ITER x-ray diagnostic studies

Present-day tokamak x-ray imaging (XIS) and pulse height analysis (PHA) diagnostics will require special shielding and x-ray optics to permit use on fusion reactors without prohibitive noise and detector damage from neutrons and gamma rays; x-ray curved-crystal spectrometers (XCS) may work with extensive shielding and collimation, but radiation damage of crystals and attainment of adequate impurity concentrations for ion-temperature measurement are concerns. We consider the use of one or more reflections at grazing incidence from x-ray mirrors or from Bragg layered synthetic microstructures (LSM) to decouple the x-ray diagnostic from the direct fusion neutron beam. We present calculations of expected x-ray line brightnesses from ITER and total instrument throughput. We also consider the use of hollow glass capillaries embedded in radiation shields to precede the XIS detector and reduce the ratio of neutron plus gamma radiation to x rays by a factor of ∼0.01 or better. Compatibility of capillary schemes with the PHA and XCS are discussed.