Characterization of the fast ions distribution from ion cyclotron emission measurements

D’Incà, R.; Noterdaeme, J.-M.

doi:10.1063/1.4864533

Cited by 13 publications

(19 citation statements)

References 6 publications

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“…The first comprises energetic ions that are marginally confined in the outer edge region, whether fusion-born or NBI. The second, following recent observations of transient ICE from the centre of ASDEX-Upgrade [8,13,14] and DIII-D [15,16], probably comprises ions born in the core plasma while the fusion reactivity is rising. These populations spontaneously communicate with the observer through the medium of ICE.…”

Section: Discussionmentioning

confidence: 92%

“…The measured intensity of the ICE signal scaled linearly with the measured neutron flux and with the inferred alpha-particle concentration, and hence with fusion reactivity [6]. ICE from the outer edge of the vessel has been detected from the largest contemporary toroidal plasmas including DIII-D [7], ASDEX-Upgrade [8], JT-60U [9], KSTAR [10,11], and LHD [12]. Recently, ICE due to both fusion-born and neutral beam injected (NBI) ions in the core of the tokamak has been detected on ASDEX-Upgrade [13,14], DIII-D [15,16], and TUMAN-3M [17].…”

Section: Introductionmentioning

confidence: 95%

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Interpretation of suprathermal emission at deuteron cyclotron harmonics from deuterium plasmas heated by neutral beam injection in the KSTAR tokamak

et al. 2019

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Intense bursts of suprathermal radiation, with spectral peaks at frequencies corresponding to the deuteron cyclotron frequency in the outer midplane edge region, are often detected from deuterium plasmas in the KSTAR tokamak that are heated by tangential neutral beam injection (NBI) of deuterons at 100 keV. Identifying the physical process by which this deuterium ion cyclotron emission (ICE) is generated, typically during the crash of edge localised modes, assists the understanding of collective energetic ion behaviour in tokamak plasmas. In the context of KSTAR deuterium plasmas, it is also important to distinguish deuterium ICE from the ICE at cyclotron harmonics of fusion-born protons examined by Chapman et al (2017 Nucl. Fusion 57 124004; 2018 Nucl. Fusion 58 096027). We use particle orbit studies in KSTAR-relevant magnetic field geometry, combined with a linear analytical treatment of the magnetoacoustic cyclotron instability (MCI), to identify the sub-population of freshly ionised NBI deuterons that is likely to excite deuterium ICE. These deuterons are then represented as an energetic minority, together with the majority thermal deuteron population and electrons, in first principles kinetic particle-in-cell (PIC) computational studies. By solving the Maxwell–Lorentz equations directly for hundreds of millions of interacting particles with resolved gyro-orbits, together with the self-consistent electric and magnetic fields, the PIC approach enables us to study the collective relaxation of the energetic deuterons through the linear phase and deep into the saturated regime. The Fourier transform of the excited fields displays strong spectral peaks at multiple successive deuteron cyclotron harmonics, mapping well to the observed KSTAR deuterium ICE spectra. This outcome, combined with the time-evolution of the energy densities of the different particle populations and electric and magnetic field components seen in the PIC computations, supports our identification of the driving sub-population of NBI deuterons, and the hypothesis that its relaxation through the MCI generates the observed deuterium ICE signal. We conclude that the physical origin of this signal in KSTAR is indeed distinct from that of KSTAR proton ICE, and is in the same category as the NBI-driven ICE seen notably in the TFTR tokamak and LHD heliotron–stellarator plasmas. ICE has been proposed as a potential passive diagnostic of energetic particle populations in ITER plasmas; this is assisted by clarifying and extending the physics basis of ICE in contemporary magnetically confined plasmas.

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Section: Discussionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 95%

Interpretation of suprathermal emission at deuteron cyclotron harmonics from deuterium plasmas heated by neutral beam injection in the KSTAR tokamak

et al. 2019

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“…Note that a similar case has been made previously by McClements et al 1 , our paper strengthens their case with core ICE observations. ICE is a frequently observed phenomenon in toroidal magnetized plasma devices such as tokamaks and stellarators [2][3][4][5][6][7][8] . The emission consists of radio frequency (RF) waves generated by a resonant interaction between fast ions and a plasma instability.…”

Section: Introductionmentioning

confidence: 99%

Observations of core ion cyclotron emission on ASDEX Upgrade tokamak

Ochoukov

Bobkov

Chapman-Oplopoiou

et al. 2018

Review of Scientific Instruments

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(Presented XXXXX; received XXXXX; accepted XXXXX; published online XXXXX) (Dates appearing here are provided by the Editorial Office) The B-dot probe diagnostic suite on the ASDEX Upgrade tokamak has recently been upgraded with a new 125 MHz, 14 Bit resolution digitizer to study ion cyclotron emission (ICE). While classic edge emission from the low field side plasma is often observed, we also measure waves originating from the core with fast fusion protons or beam injected deuterons being possible emission driver. Comparing the measured frequency values with ion cyclotron harmonics present in the plasma places the origin of this emission on the magnetic axis, with the fundamental hydrogen/second deuterium cyclotron harmonic matching the observed values. The actual values range from ~27 MHz at on-axis toroidal field B T = -1.79 T to ~40 MHz at B T = -2.62 T. When the magnetic axis position evolves during this emission, the measured frequency values track the changes in the estimated on-axis cyclotron frequency values. Core ICE is usually a transient event lasting ~100 ms during the neutral beam startup phase. However, in some cases core emission occurs in steady-state plasmas and lasts for longer than 1 s. These observations suggest an attractive possibility of using a non-perturbing ICE-based diagnostic to passively monitor fusion alpha particles at the location of their birth in the plasma core, in deuterium-tritium burning devices such as ITER and DEMO.

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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%

“…Most of the early ICE observations were localised to the outer midplane edge region of the MCF plasmas [1,2,3,4,5,6,7,11,19,20], but recently ICE has also been detected from the core plasmas of ASDEX-Upgrade [8,9,10] and DIII-D [12,13,14]. Figure 5a of Ref.…”

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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Characterization of the fast ions distribution from ion cyclotron emission measurements

Cited by 13 publications

References 6 publications

Interpretation of suprathermal emission at deuteron cyclotron harmonics from deuterium plasmas heated by neutral beam injection in the KSTAR tokamak

Interpretation of suprathermal emission at deuteron cyclotron harmonics from deuterium plasmas heated by neutral beam injection in the KSTAR tokamak

Observations of core ion cyclotron emission on ASDEX Upgrade tokamak

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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