Enhanced Localized Energetic-Ion Losses Resulting from Single-Pass Interactions with Alfvén Eigenmodes

Chen, X.; Austin, M. E.; Fisher, R. K.; Heidbrink, W. W.; Kramer, G. J.; Nazikian, R.; Pace, D. C.; Petty, C. C.; Zeeland, M. A. Van

doi:10.1103/physrevlett.110.065004

Cited by 28 publications

(36 citation statements)

References 21 publications

(12 reference statements)

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“…An example (first reported in Ref. 21) is shown in Fig. 4, during the early plasma current ramping phase in a neutral beam heated reversed magnetic shear plasma, two tangential co-current neutral beams are alternatively injected.…”

Section: B Radial Displacement Of Fast Ions Due To Individual Alfvénmentioning

confidence: 99%

Using neutral beams as a light ion beam probe (invited)

Chen

Heidbrink

Zeeland

et al. 2014

Review of Scientific Instruments

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By arranging the particle first banana orbits to pass near a distant detector, the light ion beam probe (LIBP) utilizes orbital deflection to probe internal fields and field fluctuations. The LIBP technique takes advantage of (1) the in situ, known source of fast ions created by beam-injected neutral particles that naturally ionize near the plasma edge and (2) various commonly available diagnostics as its detector. These born trapped particles can traverse the plasma core on their inner banana leg before returning to the plasma edge. Orbital displacements (the forces on fast ions) caused by internal instabilities or edge perturbing fields appear as modulated signal at an edge detector. Adjustments in the q-profile and plasma shape that determine the first orbit, as well as the relative position of the source and detector, enable studies under a wide variety of plasma conditions. This diagnostic technique can be used to probe the impact on fast ions of various instabilities, e.g., Alfvén eigenmodes (AEs) and neoclassical tearing modes, and of externally imposed 3D fields, e.g., magnetic perturbations. To date, displacements by AEs and by externally applied resonant magnetic perturbation fields have been measured using a fast ion loss detector. Comparisons with simulations are shown. In addition, nonlinear interactions between fast ions and independent AE waves are revealed by this technique.

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Section: B Radial Displacement Of Fast Ions Due To Individual Alfvénmentioning

confidence: 99%

Using neutral beams as a light ion beam probe (invited)

Chen

Heidbrink

Zeeland

et al. 2014

Review of Scientific Instruments

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“…The "local resonance" is also called "single-pass resonance" for particles which are lost after interacting with the AE mode in a single bounce orbit in some papers. 5,11 The calculated radial displacement (about a few centimeters) after one bounce is proportional to the AE amplitude with the same frequency. The local resonance condition is given by…”

Section: Introductionmentioning

confidence: 97%

“…[1][2][3][4][5][6][7][8][9] The losses were measured using a Fast Ion Loss Detector (FILD) with a high frequency response and were coherent with the Alfv en eigenmodes. It was shown that the coherent losses in DIII-D mainly come from trapped particles whose orbits are close to the tokamak wall.…”

Section: Introductionmentioning

confidence: 99%

“…It was shown that the coherent losses in DIII-D mainly come from trapped particles whose orbits are close to the tokamak wall. 5,6 These trapped ions are first ionized close to the edge of the plasma, are "kicked out" radially by the Alfv en modes via wave particle interactions, and are then lost to the wall within one bounce of the banana orbits. The coherent FILD signals oscillate at the same frequencies of the corresponding AEs, while the amplitudes of the FILD signals are proportional to those of the AEs.…”

Section: Introductionmentioning

confidence: 99%

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Numerical study on wave-induced beam ion prompt losses in DIII-D tokamak

Feng

Zhu

et al. 2017

Physics of Plasmas

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A numerical study is performed on the coherent beam ion prompt losses driven by Alfv en eigenmodes (AEs) in DIII-D plasmas using realistic parameters and beam ion deposition profiles. The synthetic signal of a fast-ion loss detector (FILD) is calculated for a single AE mode. The first harmonic of the calculated FILD signal is linearly proportional to the AE amplitude with the same AE frequency in agreement with the experimental measurement. The calculated second harmonic is proportional to the square of the first harmonic for typical AE amplitudes. The coefficient of quadratic scaling is found to be sensitive to the AE mode width. The second part of this work considers the AE drive due to coherent prompt loss. It is shown that the loss-induced mode drive is much smaller than the previous estimate and can be ignored for mode stability. Published by AIP Publishing. [http://dx

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“…For a loss detector, the signal from this toroidally localized source is often much larger than axisymmetric losses [7]. Since the beam deposition and equilibrium fast-ion orbits are well understood, these ions can be used to measure the effect of waves that deflect the orbits [7,8].…”

Section: Introductionmentioning

confidence: 99%

Measurement and simulation of passive fast-ion D-alpha emission from the DIII-D tokamak

Bolte¹,

Heidbrink²,

Pace³

et al. 2016

Nucl. Fusion

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A sudden loss of fast ions would not only jeopardize plasma performance, but could also-especially in near-reactor conditions-seriously damage the inner wall of the vessel. Accordingly, detection of fast ions near the walls is an important diagnostic challenge.Two types of fast-ion diagnostics utilize charge exchange (CX) reactions between fast ions and neutrals: neutral particle analysis (NPA) and fast-ion D-alpha (FIDA) spectroscopy. A distinction is made between active beam measurements that use CX with injected neutrals and passive measurements that use background neutrals. For active measurements, signals originate near the intersection of the diagnostic sightline with AbstractSpectra of passive fast-ion D-alpha (FIDA) light from beam ions that charge exchange with background neutrals are measured and simulated. The fast ions come from three sources: ions that pass through the diagnostic sightlines on their first full orbit, an axisymmetric confined population, and ions that are expelled into the edge region by instabilities. A passive FIDA simulation (P-FIDASIM) is developed as a forward model for the spectra of the first-orbit fast ions and consists of an experimentally-validated beam deposition model, an ion orbit-following code, a collisional-radiative model, and a synthetic spectrometer. Model validation consists of the simulation of 86 experimental spectra that are obtained using 6 different neutral beam fast-ion sources and 13 different lines of sight. Calibrated spectra are used to estimate the neutral density throughout the cross-section of the tokamak. The resulting 2D neutral density shows the expected increase toward each X-point with average neutral densities of 8 10 cm 9 3 × − at the plasma boundary and 1 10 cm 11 3 × − near the wall. Fast ions that are on passing orbits are expelled by the sawtooth instability more readily than trapped ions. In a sample discharge, approximately 1% of the fast-ion population is ejected into the high neutral density region per sawtooth crash.

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Enhanced Localized Energetic-Ion Losses Resulting from Single-Pass Interactions with Alfvén Eigenmodes

Cited by 28 publications

References 21 publications

Using neutral beams as a light ion beam probe (invited)

Using neutral beams as a light ion beam probe (invited)

Numerical study on wave-induced beam ion prompt losses in DIII-D tokamak

Measurement and simulation of passive fast-ion D-alpha emission from the DIII-D tokamak

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