Synthetic Mirnov diagnostic for the validation of experimental observations

cases have been developed, with

A synthetic Mirnov diagnostic has been developed to investigate the capabilities and limitations of an arrangement of Mirnov coils in terms of a mode analysis.

Eight test cases have been developed, with different coil arrangements and magnetic field configurations…
It is observed, that for a high triangularity of the flux surfaces the arrangement of the coils plays a significant role for the exact determination of the poloidal mode number.
For the mode analysis torus and PEST coordinates have been used, where in most cases the reconstruction of the poloidal mode number of a prescribed mode is more accurate in PEST coordinates.

Abstract
A synthetic Mirnov diagnostic has been developed to investigate the capabilities and limitations of an arrangement of Mirnov coils in terms of a mode analysis.

Eight test cases have been developed, with different coil arrangements and magnetic field configurations…
It is observed, that for a high triangularity of the flux surfaces the arrangement of the coils plays a significant role for the exact determination of the poloidal mode number.
For the mode analysis torus and PEST coordinates have been used, where in most cases the reconstruction of the poloidal mode number of a prescribed mode is more accurate in PEST coordinates.
As an application, the signal of an Alfvén eigenmode, which has been calculated with a three dimensional magnetohydrodynamics code, is compared to experimental observations at Wendelstein 7-X.

Abstract
A synthetic Mirnov diagnostic has been developed to investigate the capabilities and limitations of an arrangement of Mirnov coils in terms of a mode analysis.

Eight test cases have been developed, with different coil arrangements and magnetic field configurations…
It is observed, that for a high triangularity of the flux surfaces the arrangement of the coils plays a significant role for the exact determination of the poloidal mode number.
For the mode analysis torus and PEST coordinates have been used, where in most cases the reconstruction of the poloidal mode number of a prescribed mode is more accurate in PEST coordinates.
As an application, the signal of an Alfvén eigenmode, which has been calculated with a three dimensional magnetohydrodynamics code, is compared to experimental observations at Wendelstein 7-X.
For the chosen example the calculated and measured mode spectra agree very well and additional information on the toroidal mode number and localization of the mode has been inferred.

Abstract
With a synthetic diagnostic, the capability of an experimental diagnostic can be tested.

Motivation
With a synthetic diagnostic, the capability of an experimental diagnostic can be tested.
A synthetic diagnostic provides a connection between experimental measurements and numerical simulations.

Motivation
With a synthetic diagnostic, the capability of an experimental diagnostic can be tested.
A synthetic diagnostic provides a connection between experimental measurements and numerical simulations.
For W7-AS S. Zegenhagen et al. [6] used artificial data to investigate the capability of the installed Mirnov diagnostic with respect to different mode numbers, noise as well as the superposition of modes.Motivation [6]  With a synthetic diagnostic, the capability of an experimental diagnostic can be tested.
A synthetic diagnostic provides a connection between experimental measurements and numerical simulations.
For W7-AS S. Zegenhagen et al. [6] used artificial data to investigate the capability of the installed Mirnov diagnostic with respect to different mode numbers, noise as well as the superposition of modes.
A Bayesian approach, modelling current distribution in a tokamak, is proposed in Ref. [7].Here several diagnostics can be included in the analysis… Motivation [6]  With a synthetic diagnostic, the capability of an experimental diagnostic can be tested.
A synthetic diagnostic provides a connection between experimental measurements and numerical simulations.
For W7-AS S. Zegenhagen et al. [6] used artificial data to investigate the capability of the installed Mirnov diagnostic with respect to different mode numbers, noise as well as the superposition of modes.
A Bayesian approach, modelling current distribution in a tokamak, is proposed in Ref. [7].Here several diagnostics can be included in the analysis…

Effects of geometrical properties
In most cases the reconstruction of the poloidal mode number is more accurate in PEST coordinates.
For a triangular plasma shape, the resolution highly depends on the coil arrangement.

Effects of geometrical properties
In most cases the reconstruction of the poloidal mode number is more accurate in PEST coordinates.
For a triangular plasma shape, the resolution highly depends on the coil arrangement.
Experimental mode in a high performance plasma at W7-X during OP1.2 Experimental mode in a high performance plasma at W7-X during OP1.2

Comparison of calculated mode to experimental results
experimental calculated

Comparison of calculated mode to experimental results
The experimental mode can be described as an EAE with m = 2, 4 and  = 3, 3 located in the outer region of the plasma.
experimental calculated • For a triangular plasma shape, the resolution highly depends on the coil arrangement.

Conclusions
• The capability of a Mirnov diagnostic depends on geometrical properties and can vary for different magnetic field configurations (e.g.different experimental programs).
• For a triangular plasma shape, the resolution highly depends on the coil arrangement.
• PEST coordinates have a higher poloidal mode number resolution than torus coordinates in the eight test cases investigated.
• With the synthetic Mirnov diagnostic, it is possible to directly compare experimental and calculated mode spectra and receive further information about the experimental mode, as e.g. the toroidal mode number and its localization.

FocusingContribution 1 . 2 .Contribution 1 . 2 . 3 .
on the capabilities of the hardware and software of the Mirnov diagnostic, an end-end simulation has been developed by D. Testa et al. [8] … Motivation [6] S. Zegenhagen et al., Plasma Physics and Controlled Fusion, 48(9):1333, 08 2006 [7] N. Bohlsen et al., Plasma Physics and Controlled Fusion, 65(10):105003, 08 2023 [8] D. Testa et al., Fusion Engineering and Design, 188:113406, 2023 1. Systematic analysis about the effect of geometrical properties of the Mirnov coil array and the flux surfaces on the ability to determine the poloidal mode number with the Mirnov diagnostic.Systematic analysis about the effect of geometrical properties of the Mirnov coil array and the flux surfaces on the ability to determine the poloidal mode number with the Mirnov diagnostic.Calculation of the signal of an Alfvén eigenmode in the Mirnov coils for a direct comparison to experimental measurements at Wendelstein 7-X.Systematic analysis about the effect of geometrical properties of the Mirnov coil array and the flux surfaces on the ability to determine the poloidal mode number with the Mirnov diagnostic.Calculation of the signal of an Alfvén eigenmode in the Mirnov coils for a direct comparison to experimental measurements at Wendelstein 7-X.Using two different coordinate systems to investiagte the effect on the reconstruction of the poloidal mode number of a prescribed mode.Contribution Implementation [10] M. Drevlak, Nuclear Fusion, 45(7):731, 2005 Implementation [10] M. Drevlak, Nuclear Fusion, 45(7):731, 2005 Implementation [10] M. Drevlak, Nuclear Fusion, 45(7):731, 2005 Implementation Calculation of the Mirnov signal at the coil positions of a prescribed mode taking into account the spatial distance between the mode and the Mirnov coils.[10] M. Drevlak, Nuclear Fusion, 45(7):731, 2005 Effects of geometrical properties: 8 test cases Eight test cases with varying magnetic field configurations and different arrangements of 41 Mirnov coils.Effects of geometrical properties: 8 test cases m 1st peak = m input m 1st peak ≠ m input Eight test cases with varying magnetic field configurations and different arrangements of 41 Mirnov coils.(In)correct determination of the poloidal mode number Effects of geometrical properties on the mode spectrum PEST coordinates have a higher resolution than torus coordinates.

3 Conclusions
Link Pinboard: https://users.euro-fusion.org/repository/pinboard/EFDA-JET/journal/110202_synthetic_mirnov_diagnostic.pdfSY N T H E T I C M I R N O V D I A G N O S T I C M A X -P L A N C K -I N S T I T U T F Ü R P L A S M A P H Y S I K | C H A R L O T T E B Ü S C H E L | 2 2 .11 .2 0 2Further distinction of the quality of a mode spectrum IMP (input mode's peak): Amplitude of the poloidal mode number of the prescribed mode FAP (first additional peak): Amplitude of the highest peak in the mode spectrum that is not the IMP  With increasing poloidal mode number  the IMP gets less pronounced Mirnov signal and resolution depending on the localization of the mode   =  For core localized modes a correct determination of the poloidal mode number is not possible due to a strong decay of the signals amplitude, even for low poloidal mode numbers.