Edge and core Thomson scattering systems and their calibration on the ASDEX Upgrade tokamak

Kurzan, B.; Mürmann, H.

doi:10.1063/1.3643771

Cited by 98 publications

(90 citation statements)

References 5 publications

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“…The data shown is from the intervals 2.65 -2.95 s and 3.65 -3.95 s in order to only investigate the plasma once it has reached the new equilibrium. The circles are calculated mean values of the individual measurements at each Thomson scattering (TS) channel [64]. The TS channel at ρ pol = 0.7 was not properly calibrated and thus shows a slightly elevated value.…”

Section: Impact Of Additional Ecrh On Plasma Profilesmentioning

confidence: 99%

Core turbulence behavior moving from ion-temperature-gradient regime towards trapped-electron-mode regime in the ASDEX Upgrade tokamak and comparison with gyrokinetic simulation

et al. 2015

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Additional electron cyclotron resonance heating (ECRH) is used in an ion-temperature-gradient instability (ITG) dominated regime to increase R/L Te in order to approach the trapped-electron-mode instability (TEM) regime. The radial ECRH deposition location determines to a large degree the effect on R/L Te . Accompanying scale-selective turbulence measurements at perpendicular wavenumbers between k ⊥ = 4 -18 cm −1 (k ⊥ ρ s = 0.7 -4.2) show a pronounced increase of large-scale density fluctuations close to the ECRH radial deposition location at mid-radius, along with a reduction in phase velocity of large-scale density fluctuations. Measurements are compared with results from linear and non-linear flux-matched gyrokinetic (GK) simulations with the gyrokinetic code gene. Linear GK simulations show a reduction of phase velocity, indicating a pronounced change in the character of the dominant instability. Comparing measurement and non-linear GK simulation, as a central result, agreement is obtained in the shape of radial turbulence level profiles. However, the turbulence intensity is increasing with additional heating in the experiment, while gyrokinetic simulations show a decrease.

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Section: Impact Of Additional Ecrh On Plasma Profilesmentioning

confidence: 99%

Core turbulence behavior moving from ion-temperature-gradient regime towards trapped-electron-mode regime in the ASDEX Upgrade tokamak and comparison with gyrokinetic simulation

et al. 2015

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“…The discharges are heated with neutral beam injection launched in a single power step from 0 to P NBI marginally above the L-H power threshold. Examples of this type of discharges are given in figures 1 and 3 By means of this set of discharges, we study the dependence of the LCO frequency during the first 60 LCO cycles on the edge density (approximated by the line averaged edge densityn e,edge ), electron temperature T e measured with Thomson scattering [55] at ρ pol = 0.95, toroidal magnetic field B t , toroidal plasma current I p , and edge safety factor q 95 .…”

Section: Frequency Scaling Of Lcosmentioning

confidence: 99%

Magnetic structure and frequency scaling of limit-cycle oscillations close to L- to H-mode transitions

et al. 2016

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Limit-cycle oscillations (LCOs) close to the power threshold of L-to H-mode transitions are investigated in plasmas of ASDEX Upgrade. During this phase, referred to as I-phase, a strong magnetic activity in the poloidal magnetic fieldḂ θ with an up-down asymmetry is found. In some cases, the regular LCOs during I-phase transition smoothly into a phase with intermittent bursts which have similar properties to type-III edge localised modes (ELMs). Indications of precursors during the intermittent phase as well as in the regular LCO phase point to a common nature of the I-phase and type-III ELMs. The LCO frequency measured in a set of discharges with different plasma currents and magnetic fields scales as f ∼ (B 1/2 t I 3/2 p )/(nT ).

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“…But In principle, the improvements and the gain in photon flux allows electron density profiles to be delivered with a temporal resolution of 5 µs. Comparison of the electron density profiles from Li-BES using the new optical system (blue triangles) and the old one (green diamonds), the core and edge Thomson scattering system [29] (rectangles) and the reflectometer system (REF) [30] (purple stars) during a radial plasma sweep in L-mode. The diagnostics agree very well within their uncertainties.…”

Section: High Accuracy Electron Density Profilesmentioning

confidence: 99%

“…To compare the density profiles from the Li-BES system with other diagnostics, dedicated experiments were performed in which various electron density diagnostics at ASDEX Upgrade measured simultaneously. A comparison between the Li-BES, Reflectometry (REF) [27,28], core and edge Thomson scattering (TS) [29] diagnostics during a radial plasma sweep in ohmic L-mode is shown in figure 4. The electron density profiles agree well within the uncertainties.…”

Section: High Accuracy Electron Density Profilesmentioning

confidence: 99%

Characterization of the Li-BES at ASDEX Upgrade

Willensdorfer

Birkenmeier

Fischer

et al. 2014

Plasma Phys. Control. Fusion

100

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Abstract.The lithium beam emission spectroscopy (Li-BES) is a powerful diagnostic to resolve the plasma edge density with high temporal and spatial resolution. The recent upgrades of the Li-BES at ASDEX Upgrade and the resulting gain in photon flux allow the plasma edge density to be determined with an advanced level of accuracy. Furthermore, electron density fluctuations are measured using Li-BES. The Li-BES capabilities and limitations to measure electron density profiles as well as density fluctuations are presented. Li-BES is well suited to characterize electron density turbulence in the scrape off layer (SOL) with decreasing sensitivity towards the plasma core. This is demonstrated by simulations as well as by comparisons with other diagnostics. Li-BES is an appropriate tool to study transport phenomena in the SOL over a wide range of plasma parameters due to its robustness and routine usage.

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Edge and core Thomson scattering systems and their calibration on the ASDEX Upgrade tokamak

Cited by 98 publications

References 5 publications

Core turbulence behavior moving from ion-temperature-gradient regime towards trapped-electron-mode regime in the ASDEX Upgrade tokamak and comparison with gyrokinetic simulation

Core turbulence behavior moving from ion-temperature-gradient regime towards trapped-electron-mode regime in the ASDEX Upgrade tokamak and comparison with gyrokinetic simulation

Magnetic structure and frequency scaling of limit-cycle oscillations close to L- to H-mode transitions

Characterization of the Li-BES at ASDEX Upgrade

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