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The perturbations of electron density and temperature profiles in a tokamak following a sawtooth collapse are considered. An analytical model for the interpretation of such perturbations is presented. It is shown that the perturbation can be decomposed into two contributions, which are eigenmodes of the linearised coupled diffusion equations for particles and energy. The approximations made in the analytical treatment are checked using computer simulations. Measurements of heat and density pulses in JET are used to illustrate the power of the new approach. It is shown that using the coupled equations, an improved description of the heat and density pulses is obtained. The analysis yields the four diffusion coefficients in the linearised transport matrix. The non-zero off-diagonal elements explain certain salient features of the measurements, notably a marked decrease of the local density which occurs during the maximum of the temperature pulse.

Additional information

Authors: DE HAAS J C M, General Atomics, San Diego (US);O'ROURKE J, JET Joint Undertaking, Abingdon, Oxon. (GB);SIPS A C C, FOM-Instituut voor Plasmafysica "Rijnhuizen", Nieuwegein (NL);LOPES CARDOZO N J, FOM-Instituut voor Plasmafysica "Rijnhuizen", Nieuwegein (NL)
Bibliographic Reference: Report: JET-R(90)04 EN (1990) 29 pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 199011473 / Last updated on: 1994-12-02
Original language: en
Available languages: en
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