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

• Published in: Space Weather 2016-11, Vol.14 (11), p.1011-1025
• Main Authors: Straume, T., Mertens, C. J., Lusby, T. C., Gersey, B., Tobiska, W. K., Norman, R. B., Gronoff, G. P., Hands, A.
• Format: Article
• Language: English
• Subjects: Balloon flight; Benchmarks; Calibration; Dosimeters; dosimetry; Environment; Equivalence; Evaluation; Exposure; Fission; Gamma rays; High altitude balloons; high‐altitude; Missions; NASA; Onboard; Personnel; Radiation; Sensors; Stratosphere
• ISSN: 1542-7390; 1539-4964; 1542-7390
• DOI: 10.1002/2016SW001406

Results are presented from evaluations of radiation dosimeters prior to a NASA high‐altitude balloon flight, the RaD‐X mission. Four radiation dosimeters were on board RaD‐X: a Far West Hawk (version 3), a Teledyne dosimeter (UDOS001), a Liulin dosimeter (MDU 6SA1), and a RaySure dosimeter (version 3b). The Hawk is a tissue‐equivalent proportional counter (TEPC) and the others are solid‐state Si sensors. The Hawk served as the “flight standard” and was calibrated for this mission. The Si‐based dosimeters were tested to make sure they functioned properly prior to flight but were not calibrated for the radiation environment in the stratosphere. The dosimeters were exposed to 60Co gamma rays and 252Cf fission radiation (which includes both neutrons and gamma rays) at the Lawrence Livermore National Laboratory (LLNL). The measurement results were compared with results from standard “benchmark” measurements of the same sources and source‐to‐detector distances performed contemporaneously by LLNL calibration facility personnel. For 60Co gamma rays, the dosimeter‐to‐benchmark ratios were 0.84 ± 0.06, 1.07 ± 0.32, 1.31 ± 0.07, and 0.82 ± 0.24 for the TEPC, Teledyne, Liulin, and RaySure, respectively. For 252Cf radiation, the dosimeter‐to‐benchmark ratios were 0.94 ± 0.15, 0.55 ± 0.18, 0.58 ± 0.08, and 0.33 ± 0.12 for the TEPC, Teledyne, Liulin, and RaySure. Some examples of how the results were used to help interpret the flight data are also presented. Key Points Three Si‐based dosimeters were functionally tested for the NASA RaD‐X mission using 60Co gamma ray and 252Cf fission sources Two TEPCs were calibrated, one served as the “flight standard” for comparison and the other as a backup unit Ground‐based results from all dosimeters and some initial flight results are presented and discussed