Modeling the response of a fast ion loss detector using orbit tracing techniques in a neutral beam prompt-loss study on the DIII-D tokamak

Pace, D. C.; Fisher, R. K.; García-Muñoz, M.; Darrow, D. S.; Heidbrink, W. W.; Muscatello, C. M.; Nazikian, R.; Zeeland, M. A. Van; Zhu, Y. B.

doi:10.1063/1.3478996

Cited by 21 publications

(18 citation statements)

References 15 publications

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“…This paper describes the detailed analysis and modeling of an experiment designed to investigate fast-ion loss induced by internal coil (I-coil) imposed rotating n = 2 (n = toroidal mode number) magnetic perturbations in the DIII-D tokamak. In the experiment, loss of 80 keV injected beam ions was observed by two energy and pitch angle resolving fast-ion loss detectors (FILDs) located near the outboard midplane (FILD-mid) and significantly below the outboard midplane (FILD-low) [8][9][10]. The dominant loss signal observed by each detector was found to be due to prompt beam ion loss and the midplane FILD observed modulation of the prompt beam ion losses synchronized with the n = 2 fields.…”

Section: Introductionmentioning

confidence: 99%

Modulation of prompt fast-ion loss by appliedn= 2 fields in the DIII-D tokamak

Zeeland¹,

Ferraro²,

Heidbrink³

et al. 2013

Plasma Phys. Control. Fusion

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Energy and pitch angle resolved measurements of escaping neutral beam ions (E ≈ 80 keV) have been made during DIII-D L-mode discharges with applied, slowly rotating, n = 2 magnetic perturbations. Data from separate scintillator detectors (FILDs) near and well below the plasma midplane show fast-ion losses correlated with the internal coil (I-coil) fields. The dominant fast-ion loss signals are observed to decay within one poloidal transit time after beam turn-off indicating they are primarily prompt loss orbits. Also, during application of the rotating I-coil fields, outboard midplane edge density and bremsstrahlung emission profiles exhibit a radial displacement of up to δR ≈ 1 cm. Beam deposition and full orbit modeling of these losses using M3D-C1 calculations of the perturbed kinetic profiles and fields reproduce many features of the measured losses. In particular, the predicted phase of the modulated loss signal with respect to the I-coil currents is in close agreement with FILD measurements as is the relative amplitudes of the modulated losses for the co and counter-current beam used in the experiment. These simulations show modifications to the beam ion birth profile and subsequent prompt loss due to changes in the edge density; however, the dominant factor causing modulation of the losses to the fast-ion loss detectors is the perturbed magnetic field (δB/B ≈ 10 −3 in the plasma). Calculations indicate total prompt loss to the DIII-D wall can increase with application of the n = 2 perturbation by up to 7% for co-current injected beams and 3% for counter-current injected beams depending on phase of the perturbation relative to the injected beam.

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Section: Introductionmentioning

confidence: 99%

Modulation of prompt fast-ion loss by appliedn= 2 fields in the DIII-D tokamak

Zeeland¹,

Ferraro²,

Heidbrink³

et al. 2013

Plasma Phys. Control. Fusion

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“…Even with acquisition rates below 1 kHz, camera data are useful for confirming the accuracy of strike maps based on alignment between the grid and stripes produced by neutral beam prompt losses. 45,46 The C-Mod installation does not allow for the necessary optics to transmit the en- tire scintillator surface outside of the vessel, and this initial probe design is limited to four fiber optic views. Commissioning of the FILD, therefore, includes operation during Ohmic plasma experiments in order to determine its typical response to scrape-off layer (SOL) plasma light and hard x-rays.…”

Section: Analysis and Initial Resultsmentioning

confidence: 99%

Energetic ion loss detector on the Alcator C-Mod tokamak

Pace

Granetz

Vieira

et al. 2012

Review of Scientific Instruments

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A scintillator-based energetic ion loss detector has been successfully commissioned on the Alcator C-Mod tokamak. This probe is located just below the outer midplane, where it captures ions of energies up to 2 MeV resulting from ion cyclotron resonance heating. After passing through a collimating aperture, ions impact different regions of the scintillator according to their gyroradius (energy) and pitch angle. The probe geometry and installation location are determined based on modeling of expected lost ions. The resulting probe is compact and resembles a standard plasma facing tile. Four separate fiber optic cables view different regions of the scintillator to provide phase space resolution. Evolving loss levels are measured during ion cyclotron resonance heating, including variation dependent upon individual antennae.

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“…This orbit modelling also allowed for the determination, using an established FILD analysis [26], that none of the FILD phase space is populated by prompt losses from the co-current injecting neutral beams that are used during the time of initial fast wave injection. There are three areas of phase space for which this modelling and the measurements appear to contrast.…”

Section: Phase Space Resolved Losses Measured By Fildmentioning

confidence: 99%

Scrape-off layer ion acceleration during fast wave injection in the DIII-D tokamak

Pace¹,

Pinsker²,

Heidbrink³

et al. 2012

Nucl. Fusion

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Fast wave injection is employed on the DIII-D tokamak as a current drive and electron heating method. Bursts of energetic ions with energy E o > 20 keV are observed immediately following fast wave injection in experiments featuring the 8th ion cyclotron harmonic near the antenna. Using the energy and pitch angle of the energetic ion burst as measured by a fast-ion loss detector, it is possible to trace the origin of these ions to a particular antenna. The ion trajectories exist entirely within the scrape-off layer. These observations are consistent with the presence of parametric decay instabilities near the antenna strap. It is suggested that the phase space capabilities of the loss detector diagnostic can improve studies of wave injection coupling and efficiency in tokamaks by directly measuring the effects of parametric decay thresholds.

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Modeling the response of a fast ion loss detector using orbit tracing techniques in a neutral beam prompt-loss study on the DIII-D tokamak

Cited by 21 publications

References 15 publications

Modulation of prompt fast-ion loss by appliedn= 2 fields in the DIII-D tokamak

Modulation of prompt fast-ion loss by appliedn= 2 fields in the DIII-D tokamak

Energetic ion loss detector on the Alcator C-Mod tokamak

Scrape-off layer ion acceleration during fast wave injection in the DIII-D tokamak

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