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MHD nestability plazmatu pozorované ve výbojích tokamaku COMPASS
Kripner, Lukáš ; Němeček, Zdeněk (advisor) ; Havlíček, Josef (referee)
Compass tokamak (R = 0.56 m, a = (0.23 × 0.38) m, Ip = 200 − 400 kA, BT = 1.2 − 2.1 T and pulse length up to 1 s) is the smallest device with ITER-relevant plasma geometry with scale 1:10 to the ITER size. A tokamak plasma confinement is strongly limited by an occurrence of magnetohydrodynamic (MHD) instabilities occurring during the discharge. In the thesis, theoretical considerations and a typical behaviour of the tokamak plasma MHD instabilites are summarized based on the lite- rature overview. This discussion is complemented with an overview of the Compass diagnostics and different data analysis techniques. Finally, the examples of the Compass plasma behaviour influenced by sawtooth instability and tearing modes are shown and discussed. 1
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MHD nestability plazmatu pozorované ve výbojích tokamaku COMPASS
Kripner, Lukáš ; Němeček, Zdeněk (advisor) ; Havlíček, Josef (referee)
Compass tokamak (R = 0.56 m, a = (0.23 × 0.38) m, Ip = 200 − 400 kA, BT = 1.2 − 2.1 T and pulse length up to 1 s) is the smallest device with ITER-relevant plasma geometry with scale 1:10 to the ITER size. A tokamak plasma confinement is strongly limited by an occurrence of magnetohydrodynamic (MHD) instabilities occurring during the discharge. In the thesis, theoretical considerations and a typical behaviour of the tokamak plasma MHD instabilites are summarized based on the lite- rature overview. This discussion is complemented with an overview of the Compass diagnostics and different data analysis techniques. Finally, the examples of the Compass plasma behaviour influenced by sawtooth instability and tearing modes are shown and discussed. 1
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Observation of Sawtooth Oscillations in the COMPASS Tokamak
Imríšek, Martin ; Havlíček, Josef ; Weinzettl, Vladimír ; Mlynář, Jan
The sawtooth instability in tokamak plasmas results in periodic relaxations of the core plasma density and temperature. The physics of sawtooth is still not fully understood. It is predicted that fusion-born alpha particles will lead to long sawteeth. However, longer sawteeth can seed other instabilities which cause further degradation of plasma confinement. This paper provides brief introduction into sawtooth physics and observations of sawtooth instability in COMPASS. Furthermore, evidence of triggering transition to high confinement regime by sawtooth crash is presented
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