Error field correction strategies in preparation to MAST-U operation
Abstract
In magnetic fusion devices, unwanted non-axisymmetric magnetic field perturbations, known as error fields (EF), can have detrimental effects on plasma stability and confinement. Such EFs may originate from several sources, such as axi-symmetric coil misalignments, coil feeds, 3D structures in the wall surrounding the plasma, presence of ferromagnetic materials near the plasma surface, blanket materials in future devices. To minimize their impact on plasma performance and on the available operational space, it is important to identify the EF sources and develop EF control strategies. MAST Upgrade (MAST-U) is a spherical tokamak which will operate in the near future after a series of enhancements from the previous MAST experiment. To deliver a machine with EF amplitude low enough to allow a high quality experimental programme, systematic analysis of the intrinsic EF sources has been carried out for poloidal eld (P) and divertor (D) coils. To deliver a machine with EF amplitude low enough to allow a high quality experimental programme, systematic analysis of the intrinsic EF sources has been carried out for poloidal field (P) and divertor (D) coils, whose magnetic eld measurements were available when writing this paper. Such measurements reveal that P and D coils are 3D deformed andmore »
- Authors:
-
- Universita’ degli Studi di Padova (Italy); Consorzio RFX, Padova (Italy); Culham Science Centre, Abingdon (United Kingdom)
- Culham Science Centre, Abingdon (United Kingdom)
- Culham Science Centre, Abingdon (United Kingdom); General Atomics, San Diego, CA (United States)
- Publication Date:
- Research Org.:
- General Atomics, San Diego, CA, United States
- Sponsoring Org.:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- OSTI Identifier:
- 1658366
- Grant/Contract Number:
- SC0018992
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Fusion Engineering and Design
- Additional Journal Information:
- Journal Volume: 161; Journal ID: ISSN 0920-3796
- Publisher:
- Elsevier
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Error field control; Plasma; Model-based optimization
Citation Formats
Piron, L., Kirk, A., Liu, Y. Q., Cunningham, G., Carr, M., Gowland, R., Katramados, I., and Martin, R. Error field correction strategies in preparation to MAST-U operation. United States: N. p., 2020.
Web. doi:10.1016/j.fusengdes.2020.111932.
Piron, L., Kirk, A., Liu, Y. Q., Cunningham, G., Carr, M., Gowland, R., Katramados, I., & Martin, R. Error field correction strategies in preparation to MAST-U operation. United States. https://doi.org/10.1016/j.fusengdes.2020.111932
Piron, L., Kirk, A., Liu, Y. Q., Cunningham, G., Carr, M., Gowland, R., Katramados, I., and Martin, R. Tue .
"Error field correction strategies in preparation to MAST-U operation". United States. https://doi.org/10.1016/j.fusengdes.2020.111932. https://www.osti.gov/servlets/purl/1658366.
@article{osti_1658366,
title = {Error field correction strategies in preparation to MAST-U operation},
author = {Piron, L. and Kirk, A. and Liu, Y. Q. and Cunningham, G. and Carr, M. and Gowland, R. and Katramados, I. and Martin, R.},
abstractNote = {In magnetic fusion devices, unwanted non-axisymmetric magnetic field perturbations, known as error fields (EF), can have detrimental effects on plasma stability and confinement. Such EFs may originate from several sources, such as axi-symmetric coil misalignments, coil feeds, 3D structures in the wall surrounding the plasma, presence of ferromagnetic materials near the plasma surface, blanket materials in future devices. To minimize their impact on plasma performance and on the available operational space, it is important to identify the EF sources and develop EF control strategies. MAST Upgrade (MAST-U) is a spherical tokamak which will operate in the near future after a series of enhancements from the previous MAST experiment. To deliver a machine with EF amplitude low enough to allow a high quality experimental programme, systematic analysis of the intrinsic EF sources has been carried out for poloidal eld (P) and divertor (D) coils. To deliver a machine with EF amplitude low enough to allow a high quality experimental programme, systematic analysis of the intrinsic EF sources has been carried out for poloidal field (P) and divertor (D) coils, whose magnetic eld measurements were available when writing this paper. Such measurements reveal that P and D coils are 3D deformed and thus are responsible for intrinsic EFs, with mainly n=1 and n=2 toroidal mode numbers. In preparation to MAST-U operation, both passive and active EF control strategies have been adopted for n=1 and n=2 EFs compensation. Passive EF control consisted of installing finely each D and P coil within MAST-U device so as to minimize the intrinsic n=1 EF amplitude. The optimal coil alignment has been determined based on magnetic eld measurements and the corresponding 3D electro-magnetic modelling, and envisaged coil shift and tilt of 3.2 mm and 0.7 mrad, respectively, in the case of P coil named P4. Conversely, active control will be use during MAST-U operation to reduce the n=2 EF which is associated mainly with P4 and P5, as well. Since these coils have been re-used from the MAST device, studies attempting n=2 EF control, based on MAST plasmas, have been modelled utilizing the MARS-F code to interpret experimental results in MAST and to give hints for future n=2 EF control studies in MAST-U. Here, a model-based control set for n=2 EF control has been identified which would allow for the minimization of rotation braking, of the resonant magnetic field at the q=2 and of the plasma displacement in MAST-U, simultaneously.},
doi = {10.1016/j.fusengdes.2020.111932},
journal = {Fusion Engineering and Design},
number = ,
volume = 161,
place = {United States},
year = {Tue Aug 11 00:00:00 EDT 2020},
month = {Tue Aug 11 00:00:00 EDT 2020}
}
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