Control of neoclassical tearing modes

Maraschek, M.

doi:10.1088/0029-5515/52/7/074007

Cited by 66 publications

(66 citation statements)

References 97 publications

(172 reference statements)

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“…As discussed already in [15,17] there is an intrinsic phase delay between the Mirnov signal and the ECCD modulation due to two independent effects. The O-point corresponds to the zero ofḂ R where the sign ofḂ R changes from positive to negative, resulting in a phase difference of 90…”

Section: Ntm Stabilisation With Modulated Eccdmentioning

confidence: 83%

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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Section: Ntm Stabilisation With Modulated Eccdmentioning

confidence: 83%

Feedback-controlled NTM stabilization on ASDEX Upgrade

Stober

Barrera

Behler

et al. 2015

EPJ Web of Conferences

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“…For control and monitoring in DCS raw sensor signals are processed to reconstruct main physics quantities such as plasma separatrix geometry [6], magnetic flux coordinates [7], electron and neutral density and density profiles [8], radiated power, power fluxes, effective heating power components, stored energy, plasma confinement parameters [9,10], MHD and locked mode amplitudes and locations [11,12] and disruption precursors [13,14]. To distribute and parallelise the working load, part of these quantities are not computed by DCS but directly by real-time enabled digital diagnostic systems [15].…”

Section: Measurements and Plasma Reconstructionmentioning

confidence: 99%

ASDEX Upgrade Discharge Control System—A real-time plasma control framework

Treutterer

Cole²,

Lüddecke³

et al. 2014

Fusion Engineering and Design

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ASDEX Upgrade is a fusion experiment with a size and complexity to allow extrapolation of technical and physical conditions and requirements to devices like ITER and even beyond. In addressing advanced physics topics it makes extensive use of sophisticated real-time control methods. It comprises real-time diagnostic integration, dynamically adaptable multivariable feedback schemes, actuator management including load distribution schemes and a powerful monitoring and pulse supervision concept based on segment scheduling and exception handling. The Discharge Control System (DCS) supplies all this functionality on base of a modular software framework architecture designed for real-time operation. It provides system-wide services like workflow management, logging and archiving, self-monitoring and inter-process communication on Linux, VxWorks and Solaris operating systems. By default DCS supports distributed computing, and a communication layer allows multi-directional signal transfer and data-driven process synchronisation over shared memory as well as over a number of real-time networks. The entire system is built following the same common design concept combining a rich set of re-usable generic but highly customisable components with a configurationdriven component deployment method.We will give an overview on the architectural concepts as well as on the outstanding capabilities of DCS in the domains of inter-process communication, generic feedback control and pulse supervision. In each of these domains, DCS has contributed important ideas and methods to the on-going design of the ITER plasma control system. We will identify and describe these essential features and illustrate them with examples from ASDEX Upgrade operation.

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“…1 The primary tactic for controlling and suppressing NTMs is to apply electron cyclotron current drive (ECCD) in a localized area inside the magnetic islands. [2][3][4][5][6][7] In the limit of low plasma beta, the neoclassical bootstrap current, which distinguishes a neoclassical tearing mode from a classical tearing mode, is negligibly small. The low beta limit represents a simplification of the full physics of fusion plasmas, which is still of interest.…”

Section: Introductionmentioning

confidence: 99%

“…Changes in the island width can also be calculated from the magnetic field perturbation, which is constructed from an integrated and weighted sum of Mirnov coil measurements. 7,11 However, experiments have not been able to produce a complete picture of the dynamics internal to the island during stabilization. A deeper understanding of this physical process is necessary in order to ultimately build a more detailed theory of stabilization than the generalized Rutherford equation provides.…”

Section: Introductionmentioning

confidence: 99%

Early evolution of electron cyclotron driven current during suppression of tearing modes in a circular tokamak

2016

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When electron cyclotron (EC) driven current is first applied to the inside of a magnetic island, the current spreads throughout the island and after a short period achieves a steady level. Using a two equation fluid model for the EC current that allows us to examine this early evolution in detail, we analyze high-resolution simulations of a 2/1 classical tearing mode in a low-beta large aspectratio circular tokamak. These simulations use a nonlinear 3D reduced-MHD fluid model and the JOREK code. During the initial period where the EC driven current grows and spreads throughout the magnetic island, it is not a function of the magnetic flux. However, once it has reached a steady-state, it should be a flux function. We demonstrate numerically that if sufficiently resolved toroidally, the steady-state EC driven current becomes approximately a flux function. We discuss the physics of this early period of EC evolution and its impact on the size of the magnetic island.

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Control of neoclassical tearing modes

Cited by 66 publications

References 97 publications

Feedback-controlled NTM stabilization on ASDEX Upgrade

Feedback-controlled NTM stabilization on ASDEX Upgrade

ASDEX Upgrade Discharge Control System—A real-time plasma control framework

Early evolution of electron cyclotron driven current during suppression of tearing modes in a circular tokamak

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