SOLPS-ITER validation with TCV L-mode discharges

Wensing, M.; Reimerdes, H.; Février, O.; Colandrea, C.; Martinelli, L.; Verhaegh, K.; Bagnato, F.; Blanchard, P.; Vincent, Benjamin; Perek, A.; Gorno, S.; Oliveira, H. De; Theiler, C.; Duval, B. P.; Tsui, C.; Baquero-Ruiz, M.; Wischmeier, M.; Team, Tcv; Team, Mst

doi:10.1063/5.0056216

“…Strong electric fields in the divertor volume of highdensity discharges are predicted and observed experimentally [54][55][56], leading to E × B flows in the poloidal plane [57,58] Our simulations confirm the presence of these flows.…”

Section: Plasma Potential and Ohm's Lawsupporting

confidence: 77%

Self-consistent multi-component simulation of plasma turbulence and neutrals in detached conditions

Mancini,

Ricci,

Vianello

et al. 2023

Nucl. Fusion

1

0

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Simulations of high-density deuterium plasmas in a lower single-null magnetic configuration based on a TCV discharge are presented. We evolve the dynamics of three charged species (electrons, D + and D 2 + ), interacting with two neutrals species ( D and D 2 ) through ionization, charge-exchange, recombination and molecular dissociation processes. The plasma is modelled by using the drift-reduced fluid Braginskii equations, while the neutral dynamics is described by a kinetic model. To control the divertor conditions, a D 2 puffing is used and the effect of increasing the puffing strength is investigated. The increase in fuelling leads to an increase of density in the scrape-off layer and a decrease of the plasma temperature. At the same time, the particle and heat fluxes to the divertor target decrease and the detachment of the inner target is observed. The analysis of particle and transport balance in the divertor volume shows that the decrease of the particle flux is caused by a decrease of the local neutral ionization together with a decrease of the parallel velocity, caused by the lower plasma temperature and the increase in momentum losses. The relative importance of the different collision terms is assessed, showing the crucial role of molecular interactions, as they are responsible for increasing the atomic neutral density and temperature, since most of the D neutrals are produced by molecular activated recombination and D 2 dissociation. The presence of strong electric fields in high-density plasmas is also shown, revealing the role of the E × B drift in setting the asymmetry between the divertor targets. Simulation results are in agreement with experimental observations of increased density decay length, attributed to a decrease of parallel transport, together with an increase of plasma blob size and radial velocity.

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“…DIII-D [33] and ASDEX Upgrade [34][35][36][37]. In absence of a physics model for turbulent cross-field transport, spatially constant anomalous transport coefficients D ⊥ = 0.2 m 2 s −1 and χ e,i,⊥ = 1.0 m 2 s −1 are used to obtain fall-off length λ n ∼ 1.4 cm, λ T ∼ 1.1 cm that provide a reasonable match to the experimental upstream profiles obtained from TS [32].…”

Section: Simulation Setupmentioning

confidence: 98%

A spectroscopic inference and SOLPS-ITER comparison of flux-resolved edge plasma parameters in detachment experiments on TCV

Perek

¹

,

Wensing

²

,

Verhaegh

³

et al. 2022

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This work presents the use of a collisional-radiative model to infer plasma parameters from 2D emissivities of several deuterium Balmer lines. The emissivities were obtained by MANTIS, an absolutely calibrated, 10-camera imaging polychromator with < 5 mm spatial resolution, up to 800 Hz frame rate, viewing the lower divertor tangentially. Our analysis of those image frames generates 2D maps of plasma parameters such as electron density, temperature, neutral atomic density and the reaction rates for ionisation, recombination and charge exchange as a function of time. The analysis is compared and validated against a SOLPS-ITER simulation accounting for drifts. The results are compared against the simulation in 2D, radial and poloidal profiles to probe the numerous effects of particle transport in the Scrape- Off Layer, in particular in the approach to detached divertor leg conditions. The inferred inner divertor leg radial profiles of the electron density and temperature were consistent with the SOLPS-ITER predictions. A significant transport of particles to the private flux region is found experimentally, that is not captured in the simulation. The simulation diverges from the experiment at the outer divertor target, where the plasma emission appears to be consistent with the emission driven by plasma-molecule interactions. Our analysis also shows prospects for aiding the power exhaust control efforts by potentially providing an optical tracking of the particle balance in the divertor.

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“…The 50% emissivity decrease along the leg is then computed to pinpoint the CIII front location (as in the experiments), which is then translated to y CIII by taking the poloidal distance along the seperatrix from the target to this point. From the simulations, an electron temperature of 7-10 eV at the CIII front position was identified [35]. Figure 6 shows the resulting identified front location for a relatively low-and high gas puff SOLPS-ITER simulation from the performed scan, these correspond to a low and high CIII front location respectively.…”

Section: Estimation Of the Dc-gain Using Solps-itermentioning

confidence: 99%

“…The dashed lines indicate the lower and upper bound of the experimentally identifiable frequency range. kinetic neutrals and carbon impurities [35]. During the scan of simulations the D 2 gas puff was increased from 0.5 × 10 20 to 5 × 10 20 D 2 s −1 .…”

Section: Estimation Of the Dc-gain Using Solps-itermentioning

confidence: 99%

Systematic extraction of a control-oriented model from perturbative experiments and SOLPS-ITER for emission front control in TCV

Koenders

¹

,

Wensing

²

,

Ravensbergen

³

et al. 2022

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Systematic extraction of locally valid dynamic models from experiments is necessary for controller design and the validation of high fidelity models. This paper describes the extraction of a dynamic model in the form of a transfer function, giving the dynamic response of the CIII (465.0 nm) emission front position to deuterium gas puffing in the TCV divertor during flattop, relevant for heat exhaust control. The model is extracted using frequency response data from both SOLPS-ITER simulations and perturbative experiments. We use the steady-state solutions of the model SOLPS-ITER to obtain an additional data point at the zero frequency, as the identifiable frequency range by perturbative experiments is lower bounded by discharge time. We specifically approach the problem from a control engineering point of view, aiming to develop control-oriented models for the systematic design of impurity emission front controllers. We find a transfer function structure based on a diffusive process to best describe the obtained frequency response data. The resulting transfer function model accurately reproduces the local dynamic response measured during experiments, so it can be used to assess new controllers offline for similar discharge scenarios.

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SOLPS-ITER validation with TCV L-mode discharges

Cited by 14 publications

References 23 publications

Self-consistent multi-component simulation of plasma turbulence and neutrals in detached conditions

Self-consistent multi-component simulation of plasma turbulence and neutrals in detached conditions

A spectroscopic inference and SOLPS-ITER comparison of flux-resolved edge plasma parameters in detachment experiments on TCV

Systematic extraction of a control-oriented model from perturbative experiments and SOLPS-ITER for emission front control in TCV

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