抄録
Experimental studies on mesoscale erosion of tungsten surface due to low-energy and high-flux helium/deuterium exposure are systematically described. Following the historical description of the accidental finding of helium bubbles and holes, possible changes in tungsten properties like the A coefficient and the work function of the rmo electron emission, the emissivity and the energy reflection coefficient are discussed in terms of thermal bifurcation. Multi-dimensional parameter area for He bubble formation is identified in the space of tungsten temperature, ion fluence and incident ion energy. In particular, the threshold energy was surprisingly found to be as low as 6 eV, in association with which the formation mechanism is proposed. Finally, the effect of bubbles and holes formation on deuterium retention is quantitatively clarified.
