Explosive-like erosion of graphite in the GOL-3 disruption simulation experiments

During the tokamak disruption event, a hot plasma streams along the field to the divertor plates. Under the ITER conditions the material erosion rate will determine the divertor plates durability. At the existing tokamaks the ITER disruption parameters (power density ∼10 MW/cm2, energy density ∼10 MJ/m2) are not achievable. Therefore the divertor material behavior has to be studied on alternative devices. The GOL-3 facility (7m long open trap) was used for this purpose. Plasma is heated there with a relativistic electron beam. Plasma have temperature of the bulk electrons 1015 cm-3 up to 1 keV and open-quotes tailclose quotes of the distribution function up to tens of keV. Such a plasma stream affect the target placed at the magnetic field 5-10 T. As a result of plasma-target interaction the surface erosion, generation of vapors and their further expansion occurs. The erosion of the fine grain dense graphite looks like explosive above some threshold. The depth of erosion exceeds 500 μm at maximal parameters. This value is up to a factor of 10 more than expected from simple energetic consideration. The experimental estimation of the energy of graphite damage is less then the evaporation energy. The possible mechanism of graphite explosive-like erosion is discussed