COREDIV modelling of nitrogen and krypton seeding at the ASDEX Upgrade tokamak

Abstract

Self-consistent core-scrape-off layer numerical simulations of an ASDEX-Upgrade discharge where the nitrogen (N) seeding is gradually replaced with the krypton (Kr) seeding during the plasma current flat-top phase are presented. These simulations are performed with the COREDIV code focusing on the prediction of the impurity evolution (W, Kr, N) with matched global plasma parameters: total and core radiation, temperature at the target plate and W concentration. The numerical results are compared with experimental measurements for shot #30503 at three different time points: 2.5 s (only N seeding), 4.2 s (N + Kr seeding) and 5.2 s (only Kr seeding). The calculated electron temperature at the divertor plate can be reduced to 3 eV with the highest Kr seeding. A good agreement between modelling results and experimental observations is reported.

Divertor power spreading in the Divertor Tokamak Test facility for a full power scenario with Ar and Ne seeding

“…This work describes integrated numerical modelling applied to the DTT scenarios with tungsten wall in SN divertor configuration using the COREDIV code [9], which self-consistently solves 1D radial transport equations for the main plasma and impurities in the core region and 2D multifluid transport in the SOL. We note that the COREDIV code has been successfully benchmarked against several JET discharges with a tungsten divertor and a beryllium wall (JET ILW) with nitrogen [10] and neon [11] seeding, and against ASDEX discharges (full tungsten machine) [12], proving its ability to reproduce the main features of seeded discharges.…”

Study of Electron Impact Excitation of Na-like Kr Ion for Impurity Seeding Experiment in Large Helical Device

“…Kr 7+ and Kr 5+ , were investigated to examine the relevance of different ionization states in divertor detachment operation in a Large Helical Device (LHD) [17,18]. However, in ASDEX Upgrade (AUG) and JT-60SA tokamaks, numerical simulation and experimental studies have been conducted using Kr gas and Kr+N 2 gases in support of ITER experiments and the development of impurity scenarios for a large-scale fusion DEMOnstration reactor (DEMO) [19]. In high-atomic-number (Z) impurities, Kr gas is the favorable atomic element as it is chemically non-invasive and radiates efficiently in the Scrape-Off Layer (SOL) and core regions [19].…”

“…However, in ASDEX Upgrade (AUG) and JT-60SA tokamaks, numerical simulation and experimental studies have been conducted using Kr gas and Kr+N 2 gases in support of ITER experiments and the development of impurity scenarios for a large-scale fusion DEMOnstration reactor (DEMO) [19]. In high-atomic-number (Z) impurities, Kr gas is the favorable atomic element as it is chemically non-invasive and radiates efficiently in the Scrape-Off Layer (SOL) and core regions [19]. The presence of Highly Charged Ions (HCIs) of such impurity leads to lower dilution within the core plasma and helps in facilitating the identification of an impurity scenario that enables the optimization of plasma performance in terms of power exhaust and confinement.…”