14 MeV calibration of JET neutron detectors-phase 1: Calibration and characterization of the neutron source

P Batistoni (Corresponding Author), S. Popovichev, A. Cufar, Z. Ghani, L. Giacomelli, S. Jednorog, A. Klix, S. Lilley, E. Laszynska, S. Loreti, L. Packer, A. Peacock, M. Pillon, R. Price, M. Rebai, D. Rigamonti, N. Roberts, M. Tardocchi, D. Thomas, Leena Aho-MantilaMarkus Airila, Antti Hakola, Haesik Kim, Seppo Koivuranta, Aapeli Lahtinen, Jari Likonen, Yingying Liu, Tapani Makkonen, Henrik Nordman, Antti Salmi, Paula Siren, Tuomas Tala

    Research output: Contribution to journalArticleScientificpeer-review

    13 Citations (Scopus)

    Abstract

    In view of the planned DT operations at JET, a calibration of the JET neutron monitors at 14 MeV neutron energy is needed using a 14 MeV neutron generator deployed inside the vacuum vessel by the JET remote handling system. The target accuracy of this calibration is 10% as also required by ITER, where a precise neutron yield measurement is important, e.g. for tritium accountancy. To achieve this accuracy, the 14 MeV neutron generator selected as the calibration source has been fully characterised and calibrated prior to the in-vessel calibration of the JET monitors. This paper describes the measurements performed using different types of neutron detectors, spectrometers, calibrated long counters and activation foils which allowed us to obtain the neutron emission rate and the anisotropy of the neutron generator, i.e.The neutron flux and energy spectrum dependence on emission angle, and to derive the absolute emission rate in 4π sr. The use of high resolution diamond spectrometers made it possible to resolve the complex features of the neutron energy spectra resulting from the mixed D/T beam ions reacting with the D/T nuclei present in the neutron generator target. As the neutron generator is not a stable neutron source, several monitoring detectors were attached to it by means of an ad hoc mechanical structure to continuously monitor the neutron emission rate during the in-vessel calibration. These monitoring detectors, two diamond diodes and activation foils, have been calibrated in terms of neutrons/counts within ± 5% total uncertainty. A neutron source routine has been developed, able to produce the neutron spectra resulting from all possible reactions occurring with the D/T ions in the beam impinging on the Ti D/T target. The neutron energy spectra calculated by combining the source routine with a MCNP model of the neutron generator have been validated by the measurements. These numerical tools will be key in analysing the results from the in-vessel calibration and to derive the response of the JET neutron detectors to DT plasma neutrons starting from the response to the generator neutrons, and taking into account all the calibration circumstances.

    Original languageEnglish
    Article number026012
    Number of pages24
    JournalNuclear Fusion
    Volume58
    Issue number2
    DOIs
    Publication statusPublished - 1 Feb 2018
    MoE publication typeNot Eligible

    Keywords

    • Fusion reactor
    • Neutron calibration
    • Neutron generator
    • OtaNano

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