Impurity Seeding in ASDEX Upgrade Tokamak Modeled by COREDIV Code

Abstract

The self-consistent COREDIV code is used to simulate discharges in a tokamak plasma, especially the influence of impurities during nitrogen and argon seeding on the key plasma parameters. The calculations are performed with and without taking into account the W prompt redeposition in the divertor area and are compared to the experimental results acquired on ASDEX Upgrade tokamak (shots #29254 and #29257).For both impurities the modeling shows a better agreement with the experiment in the case without prompt redeposition. It is attributed to higher average tungsten concentration, which on the other hand seriously exceeds the experimental value. By turning the prompt redeposition process on, the W concentration is lowered, what, in turn, results in underestimation of the radiative power losses. By analyzing the influence of the transport coefficients on the radiative power loss and average W concentration it is concluded that the way to compromise the opposing tendencies is to include the edge-localized mode flushing mechanism into the code, which dominates the experimental particle and energy balance. Also performing the calculations with both anomalous and neoclassical diffusion transport mechanisms included is suggested.

Numerical analyses of JT-60SA scenarios with the COREDIV code

“…In the case of the COREDIV simulations, we have already performed a number of simulations to investigate the influence of the SOL radial transport on simulation results. It has been done for present day experiments (JET[jet- [7,17], ASDEX-U [18]) and for future devices (ITER [19], DEMO [20]). The main conclusion from these simulations is that the stronger radial transport in the SOL helps to keep the impurities in the SOL and leads to the increased impurity radiation in the SOL.…”

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

“…The code includes atomic processes such as ionization, recombination, excitation and charge exchange as well as sputtering processes on the tungsten plate by deuterium and all impurities. In our earlier simulations for AUG with N seeding [20], we have investigated the influence of the prompt redeposition on the simulation results. It appears that the effect of the reduced sputtering yield due to the prompt re-deposition process is only important for relatively small levels of seeding [20,[26][27][28], therefore, in the present study with relatively strong and combined N and Kr seeding, the effect of the prompt re-deposition is neglected.…”

“…Our approach is based on integrated numerical modelling of plasma parameters using the COREDIV code, which selfconsistently solves the 1D radial transport equations of plasma and impurities in the core region and 2D multi-fluid transport in the SOL, which is very important, especially for AUG equipped with a tungsten divertor. The COREDIV code has been successfully benchmarked with a number of JET ILW discharges, including N seeding in H-mode and L-mode [15][16][17][18] and with AUG data [19,20].…”

Analysis of the performances of a fusion reactor in a reduced H-mode confinement

“…The COREDIV code has been used to investigate self consistently many current experiments in particular JET [25] and Asdex [26]. The first step of the present exercise is to analyse the effect of the main plasma parameters: geometry (tokamak major radius R) and toroidal magnetic field (B T ) values, on the Q-factor, on the power crossing the separatrix (P SOL ) and on that deposited onto the divertor plates.…”