Neutron activation for ITER

There are three primary goals for the Neutron Activation system for ITER: to maintain a robust relative measure of fusion power with stability and wide dynamic range (seven orders of magnitude), allow an absolute calibration of fusion power production, and provide a flexible and reliable system for materials testing. The nature of the activation technique is such that stability and wide dynamic range can be intrinsic properties of the system. It has also been the technique that demonstrated (on JET and TFTR) the most accurate neutron measurements in DT operation. Since the detectors for assaying the radioactivity are not located on the tokamak and are therefore amenable to accurate characterization, and if the activation samples are placed very close to the ITER plasma with minimal scattering or attenuation, high overall accuracy in the fusion energy production (7%-10%) should be achievable on ITER. In the paper, a conceptual design is presented. A system is shown to be capable of meeting these three goals, and unresolved design issues are identified.