Radiation transport modelling for the interpretation of oblique ECE measurements

Denk, S. S.; Fischer, R.; Maj, O.; Poli, E.; Stober, J.; Stroth, U.; Vanovac, B.; Suttrop, W.; Willensdorfer, M.

doi:10.1051/epjconf/201714702002

Cited by 12 publications

(23 citation statements)

References 11 publications

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“…[51]), which is found to be in good agreement with the TORBEAM code [52]. The ray tracing code calculates the ray path of each channel until the ray hits the wall.…”

Section: Definition Of the 'Warm' Resonance Positionsupporting

confidence: 53%

“…The combination of forward modeling and ray tracing allows us to determine exactly the origin of the observed intensity. The distribution of the observed intensity (D ω ) [51] is the normalized product of the emissivity j w (s) and the transmittance T ω (s) along the ray path coordinate s: Figure 7(a) and (b) illustrate j w , T ω [51] and the resulting D ω , respectively, versus ρ pol calculated for one 1D-ECE channel in the pedestal region. The used T e profile and the modeled T rad (T rad,mod ) value of this channel at its cold resonance position are also shown.…”

Section: Definition Of the 'Warm' Resonance Positionmentioning

confidence: 99%

See 1 more Smart Citation

Plasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium

Willensdorfer

Denk

Strumberger

et al. 2016

Plasma Phys. Control. Fusion

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Abstract. The plasma response from an external n = 2 magnetic perturbation field in ASDEX Upgrade has been measured using mainly electron cyclotron emission (ECE) diagnostics and a rigid rotating field. To interpret ECE and ECE-imaging (ECE-I) measurements accurately, forward modeling of the radiation transport has been combined with ray tracing. The measured data is compared to synthetic ECE data generated from a 3D ideal magnetohydrodynamics (MHD) equilibrium calculated by VMEC.The measured amplitudes of the helical displacement around the low field side midplane are in reasonable agreement with the one from the synthetic VMEC diagnostics. Both exceed the prediction from the vacuum field calculations and indicate the presence of a kink response at the edge, which amplifies the perturbation. VMEC and MARS-F have been used to calculate the properties of this kink mode. The poloidal mode structure of the magnetic perturbation of this kink mode at the edge peaks at poloidal mode numbers larger than the resonant components |m| > |nq|, whereas the poloidal mode structure of its displacement is almost resonant |m| ≈ |nq|. This is expected from ideal MHD in the proximity of rational surfaces. The displacement measured by ECE-I confirms this resonant response.

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“…[51]), which is found to be in good agreement with the TORBEAM code [52]. The ray tracing code calculates the ray path of each channel until the ray hits the wall.…”

Section: Definition Of the 'Warm' Resonance Positionsupporting

confidence: 53%

Section: Definition Of the 'Warm' Resonance Positionmentioning

confidence: 99%

Plasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium

Willensdorfer

Denk

Strumberger

et al. 2016

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…A 2D Gaussian function in the R, z plane is used to model the finite volume of the real measurements. The radial size of the Gaussian function is taken from a fit to the emissivity function [46], determined using a standard ECE radiation transport model (ECFM) [47]. This model takes into account the finite bandwidth of the IF filters (B IF ), the relativistic broadening and ECE frequency downshift, the Doppler broadening at finite toroidal angle and beam refraction in the plasma.…”

Section: Cece Synthetic Diagnosticmentioning

confidence: 99%

Validation of gyrokinetic simulations with measurements of electron temperature fluctuations and density-temperature phase angles on ASDEX Upgrade

et al. 2018

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Measurements of turbulent electron temperature fluctuation amplitudes, δT e⊥ /Te, frequency spectra and radial correlation lengths, Lr(T e⊥ ), have been performed at ASDEX Upgrade using a newly upgraded Correlation ECE diagnostic in the range of scales k ⊥ < 1.4cm −1 , kr < 3.5cm(k ⊥ ρs < 0.28 and krρs < 0.7). The phase angle between turbulent temperature and density fluctuations, αnT , has also been measured by using an ECE radiometer coupled to a reflectometer along the same line of sight. These quantities are used simultaneously to constrain a set of ion-scale nonlinear gyrokinetic turbulence simulations of the outer core (ρtor = 0.75) of a low density, electron heated L-mode plasma, performed using the gyrokinetic simulation code, GENE. The ion and electron temperature gradients were scanned within uncertainties. It is found that GK simulations are able to match simultaneously the electron and ion heat flux at this radius within the experimental uncertainties. The simulations were performed based on a reference discharge for which δT e⊥ /Te measurements were available, and Lr(T e⊥ ) and αnT were then predicted using synthetic diagnostics prior to measurements in a repeat discharge. While temperature fluctuation amplitudes are overestimated by > 50% for all simulations within the sensitivity scans performed, good quantitative agreement is found for Lr(T e⊥ ) and αnT . A validation metric is used to quantify the level of agreement of individual simulations with experimental measurements, and the best agreement is found close to the experimental gradient values.

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“…At ASDEX Upgrade we routinely use the radiation transport model for interpreting measurements of ECE and ECE-I diagnostics [12,13]. The radiation transport model accounts for the geometry of the detection systems, and radiation transport effects.…”

Section: Electron Cyclotron Radiation Transport Forward Modelmentioning

confidence: 99%

Mode analysis limitations of ECE-I & ECE measurements at the plasma edge

et al. 2019

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Interpretation of the Electron Cyclotron Emission (ECE) and ECE Imaging (ECE-I) measurements concerning the measurement position and the radiation temperature (Trad) at the plasma edge is associated with signiﬁcant uncertainty. Various limitations such as low and high-density limits, relativistic and Doppler shift-broadening, mode overlap were identiﬁed in the past. Here, we analyse the inﬂuence of density proﬁle variation onto the radiation temperature in H-mode plasmas at ASDEX Upgrade tokamak. We show that, in the region of steep gradients, the variation of the density proﬁle leads to an outward-shift of the measurement position, towards lower Trad. The analysis is extended towards the study of the contribution of the ordinary mode (O-mode) emission to the measured Trad at the plasma edge. With this analysis, we show the qualitative agreement between experimental observations and modeling when taking into account the O-mode contribution to the ECE measurements. All of these eﬀects are assessed via the Electron Cyclotron Radiation transport forward model that is now routinely used to model the response of the ECE-I and ECE systems in diﬀerent plasma scenarios.

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Radiation transport modelling for the interpretation of oblique ECE measurements

Cited by 12 publications

References 11 publications

Plasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium

Plasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium

Validation of gyrokinetic simulations with measurements of electron temperature fluctuations and density-temperature phase angles on ASDEX Upgrade

Mode analysis limitations of ECE-I & ECE measurements at the plasma edge

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