Problems and methods of self-consistent reconstruction of tokamak equilibrium profiles from magnetic and polarimetric measurements

Blum, Jacques; Lazzaro, E.; O’Rourke, J.; Keegan, B.; Stéphan, Y.

doi:10.1088/0029-5515/30/8/007

Cited by 101 publications

(75 citation statements)

References 25 publications

(56 reference statements)

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“…1,2 Another early example is the calibration of the central q value from the observation of sawteeth and the input of constraints (as the sawtooth inversion radius or the radial position of low mode number tearing modes) in the codes IDENTC and IDENTD. 3 The localization of the (1,1) snake observed after D 2 pellet injection has provided the evolution of the q =1 surface in between sawtooth crashes in plasmas with monotonic q profiles. 4 More recently, MHD modes have been extensively used to calibrate q profiles obtained with the code EFIT taking into account MSE measurements.…”

Section: Introductionmentioning

confidence: 99%

On the use of MHD mode analysis as a technique for determination of q-profiles in JET plasmas

Nave¹,

Borba²,

Galvão³

et al. 2004

Review of Scientific Instruments

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JET plasmas show fluctuations from a large variety of MHD instabilities. A combination of spectral analysis, mode number analysis, and determination of mode radial position has the potential as a diagnostic for the plasma q profile. Mode frequencies and mode numbers are obtained from spectral and phase analysis from fast magnetic pickup signals. Cross correlation of magnetic and multiarray signals from ECE, SXR, and reflectometer systems provide the mode localization. The present status of the diagnostic systems used for fluctuation analysis is summarized, with particular emphasis on the fast magnetic pickup system. A new data collection system allows the magnetic signals to be recorded at 2 MHz for up to 32 s in each pulse. An example of q-profile validation from the observation of Alfven eigenmode cascades and a snake is given. At JET, Alfven cascades are used to determine q min in optimized shear discharges, while a variety of low frequency modes (such as the snake) allow the determination of the radial position of q integer values in monotonic and reversed shear q profiles.

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Section: Introductionmentioning

confidence: 99%

On the use of MHD mode analysis as a technique for determination of q-profiles in JET plasmas

Nave¹,

Borba²,

Galvão³

et al. 2004

Review of Scientific Instruments

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“…The sawtooth crash is usually accompanied by the internal kink mode m=n=1 which can be seen as precursor oscillations before the sawtooth crash. Kadomtsev model 10 has provided a starting point for an understanding of the sawtooth crash, however, it is in contradiction with several measurements 11,12 Presently, a partial reconnection model 13 is often preferred for the interpretation of the sawtooth crash. For example, oscillations of the hot core in reconstructed radial profile ( see FIG.…”

Section: Studies Of Sawtooth Instabilitymentioning

confidence: 99%

Use of soft x-ray diagnostic on the COMPASS tokamak for investigations of sawteeth crash neighborhood and of plasma position using fast inversion methods

Imríšek

Weinzettl

Mlynář

et al. 2014

Review of Scientific Instruments

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(Presented XXXXX; receivedXXXXX; accepted XXXXX; published online XXXXX) The soft x-ray diagnostic is suitable for monitoring plasma activity in the tokamak core, e.g. sawtooth instability. Moreover, spatially resolved measurements can provide information about plasma position and shape, which can supplement magnetic measurements. In this contribution, fast algorithms with the potential for a real-time use are tested on the data from the COMPASS tokamak. In addition, the soft x-ray data are compared with data from other diagnostics in order to discuss possible connection between sawtooth instability on one side and the transition to higher confinement mode, Edge localized modes and runaway electrons on the other side.

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“…The problem is thus resumed to find a solution that minimizes the cost function defined as: with mse the reconstructed measurement and K 1 to K 3 the weighting parameters enabling to give more or less importance to the corresponding experimental measurements [8]. The inverse problem of the determination of A and B is ill-posed.…”

Section: B Statement Of the Inverse Problemmentioning

confidence: 99%

Real-time identification of the current density profile in the JET tokamak: method and validation

Mazon

Blum²,

Boulbe³

et al. 2009

Proceedings of the 48h IEEE Conference on Decision and Control (CDC) Held Jointly With 2009 28th Chinese Control Conference

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Abstract-The real-time reconstruction of the plasma magnetic equilibrium in a Tokamak is a key point to access high performance regimes. Indeed, the shape of the plasma current density profile is a direct output of the reconstruction and has a leading effect for reaching a steady-state high performance regime of operation. In this paper we present the methodology followed to identify numerically the plasma current density in a Tokamak and its equilibrium. In order to meet the real-time requirements a C++ software has been developed using the combination of a finite element method, a nonlinear fixed point algorithm associated to a least square optimization procedure. The experimental measurements that enable the identification are the magnetics on the vacuum vessel, the interferometric and polarimetric measurements on several chords and the motional Stark effect. Details are given about the validation of the reconstruction on the JET tokamak, either by comparison with 'off-line' equilibrium codes or real time software computing global quantities. I. INTRODUCTIONN present days tokamaks the shape of the plasma boundary is routinely identifiable in real-time in less than few milliseconds using a set of magnetic and diamagnetic coils spread around the vessel [1]. This information is mainly used for controlling the plasma shape in real-time during a plasma discharge using coils current in a feedback control loop. The idea is to achieve a required shape and to maintain it in a stationary manner in order to avoid for example sudden termination of the plasma when the plasma touches the first wall. In JET the so-called XLOC code is J. Blum is with the Laboratoire J-A Dieudonné (UMR 66 21

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Problems and methods of self-consistent reconstruction of tokamak equilibrium profiles from magnetic and polarimetric measurements

Cited by 101 publications

References 25 publications

On the use of MHD mode analysis as a technique for determination of q-profiles in JET plasmas

On the use of MHD mode analysis as a technique for determination of q-profiles in JET plasmas

Use of soft x-ray diagnostic on the COMPASS tokamak for investigations of sawteeth crash neighborhood and of plasma position using fast inversion methods

Real-time identification of the current density profile in the JET tokamak: method and validation

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