The phase-space dependence of fast-ion interaction with tearing modes

W. W. Heidbrink; L. Bardoczi; C. S. Collins; G. J. Kramer; R. J. La Haye; D. J. Lin; C. M. Muscatello; M. Podestà; L. Stagner; M. A. Van Zeeland; Y. B. Zhu

doi:10.1088/1741-4326/aab7b6

The phase-space dependence of fast-ion interaction with tearing modes

W. W. Heidbrink, L. Bardoczi, C. S. Collins, G. J. Kramer, R. J. La Haye, D. J. Lin, C. M. Muscatello, M. Podestà, L. Stagner, M. A. Van Zeeland, Y. B. Zhu

Research output: Contribution to journal › Article › peer-review

28 Scopus citations

Abstract

Modulation of various neutral beam sources probes the interaction of fast ions with tearing modes (TM) in the DIII-D tokamak. As measured by electron cyclotron emission, the (m, n) = (2, 1) tearing modes have an island width of ∼8 cm and change phase 180° at the q = 2 surface. (Here, m is the poloidal mode number and n is the toroidal mode number.) Deuterium neutral beam injection by six sources with differing injection geometries produces the fast ions. To study the interaction in different parts of phase space, on successive discharges, one of the six sources is modulated at 20 Hz to populate different fast-ion orbits. The modulation only changes the island width by a few millimeters, implying that any fast-ion effect on mode stability is below detection limits. When compared to the expected signals in the absence of TM-induced transport, both the average and modulated neutron signals deviate, implying that fast-ion transport occurs in much of phase space. Fast-ion D_α (FIDA) measurements detect reductions in signal at wavelengths that are sensitive to counter-passing ions. Neutral particle analyzer data imply poor confinement of trapped fast ions. Calculations of the expected fast-ion transport that use measured TM properties successfully reproduce the data.

Original language	English
Article number	082027
Journal	Nuclear Fusion
Volume	58
Issue number	8
DOIs	https://doi.org/10.1088/1741-4326/aab7b6
State	Published - Jul 3 2018
Externally published	Yes

Funding

We thank the entire DIII-D team for their support and Eric Fredrickson for helpful suggestions. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Award DE-FC02-04ER54698. DIII-D data shown in this paper can be obtained in digital format by following the links at https://fusion.gat.com/global/D3D_DMP.

Funders	Funder number
DOE Office of Science
U.S. Department of Energy
Office of Science	DE-FC02-04ER54698
Fusion Energy Sciences

Keywords

FIDA
fast ions
tearing modes

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1088/1741-4326/aab7b6

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title = "The phase-space dependence of fast-ion interaction with tearing modes",

abstract = "Modulation of various neutral beam sources probes the interaction of fast ions with tearing modes (TM) in the DIII-D tokamak. As measured by electron cyclotron emission, the (m, n) = (2, 1) tearing modes have an island width of ∼8 cm and change phase 180° at the q = 2 surface. (Here, m is the poloidal mode number and n is the toroidal mode number.) Deuterium neutral beam injection by six sources with differing injection geometries produces the fast ions. To study the interaction in different parts of phase space, on successive discharges, one of the six sources is modulated at 20 Hz to populate different fast-ion orbits. The modulation only changes the island width by a few millimeters, implying that any fast-ion effect on mode stability is below detection limits. When compared to the expected signals in the absence of TM-induced transport, both the average and modulated neutron signals deviate, implying that fast-ion transport occurs in much of phase space. Fast-ion Dα (FIDA) measurements detect reductions in signal at wavelengths that are sensitive to counter-passing ions. Neutral particle analyzer data imply poor confinement of trapped fast ions. Calculations of the expected fast-ion transport that use measured TM properties successfully reproduce the data.",

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AU - Bardoczi, L.

AU - Collins, C. S.

AU - Kramer, G. J.

AU - La Haye, R. J.

AU - Lin, D. J.

AU - Muscatello, C. M.

AU - Podestà, M.

AU - Stagner, L.

AU - Van Zeeland, M. A.

AU - Zhu, Y. B.

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N2 - Modulation of various neutral beam sources probes the interaction of fast ions with tearing modes (TM) in the DIII-D tokamak. As measured by electron cyclotron emission, the (m, n) = (2, 1) tearing modes have an island width of ∼8 cm and change phase 180° at the q = 2 surface. (Here, m is the poloidal mode number and n is the toroidal mode number.) Deuterium neutral beam injection by six sources with differing injection geometries produces the fast ions. To study the interaction in different parts of phase space, on successive discharges, one of the six sources is modulated at 20 Hz to populate different fast-ion orbits. The modulation only changes the island width by a few millimeters, implying that any fast-ion effect on mode stability is below detection limits. When compared to the expected signals in the absence of TM-induced transport, both the average and modulated neutron signals deviate, implying that fast-ion transport occurs in much of phase space. Fast-ion Dα (FIDA) measurements detect reductions in signal at wavelengths that are sensitive to counter-passing ions. Neutral particle analyzer data imply poor confinement of trapped fast ions. Calculations of the expected fast-ion transport that use measured TM properties successfully reproduce the data.

AB - Modulation of various neutral beam sources probes the interaction of fast ions with tearing modes (TM) in the DIII-D tokamak. As measured by electron cyclotron emission, the (m, n) = (2, 1) tearing modes have an island width of ∼8 cm and change phase 180° at the q = 2 surface. (Here, m is the poloidal mode number and n is the toroidal mode number.) Deuterium neutral beam injection by six sources with differing injection geometries produces the fast ions. To study the interaction in different parts of phase space, on successive discharges, one of the six sources is modulated at 20 Hz to populate different fast-ion orbits. The modulation only changes the island width by a few millimeters, implying that any fast-ion effect on mode stability is below detection limits. When compared to the expected signals in the absence of TM-induced transport, both the average and modulated neutron signals deviate, implying that fast-ion transport occurs in much of phase space. Fast-ion Dα (FIDA) measurements detect reductions in signal at wavelengths that are sensitive to counter-passing ions. Neutral particle analyzer data imply poor confinement of trapped fast ions. Calculations of the expected fast-ion transport that use measured TM properties successfully reproduce the data.

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The phase-space dependence of fast-ion interaction with tearing modes

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Keywords

UN SDGs

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