Impact of fast ions on a trapped-electron-mode dominated plasma in a JT-60U hybrid scenario

Mazzi, S.; Zarzoso, D.; García, J.; Görler, T.; Siena, A. Di; Camenen, Y.; Benkadda, S.; Yoshida, M.; Hayashi, Nobuhiko; Shinohara, K.

doi:10.1088/1741-4326/ab74a1

Cited by 17 publications

(16 citation statements)

References 44 publications

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“…These JET experimental observations are corroborated by modelling with the local (or 'flux-tube') version of the state-of-the-art gyrokinetic code GENE 36 that successfully reproduced turbulence properties for various tokamak experiments (see, for example, refs. 6,7,[37][38][39] ). For analysis of JET pulse #94701, we choose a flux tube around ρ tor = 0.23 (R = 3.25 m) as this region is characterized by large temperature gradients and a significant population of fast ions and TAEs.…”

Section: Numerical Modelling Of Turbulence Suppressionmentioning

confidence: 99%

Enhanced performance in fusion plasmas through turbulence suppression by megaelectronvolt ions

Mazzi

Benkadda²,

Abid³

et al. 2022

Nat. Phys.

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Alpha particles with energies on the order of megaelectronvolts will be the main source of plasma heating in future magnetic confinement fusion reactors. Instead of heating fuel ions, most of the energy of alpha particles is transferred to electrons in the plasma. Furthermore, alpha particles can also excite Alfvénic instabilities, which were previously considered to be detrimental to the performance of the fusion device. Here we report improved thermal ion confinement in the presence of megaelectronvolts ions and strong fast ion-driven Alfvénic instabilities in recent experiments on the Joint European Torus. Detailed transport analysis of these experiments reveals turbulence suppression through a complex multi-scale mechanism that generates large-scale zonal flows. This holds promise for more economical operation of fusion reactors with dominant alpha particle heating and ultimately cheaper fusion electricity.

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Section: Numerical Modelling Of Turbulence Suppressionmentioning

confidence: 99%

Enhanced performance in fusion plasmas through turbulence suppression by megaelectronvolt ions

Mazzi

Benkadda²,

Abid³

et al. 2022

Nat. Phys.

Self Cite

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“…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%

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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“…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 . Therefore, interactions between energetic particles and TEM/ETG turbulence are expected to be weak.…”

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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Impact of fast ions on a trapped-electron-mode dominated plasma in a JT-60U hybrid scenario

Cited by 17 publications

References 44 publications

Enhanced performance in fusion plasmas through turbulence suppression by megaelectronvolt ions

Enhanced performance in fusion plasmas through turbulence suppression by megaelectronvolt ions

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

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