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An analysis of sawtooth postcursor oscillations in JET is presented. From electron cyclotron emission measurements, the radial T(e)-profile on the equatorial plane is obtained with high time resolution. The plasma rotation is used to reconstruct the constant temperature contours in the poloidal plane from the T(e)-profile. The postcursor oscillation observed after a partial collapse shows a cold region with a structure very much like that of an m = 1 magnetic island, while the hot plasma core is displaced but still has concentric T(e)-contours. After a full collapse a cold region of similar structure is seen, while the hot core is displaced over a much larger distance and is squeezed into a crescent shape. Also a large amount of energy has been lost from the hot core. It is concluded that partial and full collapses are likely to be due to the same instability and that reconnection is involved in the non-linear evolution of the instability. It is suggested that the amplitude at which the instability saturates determines the type of sawtooth collapse and the amplitude of the postcursor oscillation.

Additional information

Authors: WESTERHOFF E, FOM-Instituut Voor Plasmafysica, "Rijnhuizen" Nieuwegein (The Netherlands);LOPES-CARDOZO N, FOM-Instituut Voor Plasmafysica, "Rijnhuizen" Nieuwegein (The Netherlands);SMEULDERS P, Jet Joint Undertaking, Abingdon, Oxon (GB)
Bibliographic Reference: Report: JET-P(88)73 EN (1988)
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 198910667 / Last updated on: 1994-12-01
Original language: en
Available languages: en
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