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Related Experiment Videos

Air activation by an electron synchrotron

T Kosako, T Nakamura

    Health Physics
    |July 1, 1982
    PubMed
    Summary

    This study measured nitrogen-13 (13N) and oxygen-15 (15O) activation in an electron synchrotron room. Photoneutron production calculations revealed that backscattered photons, not forward bremsstrahlung, dominate the spectrum, impacting activation estimations.

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    Area of Science:

    • Nuclear Physics
    • Radiation Physics
    • Accelerator Physics

    Background:

    • Electron synchrotrons generate high-energy photons, leading to activation of surrounding air.
    • Accurate estimation of induced radioactivity is crucial for radiation safety and environmental monitoring around accelerators.

    Purpose of the Study:

    • To estimate the activation of nitrogen-13 (13N) and oxygen-15 (15O) in the air of an electron synchrotron room.
    • To evaluate the accuracy of model calculations for photoneutron production and compare them with experimental measurements.
    • To investigate the photon emission spectrum characteristics relevant to activation at electron accelerators.

    Main Methods:

    • Experimental measurement of 13N and 15O induced activity using an NaI(Tl) scintillator.
    • Monte Carlo code (EGS) simulation to calculate photon flux and distribution for electromagnetic cascade showers.
    • Multiplication of photon distributions by (gamma, n) photoneutron reaction cross sections to determine 13N and 15O production.

    Main Results:

    • Total induced activity of 13N and 15O measured at 119.7 and 47.0 muCi, respectively, after synchrotron operation.
    • Model calculations underestimated photoneutron generation by approximately 20%.
    • Analysis indicated that photons are primarily emitted via backscattering, resulting in a softer spectrum than thin-target bremsstrahlung, especially for bulk structures or grazing incidence.

    Conclusions:

    • The conventional method of estimating photon spectra using forward bremsstrahlung is inaccurate for bulk targets or grazing incidence.
    • Backscattered photons significantly influence the photoneutron production and air activation in electron accelerator environments.
    • Accurate modeling of photon emission, considering backscattering, is essential for reliable radiation safety assessments at electron accelerators.

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