The effect of the plasma position control system on the three-dimensional distortion of the plasma boundary when magnetic perturbations are applied in MAST

Chapman, I. T.; Holgate, Joshua; Ayed, N. Ben; Cunningham, G.; Ham, Christopher; Harrison, James R.; Kirk, A.; McArdle, G.; Patel, A.; Scannell, R.

doi:10.1088/0741-3335/56/7/075004

Cited by 15 publications

(20 citation statements)

References 31 publications

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“…This depends on the relative phase between the position of the B Θ arrays and the used profile diagnostics (discussed in Ref. [22]). We can exclude this in the midplane for two reasons.…”

Section: Discussion Of the Amplitude Comparisonmentioning

confidence: 99%

“…2). A feedback controlled system solely based on measurements of one toroidal position would counteract the 3D distortion [22] and, therefore, the modulation at the position of the CXRS system would be compensated. Because of the fact that the displacement from edge CXRS also exceeds the prediction from VMEC (see Fig.…”

Section: Discussion Of the Amplitude Comparisonmentioning

confidence: 99%

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Plasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium

Willensdorfer

Denk

Strumberger

et al. 2016

Plasma Phys. Control. Fusion

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Abstract. The plasma response from an external n = 2 magnetic perturbation field in ASDEX Upgrade has been measured using mainly electron cyclotron emission (ECE) diagnostics and a rigid rotating field. To interpret ECE and ECE-imaging (ECE-I) measurements accurately, forward modeling of the radiation transport has been combined with ray tracing. The measured data is compared to synthetic ECE data generated from a 3D ideal magnetohydrodynamics (MHD) equilibrium calculated by VMEC.The measured amplitudes of the helical displacement around the low field side midplane are in reasonable agreement with the one from the synthetic VMEC diagnostics. Both exceed the prediction from the vacuum field calculations and indicate the presence of a kink response at the edge, which amplifies the perturbation. VMEC and MARS-F have been used to calculate the properties of this kink mode. The poloidal mode structure of the magnetic perturbation of this kink mode at the edge peaks at poloidal mode numbers larger than the resonant components |m| > |nq|, whereas the poloidal mode structure of its displacement is almost resonant |m| ≈ |nq|. This is expected from ideal MHD in the proximity of rational surfaces. The displacement measured by ECE-I confirms this resonant response.

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“…This depends on the relative phase between the position of the B Θ arrays and the used profile diagnostics (discussed in Ref. [22]). We can exclude this in the midplane for two reasons.…”

Section: Discussion Of the Amplitude Comparisonmentioning

confidence: 99%

Section: Discussion Of the Amplitude Comparisonmentioning

confidence: 99%

Plasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium

Willensdorfer

Denk

Strumberger

et al. 2016

Plasma Phys. Control. Fusion

Self Cite

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“…Whilst the predictions from an ideal 3D equilibrium code such as VMEC have replicated the measured displacements in MAST [24,35], the code assumes nested flux surfaces. Since the lobe structures near the lower divertor illustrated in figure 5 are consistent with field line reconnection, we have also applied a resistive MHD model to consider the boundary displacements.…”

Section: Corrugation At the Midplanementioning

confidence: 99%

“…The purpose of this figure is to illustrate that the density gradient is also toroidally varying. The effect of the radial position control when RMPs are applied is discussed in more detail in [35]. Since there is a density pedestal height drop on application of RMP, the density width is contracting to cause an increase in gradient.…”

Section: Pedestal Structurementioning

confidence: 99%

Assessing the merits of resonant magnetic perturbations with different toroidal mode numbers for controlling edge localised modes

et al. 2014

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Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publicationCitation for published version (APA): Chapman, I. T., Kirk, A., Akers, R. J., Ham, C. J., Harrison, J. R., Hawke, J. N., ... Thorton, A. J. (2014). Assessing the merits of resonant magnetic perturbations with different toroidal mode numbers for controlling edge localised modes. Nuclear Fusion, 54(12), 123003-1/15. [123003]. DOI: 10.1088/0029-5515/54/12/123003 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. AbstractAn increase in ELM frequency has been demonstrated in MAST by applying resonant magnetic perturbations (RMPs) with toroidal mode number, n RMP = 2, 3, 4, 6. It has been observed that the mitigated ELM frequency increases with the amplitude of the applied field provided it is above a critical threshold. This threshold value depends on the mode number of the RMP, with higher n RMP having a larger critical value. For the same ELM frequency, the reduction in the peak heat load on the divertor plates is approximately the same for all RMP configurations. The RMPs give rise to perturbations to the plasma shape, with lobe structures occurring due to the tangled magnetic fields near the X-point, and corrugations of the plasma boundary at the midplane. The X-point lobe length increases linearly with the applied field when above a threshold, with RMPs of higher toroidal mode number giving rise to longer lobes for the same applied resonant field. Similarly, the midplane displacements increase with the applied field strength, though the corrugation amplitude is less dependent upon the RMP configuration. For all n RMP , the RMPs ...

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“…A fast visible camera, as a kind of imaging device, can obtain the radiation images in real-time during the plasma discharge (Jia et al 2015; Yuan et al 2013; Chapman et al 2014). This paper mainly discussed how to acquire the plasma image and detect the spatial position of plasma boundary in EAST.…”

Section: Introductionmentioning

confidence: 99%

Plasma image edge detection based on the visible camera in the EAST device

Shu

Chen

et al. 2016

SpringerPlus

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The controlling of plasma shape and position are essential to the success of Tokamak discharge. A real-time image acquisition system was designed to obtain plasma radiation image during the discharge processes in the Experimental Advanced Superconducting Tokamak (EAST) device. The hardware structure and software design of this visible camera system are introduced in detail. According to the general structure of EAST and the layout of the observation window, spatial location of the discharging plasma in the image was measured. An improved Sobel edge detection algorithm using iterative threshold was proposed to detect plasma boundary. EAST discharge results show that the proposed method acquired plasma position and boundary with high accuracy, which is of great significance for better plasma control.

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The effect of the plasma position control system on the three-dimensional distortion of the plasma boundary when magnetic perturbations are applied in MAST

Abstract: The effect of the plasma position control system on the three-dimensional distortion of the plasma boundary when magnetic perturbations are applied in MAST

Cited by 15 publications

References 31 publications

Plasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium

Plasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium

Assessing the merits of resonant magnetic perturbations with different toroidal mode numbers for controlling edge localised modes

Plasma image edge detection based on the visible camera in the EAST device

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