Full‐torus impurity transport simulation for optimizing plasma discharge operation using a multi‐species impurity powder dropper in the large helical device

Shoji, M.; Kawamura, G.; Smirnov, R.D.; Tanaka, Yasunori; Masuzaki, S.; Uesugi, Yoshihiko; Ashikawa, N.; Gilson, Erik; Lunsford, R.

doi:10.1002/ctpp.201900101

Cited by 14 publications

(18 citation statements)

References 18 publications

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“…18 ) codes, after ref. 14 . EMC3 is a fully-3D Monte Carlo code modelling the plasma transport in the edge and scrape-off layer and it is coupled to EIRENE, which describes the neutral dynamics.…”

Section: Methodsmentioning

confidence: 99%

“…Indeed, the LHD is capable of extremely long discharges of up to one hour. The installation of the IPD on the LHD has been guided by predictive simulations with the coupled EMC3-EIRENE and DUSTT codes 14 , maximising the penetration of the powder into the plasma. The successful injection of B and BN powder in the unique LHD plasma configuration, featuring a double-null-like cross section with a predominantly poloidal magnetic field in the divertor coupled to the confined plasma by a thick ergodic layer, has been demonstrated in four-second-long plasmas 15 for a wide range of mass injection rates, plasma density and heating power.…”

Section: Impurity Powder Injection Experimentsmentioning

confidence: 99%

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Observation of a reduced-turbulence regime with boron powder injection in a stellarator

et al. 2022

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In state-of-the-art stellarators, turbulence is a major cause of the degradation of plasma confinement. To maximize confinement, which eventually determines the amount of nuclear fusion reactions, turbulent transport needs to be reduced. Here we report the observation of a confinement regime in a stellarator plasma that is characterized by increased confinement and reduced turbulent fluctuations. The transition to this regime is driven by the injection of submillimetric boron powder grains into the plasma. With the line-averaged electron density being kept constant, we observe a substantial increase of stored energy and electron and ion temperatures. At the same time, the amplitude of the plasma turbulent fluctuations is halved. While lower frequency fluctuations are damped, higher frequency modes in the range between 100 and 200 kHz are excited. We have observed this regime for different heating schemes, namely with both electron and ion cyclotron resonant radio frequencies and neutral beams, for both directions of the magnetic field and both hydrogen and deuterium plasmas.

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Section: Methodsmentioning

confidence: 99%

Section: Impurity Powder Injection Experimentsmentioning

confidence: 99%

Observation of a reduced-turbulence regime with boron powder injection in a stellarator

et al. 2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…Indeed, LHD is capable of extremely long discharges, up to one hour. The installation of the IPD on LHD has been guided by predictive simulations with the coupled EMC3-EIRENE and DUSTT codes [10], maximising the penetration of the powder into the plasma. The successful injection of B and BN powder in the unique LHD plasma configuration, featuring a double-null like cross section with predominantly poloidal magnetic field in the divertor, coupled to the confined plasma by a thick ergodic layer, has been demonstrated in 4-seconds-long plasmas [11], for a wide range of mass injection rates, plasma density, and heating power.…”

Section: Motivationmentioning

confidence: 99%

“…Interpretative simulations are performed with the coupled EMC3-EIRENE [13] and DUSTT [14] codes, after Ref. [10]. EMC3 is a fully 3D Monte Carlo code modelling the plasma transport in the edge and scrape-off layer, and it is coupled to EIRENE, describing the neutrals dynamics.…”

Section: Simulations With Emc3-eirene and Dusttmentioning

confidence: 99%

Observation of a novel reduced-turbulence regime with boron powder injection in a stellarator

Nespoli¹,

Masuzaki²,

Tanaka³

et al. 2021

Preprint

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We report the first observation of a novel confinement regime in a stellarator plasma, characterized by increased confinement and reduced turbulent fluctuations. The transition to this new regime is driven by the injection of sub-millimetric boron powder grains into the plasma. With the line averaged electron density being kept constant, substantial increase of stored energy, electron and ion temperature have been observed. At the same time, the amplitude of the plasma turbulent fluctuations is halved. While lower frequency fluctuations are damped, higher frequency modes in the range 100 ≤ f [kHz] ≤ 200 are excited. The access to this regime has been observed for different heating schemes, namely with both electron and ion cyclotron resonant radio frequency, and neutral beams, for both directions of the magnetic field, and for both hydrogen and deuterium plasmas.

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“…This problem includes both plasma and material physics, and is highly non-linear. So far, all existing investigations of dust dynamics employed time-independent background plasma profiles computed from transport codes, in 2D for axisymmetric devices and in 3D for stellarators [18]. The effects of plasma turbulence on dust dynamics are therefore usually neglected, or at best modeled with random scattering, set by an arbitrary parameter [9].…”

Section: Introductionmentioning

confidence: 99%

Hyperdiffusion of dust particles in a turbulent tokamak plasma

et al. 2021

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The effect of plasma turbulence on the trajectories of dust particles is investigated for the first time. The dynamics of dust particles is computed using the ad-hoc developed Dust Injection Simulator code, using a 3D turbulent plasma background computed with the TOKAM3X code. As a result, the evolution of the particle trajectories is governed by the ion drag force, and the shape of the trajectory is set by the Stokes number St ∝ a d /n 0 , with a d the dust radius and n 0 the density at the separatrix. The plasma turbulence is observed to scatter the dust particles, exhibiting a hyperdiffusive regime in all cases. The amplitude of the turbulent spread of the trajectories ∆r 2 is shown to depend on the ratio Ku/St, with Ku ∝ u rms the Kubo number and u rms the fluctuation level of the plasma flow. These results are compared with a simple analytical model, predicting ∆r 2 ∝ (Ku/St) 2 t 3 , or ∆r 2 ∝ (u rms n 0 /a d ) 2 t 3 . As the dust is heated by the plasma fluxes, thermionic emission sets the dust charge, originally negative, to slightly positive values. This results in a substantial reduction of the ion drag force through the suppression of its Coulomb scattering component. The dust grain inertia is then no longer negligible, and drives the transition from a hyperdiffusive regime towards a ballistic one.

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Full‐torus impurity transport simulation for optimizing plasma discharge operation using a multi‐species impurity powder dropper in the large helical device

Cited by 14 publications

References 18 publications

Observation of a reduced-turbulence regime with boron powder injection in a stellarator

Observation of a reduced-turbulence regime with boron powder injection in a stellarator

Observation of a novel reduced-turbulence regime with boron powder injection in a stellarator

Hyperdiffusion of dust particles in a turbulent tokamak plasma

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