Ground-based evaluation of dosimeters for NASA high-altitude balloon flight

Straume, T.; Mertens, Christopher J.; Lusby, Terry C.; Gersey, Brad; Tobiska, W. Kent; Norman, Ryan B.; Gronoff, Guillaume; Hands, A.

doi:10.1002/2016sw001406

Cited by 17 publications

(44 citation statements)

References 27 publications

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“…The differences in material and detector size both support the notion that the Liulin should measure a dose lower than the TEPC in the upper atmosphere. Straume et al [] found that the Liulin may be biased high by 30%, so the calibration studies using the same instruments are consistent with the measurement results.…”

Section: Discussionsupporting

confidence: 55%

“…Table shows the RaD‐X TEPC dose rate measurement along with dose rate in tissue calculated using the three GCR models. The TEPC was shown to perform extremely well when compared to National Institute of Standards and Technology‐traceable sources during calibration as shown in Straume et al []. For both altitudes, the DLR model provided the boundary flux which came closest to modeling the TEPC dose rate.…”

Section: Comparison To Rad‐x Dose Measurementsmentioning

confidence: 93%

“…All three GCR models provide a boundary flux that underpredicts the Liulin measurements. The Liulin, however, may be biased high by 30% [ Straume et al , ]. Compared to the TEPC dose rate, the Liulin dose rate is slightly higher than expected.…”

Section: Comparison To Rad‐x Dose Measurementsmentioning

confidence: 99%

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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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Section: Discussionsupporting

confidence: 55%

Section: Comparison To Rad‐x Dose Measurementsmentioning

confidence: 93%

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

2016

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“…The activity levels for the 252 Cf source used in our simulations are 2.04 ± 0.1 ×10 6 s −1 for the neutron activity [ Kelm , ; Straume et al , ] and 9.06 ×10 6 s −1 for the gamma‐ray activity (in agreement with Fortune [] but higher than Chyzh et al []). The neutron and gamma‐ray Cf fission spectra were simulated using realistic functions, based on measurements, which follow a power law function at high energies [ Verbinski et al , ; Fortune , ; Billnert et al , ].…”

Section: Validation Of the Geant‐4 Modelsupporting

confidence: 82%

Assessment of the influence of the RaD-X balloon payload on the onboard radiation detectors

et al. 2016

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The NASA Radiation Dosimetry Experiment (RaD‐X) stratospheric balloon flight mission, launched on 25 September 2015, provided dosimetric measurements above the Pfotzer maximum. The goal of taking these measurements is to improve aviation radiation models by providing a characterization of cosmic ray primaries, which are the source of radiation exposure at aviation altitudes. The RaD‐X science payload consists of four instruments. The main science instrument is a tissue‐equivalent proportional counter (TEPC). The other instruments consisted of three solid state silicon dosimeters: Liulin, Teledyne total ionizing dose (TID) and RaySure detectors. The instruments were housed in an aluminum structure protected by a foam cover. The structure partially shielded the detectors from cosmic rays but also created secondary particles, modifying the ambient radiation environment observed by the instruments. Therefore, it is necessary to account for the influence of the payload structure on the measured doses. In this paper, we present the results of modeling the effect of the balloon payload on the radiation detector measurements using a Geant‐4 (GEometry ANd Tracking) application. Payload structure correction factors derived for the TEPC, Liulin, and TID instruments are provided as a function of altitude. Overall, the payload corrections are no more than a 7% effect on the radiation environment measurements.

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“…The explanation for this may be systematic. In pre‐flight calibrations, using a Co‐60 gamma source, the TEPC was observed to underestimate absorbed dose by approximately 16% [ Straume et al, ]. During the same experiments the ratio between a facility reference value of absorbed dose in tissue, and the value measured by RaySure in silicon, was 1.21.…”

Section: Comparison With Tepc Datamentioning

confidence: 97%

The disappearance of the pfotzer-regener maximum in dose equivalent measurements in the stratosphere

2016

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The NASA Radiation Dosimetry Experiment (RaD‐X) successfully deployed four radiation detectors on a high‐altitude balloon for a period of approximately 20 h. One of these detectors was the RaySure in‐flight monitor, which is a solid‐state instrument designed to measure ionizing dose rates to aircrew and passengers. Data from RaySure on RaD‐X show absorbed dose rates rising steadily as a function of altitude up to a peak at approximately 60,000 feet, known as the Pfotzer‐Regener maximum. Above this altitude absorbed dose rates level off before showing a small decline as the RaD‐X balloon approaches its maximum altitude of around 125,000 feet. The picture for biological dose equivalent, however, is very different. At high altitudes the fraction of dose from highly ionizing particles increases significantly. Dose from these particles causes a disproportionate amount of biological damage compared to dose from more lightly ionizing particles, and this is reflected in the quality factors used to calculate the dose equivalent quantity. By calculating dose equivalent from RaySure data, using coefficients derived from previous calibrations, we show that there is no peak in the dose equivalent rate at the Pfotzer‐Regener maximum. Instead, the dose equivalent rate keeps increasing with altitude as the influence of dose from primary cosmic rays becomes increasingly important. This result has implications for high altitude aviation, space tourism and, due to its thinner atmosphere, the surface radiation environment on Mars.

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Ground-based evaluation of dosimeters for NASA high-altitude balloon flight

Cited by 17 publications

References 27 publications

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

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

Assessment of the influence of the RaD-X balloon payload on the onboard radiation detectors

The disappearance of the pfotzer-regener maximum in dose equivalent measurements in the stratosphere

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