Analytical solution of tokamak vibrations during axisymmetric plasma disruptions

0555331 - ÚFP 2022 RIV CH eng J - Journal Article
Ortwein, R. - Świerblewski, J. - Hromádka, Jakub - Kovařík, Karel - Havlíček, Josef - Šesták, David - Patel, Nisarg - Yanovskiy, Vadim - Pánek, Radomír
Analytical solution of tokamak vibrations during axisymmetric plasma disruptions.
Fusion Engineering and Design. Roč. 174, January (2022), č. článku 112997. ISSN 0920-3796. E-ISSN 1873-7196
R&D Projects: GA MŠMT(CZ) EF16_019/0000768
Institutional support: RVO:61389021
Keywords : Analytical * compass-u * Dynamic analysis * Net forces * Tokamak * Transient
OECD category: Fluids and plasma physics (including surface physics)
Impact factor: 1.7, year: 2022
Method of publishing: Limited access
https://www.sciencedirect.com/science/article/pii/S0920379621007729?via%3Dihub

Tokamaks are structures containing a massive supporting structure housing a vacuum vessel with hot plasma. Due to the vacuum vessel heating and temperatures up to 500 ⁰C as for the COMPASS-U, flexible connections need to be used between the main support and the vacuum vessel to accommodate the thermal expansion. Large electromagnetic forces are generated during plasma disruption events, such as Vertical Displacement Events (VDE), inside the vacuum vessel and in the coil system: Central Solenoid (CS), Poloidal Field (PF) coils and Toroidal Field (TF) coils directly attached to the support. In the present paper a parametric analytical model of tokamak vibrations due to axisymmetric plasma disruptions was presented, allowing predictions of the vacuum vessels and the main tokamak structure displacements, velocities and accelerations as well as the dynamic forces transmitted to the foundations. A tokamak was modelled as a 2 DOF dynamic system, including the mass of the main support and the vacuum vessel and the axial stiffnesses and damping values of their supports. A close-form analytical solution was found assuming proportional (Rayleigh) damping for the most general shape of the force functions – described with a series of piecewise linear functions. The electromagnetic forces during axisymmetric VDE were derived from a dedicated 3D model. Detailed solution for the most recent design of the COMPASS-U tokamak was presented, as well as a number of parametric studies checking the sensitivity to the design parameters. The conditions at which large part of the electromagnetic force is transmitted to the concrete foundations were identified. The accuracy of the derived analytical solution was verified with direct numerical integration of the equations of motion.
Permanent Link: http://hdl.handle.net/11104/0329847