Rotation Braking and Error Field Correction of the Test Blanket Module Induced Magnetic Field Error in ITER

H. Reimerdes, J.M. Hanson, Y. In, M. Okabayashi, N. Oyama, J.-K. Park, Antti Salmi, M.J. Schaffer, J.A. Snipes, W.M. Solomon, E.J. Strait, Tuomas Tala

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Abstract

Experiments on DIII-D confirm that the tritium breeding test blanket modules (TBMs) in ITER will lead to a decrease of the plasma rotation in H-modes [M.J. Schaffer, et al., Nucl. Fusion 51 (2011) 103028]. Moreover, they suggest that long-wavelength correction fields applied with non-axisymmetric saddle coils will only be able to ameliorate a fraction of such a rotation reduction. The new finding obtained in rotating H-modes with parameters similar to the ITER baseline scenario contrasts previous experiments, which showed that saddle coils are very effective in restoring resilience to locked modes in L-mode plasmas. The experiments use a TBM mock-up coil that has been especially designed to simulate the error field induced by the ferromagnetic steel of a pair of TBMs in one ITER port. The n = 1 error field correction (EFC) is applied with a set of non-axisymmetric saddle coils (I-coil), whose currents are optimized in the presence of the TBM mock-up field using a newly developed non-disruptive technique that maximizes the angular momentum. However, a test of the effectiveness of the TBM EFC yields that the optimized EFC can only recover approximately a quarter of the ~20% rotation decrease attributed to the TBM error field. An alternative criterion to evaluate EFC has been its effectiveness in canceling the n = 1 plasma response to the field error. Plasma response measurements in the TBM experiment show that the I-coil can indeed cancel the magnetic measurements of the n = 1 plasma response to the TBM mock-up field. The required currents agree within the uncertainties of the estimates with the currents that maximize the angular momentum. The contrast between the limited effectiveness of n = 1 EFC in rotating H-modes and their ability to recover a low locking density in L-mode plasmas shows that the components of the non-axisymmetric field that brake the plasma at higher values of beta or higher rotation differ from the components that are responsible for the field penetration in low density L-modes.
Original languageEnglish
Title of host publicationProgramme, Abstracts, Presentations & Proceedings
Subtitle of host publication24th IAEA Fusion Energy Conference, October 8-13, 2012, San Diego, USA
PublisherInternational Atomic Energy Agency IAEA
Number of pages8
Publication statusPublished - 2012
MoE publication typeA4 Article in a conference publication
Event24th IAEA Fusion Energy Conference - San Diego, United States
Duration: 8 Oct 201213 Oct 2012
http://www-naweb.iaea.org/napc/physics/FEC/FEC2012/html/proceedings.pdf (Full proceedings)

Conference

Conference24th IAEA Fusion Energy Conference
CountryUnited States
CitySan Diego
Period8/10/1213/10/12
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Reimerdes, H., Hanson, J. M., In, Y., Okabayashi, M., Oyama, N., Park, J-K., Salmi, A., Schaffer, M. J., Snipes, J. A., Solomon, W. M., Strait, E. J., & Tala, T. (2012). Rotation Braking and Error Field Correction of the Test Blanket Module Induced Magnetic Field Error in ITER. In Programme, Abstracts, Presentations & Proceedings: 24th IAEA Fusion Energy Conference, October 8-13, 2012, San Diego, USA [EX/P4-09] International Atomic Energy Agency IAEA. http://www-naweb.iaea.org/napc/physics/FEC/FEC2012/papers/339_EXP409.pdf