A data acquisition system for real-time magnetic equilibrium reconstruction on ASDEX Upgrade and its application to NTM stabilization experiments

Giannone, L.; Reich, M.; Maraschek, M.; Poli, E.; Rapson, C.; Barrera, L.; McDermott, R. M.; Mlynek, A.; Ruan, Qingwei; Treutterer, W.; Wenzel, L.; Bock, A.; Conway, G. D.; Fischer, R.; Fuchs, Julien; Lackner, K.; McCarthy, Patrick J.; Preuss, R.; Rampp, Markus; Schuhbeck, K. H.; Stober, J.; Zohm, H.

doi:10.1016/j.fusengdes.2013.10.008

Cited by 24 publications

(36 citation statements)

References 45 publications

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“…6, the measured diamagnetic flux is compared to that predicted by the TRANSP simulation for a discharge with neutral beam and electron cyclotron heating. The poloidal beta inferred from the diamagnetic flux measurement, 19 β DIA , is in good agreement with the values calculated from the real-time 20,21 and offline magnetic equilibrium reconstruction codes, β MHD , in the steady state phase of the discharges. In the discharge with electron cyclotron heating, the increase in poloidal beta with time is due to a steady increase in the nitrogen seeding introduced for reduction of the heat load to the divertor target.…”

Section: Transp Simulationssupporting

confidence: 77%

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Real-time diamagnetic flux measurements on ASDEX Upgrade

Giannone

Geiger

Bilato

et al. 2016

Review of Scientific Instruments

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Author(s)Giannone, L.; Geiger, B.; Bilato, R.; Maraschek, M.; Odstrčil, T.;Fischer, R.; Fuchs, J. C.; McCarthy, Patrick J.; Mertens, V.; Schuhbeck, K. H. Publication date 2016-05-24Original citation Giannone, L., Geiger, B., Bilato, R., Maraschek, M., Odstrčil, T., Real-time diamagnetic flux measurements are now available on ASDEX Upgrade. In contrast to the majority of diamagnetic flux measurements on other tokamaks, no analog summation of signals is necessary for measuring the change in toroidal flux or for removing contributions arising from unwanted coupling to the plasma and poloidal field coil currents. To achieve the highest possible sensitivity, the diamagnetic measurement and compensation coil integrators are triggered shortly before plasma initiation when the toroidal field coil current is close to its maximum. In this way, the integration time can be chosen to measure only the small changes in flux due to the presence of plasma. Two identical plasma discharges with positive and negative magnetic field have shown that the alignment error with respect to the plasma current is negligible. The measured diamagnetic flux is compared to that predicted by TRANSP simulations. The poloidal beta inferred from the diamagnetic flux measurement is compared to the values calculated from magnetic equilibrium reconstruction codes. The diamagnetic flux measurement and TRANSP simulation can be used together to estimate the coupled power in discharges with dominant ion cyclotron resonance heating.[http://dx

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Section: Transp Simulationssupporting

confidence: 77%

“…22 The details of implementation of the real-time equilibrium code, JANET, and the differences between the real-time and offline equilibrium code, CLISTE, have been discussed. 20 It can be seen in the early phases of the discharges in Figs. 5 and 6 that the difference between β DIA and β MHD increased with decreasing β MHD .…”

Section: Transp Simulationsmentioning

confidence: 91%

Real-time diamagnetic flux measurements on ASDEX Upgrade

Giannone

Geiger

Bilato

et al. 2016

Review of Scientific Instruments

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“…1 of Ref. 28). The vertical stabilization coils may be too far from the plasma for a fast vertical position correction.…”

Section: Discussionmentioning

confidence: 98%

“…1 of Ref. 28). The applied voltages modify the currents in the field coils, generating inductive magnetic fields that react back on the plasma.…”

Section: Introductionmentioning

confidence: 88%

Control system-plasma synchronization and naturally occurring edge localized modes in a tokamak

et al. 2018

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Edge Localised Modes (ELMs) naturally occur in tokamak plasmas in high confinement mode. We find in ASDEX Upgrade that the plasma can transition into a state in which the control system field coil currents, required to continually stabilize the plasma, continually oscillate with the plasma edge position and total MHD energy. These synchronous oscillations are one-to-one correlated with the occurrence of natural ELMs; the ELMs all occur when the control system coil current is around a specific phase. This suggests a phase synchronous state in which nonlinear feedback between plasma and control system is intrinsic to natural ELMing, and in which the occurrence time of a natural ELM is conditional on the phase of the control system field coil current.

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“…By correlating all fast ECE channels separately with this characteristic signal the mode related content of the T e fluctuations is extracted and the expected radial phase jump in these fluctuations can be determined and is assigned to the mode position [8]. Initially the result is a fractional ECEchannel-number which can be translated into a rho-value using the real-time equilibrium [9] and the ECE-optics. Since the ECE-antenna is located at the outboard midplane and the optical axis is almost perpendicular to the flux surfaces (at least up to half radius where the NTMs are located) we neglect (so far) any bending of the ECEviewing-geometry by density gradients.…”

Section: Feedback Controlled Ntm-stabilisationmentioning

confidence: 99%

Feedback-controlled NTM stabilization on ASDEX Upgrade

Stober

Barrera

Behler

et al. 2015

EPJ Web of Conferences

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Abstract. On ASDEX Upgrade a concept for real-time stabilization of NTMs has been realized and successfully applied to (3,2)-and (2,1)-NTMs. Since most of the work has meanwhile been published elsewhere, a short summary with the appropriate references is given. Limitations, deficits and future extensions of the system are discussed. In a second part the recent work on using modulated ECCD for NTM stabilisation is described in some detail. In these experiments ECCD power is modulated according to a magnetic footprint of the rotating NTM. In agreement with earlier results it could be shown that O-point heating reduces the necessary average power for stabilisation whereas X-point heating hampers stabilisation. Although this modulated scheme is not relevant for routine NTM stabilisation on ASDEX Upgrade it may be mandatory for ITER or DEMO. On ASDEX Upgrade it has been re-developed to demonstrate the usage of a FAst DIrectional Switch to continously heat the O-point of the rotating island with only one gyrotron switching between two launchers which target the mode at locations separated in phase by 180 degrees as described in [1].

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A data acquisition system for real-time magnetic equilibrium reconstruction on ASDEX Upgrade and its application to NTM stabilization experiments

Cited by 24 publications

References 45 publications

Real-time diamagnetic flux measurements on ASDEX Upgrade

Real-time diamagnetic flux measurements on ASDEX Upgrade

Control system-plasma synchronization and naturally occurring edge localized modes in a tokamak

Feedback-controlled NTM stabilization on ASDEX Upgrade

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