Numerical studies for plasmas of a linear plasma device HIT-PSI with geometry modified SOLPS-ITER

The HIT-PSI is a linear plasma device built for physically simulating the high heat flux environment of future reactor divertors to test/develop advanced target plate materials.In this study,the geometry-modified SOLPS-ITER program is employed to examine the effects of the magnetic field strength and neutral pressure in the device on the heat flux experienced by the target plate of the HIT-PSI device.The findings of the numerical simulation indicate a positive correlation between the magnetic field strength and the heat flux density.Conversely,there is a negative correlation observed between the heat flux density and the neutral pressure.When the magnetic field strength at the axis exceeds 1 tesla and the neutral pressure falls below 10 Pa,the HIT-PSI has the capability to attain a heat flux of 10 MW·m-2 at the target plate.The simulation results offer a valuable point of reference for subsequent experiments at HIT-PSI.

Simulation studies of tungsten impurity behaviors during neon impurity seeding with tungsten bundled charge state model using SOLPS-ITER on EAST

An investigation into tungsten(W)impurity behaviors with the update of the EAST lower W divertor for H-mode has been carried out using SOLPS-ITER.This work aims to study the effect of external neon(Ne)impurity seeding on W impurity sputtering with the bundled charge state model.As the Ne seeding rate increases,plasma parameters,W concentration(C_(W)),and eroded W flux(Γ_(W)^(Ero))at both targets are compared and analyzed between the highly resolved bundled model‘jett’and the full W charge state model.The results indicate that‘jett’can produce divertor behaviors essentially in agreement with the full W charge state model.The bundled scheme with high resolution in low W charge states(<W^(20+))has no obvious effect on the Ne impurity distribution and thus little effect on W sputtering by Ne.Meanwhile,parametric scans of radial particle and thermal transport diffusivities(D_(⊥)andχ_(e,i))in the SOL are simulated using the‘jett’bundled model.The results indicate that the transport diffusivity variations have significant influences on the divertor parameters,especially for W impurity sputtering.

Numerical simulation of fueling pellet ablation and transport in the EAST H-mode discharge

To understand the effect of injected deuterium(D)pellets on background plasma,the ablation of D pellets and the transport of D species in both atomic and ionic states in the EAST device are simulated using a modified dynamic neutral gas shield model combined with the edge plasma code SOLPS-ITER.The simulation results show that there is a phenomenon of obvious atomic deposition in the scrape-off layer(SOL)after pellet injection,which depends strongly on the injection velocity.With increasing injection velocity,the atomic density in the SOL decreases evidently and the deposition time is relatively shortened.Possible effects for triggering of edge localized modes(ELMs)by D and Li pellets are also discussed.With the same pellet size and injection velocity,the maximum perturbation pressure caused by D pellets is obviously higher.It is found that the resulting maximum perturbed pressure is remarkably enhanced when the injection velocity is reduced from 300 m/s to 100 m/s for a pellet with a cross section of 1.6 mm,which indicates that the injection velocity is important for ELM pacing.This work can provide reasonable guidance for choosing pellet parameters for fueling and ELM triggering.

Numerical studies of the influence of seeding locations on D-SOL plasmas in EAST

Impurity seeding has been found effective for divertor detachment operations and the seeding location plays a key role in this process.In this work,we use the fluid code SOLPS-ITER to study the influence of seeding locations on divertor and scrape-off layer(D-SOL)plasmas in Experimental Advanced Superconducting Tokamak(EAST)with neon seeding.Simulation results indicate that the neon is a highly effective impurity in mitigating the heat flux and electron temperature peaks on the target of the divertor and achieving the partial detachment on both inner and outer targets.Further,by comparing results of the seeding at the private-flux region(PFR)plate(called‘TP’location)and the outer target(called‘XP’location),we find that the impurity density and power radiation for TP case are higher in core and upstream regions and lower in the divertor region than that for seeding at the XP,and the difference becomes more and more obvious as the seeding rate increases.It clearly demonstrates that the seeding at the XP location is more appropriate than at the TP location,especially in high seeding rate conditions.

Closed corner divertor with B×▽B away from the divertor:a promising divertor scenario for tokamak power exhaust

A major challenge facing the steady-state operation of tokamak fusion reactors is to develop a viable divertor solution with order-of-magnitude increase in power handling capability as compared with present experience.A recently developed divertor concept for this end has been tested recently on EAST tokamak through combining the effects of a closed divertor corner and E×B drifts.The E×B drifts in the divertor move particles towards the outer divertor corner area in the scrape-off layer for B×▽B directed away from the divertor,which can significantly enhance the particle concentration there,facilitating divertor detachment.In recent EAST experiments,the effects have been demonstrated where the lowest electron temperature at the divertor plate is obtained with strike point located close to the corner in the horizontal target and with B×▽B away from the divertor.These experimental results are in reasonable agreement with SOLPS-ITER simulations including drift effects,suggesting that the new divertor concept potentially provides a promising divertor solution for long-pulse operations of future tokamak fusion reactors with much higher power fluxes.