Characteristics of tongue-shaped deformations in hydrogen and deuterium plasmas in the Large Helical Device

Voermans, S.; Ida, K.; Kobayashi, Tatsuya; Yoshinuma, M.; Takahashi, Hayato; Akiyama, Tsuyoshi; Emoto, M.

doi:10.1088/1741-4326/ab3a69

Cited by 8 publications

(3 citation statements)

References 19 publications

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“…In addition, once the 3/4 mode is destabilized, the perturbation expands outward from r/a = 0.75 to 0.85 (white dotted arrow) followed by the inward expansion of the 1/1 perturbation from r/a = 0.9 to 0.78 (gray dotted arrow). Such consecutive counter-propagating perturbations are also observed in the experiment [33]. After the burst event is triggered during phase III (solid yellow line) the 1/1, 3/4 and 2/3 perturbations overlap and the instability propagates further inward (dotted yellow line), consistent with the inward propagation of the instability observed in the experiment between r/a = 0.88 and 0.65.…”

Section: Conclusion and Discussionsupporting

confidence: 84%

Theoretical analysis of the saturation phase of the 1/1 energetic-ion-driven resistive interchange mode

et al. 2021

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The aim of the present study is to analyze the saturation regime of the energetic-ion-driven resistive interchange mode (EIC) in the LHD plasma. A set of non linear simulations are performed by the FAR3d code that uses a reduced MHD model for the thermal plasma coupled with a gyrofluid model for the energetic particles (EP) species. The hellically trapped EP component is introduced through a modification of the averaged drift velocity operator to include their precessional drift. The non linear simulation results show similar 1/1 EIC saturation phases with respect to the experimental observations, reproducing the enhancement of the n/m = 1/1 resistive interchange modes (RIC) amplitude and width as the EP β increases, the EP β threshold for the 1/1 EIC excitation, the further destabilization of the 1/1 EIC as the population of the helically trapped EP increases and the triggering of burst events. The frequency of the 1/1 EIC calculated during the burst event is 9.4 kHz and the 2/2 and 3/3 overtones are destabilized, consistent with the frequency range and the complex mode structure measured in the experiment. In addition, the simulation shows the inward propagation of the 1/1 EIC due to the non linear destabilization of the 3/4 and 2/3 EPMs, leading to the partial overlapping between resonances during the burst event. Finally, the analysis of the 1/1 EIC stabilization phase shows the excitation of the 1/1 RIC as soon as the flattening induced by the 1/1 EIC in the pressure profile vanishes, leading to the retrieval of the pressure gradient at the plasma periphery and the overcoming of the RIC stability limit.

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Section: Conclusion and Discussionsupporting

confidence: 84%

Theoretical analysis of the saturation phase of the 1/1 energetic-ion-driven resistive interchange mode

et al. 2021

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“…and are not localized but are radially propagating. The displacement of tongue-shaped deformation reaches up to 2 cm at the end of the formation, which is much larger than the displacement (0.2 ∼ 0.5 cm) observed at the two rational surfaces of ι=0.5 and 1.0 [57]. The tongue-shaped deformation typically quickly decays within one or a few cycles, while the displacement at the rational surface continues to oscillate.…”

Section: Energetic Particle-driven Mhd Collapsementioning

confidence: 84%

On the interplay between MHD instabilities and turbulent transport in magnetically confined plasmas

Ida

2019

Plasma Phys. Control. Fusion

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Interplay between MHD and turbulence is an interesting topic in magnetically confined plasma and solar plasma. Recently experimental observations below suggest the coupling and interplay between MHD and turbulence in magnetically confined toroidal plasmas. 1) Turbulence spreading into the magnetic island, 2) self-organized change in topology and turbulence in magnetic island, 3) flow damping by stochastic magnetic field, 4) trigger mechanism for the MHD bursts, 5) impact of MHD bursts on the ion velocity distribution and potential, and 6) turbulence exhausts at the MHD burst event. In this paper, experimental evidence for the interplay between MHD and turbulence in toroidal plasmas is reviewed. The physics mechanism of the interplay and a possible link to astrophysical plasma physics are also discussed.

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“…For examples of recent progress of the fast ion measurements, a time resolved neutral particle analyzer revealed the slowing down process related to toroidal Alfén eigen mode 14 . Lately, helically trapped fast ions induced tongue deformation [15][16][17][18] and subsequent MHD bursts have been studied in the larger helical device (LHD) 19,20 . The transport of fast ions associated with the MHD burst was found by multi-code lineintegrated neutron measurements 21,22 , which is also a time resolved fast particle diagnostic.…”

Section: Introductionmentioning

confidence: 99%

Fast-sampling fast-ion D-alpha measurement using multi-anode photomultiplier tube in large helical device

Kawachi,

Ogawa,

Osakabe

et al. 2023

Review of Scientific Instruments

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A fast-sampling fast-ion D-alpha (F-FIDA) measurement has been developed in the large helical device in order to investigate fast ion dynamics associated with helically trapped fast-ion-driven Magnetohydrodynamic (MHD) bursts. F-FIDA consists of a multi-anode photomultiplier tube (PMT) and achieves a sampling rate of 10 kHz. During the deuterium experiment campaign in 2022, F-FIDA measured the spectrum of perpendicular fast ions, using perpendicular lines of sight. We compared F-FIDA with conventional FIDA, using an electron multiplying charge coupled device, and confirmed that the time-averaged images were generally consistent between the two. The statistical properties of the temporal evolution associated with MHD bursts were analyzed using a conditional sampling technique. The results showed that the PMT signal varied in different spatial and wavelength channels. Although the signal-to-noise ratio was poor and there was room for improvement, it could provide useful information for studies on the phase-space dynamics of fast ions.

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Characteristics of tongue-shaped deformations in hydrogen and deuterium plasmas in the Large Helical Device

Cited by 8 publications

References 19 publications

Theoretical analysis of the saturation phase of the 1/1 energetic-ion-driven resistive interchange mode

Theoretical analysis of the saturation phase of the 1/1 energetic-ion-driven resistive interchange mode

On the interplay between MHD instabilities and turbulent transport in magnetically confined plasmas

Fast-sampling fast-ion D-alpha measurement using multi-anode photomultiplier tube in large helical device

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