Magnetic field coils misaligments on the COMPASS-U tokamak Kripner, L.1), 2), Krbec, J.1), Zelda, J.1), Hacek, P.1), Markovic, T.1), 2), Ficker, O.1), 3), Vondracek, P.1), COMPASS team4) 1)Institute of Plasma Physics of the CAS, Za Slovankou 3, Prague, Czech Republic 2)Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic 3)Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague, Czech Republic 4) See author list of "M. Hron et. al 2021 'Overview of the COMPASS results' submitted to Nucl. Fusion" Introduction Toroidal magnetic ripple ● The finite magnetic coil winding, and assembly mialigments introduce toroidal asymmetry in magnetic field . ● The toroidal asymmetry of the tokamak magnetic field can lead to unwanted MHD instabilities and decrease plasma confinement. ● Magnetic field is calculated using Biot-Savart law with realistic winding Midplane cut of |B| of toroidal field (TF) coils. ● The effects of toroidal coils misalignments are analysed using Monte [Scott, S. D. et al., J. Plasma Phys. 100, (2020).] Carlo calculations. ● Each deviation type is explored separately. Toroidal field configuration & z y Sliding x displacement joint Distribution of current in the TF coils during the discharge Upper limb Core Midplane bolted joint Ripple with displacement Bottom bolted joint Lower limb Deviation 3 σ arrows indicates worst case Radial shift [+-0.5,+-1, scenarios (shift z) +-1.5, +-2.0] mm Vertical shift [+-0.5,+-1, (shift z) +-1.5, +-2.0] mm Normal shift [+-0.05,+-0.2, (shift x) +-0.6] mm in-plane tilt [+-0.5,+-1.0, (rotate x) +-1.5, +-2.0] mm out-of-plane tilt [+-0.05,+-0.2, (rotate y) +-0.6] mm axis tilt [+-0.5,+-1.0, (rotate z) +-1.5, +-2.0] mm 3 σ Fourier analysis 3 σ Conclusions ● Edge areas are not significantly affected by coil displacements (~3%) toroidal components of Babs ● PF inside CS coils results in the effect of toroidal ripple mainly on the high field side ● Stable n = 16 component ● R = 0.7 m ● Standard deviation plays major role in R = 1.1 m Most significant displacement: resulting error field 3 σ ○ Axis tilt, radial shift 3 σ ● Suspicious significant displacement for limbs: normal shift std (Babs) ● Presented result are in agreement with SPARC: [Scott, S. D. et al., J. Plasma Phys. 100, (2020).] Acknowledgement This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 and 2019-2020 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission and within the framework of the project COMPASS-U: Tokamak for cutting-edge fusion research (No. CZ.02.1.01/0.0/0.0/16\_019/0000768) and co-funded from European structural and investment funds..