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An overview of experimental observations on fast particle behaviour in JET plasmas is presented. The material is drawn directly from the results of measurements based on nuclear detection techniques. Earliest observations concern escaping 15 MeV protons from the 3He,D reaction; they are detected in the form of spikes at the time of sawtooth crashes. Subsequent observations with a neutron multicollimator show that sawteeth expel NBI injected 80 keV deuterons from the central region of the plasma (but not necessarily out of the plasma). Extensive use is made of the detection of gamma rays created when RF-driven fast ions react with plasma fuel ions and with the main plasma impurity ions C, O and Be. Threshold reactions show that RF-driven ions can exceed energies of 7.5 MeV. Using ratios of gamma-ray intensities, tail temperatures in the MeV range are diagnosed. The energy content of these ions can exceed 1 MJ and can be as much as one third of the total energy content of the plasma. Finally, the measurement of 14 MeV neutrons emitted during the burn-up of tritons generated by the D,D reaction indicates that the single particle behaviour of 1 MeV tritons is classical within 20%, which implies similar behaviour for 3.5 MeV alpha-particles in D-T plasmas.

Additional information

Authors: SADLER G, JET Joint Undertaking, Abingdon, Oxon. (GB);JARVIS O N, JET Joint Undertaking, Abingdon, Oxon. (GB);VAN BELLE P, JET Joint Undertaking, Abingdon, Oxon. (GB);HONE M, JET Joint Undertaking, Abingdon, Oxon. (GB);CONROY S, Imperial College of Science and Technology, London (GB);ADAMS J M, Harwell Laboratory, UKAEA, Didcot, Oxon (GB)
Bibliographic Reference: Report: JET-P(89)77 EN (1989)
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
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