Measurement of Ion Cyclotron Emissions by Using High-Frequency Magnetic Probes in the LHD

Saito, Kenji; Kumazawa, R.; Seki, T.; Kasahara, Hiroshi; Nomura, G.

doi:10.1088/1009-0630/15/3/03

Cited by 54 publications

(66 citation statements)

References 9 publications

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“…The displacement decays in a few hundred μ sec and becomes less than a few mm during the MHD oscillation (0.2 < Δ t < 2 ms). The abrupt increase of RF intensity measured with RF radiation probes17 seen in Fig. 1f indicates the rapid increase of ion cyclotron emission (ICE) at high order harmonic frequency due to the reversal of energy distribution of the energetic ion injected by the neutral beam181920.…”

Section: Resultsmentioning

confidence: 98%

Abrupt onset of tongue deformation and phase space response of ions in magnetically-confined plasmas

Ida

Kobayashi

Itoh

et al. 2016

Sci Rep

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An abrupt onset of the new tongue-shaped deformation of magnetic surface in magnetized plasmas, which was conjectured in since the 1960s but has not been observed, is experimentally identified just before an abrupt onset of a large-scale collapse event. Two novel properties of the event are identified. First, the transition of symmetry of perturbation (rather than a growth of linearly unstable MHD modes) was found to be a key for the onset of abrupt collapse, i.e., the transition of symmetry gives a new route to the collapse from stable state. Second, as a phase-space response of ions, the distortion from Maxwell-Boltzmann distribution of epithermal ions was observed for the first time.

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Section: Resultsmentioning

confidence: 98%

Abrupt onset of tongue deformation and phase space response of ions in magnetically-confined plasmas

Ida

Kobayashi

Itoh

et al. 2016

Sci Rep

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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%

“…Examples of ICE in tokamaks include ASDEX Upgrade , and JT-60U 7 . An example of ICE observed on a stellarator is from LHD 8 . Note that the presence of fast ions alone is not enough to generate ICE, the fast ion population must also be either non-monotonic (e.g.…”

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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“…Some radio-frequency (RF) waves in the frequency range from MHz to GHz are observed during the period of neutral beam injection (NBI) in Large Helical Device (LHD) plasmas [1][2][3]. Frequency spectra obtained near the perpendicular NBI ports show that there are some peaks near the ion cyclotron frequency and its harmonics; the ion cyclotron emissions (ICEs) are localized near the perpendicular NBI ports [1,2].…”

Section: Introductionmentioning

confidence: 99%

“…Frequency spectra obtained near the perpendicular NBI ports show that there are some peaks near the ion cyclotron frequency and its harmonics; the ion cyclotron emissions (ICEs) are localized near the perpendicular NBI ports [1,2]. In addition to the ICEs, RF waves in the Lower Hybrid Wave (LHW) frequency region are detected during the perpendicular NBI [3].…”

Section: Introductionmentioning

confidence: 99%

Simulation Study of High-Frequency Magnetosonic Waves Excited by Energetic Ions in Association with Ion Cyclotron Emission

Toida

Saito

Igami

et al. 2018

Plasma and Fusion Research

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Instabilities of high-frequency magnetosonic waves caused by energetic ions with a ring-like velocity distribution are studied with a one-dimensional electromagnetic particle code which simulates self-consistently the full ion and electron dynamics. It is shown that the magnetosonic waves with frequencies slightly smaller than the lower-hybrid resonance frequency rapidly grow to large amplitudes, in addition to electromagnetic emissions near the ion cyclotron frequency and its harmonics. The frequency of the magnetosonic wave that has the largest amplitude is in good agreement with the frequency of the most unstable mode predicted by a linear theory. The theory and simulations show that the frequency of the magnetosonic wave increases with the plasma density. The instability of the high-frequency magnetosonic waves may be an excitation mechanism for radio frequency waves in the Lower Hybrid Wave (LHW) frequency region observed in the Large Helical Device (LHD).

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Measurement of Ion Cyclotron Emissions by Using High-Frequency Magnetic Probes in the LHD

Cited by 54 publications

References 9 publications

Abrupt onset of tongue deformation and phase space response of ions in magnetically-confined plasmas

Abrupt onset of tongue deformation and phase space response of ions in magnetically-confined plasmas

Observations of core ion cyclotron emission on ASDEX Upgrade tokamak

Simulation Study of High-Frequency Magnetosonic Waves Excited by Energetic Ions in Association with Ion Cyclotron Emission

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