Active control of multiple resistive wall modes

Brunsell, Per R.; Yadikin, Dmitriy; Gregoratto, D.; Paccagnella, R.; Liu, Y Q; Bolzonella, T.; Cecconello, M.; Drake, James R.; Kuldkepp, Mattias; Manduchi, G.; Marchiori, G.; Marrelli, L.; Martin, P.; Menmuir, S.; Ortolani, S.; Rachlew, Elisabeth; Spizzo, G.; Zanca, P.

doi:10.1088/0741-3335/47/12b/s03

Cited by 29 publications

(41 citation statements)

References 18 publications

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“…• Simultaneous stabilization of several RWMs was achieved for the first time in T2R and confirmed in other devices [30,31,32].…”

Section: Rwm Interaction With External Magnetic Fieldssupporting

confidence: 60%

Physics of resistive wall modes

Igochine

2012

Nucl. Fusion

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The advanced tokamak regime is a promising candidate for steady state tokamak operation which is desirable for a fusion reactor. This regime is characterized by a high bootstrap current fraction and a flat or reversed safety factor profile, which leads to operation close to the pressure limit. At this limit, an external kink mode becomes unstable. This external kink is converted into the slowly growing Resistive Wall Mode (RWM) by the presence of a conducting wall. Reduction of the growth rate allows one to act on the mode and to stabilize it. There are two main factors which determine the stability of the RWM. The first factor comes from external magnetic perturbations (error fields, resistive wall, feedback coils, etc). This part of RWM physics is the same for tokamaks and reverse field pinch (RFP)configurations. The physics of this interaction is relatively well understood and based on classical electrodynamics. The second ingredient of RWM physics is the interaction of the mode with plasma flow and fast particles. These interactions are particularly important for tokamaks, which have higher plasma flow and stronger trapped particle effects. The influence of the fast particles will also be increasingly more important in ITER and DEMO which will have a large fraction of fusion born alpha particles. These interactions have kinetic origins which make the computations challenging since not only particles influence the mode, but also the mode acts on the particles. Correct prediction of the "plasma-RWM" interaction is an important ingredient which has to be combined with external fields influence (resistive wall, error fields and feedback) to make reliable predictions for RWM behavior in tokamaks. All these issues are reviewed in this paper.2

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“…• Simultaneous stabilization of several RWMs was achieved for the first time in T2R and confirmed in other devices [30,31,32].…”

Section: Rwm Interaction With External Magnetic Fieldssupporting

confidence: 60%

Physics of resistive wall modes

Igochine

2012

Nucl. Fusion

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“…where we adopted the notations of [23,12,24], and τ m,n is the wall diffusion time for b m,n ext , related to τ w by…”

Section: Numerical Predictionsmentioning

confidence: 99%

Error field assessment from driven rotation of stable external kinks at EXTRAP-T2R reversed field pinch

Volpe¹,

Frassinetti²,

Brunsell³

et al. 2013

Nucl. Fusion

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A new non-disruptive error field (EF) assessment technique not restricted to low density and thus low beta was demonstrated at the EXTRAP-T2R reversed field pinch. Stable and marginally stable external kink modes of toroidal mode number n=10 and n=8, respectively, were generated, and their rotation sustained, by means of rotating magnetic perturbations of the same n. Due to finite EFs, and in spite of the applied perturbations rotating uniformly and having constant amplitude, the kink modes were observed to rotate non-uniformly and be modulated in amplitude. This behavior was used to precisely infer the amplitude and approximately estimate the toroidal phase of the EF. A subsequent scan permitted to optimize the toroidal phase. The technique was tested against deliberately applied as well as intrinsic error fields of n=8 and 10. Corrections equal and opposite to the estimated error fields were applied. The efficacy of the error compensation was indicated by the increased discharge duration and more uniform mode rotation in response to a uniformly rotating perturbation. The results are in good agreement with theory, and the extension to lower n, to tearing modes and to tokamaks, including ITER, is discussed.

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“…Since a passive ideal boundary, acting as a perfect conductor during the plasma pulse of a fusion device, is not feasible, the development of successful technology for active feedback control of MHD instabilities is mandatory. Efforts to address the problem are thus currently accomplished in fusion community [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%