A comparison of depth dependence of dose and linear energy transfer spectra in aluminum and polyethylene.
A set of four tissue-equivalent proportional counters (TEPCs), with their detector heads at the centers of 0 (bare), 3, 7 and 9-inch-diameter aluminum spheres, were flown on Shuttle flight STS-89. Five such detectors at the centers of polyethylene spheres were flown 1 year earlier on STS-81. The results of dose-depth dependence for the two materials convincingly show the merits of using material rich in hydrogen to decrease the radiation exposure to the crew. A comparison of the calculated galactic cosmic radiation (GCR) absorbed dose and dose-equivalent rates using the radiation transport code HZETRN with nuclear fragmentation model NUCFRG2 and the measured GCR absorbed dose rates and dose-equivalent rates shows that they agree within root mean square (rms) error of 12.5 and 8.2%, respectively. However, there are significant depth-dependent differences in the linear energy transfer (LET) spectra. A comparison for trapped protons using the proton transport code BRYNTRN and the AP-8 MIN trapped-proton model shows a systematic bias, with the model underpredicting dose and dose-equivalent rates. These results show the need for improvements in the radiation transport and/or fragmentation models.
Badhwar
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NASA Johnson Space Center, 2101 NASA Road 1, Code SN3, Houston, Texas 77058-3696, USA.
Cucinotta
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D000535:Aluminum / Q000528:radiation effects*; D003359:Cosmic Radiation; D004307:Dose-Response Relationship, Radiation; D018499:Linear Energy Transfer; D008422:Materials Testing; D008962:Models, Theoretical; D020959:Polyethylene / Q000528:radiation effects*; D011522:Protons; D011835:Radiation Protection / Q000295:instrumentation* / Q000379:methods; D011874:Radiometry / Q000295:instrumentation*; D013026:Space Flight; D013997:Time Factors
D011522:Protons; D020959:Polyethylene; D000535:Aluminum