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Alpha particle heating has been simulated in JET discharges by using ICRF minority heating to create up to 2.5 MJ of fast ions in the MeV energy range. Discharges with monster sawteeth have been studied with particular interest since they allow anomalous fast ion losses to be deduced without the complication of redistribution by sawteeth. In most cases the fast ion energy content is well reproduced by both a Stix model and self consistent full wave/Fokker-Planck calculations using classical slowing down times and ignoring orbit effects. However, orbit effects are shown to be important for 2 MA discharges in which the central slowing down time becomes greater than 1 sec. 3He-D fusion reaction experiments have produced 100 kW of fusion power, and a Q-value of 1%, using beryllium gettering of the torus. The reduced impurity level increases the deuterium concentration to 70% of the electron density. The reactivities with both on-axis and off-axis heating agree well with the Stix model. RF power modulation experiments with 2% 3He minority concentration show novel features in the electron temperature response which can be explained in terms of solutions of the classical Fokker Planck equation with a modulated driving term. The present experiments in stable plasmas show little or no evidence for anomalous loss of fast ions, but this is unlikely to be the case close to the beta limit, where reactors will operate. The use of ICRF to create high energy 3He ions could be extremely useful during the physics phase of the next step tokamak, both in simulating the alpha-particle losses and in measuring their wall loading effects prior to D-T operation.

Additional information

Authors: START D F H ET AL., JET Joint Undertaking, Abingdon, Oxon. (GB)
Bibliographic Reference: Report: JET-P(89)84 EN (1989) 15 pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 199011035 / Last updated on: 1994-12-01
Original language: en
Available languages: en