming.

• OSTI ID: 23050282
• Journal Information: Transactions of the American Nuclear Society, Journal Name: Transactions of the American Nuclear Society Vol. 116; ISSN 0003-018X
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
61 RADIATION PROTECTION AND DOSIMETRY
ABSORBED RADIATION DOSES
ASTRONAUTS
CHARGED PARTICLES
COSMIC RADIATION
DOSIMETRY
ENERGY SPECTRA
KINETIC ENERGY
MAGNETIC FIELDS
MODULATION
NASA
PARTICLE TRACKS
PROTONS
RADIATION HAZARDS
RADIATION TRANSPORT
READOUT SYSTEMS
SILICON
SOLAR PARTICLES
SOLAR SYSTEM
SPACE
SPACE VEHICLES