Study of impurity effects on CFETR steady-state scenario by self-consistent integrated modeling

Abstract

Impurity effects on fusion performance of China fusion engineering test reactor (CFETR) due to extrinsic seeding are investigated. An integrated 1.5D modeling workflow evolves plasma equilibrium and all transport channels to steady state. The one modeling framework for integrated tasks framework is used to couple the transport solver, MHD equilibrium solver, and source and sink calculations. A selfconsistent impurity profile constructed using a steadystate background plasma, which satisfies quasineutrality and true steady state, is presented for the first time. Studies are performed based on an optimized fully noninductive scenario with varying concentrations of Argon (Ar) seeding. It is found that fusion performance improves before dropping off with increasing Z eff , while the confinement remains at high level. Further analysis of transport for these plasmas shows that lowk ion temperature gradient modes dominate the turbulence. The decrease in linear growth rate and resultant fluxes of all channels with increasing Z eff can be traced to impurity profile change by transport. The improvement in confinement levels off at higher Z eff . Over the regime of study there is a competition between the suppressed transport and increasing radiation that leads to a peak in the fusion performance at Z eff (~2.78 for CFETR). Extrinsic impurity seeding to control divertor heat load will need to be optimized around this value for best fusion performance.

Neural-network accelerated coupled core-pedestal simulations with self-consistent transport of impurities and compatible with ITER IMAS

“…Although the dilution of the D-T ions in the core raises the core plasma temperature as Z eff is increased (an effect also observed in Ref. [22] for reactor simulations) this positive effect is offset by a decrease in…”

EMC3–EIRENE simulations of neon impurity seeding effects on heat flux distribution on CFETR

“…For GP2, the neon impurity penetration into the separatrix is a little higher than that for GP3, which shows a slightly larger neon ions density inside the separatrix in figure 4(c). The effective ion charge number (Z eff ) is an important parameter to estimate the impurity concentration level, which has a strong impact on the fusion performance according to the core modelling [40,41]. The increase in Z eff in the core region can cause an increased ohmic flux consumption that should be low enough to sustain a long burning flat-top phase for CFETR [41].…”

Evaluating the effects of tungsten on CFETR phase I performance

“…A similar steady-state loop has been described in [20,21]; here we extend that workflow to deal with the effects of fuel dilution and radiation loss caused by W on plasma performance for the first time. An impurity loop was first introduced in [22] but that paper, which focused on intermediate charge impurities such as Ar, did not include neoclassical effect on the impurity profile reconstruction. Neoclassical effect could be very important for the transport of heavy impurities, thus it needs to be fully considered.…”