Carbon particles emission, brittle destruction and co-deposit formation:: Experience from electron beam experiments and controlled fusion devices

Graphite erosion leading to the formation of carbon clusters and dust particles under high power deposition has been studied using an electron beam facility and in various types of controlled fusion devices with carbon walls. It is shown that brittle destruction of graphite takes place in both systems and it results in the production of debris of a sub-millimeter to millimeter size, in electron beam experiments fine grain graphites and carbon fiber composite have been subjected to intense transient heat loads with deposited energy densities of up to several tens of MJ m(-2) in order to simulate plasma disruptions (5 ms pulse duration) or vertical displacement events (100-1000 ms pulse duration). In a reversed field pinch the brittle destruction has been caused by a pronounced mode activity (and related power loads to the wall, over 1 GW m(-2)) at the very edge of the plasma during wall locking phase of discharges. Particles or dust generated during the thermal load tests and in fusion devices have been collected and analyzed using optical and various electron microscopy methods.