Impact of scaling laws on tokamak reactor dimensioning

Sarazin, Y.; Hillairet, J.; Duchateau, J.L.; Gaudimont, K.; Varennes, R; Garbet, X.; Ghendrih, Ph.; Guirlet, R.; Pégouriè, B.; Torre, A.

doi:10.1088/1741-4326/ab48a5

Cited by 6 publications

(4 citation statements)

References 33 publications

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“…The scaling law is not homogeneous. One also recovers the expressions for the other exponents published in reference [113]. The three exponents a β , a ν and a ρ characterize the plasma:…”

Section: B1 Adimensional Scaling Of the Confinement Timesupporting

confidence: 65%

Self-consistent cross-field transport model for core and edge plasma transport

Baschetti

Bufferand²,

Ciraolo³

et al. 2021

Nucl. Fusion

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The 2D mean-field plasma edge transport description of plasma wall interaction is completed by a κ-ε model as in Reynolds Average Navier Stokes simulations for neutral fluids. The local evolution of the turbulent kinetic energy κ and its dissipation rate ε are revisited and slightly modified. It is shown that the κ-ε extends the quasilinear approach by self-consistently determining κ and the relevant time κ/ε leading to the diffusion coefficient κ 2 /ε. The κ-ε evolution is also shown to be equivalent to both coupled Ginzburg-Landau amplitude equations and predator-prey systems where κ is the prey and ε the predator. The dissipation process ε we enforce describes the small scale dissipation of Kolmogorov cascades. It depends on a free parameter akin to a velocity V . The chosen closure relates V to the the parallel connection time and the normalized Scrape-Off layer width qρ * , q is the safety factor and ρ * the ratio of the characteristic Larmor radius and plasma minor radius. A 1D model with κ-ε self-organized transport is used for comparison to empirical scaling laws of SOL width and energy confinement time in L-mode plasmas. Shortfalls of the scaling laws are analyzed. Possible changes of the closure for V are discussed. The 1D model is also used to test the transport response to a dependence of V to large scale velocity shear. Spontaneous confinement improvement when increasing the heating power 1 is observed with the development of an interface barrier at the separatrix. Plasma-wall interaction simulations for TCV and WEST are analyzed. A single scalar free parameter tunes the cross field transport. Experimental midplane and divertor profiles are compared to the simulations. Remarkable agreement is observed. The SOL width determined by the simulation for WEST is close to the experimental value with less than 20 % difference, while the scaling law for L-mode is off my more than a factor 3. The turbulent transport described by the κ-ε is not homogeneous, but ballooned as experimentally observed together with cross-field transport in the divertor SOL on the low field side, and nearly none in the private flux region.

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Section: B1 Adimensional Scaling Of the Confinement Timesupporting

confidence: 65%

Self-consistent cross-field transport model for core and edge plasma transport

Baschetti

Bufferand²,

Ciraolo³

et al. 2021

Nucl. Fusion

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“…Moreover, a generalized linear model regression is used in order to take into account the Kadomtsev constraint χ B = 0 [14]:…”

Section: Scaling Of the Energy Confinement Time Of The L-mode Dischargesmentioning

confidence: 99%

Developing high performance RF heating scenarios on the WEST tokamak

Goniche

Ostuni²,

Bourdelle³

et al. 2022

Nucl. Fusion

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High power experiments, up to 9.2 MW with LHCD and ICRH, have been carried out in the full tungsten tokamak WEST. Quasi non inductive discharges have been achieved allowing to extend the plasma duration to 53s with stationary conditions in particular with respect to tungsten contamination. Transitions in H mode are obtained lasting up to 4s with weak energy increment at the power crossing the separatrix is close to the threshold. Hot L mode plasmas (Te(0)>3keV) with a confinement time following the ITER L96 scaling are routinely obtained. The weak aspect ratio dependence of this scaling law is confirmed. Tungsten accumulation is generally not an operational issue on WEST. Difficulty of burning through tungsten can prevent from accessing to a hot core plasma in the ramp-up phase or can lead to rapid collapse of the central temperature when radiation is enhanced by a slight decrease of the temperature. Apart few pulses post-boronization, the plasma radiation is rather high (Prad/Ptot~50%) and is dominated by tungsten. This fraction does not vary as the RF power is ramped up and is quite similar in ICRH and/or LHCD heated plasmas. An estimate of the contribution of the RF antennas to the plasma contamination in tungsten is given

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“…Empirical approaches can be used [1][2][3], mostly based on statistical analyses performed on large databases of experi mental data, and these usually provide scaling laws of the plasma stored energy (or, equivalently, of the energy confine ment time) commonly in the form of multivariate log-linear regressions [4][5][6]. These scaling laws for the global plasma confinement are certainly very valuable and useful tools for zero dimensional (0D) predictions, and even in providing a scaling factor in (semi)empirical modeling for the prediction of the radial kinetic profiles.…”

Section: Introductionmentioning

confidence: 99%

Integrated modeling of ASDEX Upgrade plasmas combining core, pedestal and scrape-off layer physics

et al. 2020

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The design of future fusion reactors and their operational scenarios requires an accurate prediction of the plasma confinement. We have developed a new model that integrates different elements describing the main physics phenomena which determine plasma confinement. In particular, we are coupling a new pedestal transport model, based on empirical observations, to the ASTRA transport code, which, together with the TGLF turbulent transport model and the NCLASS neoclassical transport model, allows us to describe transport from the magnetic axis to the separatrix. We also coupled a simple scrape-off layer model to ASTRA, which provides the boundary conditions at the separatrix, which are a function of the main engineering parameters. By this way no experimental data of the kinetic profiles is needed, and the only inputs of the model are the magnetic field, the plasma current, the heating power, the fueling rate, the seeding rate, the plasma boundary, and the effective charge. In the modeling work-flow, first a scan in pedestal pressure is performed, by changing the pedestal width. Then the pedestal top pressure is determined using the MISHKA MHD stability code. This modeling framework is tested by simulating ASDEX Upgrade discharges. We show comparisons with experimental fueling, power, and current scans. The changes of the pedestal structure and the gradients in the plasma core, due to the different combinations of fueling, heating power, and plasma current, are well captured by the model. We also show that the predicted pedestal and global stored energies are in good agreement with the experimental measurements, and more accurate with respect to the prediction of the IPB98(y,2) scaling law. The long term goal is to obtain a robust and complete model which can be used to identify important hidden dependencies affecting global plasma confinement, which are difficult to capture by statistical regressions on global parameters.

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Impact of scaling laws on tokamak reactor dimensioning

Cited by 6 publications

References 33 publications

Self-consistent cross-field transport model for core and edge plasma transport

Self-consistent cross-field transport model for core and edge plasma transport

Developing high performance RF heating scenarios on the WEST tokamak

Integrated modeling of ASDEX Upgrade plasmas combining core, pedestal and scrape-off layer physics

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