Some problems arising due to plasma-surface interaction for operation of the in-vessel mirrors in a fusion reactor

Effects of two contradictory processes on the survivability of the in-vesse l mirrors for diagnosing plasma in a fusion reactor, namely, the sputtering by charge exchanged atoms and deposition of eroded material, are analyzed in detail using results of simulation experiments. The degradation rate of mirrors bombarded long-term by keV energy range ions of deuterium plasma wa s found to depend strongly not only on the mirror material but also on its initial structure and energy of projectiles. The highest resistance was dem onstrated by mirrors fabricated of monocrystal W and Mo and the lowest by m irrors fabricated of hot-pressed Be. As for the effect of mirror contaminat ion, an effective reflectance was measured and calculated for some metal mi rrors coated by thin films typical for existing fusion devices or for a fus ion reactor: boron, carbon, and beryllium. (C) 2001 Elsevier Science B.V, A ll rights reserved.