Experimental study of plasma energy transfer and material erosion under ELM-like heat loads

Novel electron beam based test facility for observation of dynamics of tungsten erosion under intense ELM-like heat loads

“…It creates too high plasma pressure on tungsten surface and on melted layer moreover the power density absorbed by the tungsten is limited by vapor shield effect [3] by the value q h =4.4-4.6 GWm -2 . It corresponds to heat flux parameter F HF =70-100 MJ m -2 s -0.5 [4]. Long pulse electron beam (LPEB) produces negligible direct pressure and has much higher limit of absorbed power density due to vapor shied effect [5].…”

Analysis of tungsten melt-layer motion and splashing under tokamak conditions at TEXTOR

“…For ITER steady EXD/6-1 state heat loads for a tungsten divertor plate are expected to range around 5 − 10M W/m 2 under normal operation conditions in the non-activated phase, loss of positioning control or additional transients as well as possible misalignment of target mono-blocks can thus lead to melting [1,2]. Studies on melt-layer motion have been performed in electron and ion beam facilities [3,4,5,6] showing significant melt motion, splashing and changes in the material structure and their power handling capabilities. Few results exist regarding behavior under tokamak conditions, including magnetic fields, large currents through the PFC surfaces and various power impact scenarios (Steady state, ELMs, VDEs or disruptions) as well as high temperature erosion.…”

“…Recent experiments have been performed in TEXTOR focussing on the melt-layer motion and the material properties after exposure. Regarding high heat-loads aspect of vapor-shielding have to be considered as seen in [3] which have been observed for transient events in QSPA ELM simulation. For pure tungsten almost 50 % of the impinging heat-flux can be observed.…”

Comparison of tungsten modification after irradiation at different facilities for PSI studies

“…Plasma pressure of 2×10 5 Pa in QSPA experiments [22] is at least one order of magnitude larger than that expected for ITER (10 4 Pa) [22] and can result in different mechanisms of droplet ejection in simulations. For example, in the QSPA Kh-50, droplets velocities may achieve several tens of m/s [23], in GOL-3, droplets with velocities of up to several hundred m/s were detected just after the beam termination [24]. The QSPA droplet velocity estimation is undervaluing, and the GOL-3 droplet velocity estimation is overrating because of: 1) the vapor shield pressure in QSPA exceeds that in ITER [22], and the vapor shield pressure in GOL-3 is less than that in ITER; 2) in QSPA, no droplets can be detected during the irradiation and 1 ms after it [25].…”