Behaviour of the PFC tiles on the ITER divertor under critical loading conditions

In the divertor most of the heat load on the vertical target (VT) is delivered by the particle flux that follows the field lines in the scrape-off layer (SOL). This flux intercepts the VT at a glancing angle (∼2–3°) causing erosion of the actively cooled carbon fibre composite (CFC) monoblock tiles that form the plasma-facing surface at the strike point. The erosion is a function of surface temperature and particle flux. Poor thermal contact between the CFC monoblock and the CuCrZr cooling tube will lead to an increased surface temperature of the CFC, and initially an increase in the surface erosion rate. The higher erosion will result in the surface being partially shaded by its well-attached neighbouring monoblock. Eventually, the erosion of the poorly attached monoblock will be the same as its well-attached neighbours, albeit with a reduced particle flux and a higher surface temperature.