Measurement of the magnetic field errors on TCV

Piras, Francesco; Moret, J.-M.; Rossel, J.

doi:10.1016/j.fusengdes.2010.04.049

Cited by 12 publications

(10 citation statements)

References 11 publications

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“…In addition, as-built metrology will be necessary to quantify the true spectral composition of ITER's intrinsic EF and properly tailor the EF correction. Sources such as asymmetries of the poloidal field coils and nearby bus work have been characterized from geometric measurements in existing facilities including NSTX [61], DIII-D [62] and C-Mod [4] while EFs have been measured with in situ magnetic diagnostics in C-Mod [4] and TCV [63] and with special apparatus in DIII-D [62] and MAST [64]. This EF data serves as input to models of vacuum sources, enabling prediction of the optimal overlap minimizing EFC validated by experimental optimization [4,7,33,61,64].…”

Section: Conclusion and Implications For Itermentioning

confidence: 99%

Empirical scaling of the n = 2 error field penetration threshold in tokamaks

Logan

Park

et al. 2020

Nucl. Fusion

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This paper presents a multi-machine, multi-parameter scaling law for the n = 2 core resonant error field threshold that leads to field penetration, locked modes, and disruptions. Here, n is the toroidal harmonic of the non-axisymmetric error field (EF). While density scalings have been reported by individual tokamaks in the past, this work performs a regression across a comprehensive range of densities, toroidal fields, and pressures accessible across three devices using a common metric to quantify the EF in each device. The metric used is the amount of overlap between an EF and the spectrum that drives the largest linear ideal MHD resonance, known as the "dominant mode overlap". This metric, which takes into account both the external field and plasma response, is scaled against experimental parameters known to be important for the inner layer physics. These scalings validate nonlinear MHD simulation scalings, which are used to elucidate the dominant inner layer physics. Both experiments and simulations show that core penetration thresholds for EFs with toroidal mode number n = 2 are of the same order as the n = 1 thresholds that are considered most dangerous on current devices. Both n = 1 and n = 2 thresholds scale to values within the ITER design tolerances, but data from additional devices with a range of sizes are needed in order to increase confidence in quantitative extrapolations of n = 2 thresholds to ITER.

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Section: Conclusion and Implications For Itermentioning

confidence: 99%

Empirical scaling of the n = 2 error field penetration threshold in tokamaks

Logan

Park

et al. 2020

Nucl. Fusion

View full text Add to dashboard Cite

show abstract

“…In a conventional aspect ratio tokamak, the mse diagnostic must be calibrated to yield measured polarization angles relative to the tokamak's toroidal field direction with an accuracy of 0.1 • to accurately constrain magnetic reconstructions. The orientation of the tokamak vacuum magnetic field is typically well known relative to gravity and to the other magnetic diagnostics 14,15 , thus the mse diagnostic is calibrated with respect to the local gravity direction.…”

Section: Motional Stark Effect Diagnostic Calibrationmentioning

confidence: 99%

Robotic calibration of the motional Stark effect diagnostic on Alcator C-Mod

Mumgaard

Scott

2014

Review of Scientific Instruments

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The capability to calibrate diagnostics, such as the Motional Stark Effect (MSE) diagnostic, without using plasma or beam-into-gas discharges will become increasingly important on next step fusion facilities due to machine availability and operational constraints. A robotic calibration system consisting of a motorized three-axis positioning system and a polarization light source capable of generating arbitrary polarization states with a linear polarization angle accuracy of <0.05° has been constructed and has been used to calibrate the MSE diagnostic deployed on Alcator C-Mod. The polarization response of the complex diagnostic is shown to be fully captured using a Fourier expansion of the detector signals in terms of even harmonics of the input polarization angle. The system's high precision robotic control of position and orientation allow it to be used also to calibrate the geometry of the instrument's view. Combined with careful measurements of the narrow bandpass spectral filters, this system fully calibrates the diagnostic without any plasma discharges. The system's high repeatability, flexibility, and speed has been exploited to quantify several systematics in the MSE diagnostic response, providing a more complete understanding of the diagnostic performance.

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“…Envisioned future applications include in particular enhanced breakdown control in standard or exploratory scenarios [41,42]. To this end, a model has been developed to derive the magnetic configuration inside the vessel at breakdown time from a set of magnetic measurements.…”

Section: Advanced Plasma Controlmentioning

confidence: 99%

Progress and scientific results in the TCV tokamak

Coda

2011

Nucl. Fusion

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The TCV tokamak has the dual mission of supporting ITER and exploring alternative paths to a fusion reactor. Its most unique tools are a 4.5 MW electron cyclotron resonance heating system with seven real-time controllable launchers and a plasma control system with 16 independent shaping coils. Recent upgrades in temperature, density and rotation diagnostics are being followed by new turbulence and suprathermal electron diagnostics, and a new digital real-time network has been commissioned. The shape control flexibility of TCV has enabled the generation and control of the first 'snowflake' divertor, characterized by a null point in which both the poloidal field and its gradient vanish. The predicted increases in flux expansion and edge magnetic shear have been verified experimentally, and stable EC-heated snowflake ELMy H-modes have been obtained and characterized. ECCD modulation techniques have been used to study the role of the current profile in energy transport, and simulations reproduce the results robustly. The relation between impurity and electron density gradients in L-mode is explained in terms of neoclassical and turbulent drives. Studies of torqueless plasma rotation have continued, highlighting the important role of MHD and sawtooth relaxations in determining the rotation profiles. A newly predicted mechanism for turbulent momentum transport associated with up-down plasma asymmetry has been verified in TCV. Sawtooth period control, neoclassical tearing mode control and soft x-ray emission profile control have been demonstrated in TCV using the new digital control hardware, as a step on the way to more complex applications.

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Measurement of the magnetic field errors on TCV

Cited by 12 publications

References 11 publications

Empirical scaling of the n = 2 error field penetration threshold in tokamaks

Empirical scaling of the n = 2 error field penetration threshold in tokamaks

Robotic calibration of the motional Stark effect diagnostic on Alcator C-Mod

Progress and scientific results in the TCV tokamak

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