Tracking of neoclassical tearing modes in TCV using the electron cyclotron emission diagnostics in quasi-in-line configuration

Rispoli, N.; Sozzi, C.; Figini, L.; Micheletti, D.; Galperti, C.; Fontana, M.; Alessi, E.; Coda, S.; Garavaglia, S.; Goodman, T. P.; Kong, M.; Maraschek, M.; Moro, A.; Porte, L.; Sauter, O.; Sheikh, U.; Testa, D.

doi:10.1016/j.fusengdes.2019.01.051

Cited by 3 publications

(2 citation statements)

References 5 publications

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“…A simple new analytical model for the time history of the magnetic Δ′ stability index, for NTMs triggered as classical tearing modes, was introduced and shown to provide accurate simulations of the island evo lution [33]. Quasiin-line ECE, nearly counter-linear with the associated ECRH actuator, was tested on TCV for monitoring the island's position, and was demonstrated to be accurate to within less than the EC beam width [34]. Though receiving less attention than NTMs in recent times, the vertical axisymmetric instability also remains a concern; while the (magnetic) stabilization technique is well understood, its economics are strongly affected by the minimum achievable stability margin in any given device.…”

Section: Real-time Controlmentioning

confidence: 99%

Physics research on the TCV tokamak facility: from conventional to alternative scenarios and beyond

Coda

Agostini²,

Albanese

et al. 2019

Nucl. Fusion

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The research program of the TCV tokamak ranges from conventional to advanced-tokamak scenarios and alternative divertor configurations, to exploratory plasmas driven by theoretical insight, exploiting the device’s unique shaping capabilities. Disruption avoidance by real-time locked mode prevention or unlocking with electron-cyclotron resonance heating (ECRH) was thoroughly documented, using magnetic and radiation triggers. Runaway generation with high-Z noble-gas injection and runaway dissipation by subsequent Ne or Ar injection were studied for model validation. The new 1 MW neutral beam injector has expanded the parameter range, now encompassing ELMy H-modes in an ITER-like shape and nearly non-inductive H-mode discharges sustained by electron cyclotron and neutral beam current drive. In the H-mode, the pedestal pressure increases modestly with nitrogen seeding while fueling moves the density pedestal outwards, but the plasma stored energy is largely uncorrelated to either seeding or fueling. High fueling at high triangularity is key to accessing the attractive small edge-localized mode (type-II) regime. Turbulence is reduced in the core at negative triangularity, consistent with increased confinement and in accord with global gyrokinetic simulations. The geodesic acoustic mode, possibly coupled with avalanche events, has been linked with particle flow to the wall in diverted plasmas. Detachment, scrape-off layer transport, and turbulence were studied in L- and H-modes in both standard and alternative configurations (snowflake, super-X, and beyond). The detachment process is caused by power ‘starvation’ reducing the ionization source, with volume recombination playing only a minor role. Partial detachment in the H-mode is obtained with impurity seeding and has shown little dependence on flux expansion in standard single-null geometry. In the attached L-mode phase, increasing the outer connection length reduces the in–out heat-flow asymmetry. A doublet plasma, featuring an internal X-point, was achieved successfully, and a transport barrier was observed in the mantle just outside the internal separatrix. In the near future variable-configuration baffles and possibly divertor pumping will be introduced to investigate the effect of divertor closure on exhaust and performance, and 3.5 MW ECRH and 1 MW neutral beam injection heating will be added.

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Section: Real-time Controlmentioning

confidence: 99%

Physics research on the TCV tokamak facility: from conventional to alternative scenarios and beyond

Coda

Agostini²,

Albanese

et al. 2019

Nucl. Fusion

View full text Add to dashboard Cite

show abstract

“…Advances in real-time (RT) equilibrium reconstructions, diagnostics and ray-tracing codes [12][13][14][15] contribute to a better estimation of mode and beam locations, while more NTM-control-oriented strategies have also been developed. For example, (quasi-)in-line electron cyclotron emission (ECE) diagnostics circumvents the requirement on RT equilibrium reconstructions or ray-tracing [16,17], though it can be technically challenging to separate the megawattlevel EC beam from the miliwatt-level ECE signals. Control algorithms seeking the minimum of island width or island width growth rate have also been developed [6,[18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Physics-based control of neoclassical tearing modes on TCV

Kong

Felici

Sauter

et al. 2022

Plasma Phys. Control. Fusion

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This paper presents recent progress on the studies of neoclassical tearing modes (NTMs) on TCV, concerning the new physics learned and how this physics contributes to a better real-time (RT) control of NTMs. A simple technique that adds a small (sinusoidal) sweeping to the target electron cyclotron (EC) beam deposition location has proven eﬀective both for the stabilization and prevention of 2⁄1 NTMs. This relaxes the strict requirement on beam-mode alignment for NTM control, which is diﬃcult to ensure in RT. In terms of the EC power for NTM stabilization, a control scheme making use of RT island width measurements has been tested on TCV. NTM seeding through sawtooth (ST) crashes or unstable current density proﬁles (triggerless NTMs) has been studied in detail. A new NTM prevention strategy utilizing only transient EC beams near the relevant rational surface has been developed and proven eﬀective for preventing ST-seeded NTMs. With a comprehensive modiﬁed Rutherford equation (co-MRE) that considers the classical stability both at zero and ﬁnite island width, the prevention of triggerless NTMs with EC beams has been simulated for the ﬁrst time. The prevention eﬀects are found to result from the local eﬀects of the EC beams (as opposed to global current proﬁle changes), as observed in a group of TCV experiments scanning the deposition location of the preemptive EC beam. The co-MRE has also proven able to reproduce well the island width evolution in distinct plasma scenarios on TCV, ASDEX Upgrade and MAST, with very similar constant coeﬃcients. The co-MRE has the potential of being applied in RT to provide valuable information such as the EC power required for NTM control with RT-adapted coeﬃcients, contributing to both NTM control and integrated control with a limited set of actuators.

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Overview of the TCV digital real-time plasma control system and its applications

Galperti,

Felici,

et al. 2024

Fusion Engineering and Design

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Tracking of neoclassical tearing modes in TCV using the electron cyclotron emission diagnostics in quasi-in-line configuration

Cited by 3 publications

References 5 publications

Physics research on the TCV tokamak facility: from conventional to alternative scenarios and beyond

Physics research on the TCV tokamak facility: from conventional to alternative scenarios and beyond

Physics-based control of neoclassical tearing modes on TCV

Overview of the TCV digital real-time plasma control system and its applications

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