Dynamics and control of resistive wall modes with magnetic feedback control coils: experiment and theory

Mauel, M. E.; Bialek, J.; Boozer, Allen H.; Cates, C.; James, R. W.; Katsuro-Hopkins, O.; Klein, A.; Liu, Y.; Maurer, D.A.; Maslovsky, D.; Navratil, G.A.; Pedersen, T. S.; Shilov, M.; Stillits, N.

doi:10.1088/0029-5515/45/4/010

Cited by 38 publications

(44 citation statements)

References 26 publications

(63 reference statements)

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“…29,30 As we discuss later, the influence of ferritic material when xs w > 1 is explored using naturally rotating kink modes; whereas, the influence of ferritic materials when xs w < 1 is explored by measurement of the plasma response to nonrotating, static resonant magnetic perturbations (RMPs) dominated by m=n ¼ 3=1.…”

Section: Kink Instabilities With Nearby Ferritic Materialsmentioning

confidence: 99%

Active and passive kink mode studies in a tokamak with a movable ferromagnetic walla)

et al. 2015

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High-resolution active and passive kink mode studies are conducted in a tokamak with an adjustable ferromagnetic wall near the plasma surface. Ferritic tiles made from 5.6 mm thick Hiperco V R 50 alloy have been mounted on the plasma-facing side of half of the in-vessel movable wall segments in the High Beta Tokamak-Extended Pulse device [D. A. Maurer et al., Plasma Phys. Controlled Fusion 53, 074016 (2011)] in order to explore ferritic resistive wall mode stability. Low-activation ferritic steels are a candidate for structural components of a fusion reactor, and these experiments examine MHD stability of plasmas with nearby ferromagnetic material. Plasma-wall separation for alternating ferritic and non-ferritic wall segments is adjusted between discharges without opening the vacuum vessel. Amplification of applied resonant magnetic perturbations and plasma disruptivity are observed to increase when the ferromagnetic wall is close to plasma surface instead of the standard stainless steel wall. Rapidly rotating m=n ¼ 3=1 external kink modes have higher growth rates with the nearby ferritic wall. Feedback suppression of kinks is still as effective as before the installation of ferritic material in vessel, in spite of increased mode growth rates. V C 2015 AIP Publishing LLC. [http://dx.

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Section: Kink Instabilities With Nearby Ferritic Materialsmentioning

confidence: 99%

Active and passive kink mode studies in a tokamak with a movable ferromagnetic walla)

et al. 2015

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“…18,19 Typical HBT-EP parameters for the discharges studied here are a toroidal magnetic field strength of 3.3 kG, plasma current < 20 kA, and major and minor radii of 0.92 and 0.15 m, respectively. 20 The new HBT-EP passive stabilizing wall, control and sensor coil Fig.…”

Section: Multimode External Kinkmentioning

confidence: 99%

High resolution detection and excitation of resonant magnetic perturbations in a wall-stabilized tokamak

et al. 2012

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We report high-resolution detection of the 3D plasma magnetic response of wall-stabilized tokamak discharges in the High Beta Tokamak-Extended Pulse [T. H. Ivers et al., Phys. Plasmas 3, 1926(1996] device. A new adjustable conducting wall has been installed on HBT-EP made up of 20 independent, movable, wall segments instrumented with three distinct sets of 40 modular coils that can be independently driven to generate a wide variety of magnetic perturbations. High-resolution detection of the plasma response is made with 216 poloidal and radial magnetic sensors that have been located and calibrated with high-accuracy. Static and dynamic plasma responses to resonant and non-resonant magnetic perturbations are observed through measurement of the step-response following a rapid change in the toroidal phase of the applied perturbations. Biorthogonal decomposition of the full set of magnetic sensors clearly defines the structures of naturally occurring external kinks as being composed of independent m/n ¼ 3/1 and 6/2 modes. Resonant magnetic perturbations were applied to discharges with pre-existing, saturated m/n ¼ 3/1 external kink mode activity. This m/n ¼ 3/1 kink mode was observed to lock to the applied perturbation field. During this kink mode locked period, the plasma resonant response is characterized by a linear, a saturated, and a disruptive plasma regime dependent on the magnitude of the applied field and value of the edge safety factor and plasma rotation. V C 2012 American Institute of Physics. [http://dx.

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“…This is compared with modeling of the artificial plasma experiment using the finite-element electromagnetic code VALEN 18 , in order to characterize the electromagnetic properties of the conducting wall in HBT-EP. VALEN contains a detailed 3-dimensional model of the close-fitting conducting wall in HBT-EP, and is used to simulate a variety of RWM feedback experiments carried out on the device 12,19,20 .…”

Section: Valen Modelingmentioning

confidence: 99%

In situ “artificial plasma” calibration of tokamak magnetic sensors

Shiraki

Levesque

Bialek

et al. 2013

Review of Scientific Instruments

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A unique in-situ calibration technique has been used to spatially calibrate and characterize the extensive new magnetic diagnostic set and close-fitting conducting wall of the High Beta Tokamak-Extended Pulse (HBT-EP) experiment. A new set of 216 Mirnov coils has recently been installed inside the vacuum chamber of the device for high-resolution measurements of magnetohydrodynamic phenomena including the effects of eddy currents in the nearby conducting wall. The spatial positions of these sensors are calibrated by energizing several large in-situ calibration coils in turn, and using measurements of the magnetic fields produced by the various coils to solve for each sensor's position. Since the calibration coils are built near the nominal location of the plasma current centroid, the technique is referred to as an "artificial plasma" calibration. The fitting procedure for the sensor positions is described, and results of the spatial calibration are compared with those based on metrology. The time response of the sensors are compared with the evolution of the artificial plasma current to deduce the eddy current contribution to each signal. This is compared with simulations using the VALEN electromagnetic code, and the modeled copper thickness profiles of the HBT-EP conducting wall are adjusted to better match experimental measurements of the eddy current decay. Finally, the multiple coils of the artificial plasma system are also used to directly calibrate a non-uniformly wound Fourier Rogowski coil on HBT-EP.

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Dynamics and control of resistive wall modes with magnetic feedback control coils: experiment and theory

Cited by 38 publications

References 26 publications

Active and passive kink mode studies in a tokamak with a movable ferromagnetic walla)

Active and passive kink mode studies in a tokamak with a movable ferromagnetic walla)

High resolution detection and excitation of resonant magnetic perturbations in a wall-stabilized tokamak

In situ “artificial plasma” calibration of tokamak magnetic sensors

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