Fast-ion transport induced by Alfvén eigenmodes in the ASDEX Upgrade tokamak

García-Muñoz, M.; Classen, I. G. J.; Geiger, B.; Heidbrink, W. W.; Zeeland, M. A. Van; Äkäslompolo, S.; Bilato, R.; Bobkov, V.; Brambilla, M.; Conway, G. D.; Graca, S. da; Igochine, V.; Lauber, P.; Luhmann, N. C.; Maraschek, M.; Méo, F.; Park, H.; Schneller, M.; Tardini, G.

doi:10.1088/0029-5515/51/10/103013

Cited by 61 publications

(65 citation statements)

References 58 publications

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“…If J views are available and I measurements in u i (CTS) or λ i (FIDA) are taken in each view, then the total number of measurements is M = I × J . W is then a transfer matrix of size M × N taking F into G. The prescription given here corresponds to stacking lines or rows on top of each other but the order of this reorganization of the matrices is arbitrary as long as we obey equation (4). The forward problem to determine g from f or equivalently G from F is straightforward given that w and consequently W are known.…”

Section: Tomographic Reconstruction Prescriptionmentioning

confidence: 99%

Tomography of fast-ion velocity-space distributions from synthetic CTS and FIDA measurements

Salewski¹,

Geiger²,

Nielsen³

et al. 2012

Nucl. Fusion

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122

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We compute tomographies of 2D fast-ion velocity distribution functions from synthetic collective Thomson scattering (CTS) and fast-ion D α (FIDA) 1D measurements using a new reconstruction prescription. Contradicting conventional wisdom we demonstrate that one single 1D CTS or FIDA view suffices to compute accurate tomographies of arbitrary 2D functions under idealized conditions. Under simulated experimental conditions, single-view tomographies do not resemble the original fast-ion velocity distribution functions but nevertheless show their coarsest features. For CTS or FIDA systems with many simultaneous views on the same measurement volume, the resemblance improves with the number of available views, even if the resolution in each view is varied inversely proportional to the number of views, so that the total number of measurements in all views is the same. With a realistic four-view system, tomographies of a beam ion velocity distribution function at ASDEX Upgrade reproduce the general shape of the function and the location of the maxima at full and half injection energy of the beam ions. By applying our method to real many-view CTS or FIDA measurements, one could determine tomographies of 2D fast-ion velocity distribution functions experimentally.

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Section: Tomographic Reconstruction Prescriptionmentioning

confidence: 99%

Tomography of fast-ion velocity-space distributions from synthetic CTS and FIDA measurements

Salewski¹,

Geiger²,

Nielsen³

et al. 2012

Nucl. Fusion

Self Cite

122

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“…2.5 MW of NBI heating (93 keV beam) was applied in the current ramp-up phase of a series of low density discharges, identical to the scenarios described in [24,25,26]. The magnetic field was 2T .…”

Section: Experimental Observationsmentioning

confidence: 99%

NBI-driven Alfvénic modes at ASDEX Upgrade

Lauber

Classen

Curran³

et al. 2012

Nucl. Fusion

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Abstract. A large variety of electromagnetic modes excited by NBI-generated energetic ions are observed in the early phase of many discharges at ASDEX Upgrade. In addition to the well known reversed shear Alfvén eigenmodes (RSAE) and the toroidal Alfvén eigenmodes (TAE), a set of modes around 70 kHz is observed as recently described in [7]. The modes were identified to be beta-induced Alfvén eigenmodes (BAE) connected with the appearance of the q = 2 and the q = 1.5 surface during the current ramp-up phase. In the view of ITER, these BAEs may occur in scenarios with q ≈ 2 (scenario 4) and therefore add significantly to the transport of energetic ions due to RSAEs and TAEs. Experimentally, the combination of ECE, Soft-X-ray and magnetic measurements allows for a very reliable mode position and mode structure determination. The measurements are compared with linear gyrokinetic calculations employing the LIGKA code that uses a fully kinetic model to describe fast-particle-driven modes in general tokamak geometry .

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“…[5][6][7][8][9] A FILD measures the energetic ions bombarding a scintillator in the vicinity of a plasma-facing component. It has been used to investigate fast ion loss and the correlation with magnetic perturbations like Alfvén eigenmodes, 8 tearing modes, 10 and external magnetic perturbations. 11 It has the benefit of enhancing the reliability of analytical predictions for the loss particle energy and pitch-angle information by allowing direct comparison with measurements.…”

Section: Introductionmentioning

confidence: 99%

Prompt loss of beam ions in KSTAR plasmas

et al. 2016

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For a toroidal plasma facility to realize fusion energy, researching the transport of fast ions is important not only due to its close relation to the heating and current drive efficiencies but also to determine the heat load on the plasma-facing components. We present a theoretical analysis and orbit simulation for the origin of lost fast-ions during neutral beam injection (NBI) heating in Korea Superconducting Tokamak Advanced Research (KSTAR) device. We adopted a two-dimensional phase diagram of the toroidal momentum and magnetic moment and describe detectable momentums at the fast-ion loss detector (FILD) position as a quadratic line. This simple method was used to model birth ions deposited by NBI and drawn as points in the momentum phase space. A Lorentz orbit code was used to calculate the fast-ion orbits and present the prompt loss characteristics of the KSTAR NBI. The scrape-off layer deposition of fast ions produces a significant prompt loss, and the model and experimental results closely agreed on the pitch-angle range of the NBI prompt loss. Our approach can provide wall load information from the fast ion loss. © 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

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Fast-ion transport induced by Alfvén eigenmodes in the ASDEX Upgrade tokamak

Cited by 61 publications

References 58 publications

Tomography of fast-ion velocity-space distributions from synthetic CTS and FIDA measurements

Tomography of fast-ion velocity-space distributions from synthetic CTS and FIDA measurements

NBI-driven Alfvénic modes at ASDEX Upgrade

Prompt loss of beam ions in KSTAR plasmas

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