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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. Rev Sci Instrum 2022; 93:113546. [PMID: 36461451 DOI: 10.1063/5.0101781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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