Erosion and screening of tungsten during inter/intra-ELM periods in the JET-ILW divertor
A. Huber, S. Brezinsek, V. Huber, M. Sertoli, G. Sergienko, I. Borodkina, M. Baruzzo, A. Kirschner, D. Borodin, J. Mailloux, S. Aleiferis, P. Carvalho, K. Lawson, Ch. Linsmeier, A. Meigs, S. Menmuir, Ph. Mertens, E. Pawelec, A. Shaw
Abstract
Intra-ELM tungsten sources, which dominate the total W source, are quantified in the inner and outer divertor of JET-ILW. The amount of the sputtered W atoms for individual ELMs demonstrates a clear dependence on the ELM frequency. It decreases when the pedestal temperature is lower and, correspondingly, the ELM frequency is higher. Nevertheless, the entire gross erosion W source (the number of eroded W atoms per second due to ELMs) increases initially with ELM frequency and reaches its maximum at fELM ≈ 50–55 Hz followed by its reduction in the high frequency range. The in/out asymmetry of the intra-ELM W sources during ELMs is a critical issue and is investigated in this contribution. At a lower ELM frequency of about 35 Hz the outer divertor gross W source is larger by a factor of 1.5. However the in/out asymmetry of the W erosion decreases strongly with ELM frequency demonstrating a nearly symmetric W source in both divertor legs at frequencies above 70 Hz. The screening of tungsten in the open magnetic configuration with strike points on tile 5 is more efficient by a factor of about 1.7 than in the corner configuration with the outer strike point at the pumping duct entrance.