Phenomenology of energetic-ion loss from the DIII-D tokamak

Zhu, Y. B.; Heidbrink, W. W.; Pickering, L.D.

doi:10.1088/0029-5515/50/8/084024

Cited by 20 publications

(20 citation statements)

References 29 publications

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“…In DIII-D, the increase of EP loss rate observed by the beam-ion loss detector (BILD) 32 coincided with the increase of the mode distortion, as shown in Fig. 10.…”

Section: A Correlation Of Ep Loss and Mode Distortionmentioning

confidence: 69%

Off-axis fishbone-like instability and excitation of resistive wall modes in JT-60U and DIII-D

Okabayashi¹,

Matsunaga²,

deGrassie³

et al. 2011

Physics of Plasmas

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An energetic-particle (EP)-driven "off-axis-fishbone-like mode (OFM)" often triggers a resistive wall mode (RWM) in JT-60U and DIII-D devices, preventing long-duration high-b N discharges. In these experiments, the EPs are energetic ions (70-85 keV) injected by neutral beams to produce high-pressure plasmas. EP-driven bursting events reduce the EP density and the plasma rotation simultaneously. These changes are significant in high-b N low-rotation plasmas, where the RWM stability is predicted to be strongly influenced by the EP precession drift resonance and by the plasma rotation near the q ¼ 2 surface (kinetic effects). Analysis of these effects on stability with a self-consistent perturbation to the mode structure using the MARS-K code showed that the impact of EP losses and rotation drop is sufficient to destabilize the RWM in low-rotation plasmas, when the plasma rotation normalized by Alfvén frequency is only a few tenths of a percent near the q ¼ 2 surface. The OFM characteristics are very similar in JT-60U and DIII-D, including nonlinear mode evolution. The modes grow initially like a classical fishbone, and then the mode structure becomes strongly distorted. The dynamic response of the OFM to an applied n ¼ 1 external field indicates that the mode retains its external kink character. These comparative studies suggest that an energetic particle-driven "off-axis-fishbone-like mode" is a new EP-driven branch of the external kink mode in wall-stabilized plasmas, analogous to the relationship of the classical fishbone branch to the internal kink mode.

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“…In DIII-D, the increase of EP loss rate observed by the beam-ion loss detector (BILD) 32 coincided with the increase of the mode distortion, as shown in Fig. 10.…”

Section: A Correlation Of Ep Loss and Mode Distortionmentioning

confidence: 69%

Off-axis fishbone-like instability and excitation of resistive wall modes in JT-60U and DIII-D

Okabayashi¹,

Matsunaga²,

deGrassie³

et al. 2011

Physics of Plasmas

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“…1 Measured profiles of the confined beam ions in DIII-D using the recently developed fast ion D ␣ ͑FIDA͒ spectroscopy 2 show that instabilities redistribute fast ions radially outward. Faraday collector-based beam ion loss detectors ͑BILD͒ have been used to obtain information on fast ion losses near the outer midplane of DIII-D. 3 We recently installed a new fast ion loss detector ͑FILD͒ on DIII-D. By correlating the beam ion loss results from the new FILD with the other fast ion diagnostics and with observations of the internal mode structures in DIII-D, we gain important information on the fast ion loss orbits and loss mechanisms involved in the instabilities. Using the measured pitch angle and energy of the fast ion losses, reverse orbit following techniques can be used to trace the lost ions to their possible origin within the plasma.…”

Section: Summary and Introductionmentioning

confidence: 99%

Scintillator-based diagnostic for fast ion loss measurements on DIII-D

Fisher

Pace

García-Muñoz

et al. 2010

Review of Scientific Instruments

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A new scintillator-based fast ion loss detector has been installed on DIII-D with the time response (>100 kHz) needed to study energetic ion losses induced by Alfvén eigenmodes and other MHD instabilities. Based on the design used on ASDEX Upgrade, the diagnostic measures the pitch angle and gyroradius of ion losses based on the position of the ions striking the two-dimensional scintillator. For fast time response measurements, a beam splitter and fiberoptics couple a portion of the scintillator light to a photomultiplier. Reverse orbit following techniques trace the lost ions to their possible origin within the plasma. Initial DIII-D results showing prompt losses and energetic ion loss due to MHD instabilities are discussed.

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“…At DIII-D, these 'prompt losses' are detected by the BILD diagnostic [11]. The clearest indication of these losses occurs during modulation of the neutral-beam sources.…”

Section: Passive Fida Light Of Classical Originmentioning

confidence: 99%

“…Figure 1 also shows the locations of several other fast-ion diagnostics. The DIII-D beamion loss detectors (BILDs) consist of a pair of foils nestled into a vacuum port just below the midplane (z −12 cm) [11]. One pair of foils measures ions that precess in the co-current direction; the other pair measures counter-current orbits.…”

Section: Apparatusmentioning

confidence: 99%

‘Beam-emission spectroscopy’ diagnostics also measure edge fast-ion light

Heidbrink

McKee

Smith

et al. 2011

Plasma Phys. Control. Fusion

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Beam-emission spectroscopy (BES) diagnostics normally detect fluctuations in the light emitted by an injected neutral beam. Under some circumstances, however, light from fast ions that charge exchange in the high neutral-density region at the edge of the plasma make appreciable contributions to the BES signals. This 'passive' fast-ion D α (FIDA) light appears in BES signals from both the DIII-D tokamak and the National Spherical Torus Experiment (NSTX). One type of passive FIDA light is associated with classical orbits that traverse the edge. Another type is caused by instabilities that expel fast ions from the core; this light can complicate measurement of the instability eigenfunction.

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Phenomenology of energetic-ion loss from the DIII-D tokamak

Cited by 20 publications

References 29 publications

Off-axis fishbone-like instability and excitation of resistive wall modes in JT-60U and DIII-D

Off-axis fishbone-like instability and excitation of resistive wall modes in JT-60U and DIII-D

Scintillator-based diagnostic for fast ion loss measurements on DIII-D

‘Beam-emission spectroscopy’ diagnostics also measure edge fast-ion light

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