Study of the Ionization Rate in the Scrape‐off Layer

Corrigan

Coster

2022

The Kinetic Code for Plasma Periphery (KIPP) models parallel (along magnetic field lines) propagation of charged particles in the scrape-off layer (SOL) and divertor of tokamaks. An iterative coupling between KIPP and a 2D edge fluid code EDGE2D, which in turn is coupled to the Monte-Carlo solver EIRENE for neutrals, was used to achieve a converged KIPP-EDGE2D-EIRENE solution. The original EDGE2D-EIRENE solution simulated SOL and divertor of JET high radiative inter-edge localized mode H-mode plasma conditions with strong nitrogen injection, leading to partial detachment at divertor targets. This work is a continuation of earlier studies of modelling kinetic electrons (Chankin et al 2018 Plasma Phys. Control. Fusion 60 115011) and ions (Chankin et al 2020 Plasma Phys. Control. Fusion 62 105022) with KIPP. For numerical reasons caused by large cell-to-cell plasma parameter variations near entrances to divertors, multipliers for parallel electron and ion conductive power fluxes (KIPP/EDGE2D ratios) which are passed onto EDGE2D, could only be used in the main SOL, outside divertors. There, the heat flux limiting effect led to an increase in maximum plasma temperatures in the main SOL and a decrease in power fluxes to divertor targets. Results of the coupling studies are consistent with earlier studies, suggesting that under investigated JET plasma conditions kinetic effects of charged particle parallel propagation do not drastically change target power deposition at divertor targets calculated by EDGE2D-EIRENE along.

Section: Setup Of Edge2d-eirene Cases and Kipp-edge2d Iterative Couplingsupporting

confidence: 76%

Section: Power Balance In Kipp-edge2d Solutionsmentioning

confidence: 99%

Coupled KIPP-EDGE2D modelling of parallel transport in the SOL and divertor of inter-ELM JET high radiative H-mode plasma

Corrigan

Coster

2022

“…Due to the presence of high energy non-Maxwellian tails of the electron distribution function, f e , near the target, kinetic rates of interaction between electrons and neutrals and impurities may increase by a large factor (see e.g. [10][11][12][13]). Such effects are, however, outside of the scope of the present paper, in which the emphasis is put on the ability of superthermal electrons to create substantial deviations of the electron heat conduction from predictions based on the classical Braginskii formula, and their impact on heat transmission factors γ e at the divertor target.…”

Section: Introductionmentioning

confidence: 99%

Assessment of the strength of kinetic effects of parallel electron transport in the SOL and divertor of JET high radiative H-mode plasmas using EDGE2D-EIRENE and KIPP codes

Corrigan

Jaervinen

et al. 2018

KInetic code for Plasma Periphery (KIPP) was used to assess the importance of kinetic effects of parallel electron transport in the SOL and divertor of JET high radiative H-mode inter-ELM plasma conditions with the ITER-like wall and strong nitrogen (N2) injection. Plasma parameter profiles along magnetic field from one of the EDGE2D-EIRENE simulation cases were used as an input for KIPP runs. Profiles were maintained by particle and power sources. KIPP generated electron distribution functions, fe, parallel power fluxes, electron-ion thermoforces, Debye sheath potential drops and electron sheath transmission factors at divertor targets. For heat fluxes in the main SOL, KIPP results showed deviations from classical (e.g. Braginskii) fluxes by factors typically ~ 1.5, sometimes up to 2, with the flux limiting for more upstream positions and flux enhancement near entrances to the divertor. In the divertor, at the same time, for radial positions closer to the separatrix, very large heat flux enhancement factors, up to 10 or even higher, indicative of a strong non-local heat transport, were found at the outer target, with heat power flux density exhibiting bump-on-tail features at high energies. Under such extreme conditions, however, contributions of conductive power fluxes to total power fluxes were strongly reduced, with convective power fluxes becoming comparable, or sometimes exceeding, conductive power fluxes. Electron-ion thermoforce, on the other hand, which is known to be determined mostly by thermal and sub-thermal electrons, was found to be in a good agreement with Braginskii formulas, including the Zeff dependence. Overall, KIPP results indicate, at least for plasma conditions used in this modelling, a sizable, but not dominant effect of kinetics on parallel electron transport.

“…The rate coefficients for atomic physics from ADAS, calculated based on the collision-radiative theory [52,53] with assuming Maxwellian electrons, are tabulated and then read as an input file in SOLPS. Previous studies [28,54,55] showed that the extended non-Maxwellian tail downstream near the target had substantial effects on enhancing the deuterium ionization rate coefficient. Particularly when electron temperature was lower than 3eV , the presence of small amount (1%) of hot electrons (20eV ) could contribute significantly to the local ionization rate coefficient [56].…”

Section: Kinetic Effects On Deuterium Ionizationmentioning

confidence: 99%

SOLPS simulations with electron kinetic effects

Zhao

Coster

2019

Power exhaust is one of the critical issues for tokamak edge plasma research. Electron kinetic effects may play an important role in future fusion devices. The KIPP code was coupled to a 1D version of SOLPS with an iterative algorithm [1, 2] to study the kinetic effects in a systematic way. The KIPP-SOLPS coupling algorithm allows us to incorporate kinetic electrons into the already sophisticated fluid model (B2) self-consistently. The KIPP-SOLPS coupling simulation results with pure deuterium and with carbon impurity in 1D geometry with stagnation point upstream and target downstream are presented. These results are then compared to the results of SOLPS simulations with different flux limiters. It shows that non-local electron parallel transport contributes to the non-Maxwellian tails of electrons near the target which reduces the electron target temperature. However, the non-Maxwellian tail has negligible impacts on deuterium ionization.