Effect of a deuterium gas puff on the edge plasma in NSTX

Zweben, S. J.; Stotler, D.P.; Bell, R. E.; Davis, W. M.; Kaye, S. M.; LeBlanc, B.; Maqueda, R. J.; Meier, Eric; Munsat, T.; Ren, Y.; Sabbagh, S. A.; Sechrest, Y.; Smith, D. R.; Soukhanovskii, V.

doi:10.1088/0741-3335/56/9/095010

Cited by 24 publications

(27 citation statements)

References 60 publications

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“…92,93 On the NSTX spherical tokamak in the US, a single GPI sightline views a gas puff manifold located just above the outer midplane through a re-entrant window port. 12,13,44,[52][53][54]58,78,80,94 This sightline has a wide angle field of view covering ∼30 cm in the poloidal direction and ∼24 cm in the radial direction.…”

Section: E Special Features Of Various Gpi Systemsmentioning

confidence: 99%

“…Since most fusion experiments use deuterium as the main fueling gas, deuterium puffing is sometimes preferable to keep the radiation losses low and can usually be done without significantly increasing the average plasma density, for example, in NSTX. 58 Helium GPI can be used to provide a greater signalto-background contrast ratio, especially where the background Balmer-α light level is high, e.g., at high plasma density or near sources of edge recycling (e.g., in Alcator C-Mod or RFXMod). Helium may also produce a more localized GPI gas puff since a deuterium puff can create high energy neutrals through molecular dissociation and charge exchange.…”

Section: Choice Of Gpi Gas and Spectral Linementioning

confidence: 99%

“…The actual gas influx rate and its density in the plasma will depend on the chosen manifold pressure and the temperature of the neutrals in the plasma. For example, at the relatively high peak gas puff rate of ∼6.6 × 10 21 deuterium atoms/s in NSTX, 58 the estimated maximum neutral atom density in the GPI cloud is n o ∼ 5 × 10 12 cm 3 (see Sec. V D), which is ∼10 times higher than the local background neutral density as calculated with DEGAS 2.…”

Section: A Gas Puffmentioning

confidence: 99%

“…For example, NSTX has used a line of thirty ∼1 mm diameter holes spaced 1 cm apart on a ∼1 cm diameter tube aligned poloidally near the outer midplane. 13,58 TEXTOR has used a nozzle of 100 holes of 0.5 mm diameter and 15 mm length drilled into a 2 cm × 6 cm rectangular matrix. 46 Alcator C-Mod has used a 1 mm diameter capillary tube to bring the GPI gas to a four-hole nozzle near the outer midplane, and single-hole nozzles at the inner wall and outer divertor target.…”

Section: A Gas Puffmentioning

confidence: 99%

See 3 more Smart Citations

Invited Review Article: Gas puff imaging diagnostics of edge plasma turbulence in magnetic fusion devices

Zweben

Terry

Stotler

et al. 2017

Review of Scientific Instruments

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Gas puff imaging (GPI) is a diagnostic of plasma turbulence which uses a puff of neutral gas at the plasma edge to increase the local visible light emission for improved space-time resolution of plasma fluctuations. This paper reviews gas puff imaging diagnostics of edge plasma turbulence in magnetic fusion research, with a focus on the instrumentation, diagnostic cross-checks, and interpretation issues. The gas puff imaging hardware, optics, and detectors are described for about 10 GPI systems implemented over the past ∼15 years. Comparison of GPI results with other edge turbulence diagnostic results is described, and many common features are observed. Several issues in the interpretation of GPI measurements are discussed, and potential improvements in hardware and modeling are suggested.

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Section: E Special Features Of Various Gpi Systemsmentioning

confidence: 99%

Section: Choice Of Gpi Gas and Spectral Linementioning

confidence: 99%

Section: A Gas Puffmentioning

confidence: 99%

Section: A Gas Puffmentioning

confidence: 99%

See 2 more Smart Citations

Invited Review Article: Gas puff imaging diagnostics of edge plasma turbulence in magnetic fusion devices

Zweben

Terry

Stotler

et al. 2017

Review of Scientific Instruments

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“…The GPI diagnostic technique has been used in a number of different studies, including blob dynamics, [18][19][20] zonal flows and geodesicacoustic modes, [21][22][23] coherent electrostatic modes, 24 and code validation. 25 This paper uses data from Alcator C-Mod only. On CMod, there are two GPI systems that view the same volume emission from the same gas puff.…”

Section: Introductionmentioning

confidence: 99%

Comparison of velocimetry techniques for turbulent structures in gas-puff imaging data

Sierchio

Cziegler²,

Terry

et al. 2016

Review of Scientific Instruments

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Recent analysis of Gas Puff Imaging (GPI) data from Alcator C-Mod found blob velocities with a modified tracking time delay estimation (TDE). These results disagree with velocity analysis performed using direct Fourier methods. In this paper, the two analysis methods are compared. The implementations of these methods are explained, and direct comparisons using the same GPI data sets are presented to highlight the discrepancies in measured velocities. In order to understand the discrepancies, we present a code that generates synthetic sequences of images that mimic features of the experimental GPI images, with user-specified input values for structure (blob) size and velocity. This allows quantitative comparison of the TDE and Fourier analysis methods, which reveals their strengths and weaknesses. We found that the methods agree for structures of any size as long as all structures move at the same velocity and disagree when there is significant nonlinear dispersion or when structures appear to move in opposite directions. Direct Fourier methods used to extract poloidal velocities give incorrect results when there is a significant radial velocity component and are subject to the barber pole effect. Tracking TDE techniques give incorrect velocity measurements when there are features moving at significantly different speeds or in different directions within the same field of view. Finally, we discuss the limitations and appropriate use of each of methods and applications to the relationship between blob size and velocity. C 2016 AIP Publishing LLC. [http://dx

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Control and data acquisition upgrades for NSTX-U

Davis

Tchilinguirian

Carroll

et al. 2016

Fusion Engineering and Design

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The extensive NSTX Upgrade (NSTX-U) Project includes major components which allow a doubling of the toroidal field strength to 1 T, of the Neutral Beam heating power to 12 MW, and the plasma current to 2 MA, and substantial structural enhancements to withstand the increased electromagnetic loads. The maximum pulse length will go from 1.5 to 5 seconds. The larger and more complex forces on the coils will be protected by a Digital Coil Protection System, which requires demanding real-time data input rates, calculations and responses. The amount of conventional digitized data for a given pulse is expected to increase from 2.5 to 5 GB per second of pulse. 2-D Fast Camera data is expected to go from 2.5 GB/pulse to 10, and another 2 GB/pulse is expected from new IR cameras. Our network capacity will be increased by a factor of 10, with 10 Gb/s fibers used for the major trunks. 32-core Linux systems will be used for several functions, including between-shot data processing, MDSplus data serving, between-shot EFIT analysis, real-time processing, and for a new capability, between-shot TRANSP. Improvements to the MDSplus events subsystem will be made through the use of both UDP and TCP/IP based methods and the addition of a dedicated "event server".

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Effect of a deuterium gas puff on the edge plasma in NSTX

Cited by 24 publications

References 60 publications

Invited Review Article: Gas puff imaging diagnostics of edge plasma turbulence in magnetic fusion devices

Invited Review Article: Gas puff imaging diagnostics of edge plasma turbulence in magnetic fusion devices

Comparison of velocimetry techniques for turbulent structures in gas-puff imaging data

Control and data acquisition upgrades for NSTX-U

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