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Two new beta radiation fields established in the medium energy range

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  • Fundamentals of Metrology
06.10.2022

For decades, the irradiation facility for beta radiation, the Beta Secondary Standard BSS 2 developed at PTB, has been in worldwide use to irradiate dosemeters, detectors and other devices with calibrated beta sources. In this work two energy-reduced radiation fields based on the 90Sr/90Y source are described. The fields with beta mean energies around 0.5 MeV and 0.6 MeV fill the gap between 0.25 MeV of 85Kr sources and 0.8 MeV of 90Sr/90Y sources.

For decades, the irradiation facility for beta radiation, the Beta Secondary Standard BSS 2 developed at PTB, has been in worldwide use to irradiate dosemeters, detectors and other devices with calibrated beta sources. It includes three different radionuclide sources with increasing beta mean energies: 147Pm with 0.07 MeV, 85Kr with 0.25 MeV, and 90Sr/90Y with 0.8 MeV; and at PTB complemented by 106Ru/106Rh with 1.2 MeV. In this work two energy-reduced radiation fields based on the 90Sr/90Y source are generated by attenuating the source through 3 mm or 4 mm plastic (PMMA). The fields with beta mean energies around 0.5 MeV and 0.6 MeV fill the gap between 0.25 MeV of 85Kr sources and 0.8 MeV of 90Sr/90Y sources, see figure 1. All the necessary correction factors, for both primary and secondary dosimetry, were determined so that the two new radiation fields can be included into the ISO 6980 standards series which is currently under revision.

 electron spectra diagram

Figure 1: Simulated electron spectra on the central axis of the radiation beam (average over an area with a radius of 1.5 cm) at 0.07 mm tissue depth. The spectra are normalized to a source specific dose of Hp(0.07) =1 mSv.

Literature

[1]        R. Behrens: “Energy-reduced beta radiation fields from 90Sr/90Y for the BSS 2”,
JINST 15 (2020), P05015, https://doi.org/10.1088/1748-0221/15/05/P05015

[2]        R. Behrens: “Correction factors for two new reference beta radiation fields”,
Metrologia 57 (2020), 065005, https://doi.org/10.1088/1681-7575/ab8829

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Opens local program for sending emailRolf Behrens, Department 6.3, Working Group 6.34

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