Understanding LOC/SOC phenomenology in tokamaks

Rice, J.E.; Citrin, J.; Cao, N. M.; Diamond, P. H.; Greenwald, M.; Grierson, B. A.

doi:10.1088/1741-4326/abac4b

Cited by 26 publications

(25 citation statements)

References 86 publications

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“…See-saw transport phenomena are also observed after the cold pulse propagation, as seen in the radial profiles of electron temperature in Fig. 8a ( Rice et al 2020). The see-saw transport is often observed after the formation of the internal transport barrier (ITB) (Ida et al 2009a, b;Yu et al 2016;Kobayashi et al 2019).…”

Section: See-saw Transportmentioning

confidence: 68%

Non-local transport nature revealed by the research in transient phenomena of toroidal plasma

Ida

2022

Rev. Mod. Plasma Phys.

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The non-local transport nature revealed by the research in transient phenomena of toroidal plasma is reviewed. The following non-local phenomena are described: core temperature rise in the cold pulse, hysteresis gradient–flux relation in the modulation ECH experiment, and see-saw phenomena at the internal transport barrier (ITB) formation. There are two mechanisms for the non-local transport which cause non-local phenomena. One is the radial propagation of gradient and turbulence. The other is a mediator of radial coupling of turbulence such as macro/mesoscale turbulence, MHD instability, and zonal flow. Non-local transport has a substantial impact on structure formations in a steady state. The turbulence spreading into the ITB region, magnetic island, and SOL are discussed.

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Section: See-saw Transportmentioning

confidence: 68%

Non-local transport nature revealed by the research in transient phenomena of toroidal plasma

Ida

2022

Rev. Mod. Plasma Phys.

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“…We speculate that this phenomenon may be related to the structure of the (Q, S) phase diagram, which is fundamental to both the density limit and the L→H transition. These questions, and Finally, we note that Rice et al [13] recently showed that much of the Ohmic phenomenology (i.e., LOC-SOC phenomenology, rotation reversal etc.) may be unified by the scaling relation n crit qR = B T which is easily seen to be equivalent to n/n G = const, where n G is Greenwald density and the constant is O(1/2).…”

Section: Accepted Manuscriptmentioning

confidence: 85%

Bounds on edge shear layer persistence while approaching the density limit

Singh

Diamond

2021

Nucl. Fusion

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This paper details the theory of edge shear layer collapse as the density approaches the Greenwald density limit. It significantly extends earlier work, which was restricted in applicability. The zonal shear flow screening length is calculated for banana, plateau and Pfirsch–Schluter regimes. Poloidal field scaling persists in the plateau regime. Neoclassical screening and drift wave–zonal flow dynamics are combined in a theory, which is then reduced to a predator–prey model. Zonal noise, due to incoherent mode coupling, is retained. The threshold condition for edge shear layer collapse is computed, and linked to a critical value of the dimensionless parameter ρ s / ρ s c L n . Here ρ s is the ion sound radius, ρ s c is the zonal flow screening length and L n is the equilibrium density scale length. The limiting initial edge density for shear layer collapse is derived and shown to scale favorably with the plasma current. The results are discussed in light of the density limit and Ohmic phenomenology.

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“…The plasma density is an additional important engineering parameter. The impact of plasma density has been largely studied in the framework of the properties of L-mode Ohmic plasma confinement, particularly in connection with the transition from linear to saturated Ohmic confinement [69].…”

Section: Density Scanmentioning

confidence: 99%

Confinement properties of L-mode plasmas in ASDEX Upgrade and full-radius predictions of the TGLF transport model

et al. 2022

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The properties of L-mode confinement have been investigated with a set of dedicated experiments in ASDEX Upgrade and with a related modelling activity with the transport code ASTRA and the quasi-linear turbulent transport model TGLF– SAT2, with boundary conditions at the separatrix. The values at the boundary have been set by the two-point model for the electron temperature, with the ion temperature proportional to the electron temperature by a constant factor, and the electron density set by a constant fraction of the volume averaged density. The influx of neutrals has been set through a feedback procedure which ensures that in the simulation the same particle content as in the experiment is obtained. The sensitivity of the results under considerable variations in the choice of the boundary conditions has been investigated and found to be limited. The predictions of this full-radius modelling set-up have been compared to experimental results covering a scan in electron cyclotron resonance heating (ECRH) power in both hydrogen and deuterium plasmas, a plasma current scan with fixed magnetic field, under both ECRH and neutral bean injection (NBI) heating, an increase in plasma density with costant ECRH power in hydrogen plasmas, as well as variations of the fraction of electron and ion heating at approximately constant total heating power, as well as a change of main ion from deuterium to hydrogen. The ASTRA-TGLF predictions have been found to reproduce all of the experimentally explored dependencies with relatively good accuracy, providing evidence, for the first time to our knowledge, that the main properties of L-mode confinement can be reproduced by conventional full-radius transport modelling with a quasi-linear turbulent transport model. Evidences of largest disagreement, although usually not exceeding the 20%, have been found at high electron heating power, where TGLF underpredicts the electron and particularly the ion thermal stored energies, and in the current dependence of confinement, which, in electron heated conditions, is predicted to be weaker than in the experiment.

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Understanding LOC/SOC phenomenology in tokamaks

Cited by 26 publications

References 86 publications

Non-local transport nature revealed by the research in transient phenomena of toroidal plasma

Non-local transport nature revealed by the research in transient phenomena of toroidal plasma

Bounds on edge shear layer persistence while approaching the density limit

Confinement properties of L-mode plasmas in ASDEX Upgrade and full-radius predictions of the TGLF transport model

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