Observation of density fluctuations from the infrared bremsstrahlung emission on TFTR

Grek, B.; Bartolick, J.; Johnson, D.

doi:10.1063/1.1143638

Cited by 7 publications

(5 citation statements)

References 3 publications

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“…Due to the n 2 e dependence, for equal scale length of the gradients in T e , Z eff and n e , ÑB is primarily a measure of mode-induced density fluctuations. Historically, visible N B measurements have been used on a single channel basis for the study of MHD modes as well as incoherent fluctuations [24], while 1D and 2D high-resolution imaging of the visible continuum radiation has been done on a slow timescale to infer background plasma Z eff profiles [1,25]. In terms of fluctuation profile measurements, the most detailed results have been made using multi-channel linear arrays and more recently tangential imaging viewing the x-ray portion of the bremsstrahlung emission spectrum [26,27].…”

Section: Bremsstrahlung Fluctuation Imagingmentioning

confidence: 99%

“…where the scaling was derived from a fit [22] [24], while 1D and 2D high-resolution imaging of the visible continuum radiation has been done on a slow timescale to infer background plasma Z eff profiles [1,25]. In terms of fluctuation profile measurements, the most detailed results have been made using multi-channel linear arrays and more recently tangential imaging viewing the x-ray portion of the bremsstrahlung emission spectrum [26,27].…”

Section: Bremsstrahlung Fluctuation Imagingmentioning

confidence: 99%

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Imaging key aspects of fast ion physics in the DIII-D tokamak

Zeeland¹,

Yu²,

Heidbrink³

et al. 2010

Nucl. Fusion

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Visible imaging has been used to provide the 2D spatial structure and temporal evolution of the profile of highenergy neutrals introduced by neutral beam injection, the fast ion profile and a variety of plasma instabilities in DIII-D plasmas; the combination of these techniques form a comprehensive fast ion physics diagnostic suite. The injected neutral profile is imaged in Doppler shifted D α light induced by collisional excitation. Fast ion profile information was obtained through imaging of Doppler shifted fast ion D α light (FIDA) emitted by re-neutralized energetic ions. Imaging of FIDA emission during sawtooth events shows a large central depletion following sawtooth crashes-indicative of a broad redistribution of fast ions. Two examples of instability structure measurements are given. Measurements of the detailed 2D poloidal structure of rotating tearing modes were obtained using spectrally filtered fast imaging of broadband visible bremsstrahlung emission, a method which is capable of imaging with high resolution the structure of coherent oscillations in the core of current and next-step fusion plasma experiments and can be applied to virtually any mode with a finite perturbed bremsstrahlung emissivity and frequency in the laboratory frame. Measurements are also presented of the n = 0 energetic particle geodesic acoustic mode which were made by observing fluctuations in active emission.

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Section: Bremsstrahlung Fluctuation Imagingmentioning

confidence: 99%

Section: Bremsstrahlung Fluctuation Imagingmentioning

confidence: 99%

Imaging key aspects of fast ion physics in the DIII-D tokamak

Zeeland¹,

Yu²,

Heidbrink³

et al. 2010

Nucl. Fusion

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show abstract

“…Due to the n 2 e dependence, ÑB is primarily a measure of mode-induced density fluctuations. Historically, visible N B measurements have been used on a single channel basis for the study of MHD modes as well as incoherent fluctuations [6], while 1D and 2D high-resolution imaging of the visible continuum radiation has been done on a slow timescale to infer background plasma Z eff profiles [7,8]. In terms of fluctuation profile measurements, the most detailed results have been made using multi-channel linear arrays and more recently tangential imaging viewing the x-ray portion of the bremsstrahlung emission spectrum [9,10].…”

Section: Technique and Experimental Resultsmentioning

confidence: 99%

Tearing mode structure in the DIII-D tokamak through spectrally filtered fast visible bremsstrahlung imaging

Zeeland

Chu

et al. 2008

Nucl. Fusion

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Time evolved measurements of the detailed 2D poloidal structure of rotating tearing modes in the DIII-D tokamak are obtained for the first time using spectrally filtered fast imaging (SFFI) of broadband visible Bremsstrahlung emission (N B ). Measurements are made along 256 × 256 different sightlines and show excellent agreement with simulations assuming a rotating helical m/n = 2/1 island structure superimposed on the equilibrium N B profile. The method described here is capable of imaging with high resolution the structure of coherent oscillations in the core of current and next-step fusion plasma experiments such as ITER and can be applied to virtually any mode with a finite perturbed N B and frequency in the laboratory frame provided sufficient signal level and detector bandwidth are available.

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“…6 -9͒ or on bremsstrahlung emissions. 10,11 For the case of H ␣ , the emission is localized at the edge, and this helps the localization along the line of sight. In addition, focusing 8 or a wavelength selec-a͒ Electronic mail: ejiri@k.u-tokyo.ac.jp tion mask 9 helps the localization.…”

Section: Introductionmentioning

confidence: 99%

“…While it is not always easy to relate H ␣ fluctuations to those of plasma parameters, bremsstrahlung emission has a strong dependence on the density, and the observed fluctuations can be attributed to the density fluctuations. 11 The conventional cross beam correlation techniques, in passive visible emission measurements, were applied to a stellarator. 12 Unfortunately, the fluctuations had a large spatial structure ͑i.e., long correlation length͒, and a tomography-like method was more suitable than the cross beam correlation techniques.…”

Section: Introductionmentioning

confidence: 99%

Four-beam correlation method for local fluctuation measurements in plasmas

Ejiri

2002

Review of Scientific Instruments

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Investigation of a high spatial resolution method based on polar coordinate maximum entropy method for analyzing electron density fluctuation data measured by laser phase contrast Rev. Sci. Instrum. 83, 013501 (2012); 10.1063/1.3673636 Reconstruction method of local density fluctuation for heavy ion beam probe measurements Rev. Sci. Instrum. 78, 063502 (2007); 10.1063/1.2745233 Comparison of different methods of electron cyclotron emission-correlation radiometry for the measurement of temperature fluctuations in the plasma core Rev. Sci. Instrum. 75, 3177 (2004); 10.1063/1.1790567Prospects for measurement of rapid equilibrium changes and electron fluctuations using a high repetition rate Thomson scattering diagnostic Rev.

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Observation of density fluctuations from the infrared bremsstrahlung emission on TFTR

Cited by 7 publications

References 3 publications

Imaging key aspects of fast ion physics in the DIII-D tokamak

Imaging key aspects of fast ion physics in the DIII-D tokamak

Tearing mode structure in the DIII-D tokamak through spectrally filtered fast visible bremsstrahlung imaging

Four-beam correlation method for local fluctuation measurements in plasmas

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