The high beta tokamak-extended pulse magnetohydrodynamic mode control research program

Maurer, D.A.; Bialek, J.; Byrne, P.J.; Bono, Bryan De; Levesque, J.P.; Li, B. Q.; Mauel, M. E.; Navratil, G. A.; Pedersen, T. S.; Rath, N.; Shiraki, D.

doi:10.1088/0741-3335/53/7/074016

Cited by 27 publications

(27 citation statements)

References 24 publications

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“…15,17 Over 200 pickup coils measure local poloidal and radial magnetic fields $1 cm from the plasma surface. Ferritic components were installed in order to explore MHD stability properties of plasmas with a nearby ferromagnetic wall.…”

Section: Hbt-epmentioning

confidence: 99%

“…14 This paper extends previous studies by describing the effects of movable ferromagnetic material installed near the plasma surface in the High Beta Tokamak-Extended Pulse (HBT-EP) experiment. [15][16][17] With newly installed nearby ferromagnetic material, high frequency (xs w ) 1) rotating kink modes grow faster, resonant field amplification is larger, and disruptions occur at smaller imposed error fields than observed in discharges with the ferritic material withdrawn from the plasma. Despite the plasma's higher sensitivity to non-axisymmetric magnetic fields, HBT-EP's magnetic feedback system 18 remains effective at suppressing rotating kink modes.…”

Section: Introductionmentioning

confidence: 99%

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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: Hbt-epmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2015

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“…The majority of sideband harmonics are nonresonant with the plasma due to having the wrong helicity (q < 0) or due to the nonexistence of certain surfaces in the plasma equilibrium (q < 1). 6 To study the interaction of the saturated kink mode with an applied resonant perturbation field, we employ a specific applied field time history that excites clearly observable plasma response. The time history of such an applied field is shown in Fig.…”

Section: External Kink Mode Locking Responsementioning

confidence: 99%

“…Recently, the High Beta Tokamak-Extended Pulse (HBT-EP) has installed a new instrumented passive stabilizing wall, which is able to excite edge resonant magnetic perturbations and detect plasma response with high resolution and accuracy, as well as explore high-speed, multimode active control of the 3D tokamak magnetic edge. 6 Non-rigid, multimode kink behavior has been theoretically predicted 7 in tokamaks, and initial experimental evidence on National Spherical Torus Experiment (NSTX) 8 and HBT-EP 9 has been reported, as well as previous detailed study of these issues for reversed field pinch (RFP) devices. 10,11 Using this new system, we have observed that the structure of naturally occurring external kink modes is composed of independent eigenmodes with mode numbers m/n ¼ 3/1 and m/n ¼ 6/2.…”

Section: Introductionmentioning

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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“…The RWM is an ideal external kink mode whose growth rate has been slowed to a magnetic diffusion time set by the presence of a nearby conducting wall. Thus HBT-EP has a close-fitting conducting wall near the plasma boundary, which has recently been upgraded 15 . The wall is made of 20 independent segments (Fig.…”

Section: Hbt-ep Device and Magneticsmentioning

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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The high beta tokamak-extended pulse magnetohydrodynamic mode control research program

Cited by 27 publications

References 24 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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