Plasma discharges in the tungsten (W) Environment Steady-state Tokamak (WEST) are strongly impacted by W contamination.In WEST experiments, due to W contamination, the power radiated in the plasma ( P _Rad ) is on average, around pixar ball keychain 50% of the total power injected into the plasma ( P _TOT ).Furthermore, this radiated power fraction ( f _Rad ) is almost insensitive to plasma conditions.
The causes behind this experimental trend are not fully understood.In this contribution, a 3D numerical model is used to analyze the W migration in the WEST boundary plasma in different plasma scenarios.The WEST experimental database is sampled to obtain a scan of simulation input parameters.
These parameters mimic the WEST plasma conditions over a chosen experimental campaign.The simulation results are compared to WEST diagnostics measurements (reflectometry, Langmuir probes, and visible spectroscopy) to verify that the simulated plasma conditions are representative of the WEST database.The W contamination trend is analyzed: the W density ( n _W ) strongly decreases when the radial distance between the separatrix and WEST antennas (Radial Outer Gap, ROG) increases.
On the caroline gardner cards sale other hand, at a given ROG, n _W increases proportionally with the power entering the scrape-off layer ( P _SOL ).P _Rad is estimated with a simple 0D model.For a fixed ROG, f _Rad is not sensitive to plasma conditions.
These trends are qualitatively and, at times, quantitatively comparable to what is observed in WEST experiments: the simulated trends are related to the poorly screened W influx caused by the erosion of the main chamber Plasma-Facing Components.Thus, this numerical analysis suggests a possible interpretation of WEST experimental trends.