Ion cyclotron emission diagnostic system on the experimental advanced superconducting tokamak and first detection of energetic-particle-driven radiation

Liu, J.; Zhu, Y. B.; Qin, Chengming; Zhao, Yanping; Yuan, Shuai; Mao, Yuzhou; Li, M. H.; Chen, Y.; Cheng, Junyi; Ping, Lanlan; Li, Hao; Ai, Li

doi:10.1063/1.5089537

Cited by 21 publications

(21 citation statements)

References 30 publications

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“…Ion cyclotron emission (ICE) is widely observed from magnetically confined fusion (MCF) plasmas [4]. In addition to historical observations from deuterium-tritium plasmas in JET [5,6] and TFTR [7], since 2017 ICE has been reported and analysed from the KSTAR [8,9], DIII-D [10], ASDEX-Upgrade [11][12][13], TUMAN-3M [14] and EAST [15] tokamaks, and the large helical device (LHD) heliotron-stellarator [16][17][18]. ICE spectra typically comprise a succession of narrow, strongly suprathermal, peaks at sequential cyclotron harmonics of an energetic ion species.…”

Section: Introductionmentioning

confidence: 99%

Density dependence of ion cyclotron emission from deuterium plasmas in the large helical device

Reman¹,

Dendy²,

Akiyama³

et al. 2021

Nucl. Fusion

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Ion cyclotron emission (ICE) driven by perpendicular neutral beam-injected (NBI) deuterons, together with the distinctive ICE driven by tangential NBI, have been observed from heliotron–stellarator plasmas in the large helical device (LHD). Radio frequency radiation in the lower hybrid range has also been observed Saito K. et al (2018 Plasma Fusion Res. 13 3402043), with frequency dependent on plasma density. Here we focus on recent measurements of ICE from deuterium plasmas in LHD, which show substantial variation in spectral character, between otherwise similar plasmas that have different local density in the emitting region. We analyse this variation by means of first principles simulations, carried out using a particle-in-cell (PIC) kinetic approach. We show, first, that this ICE is driven by perpendicular NBI deuterons, freshly ionised near their injection point in the outer midplane edge of LHD. We find that these NBI deuterons undergo collective sub-Alfvénic relaxation, which we follow deep into the nonlinear phase of the magnetoacoustic cyclotron instability (MCI). The frequency and wavenumber dependence of the saturated amplitudes of the excited fields determine our simulated ICE spectra, and these spectra are obtained for different local densities corresponding to the different LHD ICE-emitting plasmas. The variation with density of the spectral character of the simulated ICE corresponds well with that of the observed ICE from LHD. These results from heliotron–stellarator plasmas complement recent studies of density-dependent ICE from tokamak plasmas in KSTAR Thatipamula S.G. et al (2016 Plasma Phys. Control. Fusion 58 065003); Chapman B. et al (2017 Nucl. Fusion 57 124004), where the spectra vary on sub-microsecond timescales after an ELM crash. Taken together, these results confirm the strongly spatially localised character of ICE physics, and reinforce the potential of ICE as a diagnostic of energetic ion populations and of the ambient plasma.

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Section: Introductionmentioning

confidence: 99%

Density dependence of ion cyclotron emission from deuterium plasmas in the large helical device

Reman¹,

Dendy²,

Akiyama³

et al. 2021

Nucl. Fusion

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“…The ICEs are observed in many toroidal devices, e.g. JET [1], TFTR [2], JT-60U [3], DIII-D [4], ASDEX-U [5], NSTX-U [6], KSTAR [7], TUMAN-3M [8], EAST [9], and LHD [10]. There is a possibility for ICEs to be utilized for fast ion diagnostics in future fusion devices since their wave intensities depend on the fast ion populations [1,11].…”

Section: Introductionmentioning

confidence: 99%

“…There is a possibility for ICEs to be utilized for fast ion diagnostics in future fusion devices since their wave intensities depend on the fast ion populations [1,11]. One advantage of ICEs is that it can be relatively easily measured with high-frequency magnetic probes [2,5,8,10], single-loop antennas [9,12] or ICRF heating antennas in receiver mode [1,3]. However, in order to apply ICEs as a fast ion diagnostics, it is necessary to understand their emission mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Identification of slow-wave ion cyclotron emission on JT-60U

Sumida¹,

Shinohara²,

Ichimura³

et al. 2021

Nucl. Fusion

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Ion cyclotron emissions (ICEs) are generally considered to be emissions of fast waves driven by velocity-space instabilities due to fast ions. However, on JT-60U, measured properties of ICEs observed at frequencies lower than the bulk ion cyclotron frequency (L-ICEs) do not match the fast-wave dispersion relation, indicating the possibility of L-ICEs being slow-wave emissions. In this paper, we show that L-ICE observation on JT-60U can be explained in terms of a slow-wave emission driven by fast ions, i.e. a slow-wave ICE. To investigate whether the slow wave can be driven by fast ions, its linear growth rate has been calculated in a typical discharge using a wave dispersion code. This wave dispersion code is capable of performing calculations with an arbitrary spatially-localized velocity distribution. For the growth rate calculation, we have directly used fast ion velocity distributions evaluated by an orbit following Monte-Carlo simulation. It is found that negative-ion-source neutral beam (N-NB) injected fast ions can destabilize the slow wave. Its frequency and wavenumber at high linear growth rates are close to experimental observations of L-ICE. In addition, observed L-ICE frequencies agree reasonably well with frequencies based on the slow-wave dispersion relation at measured toroidal wavenumbers in several discharges. Moreover, the observed frequencies also agree with the Doppler-shifted cyclotron resonance frequencies for the N-NB injected ion. Therefore, L-ICE in JT-60U is identified as a slow-wave ICE driven by the N-NB injected fast ions and distinguished from other ICEs through a measurement of its frequency and wavenumber.

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“…Strongly suprathermal radiation known as ion cyclotron emisison (ICE) is widely observed in magnetic confinement fusion (MCF) plasmas [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23]. Its intensity is typically orders of magnitude greater than that of black-body radiation from thermal ions, and its spectral peak frequencies correspond to multiple cyclotron harmonics of one or more energetic ion species at a specific radial location.…”

Section: Introductionmentioning

confidence: 99%

Origin of ion cyclotron emission at the proton cyclotron frequency from the core of deuterium plasmas in the ASDEX-Upgrade tokamak

Chapman

Dendy

Chapman

et al. 2020

Plasma Phys. Control. Fusion

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Observations have recently been made of ion cyclotron emission (ICE) that originates from the core plasma in the DIII-D and ASDEX-Upgrade tokamaks. In some of these cases, the ICE spectral peaks correspond to the local cyclotron harmonic frequencies of fusion-born ions close to the magnetic axis. This is in contrast to the hitherto usual spatial localisation of the ICE source to the outer midplane edge in tokamak and stellarator plasmas. Here we show that a possible emission mechanism for core ICE in ASDEX-Upgrade deuterium plasmas can arise from the rapid onset and rise of local fusion reactivity. This would give rise to a transiently highly non-Maxwellian population of fusion-born protons near their birth energy, prior to collisional slowingdown on longer timescales. Such populations are often liable to fast radiative relaxation under the magnetoacoustic cyclotron instability which underpins ICE, depending also on bulk plasma parameter values. We therefore perform first principles computations of the self-consistent collective relaxation of such a population, using a particle-in-cell code, for plasma parameters appropriate to the ASDEX-Upgrade core. The resulting simulated ICE spectra include a strong peak at the proton cyclotron frequency that corresponds well to the observations.

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Ion cyclotron emission diagnostic system on the experimental advanced superconducting tokamak and first detection of energetic-particle-driven radiation

Cited by 21 publications

References 30 publications

Density dependence of ion cyclotron emission from deuterium plasmas in the large helical device

Density dependence of ion cyclotron emission from deuterium plasmas in the large helical device

Identification of slow-wave ion cyclotron emission on JT-60U

Origin of ion cyclotron emission at the proton cyclotron frequency from the core of deuterium plasmas in the ASDEX-Upgrade tokamak

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