RADIATION EFFECTS ON HEATED OPTICAL FIBERS

Optical fibers are ubiquitous on today's plasma devices, and will play a major role in future machines. However, radiation causes luminescen ce and transmission loss in fibers at troubling levels even on today's machines when they operate in DT. We have evaluated these effects and studied the use of elevated operating temperatures to reduce them. Us ing high-purity UV grade silica-silica fibers at 400 degrees C reduces transmission loss by a factor of at least 100, but has little or no e ffect on radioluminescence. The radioluminescent spectrum appears to b e Cerenkov radiation. The transmission loss spectrum depends on the fi ber material and details of the manufacture. The mode structure of tra nsmission loss is mainly simple path length attenuation, with a sugges tion of internal reflection degradation. (C) 1997 American Institute o f Physics.