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Albosta R, Geiger B, McKee G, Den Hartog D, Schellpfeffer J, Gallenberger T, Stewart S, Dux R. Design study of an edge current density diagnostic using new high-performance single-channel beam emission spectrometers at DIII-D. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:113546. [PMID: 36461451 DOI: 10.1063/5.0101781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 09/19/2022] [Indexed: 06/17/2023]
Abstract
A novel Motional Stark Effect spectroscopy system has been designed for application at the DIII-D tokamak. The system is optimized for studies of the poloidal and toroidal magnetic field in the plasma pedestal region with frame rates of up to 10 kHz. Light from an existing high-photon-throughput collection lens is analyzed using four single-channel f/2.8 Czerny-Turner spectrometers that use custom-made lens systems instead of mirrors. Each spectrometer has two separate outgoing legs and is operated in a positive grating order, which allows for simultaneous observations of D-alpha and D-beta spectra. Forward modeling using the code FIDASIM shows a radial resolution of the system close to 0.6 cm and sufficiently good spectral resolution when masking the high throughput light collection lens in the horizontal direction to avoid overly strong Doppler broadening of beam emission lines. Moreover, a detailed sensitivity study considering realistic levels of readout and photon noise shows that the poloidal and toroidal magnetic field strengths can be inferred with an uncertainty of less than 1%, which will allow the inference of changes of the plasma current during transient events.
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Affiliation(s)
- R Albosta
- Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - B Geiger
- Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - G McKee
- Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - D Den Hartog
- Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - J Schellpfeffer
- Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - T Gallenberger
- Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - S Stewart
- Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - R Dux
- Tokamak: Edge and Divertor Physics, Max-Planck-Institute for Plasma Physics, 85748 Garching, Germany
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Larakers JL, Curie M, Hatch DR, Hazeltine RD, Mahajan SM. Global Theory of Microtearing Modes in the Tokamak Pedestal. PHYSICAL REVIEW LETTERS 2021; 126:225001. [PMID: 34152172 DOI: 10.1103/physrevlett.126.225001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 04/20/2021] [Accepted: 05/07/2021] [Indexed: 06/13/2023]
Abstract
The pedestal of H-mode tokamaks displays strong magnetic fluctuations correlated with the evolution of the electron temperature. The microtearing mode (MTM), a temperature-gradient-driven instability that alters magnetic topology, is compatible with these observations. Here we extend the conventional theory of the MTM to include the global variation of the temperature and density profiles. The offset between the rational surface and the location of the pressure gradient maximum (μ) emerges as a crucial parameter for MTM stability. The extended theory matches observations on the Joint European Torus tokamak.
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Affiliation(s)
- J L Larakers
- Institute for Fusion Studies, University of Texas, Austin, Texas 78712, USA
| | - M Curie
- Institute for Fusion Studies, University of Texas, Austin, Texas 78712, USA
| | - D R Hatch
- Institute for Fusion Studies, University of Texas, Austin, Texas 78712, USA
| | - R D Hazeltine
- Institute for Fusion Studies, University of Texas, Austin, Texas 78712, USA
| | - S M Mahajan
- Institute for Fusion Studies, University of Texas, Austin, Texas 78712, USA
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Laggner F, Diallo A, Cavedon M, Kolemen E. Inter-ELM pedestal localized fluctuations in tokamaks: Summary of multi-machine observations. NUCLEAR MATERIALS AND ENERGY 2019. [DOI: 10.1016/j.nme.2019.02.030] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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