Spectrally resolved motional Stark effect measurements on ASDEX Upgrade

Reimer, R.; Dinklage, A.; Fischer, R.; Hobirk, J.; Löbhard, T.; Mlynek, A.; Reich, M.; Sawyer, Lindsay; Wolf, R. C.

doi:10.1063/1.4829665

Cited by 12 publications

(17 citation statements)

References 23 publications

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“…The potential of this latter technique was identified by Boileau [5] and first measurements of local magnetic field strength were obtained on JET by Wolf [6]. Since then, it has been refined or adapted to other fusion devices [7][8][9]. Indeed, this technique has several advantages over polarimetry.…”

Section: Introductionmentioning

confidence: 97%

A Spectrally Resolved Motional Stark Effect Diagnostic for the TJ‐II Stellarator

McCarthy¹,

Panadero

Löpez‐Fraguas³

et al. 2015

Contrib. Plasma Phys.

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A spectrally resolved motional stark effect (MSE) diagnostic has been implemented for the TJ-II stellarator to quantify the magnitude and pitch of components of the magnetic field created in this magnetic confinement device. The system includes a compact diagnostic neutral beam injector (DNBI) that provides a short pulse of accelerated neutral hydrogen atoms with an e −1 beam radius of 2.1 cm to stimulate the Doppler-displaced Balmer Hα emissions, which are the basis for this diagnostic. Measurement of the wavelength separation of the Stark splitting of the Hα spectrum, as well as of the relative line intensities of its components, allow the local magnitude and direction of the internal magnetic field components to be measured at 10 positions across the plasma. The use of a DNBI extends such measurements to the electron cyclotron resonance (ECR) heated phases of plasmas while also overcoming the need for the complicated inversion techniques that are required when such measurements are performed with a heating neutral beam injector (NBI). Moreover, the use of the shot-to-shot technique with reproducible discharges further simplifies fits to the MSE spectra as nearby impurity spectral emission lines can be eliminated or significantly reduced. After outlining the principles of this technique and the diagnostic set-up, magnetic field measurements made during ECR or NBI heating phases are reported for a range of magnetic configurations and are compared with vacuum magnetic field estimates in order to evaluate the capabilities and limitations of this diagnostic for the TJ-II.

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Section: Introductionmentioning

confidence: 97%

A Spectrally Resolved Motional Stark Effect Diagnostic for the TJ‐II Stellarator

McCarthy¹,

Panadero

Löpez‐Fraguas³

et al. 2015

Contrib. Plasma Phys.

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“…We now give a brief description of the setup of the spectroscopic diagnostic at ASDEX Upgrade, which is described in detail in 24 . Similar systems can be found on many fusion experiments 30,37-39 .…”

Section: Comparison With Experimental Data From Asdex Upgrade Amentioning

confidence: 99%

“…by non-optimal adjustment of the detection components which consists of a spectrometer, an objectives and a CCD-chip. The MSE diagnostic is described in detail in 24 3. Use of a improper profile function for the MSE lines: in the present work a gaussian profile was applied.…”

Section: Effect Of Atomic Extension Onto Experimental Quantitiesmentioning

confidence: 99%

“…This is a significant effect and needs to be considered for the calculation of the absolute value of B. The aforementioned formulation of the ZMSE case with the spin-orbit coupling and relativistic effects is now included into the forward model and the measured spectral MSE data, d, at ASDEX Upgrade are fitted using the forward model 24 . ∆B/BM SE = 1.59% In order to validate the forward model, a reference discharge has been conducted on ASDEX Upgrade.…”

Section: Effect Of Atomic Extension Onto Experimental Quantitiesmentioning

confidence: 99%

“…The model is prepared for even more refinements which can be done in future, e. g. by including contributions of radial electric fields. The recently developed MSE forward model 24 is extended and takes the Zeeman-Stark effect and the spin-orbit coupling into account in order to describe the measured MSE spectra. Finally, the results of the measurements are compared with results from equilibrium solver (CLISTE ) 25 for ASDEX Upgrade experimental conditions.…”

mentioning

confidence: 99%

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Influence of non-local thermodynamic equilibrium and Zeeman effects on magnetic equilibrium reconstruction using spectral motional Stark effect diagnostic

Reimer

Marchuk

Geiger

et al. 2017

Review of Scientific Instruments

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The prototype imaging motional Stark effect diagnostic for ASDEX upgrade

Ford

Howard

Wolf

2015

Review of Scientific Instruments

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This paper presents the development and testing of the prototype Imaging Motional Stark-Effect (IMSE) diagnostic, designed for ASDEX upgrade. A detailed description of the core hardware, theory of operation, and application to complex MSE spectra are presented and analytical evaluation methods suitable for the required accuracy are developed. The diagnostic is tested with a MSE-like polarised spectrum to assess the accuracy of different modulation modes suggested in previous works. Each is found to have small systematic errors due to non-ideal effects of the components, which must be carefully examined. In particular, the effect of intrinsic contrast that results from imperfect parallelism of the birefringent plates is found to have a strong effect. Methods to mitigate and correct for this are discussed. With the necessary corrections and calibrations, the accuracy of polarisation orientation is shown to be within ±0.2°. The effect of finite ellipticity is examined and the possibility to measure this to an accuracy of ±2.0° is demonstrated. The system is shown to be insensitive to broadband polarised background light, temperature variations, and critically to variations in the details of the MSE spectrum.

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Spectrally resolved motional Stark effect measurements on ASDEX Upgrade

Cited by 12 publications

References 23 publications

A Spectrally Resolved Motional Stark Effect Diagnostic for the TJ‐II Stellarator

A Spectrally Resolved Motional Stark Effect Diagnostic for the TJ‐II Stellarator

Influence of non-local thermodynamic equilibrium and Zeeman effects on magnetic equilibrium reconstruction using spectral motional Stark effect diagnostic

The prototype imaging motional Stark effect diagnostic for ASDEX upgrade

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