On aspects of radiation damage in tokamak diagnostics

The harsh radiation environment presented by the D-T burning plasma in next-step tokamak fusion devices can cause severe damage to critical optical components necessary for research diagnostics and control instrumentation. Using the TRIGA research reactor at the University of Illinois to simulate the radiation environment expected in fusion devices, experimental studies have been performed to examine the feasibility of using combined thermal and optical annealing techniques to maintain the optical quality during irradiation. Using pulsed operation of the reactor, in-situ measurements have been made of the transient optical effects of radiation on bulk fused silica under various continuous annealing conditions. Additional long term effects studies have also been performed under steady-state radiation conditions to examine the effect of accumulated dose and repeated annealing. The purpose of this present research is to develop a practical thermal/optical annealing program to reduce the level of radiation induced color center damage in optical components intended for next step tokamak diagnostics