Observation of accelerated beam ion population during edge localized modes in the ASDEX Upgrade tokamak

Galdón-Quiroga, J.; García-Muñoz, M.; McClements, K. G.; Nocente, M.; Denk, S. S.; Freethy, S. J.; Jacobsen, A. S.; Orain, F.; Rivero-Rodriguez, J. F.; Salewski, M.; Sanchis-Sanchez, L.; Suttrop, W.; Viezzer, E.; Willensdorfer, M.; Team, EUROfusion Mst

doi:10.1088/1741-4326/ab1376

Cited by 9 publications

(19 citation statements)

References 32 publications

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“…In previous studies, the signals of two different FILDs in AUG separated 113 • toroidally (FILD1 and FILD2) were compared, revealing a non-homogeneous distribution of the ELM-induced losses in the toroidal direction [5,6]. Now, a FILD poloidal array [20][21][22] makes it possible to study the poloidal distribution of the losses.…”

Section: Resultsmentioning

confidence: 99%

“…The proposed cause for fast-ion acceleration was an electric field parallel to the magnetic field lines arising during magnetic reconnection events, that are believed to occur during ELM crashes [7]. Observations of electron acceleration during magnetic reconnection events in MAST [8,9] and AUG [6] appear to support this hypothesis. However, a preferential acceleration parallel to the magnetic field would reduce the pitch angle (Λ = arccos( v ∥ v )) of the accelerated fast ions.…”

Section: Introductionmentioning

confidence: 93%

“…ELMs collapse the plasma pedestal, causing a burst of energy and density to the tokamak wall that is expected to be intolerable during sustained operation in future devices [3,4]. Recent experiments in the ASDEX Upgrade tokamak have revealed accelerated beam-ion losses correlated with a particular category of ELM referred to as type I [5,6]. The experiments give clear evidence that the fastions are accelerated and their losses increased by the ELM perturbation, although the particular mechanism by which fast ions are transported and accelerated is still largely unknown.…”

Section: Introductionmentioning

confidence: 99%

“…This work also combines for the first time magnetohydrodynamic (MHD) simulations from the hybrid kinetic-MHD code MEGA [11,12] and fast-ion orbit simulations from the Monte-Carlo orbit-following code ASCOT [13]. The numerical results quantify for the first time the effect of ELMs on the confined and lost fast-ion distributions using realistic MHD simulations to compute the electromagnetic perturbation, in contrast with the analytical perturbation prescribed in previous studies [5,6]. The full-orbit simulations of the fast ions use a time-evolving 3D description of the electromagnetic perturbation.…”

Section: Introductionmentioning

confidence: 99%

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Transport and acceleration mechanism of fast ions during edge localized modes in ASDEX Upgrade

et al. 2023

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Observations of enhanced fast-ion losses during edge localized modes (ELMs) have been reported in the ASDEX Upgrade tokamak, revealing losses above the injection energy. This suggests that fast ions can be accelerated and lost due to the ELMs. Recent analysis of the ELM-induced losses suggests that the fast ions are lost due to a resonant interaction with the electromagnetic perturbation during the ELM crash. The fast-ion transport and acceleration during ELMs is modelled using electromagnetic fields computed using the hybrid kinetic-MHD code MEGA, while fast-ion full orbits are tracked with the ASCOT code. Time-evolving 3D electromagnetic fields have been implemented in ASCOT to compute fast-ion orbits in the presence of fast MHD events such as ELMs. The simulations successfully reproduce a field-aligned pattern of the losses on the tokamak wall and the formation of an accelerated population in the lost fast-ion distribution, while they predict an accelerated population in the confined distribution. A parametric study of the fast-ion constants of motion suggests a resonant interaction between the fast-ions and the electromagnetic fields arising during the ELM crash. In the case of fast-ion acceleration, the perpendicular electric perturbation, with scales smaller than the fast-ion gyroradius, breaks magnetic moment conservation and resonantly modifies the fast-ion energy.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Transport and acceleration mechanism of fast ions during edge localized modes in ASDEX Upgrade

et al. 2023

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“…The signal is observed to increase linearly after the collimator slit is inserted beyond the protection limiters. The large spikes in the traces correspond to losses induced by edge-localized modes (ELMs) [12]. In figure 7(b), when beam #7 was replaced by beam #6, APD signal during ELMs and shadow region is removed, so the linear dependence of fast-ion losses on the radial position can be easily observed.…”

Section: Jinst 14 C11005mentioning

confidence: 98%

First measurements of a magnetically driven fast-ion loss detector on ASDEX Upgrade

Gonzalez-Martin¹,

García-Muñoz²,

Herrmann³

et al. 2019

J. Inst.

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A new scintillator-based fast-ion loss detector (FILD) has been deployed ~45º below the midplane of the ASDEX Upgrade tokamak. Port unavailability at this remote location requires an in-situ magnetically driven manipulator to move the diagnostic head horizontally through the scrape-off layer (SOL). The linear displacement is produced by an externally energized coil, whose magnetic dipole tries to align with the toroidal component of the tokamak magnetic field. The insertion is given by force balance between a retaining spring and the energized solenoid, whose current is regulated in real-time, opening the possibility of self-adaptive real-time control of the probe head location based on its temperature. The diagnostic head contains a scintillator screen, Faraday cup, thermocouple and collimator systems. The scintillator image is transferred to a vacuum window using a 3.5 meters quartz image guide. The light acquisition system is composed by a charge coupled device (CCD) camera, for high velocity-space resolution, and by an 8x4 channels avalanche photo diode (APD) camera, for high temporal resolution (up to 2MHz). First measurements of magnetohydrodynamic (MHD) induced fast-ion losses and radially resolved fast-ion losses are presented.

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Self-adaptive diagnostic of radial fast-ion loss measurements on the ASDEX Upgrade tokamak (invited)

Gonzalez-Martin

García-Muñoz

Sieglin

et al. 2021

Review of Scientific Instruments

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A poloidal array of scintillator-based Fast-Ion Loss Detectors (FILDs) has been installed in the ASDEX Upgrade (AUG) tokamak. While all AUG FILD systems are mounted on reciprocating arms driven externally by servomotors, the reciprocating system of the FILD probe located just below the midplane is based on a magnetic coil that is energized in real-time by the AUG discharge control system. This novel reciprocating system allows, for the first time, real-time control of the FILD position including infrared measurements of its probe head temperature to avoid overheating. This considerably expands the diagnostic operational window, enabling unprecedented radial measurements of fast-ion losses. Fast collimator-slit sweeping (up to 0.2 mm/ms) is used to obtain radially resolved velocity-space measurements along 8 cm within the scrape-off layer. This provides a direct evaluation of the neutral beam deposition profiles via first-orbit losses. Moreover, the light-ion beam probe (LIBP) technique is used to infer radial profiles of fast-ion orbit deflection. This radial-LIBP technique is applied to trapped orbits (exploring both the plasma core and the FILD stroke near the wall), enabling radial localization of internal plasma fluctuations (neoclassical tearing modes). This is quantitatively compared against electron cyclotron emission measurements, showing excellent agreement. For the first time, radial profiles of fast-ion losses in MHD quiescent plasmas as well as in the presence of magnetic islands and edge localized modes are presented.

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Observation of accelerated beam ion population during edge localized modes in the ASDEX Upgrade tokamak

Cited by 9 publications

References 32 publications

Transport and acceleration mechanism of fast ions during edge localized modes in ASDEX Upgrade

Transport and acceleration mechanism of fast ions during edge localized modes in ASDEX Upgrade

First measurements of a magnetically driven fast-ion loss detector on ASDEX Upgrade

Self-adaptive diagnostic of radial fast-ion loss measurements on the ASDEX Upgrade tokamak (invited)

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