Alfvenic behaviour of alpha particle driven ion cyclotron emission in TFTR

Cauffman, Steve; Majeski, R.; McClements, K. G.; Dendy, R. O.

doi:10.1088/0029-5515/35/12/i22

Cited by 76 publications

(122 citation statements)

References 9 publications

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“…This was strongly suggested by the original linear analytical theory approach to ICE from deuterium-tritium plasmas in JET and TFTR [1][2][3][4][5][6][7]. It is confirmed by the recent large scale kinetic simulations using PIC and hybrid codes [14,15] reviewed here.…”

Section: Discussionsupporting

confidence: 73%

“…The MCI was first identified theoretically by Belikov and Kolesnichenko [12] before it was observed in JET and TFTR tokamak plasmas, where it is driven by a subset of centrally born fusion products that lie just inside the trapped-passing boundary in velocity space, whose existence was anticipated by Stringer [13]. In both JET and TFTR, the drift orbits of these ions make large radial excursions [3,4] to the outer mid-plane edge. Since the local fusion birth rate is very small at this location, the predominant local energetic particle population comprises the super-Alfvénic centrally born ions that pass through on their drift orbits: hence there is a local population inversion in velocity space, and consequently scope for fast collective relaxation through the MCI.…”

Section: A Brief History Of Ion Cyclotron Emission From Fusion Plasmasmentioning

confidence: 94%

See 1 more Smart Citation

Ion cyclotron emission from fusion-born ions in large tokamak plasmas: a brief review from JET and TFTR to ITER

Dendy¹,

McClements²

2015

Plasma Phys. Control. Fusion

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Ion cyclotron emission (ICE) was the first collective radiative instability, driven by confined fusion-born ions, observed from deuterium-tritium plasmas in JET and TFTR. ICE comprises strongly suprathermal emission, which has spectral peaks at multiple ion cyclotron harmonic frequencies as evaluated at the outer mid-plane edge of tokamak plasmas. The measured intensity of ICE spectral peaks scaled linearly with measured fusion reactivity in JET. In other large tokamak plasmas, ICE is currently used as an indicator of fast ions physics. The excitation mechanism for ICE is the magnetoacoustic cyclotron instability (MCI); in the case of JET and TFTR, the MCI is driven by a set of centrally born fusion products, lying just inside the trapped-passing boundary in velocity space, whose drift orbits make large radial excursions to the outer mid-plane edge. Diagnostic exploitation of ICE in future experiments therefore rests in part on deep understanding of the MCI, and recent advances in computational plasma physics have led to substantial recent progress, reviewed here. Particle-in-cell simulations of the MCI, with fully kinetic ions and electrons, were reported in 2013, using plasma parameters for JET ICE observations. The hybrid approximation for plasma simulations, where ions are treated as particles and electrons as a neutralising massless fluid, was then applied and reported in 2014. These simulations extend previous studies deep into the nonlinear regime of the MCI, and corroborate predictions by linear analytical theory, thereby strengthening further the link to ICE measurements. ICE is a potential diagnostic for confined alpha-particles in ITER, where measurements of ICE could yield information on energetic ion behaviour supplementing that obtainable from other diagnostics. In addition, it may be possible to use ICE to study fast ion redistribution and loss due to MHD activity in ITER.

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Section: Discussionsupporting

confidence: 73%

Section: A Brief History Of Ion Cyclotron Emission From Fusion Plasmasmentioning

confidence: 94%

Ion cyclotron emission from fusion-born ions in large tokamak plasmas: a brief review from JET and TFTR to ITER

Dendy¹,

McClements²

2015

Plasma Phys. Control. Fusion

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“…the product of two delta-functions in parallel and perpendicular velocity, has been found to be the best few-parameter way of capturing this structure for ICE applications. This approximation has proven fruitful across more than two decades, spanning ICE measurements from deuterium-tritium plasmas in JET [11] and TFTR [12] during the mid-1990s to the most recent measurements reported from ASDEX-Upgrade in 2014 [8] and JT-60U in 2017 [13]. The new results presented here confirm the fidelity of the output of first principles PIC simulations in relation to measured ICE signals, alongside the validity of the model for ICE that is implemented in the PIC code.…”

Section: Discussionmentioning

confidence: 99%

“…This subset remains confined, because it lies on deeply passing drift orbits which carry the protons from the core to the edge and back again. Its sharply defined non-Maxellian distribution in velocity space means that this subset of the fusion-born protons can undergo the magnetoacoustic cyclotron instability (MCI) [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] in the edge plasma. The MCI drives waves on the fast Alfvén-cyclotron harmonic wave branch, both in analytical theory [16][17][18][19][20] and in first principles simulations [23][24][25], and these are likely to be the waves observed as ICE in KSTAR.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear wave interactions generate high-harmonic cyclotron emission from fusion-born protons during a KSTAR ELM crash

et al. 2018

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The radio frequency detection system on the KSTAR tokamak has exceptionally high spectral and temporal resolution. This enables measurement of previously undetected fast plasma phenomena in the ion cyclotron range of frequencies. Here we report and analyse a novel spectrally structured ion cyclotron emission (ICE) feature in the range 500 MHz to 900 MHz, which exhibits chirping on sub-microsecond timescales. Its spectral peaks correspond to harmonics l of the proton cyclotron frequency f cp at the outer midplane edge, where l = 20-36. This frequency range exceeds estimates of the local lower hybrid frequency f LH in the KSTAR deuterium plasma. The new feature is time-shifted with respect to a brighter lower-frequency chirping ICE feature in the range 200 MHz (8f cp ) to 500 MHz (20f cp ), which is probably driven (Chapman et al 2017 Nucl. Fusion 57 124004) by 3 MeV fusion-born protons undergoing collective relaxation by the magnetoacoustic cyclotron instability (MCI). Here we show that the new, fainter, higher-frequency chirping ICE feature is driven by nonlinear wave coupling between different neighbouring spectral peaks in the lower-frequency ICE feature. This follows from bispectral analysis of the measured KSTAR fields, and of the field amplitudes output from particle-in-cell (PIC) simulations of the KSTAR edge plasma containing fusionborn protons. This reinforces the identification of the MCI as the plasma physics process underlying proton harmonic ICE from KSTAR, while providing a novel instance of nonlinear wave coupling on very fast timescales.

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“…The TAE activity appears to be similar to TAE observed in conventional aspect ratio tokamaks [9]. The fishbone modes have significant differences, and, although the Ion Cyclotron Emission (ICE) observed in conventional aspect ratio tokamaks [17][18][19][20][21] may be related to compressional Alfvén waves, the strong, ubiquitous CAE activity seen in NBI heated NSTX plasmas is, thus far, unique to low aspect ratio.…”

Section: Introductionmentioning

confidence: 75%