Gyrokinetic study of slowing-down <i>α</i> particles transport due to trapped electron mode turbulence

Yang, SeongMoo; Angioni, C.; Hahm, Tae Soo; Na, D. H.; Na, Y. S.

doi:10.1063/1.5060628

Cited by 17 publications

(30 citation statements)

References 37 publications

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“…It can be seen that the diffusivity of α particles is much smaller than that of helium ash due to the factor of ρ H /ρ α , which will be shown quantitatively later. This relationship is consistent with the results from gyrokinetic simulation [33], thus the density profile of α particles can be significantly peaked as already pointed out in [2].…”

Section: Normalized Transport Coefficients Of Helium Ash In D-t Plasm...supporting

confidence: 92%

“…where ρ H = v thH /Ω H . It can be seen from equations ( 32) and (33), α particles could influence the transport of helium ash via affecting the real frequency and growth rate, and the magnitude of normalized diffusivity as well as convective velocity is related to FLR effects.…”

Section: Rv Hementioning

confidence: 99%

“…To compare the transport level of D-T ions and α particles with helium ash, we simultaneously calculate the normalized transport coefficients of D-T ions and α particles. Likewise, the normalized transport of D-T ions can be obtained just by using b D(T) and L TD(T) to replace b He and L THe in equations ( 32) and (33), respectively, and we do not repeat them again. Besides, the normalized diffusivity and convective velocity of α particles are written as…”

Section: Rv Hementioning

confidence: 99%

“…α particles are also fast ions, thus are quite possible to affect the turbulent transport of helium ash. It has been indicated that fast ions can either stabilize or destabilize CTEM turbulence [33][34][35], depending on the type of free energy source and the regime of wavelength. However, the effects of α particles on the transport of helium ash driven by CTEM turbulence have not been further considered.…”

Section: Introductionmentioning

confidence: 99%

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Effects of alpha particles on the transport of helium ash driven by collisionless trapped electron mode turbulence

Zhu¹,

Wang²,

Guo³

et al. 2022

Nucl. Fusion

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The effects of alpha (α) particles on the transport of helium ash driven by collisionless trapped electron mode (CTEM) turbulence are analytically studied using quasi-linear theory in tokamak deuterium (D) and tritium (T) plasmas. Under the parameters used in this work, the transport of helium ash is mainly determined by the diffusion due to very weak convection. It is found that the ratio between helium ash diffusivity and effective electron thermal conductivity (D_He/χ_eff) driven by CTEM turbulence, which is a proper normalized parameter for quantifying the efficiency of helium ash removal, is smaller than unity. This indicates the less efficient removal of helium ash through CTEM turbulence as compared with ion temperature gradient (ITG) turbulence in [Angioni, et al, 2009 Nucl. Fusion, 49 055013]. However, the efficiency of helium ash removal is increased 55% by the presence of 3% α particles with their density gradient being twice that of electrons, and this enhancement can be further strengthened by steeper profile of α particles. This is mainly because the enhancement of helium ash diffusivity by α particles is stronger than that of the effective electron thermal conductivity. Moreover, the higher fraction of T ions, higher temperature ratio between electrons and thermal ions as well as flatter electron density profile, the stronger enhancement of D_He/χ_eff, and α particles further strengthen the favorable effects of these parameters on the removal of helium ash.

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Section: Normalized Transport Coefficients Of Helium Ash In D-t Plasm...supporting

confidence: 92%

Section: Rv Hementioning

confidence: 99%

Section: Rv Hementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effects of alpha particles on the transport of helium ash driven by collisionless trapped electron mode turbulence

Zhu¹,

Wang²,

Guo³

et al. 2022

Nucl. Fusion

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“…This work is also limited to simulations with electrons, deuterium and tritium fuels, and helium ash, excluding energetic alpha particle dynamics. It has been reported that TEM drives low-level transport of alpha particles 39 . The resonant interactions between energetic particles and micro-instability will be significant for ITG modes 40 , 41 but not for TEM and ETG modes because the propagation directions are opposite 42 .…”

Section: Discussionmentioning

confidence: 99%

Multi-scale turbulence simulation suggesting improvement of electron heated plasma confinement

et al. 2022

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Turbulent transport is a key physics process for confining magnetic fusion plasma. Recent theoretical and experimental studies of existing fusion experimental devices revealed the existence of cross-scale interactions between small (electron)-scale and large (ion)-scale turbulence. Since conventional turbulent transport modelling lacks cross-scale interactions, it should be clarified whether cross-scale interactions are needed to be considered in future experiments on burning plasma, whose high electron temperature is sustained with fusion-born alpha particle heating. Here, we present supercomputer simulations showing that electron-scale turbulence in high electron temperature plasma can affect the turbulent transport of not only electrons but also fuels and ash. Electron-scale turbulence disturbs the trajectories of resonant electrons responsible for ion-scale micro-instability and suppresses large-scale turbulent fluctuations. Simultaneously, ion-scale turbulent eddies also suppress electron-scale turbulence. These results indicate a mutually exclusive nature of turbulence with disparate scales. We demonstrate the possibility of reduced heat flux via cross-scale interactions.

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Fast ion driven drift instability in reversed shear plasmas

Kang

Hahm

2019

Physics of Plasmas

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It is shown that electron drift waves can be destabilized by trapped fast ions produced by a fusion reaction because a significant fraction of those particles reverses their precession direction in reversed shear plasmas toward the electron diamagnetic direction and can resonate with the electron drift wave. We perform a local stability analysis and calculate the consequent quasi-linear transport caused by this new instability using bounce-averaged gyrokinetic equations in toroidal geometry and under fusion reactor conditions. We consider the equilibrium distribution function of fast ions as the slowing down distribution and compare with the equivalent Maxwellian case for illustration. The instability occurs when the temperature profile of fast ions peaks sufficiently compared to the density profile, and the magnetic shear is strongly negative. The resulting particle flux of fast ions is outward, while the particle flux of main hydrogenic ions can be inward.

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Gyrokinetic study of slowing-down α particles transport due to trapped electron mode turbulence

Cited by 17 publications

References 37 publications

Effects of alpha particles on the transport of helium ash driven by collisionless trapped electron mode turbulence

Effects of alpha particles on the transport of helium ash driven by collisionless trapped electron mode turbulence

Multi-scale turbulence simulation suggesting improvement of electron heated plasma confinement

Fast ion driven drift instability in reversed shear plasmas

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