Development of Extended Two-Point Model for Asymmetric Scrape-Off Layer

Abstract

The SYCOMORE code is a modular system code which aims at modelling future fusion power plants with all subsystems and to provide a global view of the whole plant. The code consists in different modules handling the different subsystems of the plant, from the core plasma to the conversion of heat to electricity. Among them, the divertor is one of the most important components and must withstand high heat load. While the complex magnetic configuration in tokamaks and the peculiar transport in the scrape-off layer (SOL) give rise to an asymmetry in the high field and low field energy fluxes, this issue should be properly addressed in SYCOMORE for quick and reliable predictions. In this work, the SOLDIV code which is a scrape-off-layer and divertor module in SYCOMORE has been used to investigate this asymmetry problem based on an extended two-point model. When the outgoing fluxes of particles and heat from the plasma core enter the SOL at the stagnation point, they split into two parts: one transporting to the inner divertor, and the other transporting to the outer divertor. By introducing the imbalance factor of the energy flux between the two divertor plates, the transport equations become a set of nonlinear equations that can be numerically solved for the densities and temperatures at both divertor plates and the stagnation point. Strong temperature and density differences at the targets can be found. The analysis results are validated with the transport code SolEdge2D-EIRENE for WEST test discharges. The simulation results for ITER are also investigated.