Excitation of helically-trapped-energetic-ion driven resistive interchange modes with intense deuterium beam injection and enhanced effect on beam ions/bulk plasmas of LHD

Bando, T.; Ohdachi, S.; Isobe, M.; Suzuki, Y.; Toi, K.; Nagaoka, K.; Takahashi, H.; Seki, R.; Du, Xiaodi; Ogawa, K.; Ido, T.; Shimizu, A.; Ozaki, T.

doi:10.1088/1741-4326/aac699

Cited by 19 publications

(19 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The 1/1 EIC stability can be further improved if the Deuterium is mixed with Helium. This optimization trend was already confirmed in the LHD experiments [27,60].…”

Section: Conclusion and Discussionsupporting

confidence: 71%

“…LHD is a helical device heated by three NBI lines almost parallel to the magnetic axis with an energy of 180 keV and two NBI perpendicular to the magnetic axis with an energy of 32 keV. The 1/1 EIC are destabilized in discharges with strong perpendicular NBI injection and low thermal ion density, both in Hydrogen and Deuterium plasma [27], limiting the device performance.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Theoretical analysis of energetic-ion-driven resistive interchange mode stabilization strategies using a Landau closure model

et al. 2020

Self Cite

View full text Add to dashboard Cite

The aim of the present study is to perform a theoretical analysis of different strategies to stabilize energetic-ion-driven resistive interchange mode (EIC) in LHD plasma. We use a reduced MHD 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 drift frequency to include their precessional drift. The stabilization trends of the 1/1 EIC observed experimentally with respect to the thermal plasma density and temperature are reproduced by the simulations, showing a reasonable agreement with the data. The LHD operation scenarios with stable 1/1 EIC are identified, leading to the stabilization of the 1/1 EIC if the thermal plasma density and temperature are above a given threshold. The 1/1 EIC are also stabilized if the rotational transform is modified in a way that the 1/1 rational surface is located further away than 0.9 times the normalized radius, or the magnetic shear in the plasma periphery is enhanced. Also, LHD discharges with large magnetic fields show a higher EIC destabilization threshold with respect to the thermal plasma density. If the perpendicular NBI deposition region is moved further inward than 0.875 times the normalized radius the 1/1 EIC are also stabilized. In addition,

show abstract

“…The 1/1 EIC stability can be further improved if the Deuterium is mixed with Helium. This optimization trend was already confirmed in the LHD experiments [27,60].…”

Section: Conclusion and Discussionsupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Theoretical analysis of energetic-ion-driven resistive interchange mode stabilization strategies using a Landau closure model

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…LHD is a helical device heated by three NBI lines almost parallel to the magnetic axis with an energy of 180 keV and two NBI perpendicular to the magnetic axis with an energy of 32 keV. This study is limited to LHD discharges with Hydrogen plasma where the NBIs also inject Hydrogen; the EIC events are also observed in Deuterium plasma [49]. The destabilization of EPM and AE caused by strong NBI injection was already observed in several LHD discharges [19,32,34,38,41].…”

Section: Introductionmentioning

confidence: 99%

Analysis of the MHD stability and energetic particles effects on EIC events in LHD plasma using a Landau-closure model

et al. 2019

Self Cite

View full text Add to dashboard Cite

The aim of this study is to perform a theoretical analysis of the magnetohydrodynamic (MHD) stability and energetic particle effects on a LHD equilibria, calculated during a discharge where energetic-ion-driven resistive interchange mode (EIC) events were triggered. We use the reduced MHD equations to describe the linear evolution of the poloidal flux and the toroidal component of the vorticity in a full 3D system, coupled with equations of density and parallel velocity moments for the energetic particles species, including the effect of the acoustic modes, multiple energetic particles (EP) species, helical couplings and helically trapped EP. We add the Landau damping and resonant destabilization effects using a closure relation. The simulations suggest that the helically trapped EP driven by the perpendicular neutral beam injector (NBI) further destabilizes the 1/1 MHD-like mode located at the plasma periphery (r/a = 0.88). If the β of the EP driven by the perpendicular NBI is larger than 0.0025 a 1/1 EIC with a frequency around 3 kHz is destabilized. If the effect of the passing EP driven by the tangential NBI is included on the model, any enhancement of the injection intensity of the tangential NBI below β = 0.025 leads to a decrease of the instability growth rate. The simulations indicate that the EIC in LHD 2 perpendicular NBI EP is the main driver of the EIC events, as it was observed in the experiment. If the effect of the helical couplings are added in the model, an 11/13 EIC is destabilized with a frequency around 9 kHz, inward shifted (r/a = 0.81) compared to the 1/1 EIC. Thus, one possible explanation for the EIC frequency chirping down from 9 to 3 kHz is a transition between the 11/13 to the 1/1 EIC due to a weakening of the destabilizing effect of the high n modes, caused by a decrease of the EP drive due to a loss of helically trapped EP or a change in the EP distribution function after the EIC burst. The experimental data during the EIC bursting phase shows a complex mode structure and an inward shift of the instability, although no direct evidence of the proposed transition has been observed yet.

show abstract

“…Confinement improvement that has been identified in LHD deuterium experiments should widen the scope of the operation. Quantitative assessment for start-up scenarios reaching such an identified Neutrons produced in deuterium plasmas in conjunction with a well-prepared set of neutron diagnostics [15] (e.g., neutron emission rate and triton burn-up ratio) have provided the capacity for the quantitative assessment of the energetic particles' confinement property [16,17] and their interaction with MHD modes [18,19] in LHD plasmas.…”

Section: Conceptual Design Of the Lhd-type Helical Fusion Reactor Ffhmentioning

confidence: 99%

Advanced Helical Plasma Research towards a Steady-State Fusion Reactor by Deuterium Experiments in Large Helical Device

Takeiri

2018

Atoms

View full text Add to dashboard Cite

The Large Helical Device (LHD) is one of the world’s largest superconducting helical system fusion-experiment devices. Since the start of experiments in 1998, it has expanded its parameter regime. It has also demonstrated world-leading steady-state operation. Based on this progress, the LHD has moved on to the advanced research phase, that is, deuterium experiment, which started in March 2017. During the first deuterium experiment campaign, an ion temperature of 10 keV was achieved. This was a milestone in helical systems research: demonstrating one of the conditions for fusion. All of this progress and increased understanding have provided the basis for designing an LHD-type steady-state helical fusion reactor. Moreover, LHD plasmas have been utilized not only for fusion research, but also for diagnostics development and applications in wide-ranging plasma research. A few examples of such contributions of LHD plasmas (spectroscopic study and the development of a new type of interferometer) are introduced in this paper.

show abstract

Excitation of helically-trapped-energetic-ion driven resistive interchange modes with intense deuterium beam injection and enhanced effect on beam ions/bulk plasmas of LHD

Cited by 19 publications

References 38 publications

Theoretical analysis of energetic-ion-driven resistive interchange mode stabilization strategies using a Landau closure model

Theoretical analysis of energetic-ion-driven resistive interchange mode stabilization strategies using a Landau closure model

Analysis of the MHD stability and energetic particles effects on EIC events in LHD plasma using a Landau-closure model

Advanced Helical Plasma Research towards a Steady-State Fusion Reactor by Deuterium Experiments in Large Helical Device

Contact Info

Product

Resources

About