Active control of multiple resistive wall modes

P.R. Brunsell, D. Yadikin, D. Gregoratto, R. Paccagnella, Y.Q. Liu, T. Bolzonella, M. Cecconello, J.R. Drake, M. Kuldkepp, G. Manduchi, G. Marchiori, L. Marrelli, P. Martin, S. Menmuir, S. Ortolani, E. Rachlew, G. Spizzo, P. Zanca

Research output: Contribution to journalArticle

23 Citations (Scopus)


A two-dimensional array of saddle coils at Mcpoloidal and Nctoroidal positions is used on the EXTRAP T2R reversed-field pinch (Brunsell P R et al 2001 Plasma Phys. Control. Fusion 43 1457) to study active control of resistive wall modes (RWMs). Spontaneous growth of several RWMs with poloidal mode number m ≤ 1 and different toroidal mode number n is observed experimentally, in agreement with linear MHD modelling. The measured plasma response to a controlled coil field and the plasma response computed using the linear circular cylinder MHD model are in quantitive agreement. Feedback control introduces a linear coupling of modes with toroidal mode numbers n, n′ that fulfil the condition |n - n′| ≤ Nc. Pairs of coupled unstable RWMs are present in feedback experiments with an array of Mc× Nc≤ 4 × 16 coils. Using intelligent shell feedback, the coupled modes are generally not controlled even though the field is suppressed at the active coils. A better suppression of coupled modes may be achieved in the case of rotating modes by using the mode control feedback scheme with individually set complex gains. In feedback with a larger array of Mc× Nc≤ 4 × 32 coils, the coupling effect largely disappears, and with this array, the main internal RWMs n ≤ -11, -10, +5, +6 are all simultaneously suppressed throughout the discharge (7-8 wall times). With feedback there is a two-fold extension of the pulse length, compared to discharges without feedback. © 2005 IOP Publishing Ltd.
Original languageEnglish
Pages (from-to)-
JournalPlasma Physics and Controlled Fusion
Issue number12 B
Publication statusPublished - 1 Dec 2005
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Nuclear Energy and Engineering
  • Condensed Matter Physics

Cite this

Brunsell, P. R., Yadikin, D., Gregoratto, D., Paccagnella, R., Liu, Y. Q., Bolzonella, T., ... Zanca, P. (2005). Active control of multiple resistive wall modes. Plasma Physics and Controlled Fusion, 47(12 B), -.