Note: Internal diamagnetic flux measurements on ASDEX Upgrade

Giannone, L.; Fischer, R.; Fuchs, Julien; Geiger, B.; Maraschek, M.; Rittich, D.; Sieglin, B.; Bock, A.; Hobirk, J.; Kallenbach, A.; Mertens, V.; Schuhbeck, K. H.; McCarthy, Patrick J.

doi:10.1063/1.5045543

Cited by 8 publications

(9 citation statements)

References 12 publications

(10 reference statements)

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“…The FILD measurement does not show any significant loss of fast particles during the sawtooth event 52 . This is confirmed for the present plasma discharge by diamagnetic flux measurements 28 . Fig.…”

Section: Va Pressure Profiles and Fast-ion Redistributionsupporting

confidence: 87%

Sawtooth inducedq-profile evolution at ASDEX Upgrade

Fischer¹,

Bock²,

Burckhart³

et al. 2019

Nucl. Fusion

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The sawtooth induced q-profile evolution was modelled at ASDEX Upgrade and validated with imaging motional Stark effect (IMSE) measurements. The equilibrium current distribution was estimated by the coupling of a Grad-Shafranov solver and the current diffusion equation. At ASDEX Upgrade an extensive diagnostic suite allows for a reliable modelling of the current density profile and its temporal evolution as long as neo-classical current diffusion can be assumed. The sawtooth-induced central q change, ∆q 0 , was estimated from equilibrium reconstruction between the sawtooth events without using IMSE measurements. The sawtooth-induced current relaxation is modelled with two different reconnection models, a Kadomtsev full reconnection and a newly developed fully stochastic flat-current model. Both models result in about the same sawtooth-induced ∆q 0 ≈ 0.10-0.12 but with a small difference in the absolute q 0 values. The sawtooth-induced evolution of the forward modelled MSE angles agrees well with the IMSE measurements. This confirms the assumption of neoclassical current diffusion between the sawtooth events. A sensitivity study reveals two major ingredients for a reliable interpretation of MSE measurements. Firstly, the sawtooth-induced redistribution of fast ions has to be taken into account for a reliable estimation of the Shafranov shift. The fast-ion redistribution is modelled with a particle-conserving homogeneous fast-ion pressure profile in the plasma core and a subsequent recovery time of 50 ms. Secondly, a reliable estimation of the electric field is necessary for a credible interpretation of the MSE angles.

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Section: Va Pressure Profiles and Fast-ion Redistributionsupporting

confidence: 87%

Sawtooth inducedq-profile evolution at ASDEX Upgrade

Fischer¹,

Bock²,

Burckhart³

et al. 2019

Nucl. Fusion

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“…A drift in the DIAf87 and DIAf89 signal (not shown) occurs when ELM's saturate the compensation probe integrator inputs. There is a toroidal asymmetry in the compensation probe signal leading to larger voltage spikes in the integrator input at this toroidal location [18]. The total plasma energy from TRANSP, W TOT , and the sum of thermal energy and fast-ion perpendicular energy from TRANSP, W TR DIA , are also plotted and closely match W MHD and W DIA respectively.…”

Section: Plasma Discharges With Perpendicular Neutral Beam Sourcesmentioning

confidence: 77%

“…Knowledge of the fast-ion contribution to the pressure profile is an important input for magnetic equilibrium reconstruction with pressure constraints. Earlier modelling of diamagnetic flux measurements on ASDEX Upgrade [17,18,31] used IDE equilibrium reconstruction [32] and TRANSP [33,34] for fast-ion pressure profiles. Real-time simulations of the NBI fast-ion distribution can also be calculated by the time-dependent solution of the Fokker-Planck equation (2D in velocity) based on analytic expressions by the RABBIT code [35].…”

Section: Measurements and Modellingmentioning

confidence: 99%

“…A number of tokamaks and stellarators have demonstrated the measurement of diamagnetic flux [4][5][6][7][8][9][10][11][12][13][14][15][16]. The time evolution of internal and external diamagnetic flux is routinely measured on ASDEX Upgrade [17,18]. A comparison of diamagnetic flux measurements and calculation from equilibrium reconstruction and transport simulations can identify discharge conditions where plasma anisotropy, fast-ion losses or transport are strong enough to lead to a discrepancy between measurements and modelling.…”

Section: Introductionmentioning

confidence: 99%

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Measurements and modelling of diamagnetic flux in ASDEX Upgrade

et al. 2021

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The reproducibility of diamagnetic flux measurements in vacuum field shots for the internal and external diamagnetic flux measurements in the ASDEX Upgrade tokamak is investigated. A comparison of diamagnetic flux measurements and predictions from equilibrium reconstruction, including pressure constraints from thermal and fast-ion contributions, is reported. The ideal magnetohydrodynamic model involved in interpreting diamagnetic flux measurements in a tokamak with anisotropic pressure is summarised. The plasma energy calculated from equilibrium reconstruction and inferred from diamagnetic flux measurements is compared with the respective values calculated by modelling with TRANSP and IDE/RABBIT. It is found that at low densities, in discharges with parallel neutral beam sources, the plasma energy inferred from the diamagnetic flux measurements is smaller than the plasma energy calculated from the equilibrium reconstruction. In addition, details of the modelling are discussed to stress the interdependence of the various modelling inputs and the interpretation of the results. A comparison of diamagnetic flux measurements with calculations from equilibrium reconstruction by IDE and fast-ion profiles from RABBIT and TRANSP simulations can identify anisotropic plasma discharges and provide a consistency check of the input data for modelling.

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“…During the ramping up and down phases of the toroidal magnetic field the diamagnetic flux loops pick up flux. This is not desired since only the flux change induced by the plasma is of interest for the equilibrium reconstruction [20].…”

Section: Magneticsmentioning

confidence: 99%

DCS satellite: Enhanced plant system integration on ASDEX Upgrade

Sieglin

Treutterer

Giannone

2019

Fusion Engineering and Design

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For present and future fusion experiments, a higher level of integration for plant systems into the discharge control system (DCS) is becoming increasingly important. The integration is required to enable more sophisticated control schemes where a comprehensive plasma system state is needed. This is especially the case for large fusion devices such as ITER. On ASDEX Upgrade the integration of diagnostics, actuators and evaluation codes is done in a unified concept, the DCS satellite. Here the DCS framework and signal exchange is adopted on e.g. diagnostic nodes, where specialized DCS application processes (AP) interact with the sensor hardware, import it into the DCS system and let other APs process the data. This concept allows automated configuration and identification of the current plant system setup prior to the discharge execution. A comprehensive plasma state is generated during a pulse by the DCS framework which enables information exchange between the different DCS systems. So far this concept has successfully been demonstrated for National Instruments NI-RIO based FPGA diagnostics, video real time diagnostics (VRT) using CameraLink cameras, diagnostics using IPPs in-house standard SIO2 as well as diagnostic codes such as the equilibrium reconstruction code JANET++.

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Note: Internal diamagnetic flux measurements on ASDEX Upgrade

Abstract: Internal diamagnetic flux measurements, with measurement loops and compensation magnetic probes inside the vacuum vessel, are now available on the ASDEX Upgrade tokamak. The measured diamagnetic flux is compared to

Cited by 8 publications

References 12 publications

Sawtooth inducedq-profile evolution at ASDEX Upgrade

Sawtooth inducedq-profile evolution at ASDEX Upgrade

Measurements and modelling of diamagnetic flux in ASDEX Upgrade

DCS satellite: Enhanced plant system integration on ASDEX Upgrade

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