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Global Power Balance in Non-Stationary Discharge Phases in the COMPASS Tokamak
Havlíček, Josef ; Imríšek, Martin ; Kovařík, Karel ; Weinzettl, Vladimír
The global power balance between different input power and sink/loss channels is important for understanding of tokamak physics, particularly for various scaling laws. The power balance is measured easily during stationary discharge phases because the terms for both magnetic field energy and plasma thermal energy build-up can be neglected. However, many important events in tokamak plasmas occur during non-stationary phases of the discharge. This article describes, quantifies and discusses the terms of the global power balance, including time dependent parts, and exemplifies them on the typical ohmic discharge of the COMPASS tokamak.
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Design and Preliminary Results of the COMPASS Power Supplies Filters
Havlíček, Josef ; Zajac, Jaromír
The COMPASS tokamak uses rectifying thyristor converters as Power Supplies for the major slow coils circuits. 24-pulse thyristor converter is used for Toroidal Field circuit and 12-pulse converters are used for Magnetizing, Equilibrium and Shaping Field circuits. A noise generated by the switching of the converters negatively influences diagnostics measuring the plasma. The article describes design phase and some preliminary results of the filters for the Power Supplies
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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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Charakterizace magnetických polí v tokamaku COMPASS
Havlíček, Josef ; Hronová-Bilyková, Olena
The principle of tokamak is based on the interaction of magnetic fields with the tokamak plasma. The magnetic fields generated by poloidal field coils of the COMPASS tokamak were examined. The stray magnetic field in the vicinity of the tokamak was computed. It was found out that the magnitude of this field is acceptable for operation of the Neutral Beam Injection ion source. The graphs describing magnetic field in the vacuum vessel originating from different poloidal field coils circuits are presented.
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Rekonstrukce magnetické rovnováhy v tokamaku
Havlíček, Josef ; Urban, Jakub
Equilibrium reconstruction determines the plasma shape, the current profile and pressure profile parameters in tokamaks. It is based on solving Grad-Shafranov equation describing MHD equilibrium in axially symmetric devices. This paper reports on the principles of the EFIT code and on the parallelization of the EFIT2006 code.
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