Materials issues in diagnostic systems for BPX and ITER

Diagnostic systems in advanced D-T-burning fusion devices will be subjected to intense fluxes and fluences of high-energy neutrons and gamma rays. Materials used in these systems may suffer significant degradation of structural, optical, and electrical properties, either promptly upon irradiation or after accumulation of structural damage. Of particular concern are windows, optical fibers, reflectors, and insulators. Many materials currently specified for these components are known to degrade under anticipated operating conditions. However, careful materials selection and modification based on an appropriate irradiation testing program, when combined with optimization of design-sensitive factors such as location, shielding, and ease of replacement, should help to alleviate these materials problems. 30 refs., 2 figs., 1 tab