Experimental imaging of separatrix splitting on DIII-D

M. W. Shafer; E. A. Unterberg; D. M. Orlov; T. E. Evans; J. H. Harris; D. L. Hillis; R. Maingi; R. A. Moyer; R. Nazikian; A. Wingen

doi:10.1088/0029-5515/52/12/122001

Experimental imaging of separatrix splitting on DIII-D

M. W. Shafer, E. A. Unterberg, D. M. Orlov, T. E. Evans, J. H. Harris, D. L. Hillis, R. Maingi, R. A. Moyer, R. Nazikian, A. Wingen

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Abstract

Perturbations in the plasma boundary due to the application of non-axisymmetric n = 3 fields (δB/B ∼ 10^-4-10^-3) were measured in the X-point region in DIII-D by tangential imaging of extreme ultra-violet and soft x-ray emission. Vacuum-field calculations show that these perturbations take the form of lobes extending outwards from the unperturbed separatrix. These structures can be resolved in experiment by performing a differential measurement of the image for different toroidal phases of the applied perturbation. Forward modelling of the line-integrated image with a synthetic diagnostic is used to directly compare the measurement with vacuum-field calculations. Results indicate the existence of these lobes match well with the measured data. These lobes are observed to shift poloidally on the high-field side of the magnetic axis as the edge magnetic safety factor is varied, consistent with vacuum-field calculations.

Original language	English
Article number	122001
Journal	Nuclear Fusion
Volume	52
Issue number	12
DOIs	https://doi.org/10.1088/0029-5515/52/12/122001
State	Published - Dec 2012

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title = "Experimental imaging of separatrix splitting on DIII-D",

abstract = "Perturbations in the plasma boundary due to the application of non-axisymmetric n = 3 fields (δB/B ∼ 10-4-10-3) were measured in the X-point region in DIII-D by tangential imaging of extreme ultra-violet and soft x-ray emission. Vacuum-field calculations show that these perturbations take the form of lobes extending outwards from the unperturbed separatrix. These structures can be resolved in experiment by performing a differential measurement of the image for different toroidal phases of the applied perturbation. Forward modelling of the line-integrated image with a synthetic diagnostic is used to directly compare the measurement with vacuum-field calculations. Results indicate the existence of these lobes match well with the measured data. These lobes are observed to shift poloidally on the high-field side of the magnetic axis as the edge magnetic safety factor is varied, consistent with vacuum-field calculations.",

author = "Shafer, {M. W.} and Unterberg, {E. A.} and Orlov, {D. M.} and Evans, {T. E.} and Harris, {J. H.} and Hillis, {D. L.} and R. Maingi and Moyer, {R. A.} and R. Nazikian and A. Wingen",

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doi = "10.1088/0029-5515/52/12/122001",

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T1 - Experimental imaging of separatrix splitting on DIII-D

AU - Shafer, M. W.

AU - Unterberg, E. A.

AU - Orlov, D. M.

AU - Evans, T. E.

AU - Harris, J. H.

AU - Hillis, D. L.

AU - Maingi, R.

AU - Moyer, R. A.

AU - Nazikian, R.

AU - Wingen, A.

PY - 2012/12

Y1 - 2012/12

N2 - Perturbations in the plasma boundary due to the application of non-axisymmetric n = 3 fields (δB/B ∼ 10-4-10-3) were measured in the X-point region in DIII-D by tangential imaging of extreme ultra-violet and soft x-ray emission. Vacuum-field calculations show that these perturbations take the form of lobes extending outwards from the unperturbed separatrix. These structures can be resolved in experiment by performing a differential measurement of the image for different toroidal phases of the applied perturbation. Forward modelling of the line-integrated image with a synthetic diagnostic is used to directly compare the measurement with vacuum-field calculations. Results indicate the existence of these lobes match well with the measured data. These lobes are observed to shift poloidally on the high-field side of the magnetic axis as the edge magnetic safety factor is varied, consistent with vacuum-field calculations.

AB - Perturbations in the plasma boundary due to the application of non-axisymmetric n = 3 fields (δB/B ∼ 10-4-10-3) were measured in the X-point region in DIII-D by tangential imaging of extreme ultra-violet and soft x-ray emission. Vacuum-field calculations show that these perturbations take the form of lobes extending outwards from the unperturbed separatrix. These structures can be resolved in experiment by performing a differential measurement of the image for different toroidal phases of the applied perturbation. Forward modelling of the line-integrated image with a synthetic diagnostic is used to directly compare the measurement with vacuum-field calculations. Results indicate the existence of these lobes match well with the measured data. These lobes are observed to shift poloidally on the high-field side of the magnetic axis as the edge magnetic safety factor is varied, consistent with vacuum-field calculations.

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VL - 52

JO - Nuclear Fusion

JF - Nuclear Fusion

IS - 12

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ER -

Experimental imaging of separatrix splitting on DIII-D

Abstract

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