Physics of turbulence spreading and explicit nonlocality

Yan, Qinghao; Diamond, P. H.

doi:10.1088/1361-6587/ac0a3c

Cited by 7 publications

(12 citation statements)

References 40 publications

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“…As we first pointed out in reference [40], equations ( 4) and ( 5) can be written as a PV-conserving system. Below, we will show how.…”

Section: A Pv-conserving Systemmentioning

confidence: 99%

“…Equations ( 13) and ( 14) are the system for PV we first obtained in reference [40], where the total PV is conserved up to the curvature drift. Potential vorticity is the extension of vorticity.…”

Section: A Pv-conserving Systemmentioning

confidence: 99%

“…In equations ( 25) and ( 27), apart from the contribution of the profile gradient, there are also contributions from the turbulence intensity V x (k) 2 or equivalently φ2 k . In our previous study [40], we already discussed the turbulence intensity evolution characterized by φ2 , in which we first derived the evolution of Ũ2 , then applied the Green's function and transformed Ũ2 → φ2 . We dropped the effects of Δφ Z and approximated the influence of heat flux with a constant linear growth in reference [40].…”

Section: Turbulence Intensity Evolution Equationmentioning

confidence: 99%

“…In our previous study [40], we already discussed the turbulence intensity evolution characterized by φ2 , in which we first derived the evolution of Ũ2 , then applied the Green's function and transformed Ũ2 → φ2 . We dropped the effects of Δφ Z and approximated the influence of heat flux with a constant linear growth in reference [40]. Now, with the quasi-linear fluxes, we can obtain a more complete turbulence intensity evolution equation characterized by Ũ2 as below:…”

Section: Turbulence Intensity Evolution Equationmentioning

confidence: 99%

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Staircase formation by resonant and non-resonant transport of potential vorticity

Yan

Diamond²

2022

Nucl. Fusion

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The E×B staircase is a quasi-periodic pattern of pressure profile corrugations. In this work, we present a new mechanism for E×B staircase formation, that involves resonant transport verses non-resonant transport. We start from a potential vorticity evolution system and use quasi-linear theory, a model dispersion relation, and a bi-Lorentzian spectrum approximation, to construct the relation between the fluxes and the profiles. With these fluxes, we close the profile evolution equations and the extended turbulence intensity evolution equation, which together constitute a turbulence-profile evolution system. In this system, the Doppler effect from the E×B mean flow can cause resonance between trapped ion precession motion and the trapped ion mode, which drives a resonant transport contribution to the fluxes. The profiles will be flattened where the resonant transport is switched on. In contrast, for the regions of non-resonant transport, profiles are steeper. A quasi-periodic pattern of profile corrugation (the E×B staircase) spontaneously emerges in this system, which is the two states mentioned above, arranged as alternating layers in space. The feedback processes during the staircase pattern formation are identified. An estimate of the critical value of the boundary heat flux is obtained, above which staircase formation will be triggered. An estimate scaling of the step size in the staircase pattern is obtained. The resonant turbulent transport is also a mechanism for collisionless saturation of zonal flow. This work is related to internal transport barrier(ITB) formation and suggests some new scenarios, such as an enhanced confined L mode.

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“…As we first pointed out in reference [40], equations ( 4) and ( 5) can be written as a PV-conserving system. Below, we will show how.…”

Section: A Pv-conserving Systemmentioning

confidence: 99%

Section: A Pv-conserving Systemmentioning

confidence: 99%

Section: Turbulence Intensity Evolution Equationmentioning

confidence: 99%

Section: Turbulence Intensity Evolution Equationmentioning

confidence: 99%

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Staircase formation by resonant and non-resonant transport of potential vorticity

Yan

Diamond²

2022

Nucl. Fusion

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“…Capillaries are designed and characterized at Plasma Lab facility both experimentally and by fluid simulations [5,6,7,8]. Different geometrical configurations and experimental settings are tested to enhance the reproducibility, uniformity and shot-to-shot stability of the plasma, necessary to improve the accelerated beams quality [9].…”

Section: Introductionmentioning

confidence: 99%

Characterization of plasma-discharge Capillaries for Plasma-based Particle Acceleration

Crincoli,

Anania,

Biagioni

et al. 2024

J. Phys.: Conf. Ser.

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Novel particle accelerators based on plasma technology allow a drastic reduction in size, due to the high accelerating field established inside plasmas, which are created and confined by specific devices. Plasma Wakefield Acceleration experiments are performed at the SPARC_LAB test facility (Laboratori Nazionali di Frascati - INFN) by using gas-filled capillaries, in which the plasma formation is achieved by ionizing hydrogen gas through high voltage pulses. In this work, the characterization of gas-filled plasma-discharge capillaries is presented. Several geometrical configurations are tested, including capillaries with different channel shapes and arrangement of inlets positions for the gas injection. Such configurations are designed in order to enhance the uniformity of the plasma density distribution along the plasma channel, which is necessary to improve particle beam acceleration. Plasma sources are characterized by means of the spectroscopic technique based on the Stark broadening method, which allows to measure the evolution of the plasma density profile along the channel. In addition, the CFD software OpenFoam is used to simulate the dynamics of the neutral gas during the filling of the capillary.

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SOL width broadening by spreading of pedestal turbulence

Chu¹,

Diamond²,

Guo³

2022

Nucl. Fusion

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The pedestal turbulence intensity required to convert the thin, laminar H-mode SOL(scrape-off layer) to a broad turbulent SOL is calculated using a theory of turbulence spreading. A lower bound on the pedestal turbulence level to exceed the neoclassical heuristic drift width is derived. A reduced model of SOL turbulence spreading is used to determine the SOL width as a function of intensity flux from the pedestal to the SOL. The cross-over value for exceeding the HD(Heuristic Drift model) width is then calculated. We determine the pedestal turbulence levels -- and the critical scalings thereof -- required to achieve this level of broadening. Both drift wave and ballooning mode turbulence are considered. A sensitivity analysis reveals that the key competition is that between spreading and linear E×B shear damping. The required pedestal turbulence levels scale with ρi/R.

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Physics of turbulence spreading and explicit nonlocality

Cited by 7 publications

References 40 publications

Staircase formation by resonant and non-resonant transport of potential vorticity

Staircase formation by resonant and non-resonant transport of potential vorticity

Characterization of plasma-discharge Capillaries for Plasma-based Particle Acceleration

SOL width broadening by spreading of pedestal turbulence

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