Designing far infrared diagnostics for fusion plasma experiments

It seems timely to review the performance of large far infrared plasma diagnostics, from design and concept to operation and maintenance. Experience from several recent fusion experiments suggests that a fully integrated approach is required. The teams involved in elaborating the proof of concept, developing engineering, solutions, supervising assembly and installation, as well as operating and maintaining the diagnostic should have a strong collaborative relationship. Selecting the right design and components from the beginning will have major implications on the operation of the device over its operating life. In some cases higher development costs initially can be justified by lower operating and maintenance costs over a long period. These ideas are developed from experience gained by operating some of the largest far infrared plasma diagnostics in the world. Secondly, some criteria for new far infrared devices being designed to work in completely new conditions will be presented. For the next generation of plasma experiments, diagnostics will need to cope with a quite different operating environment including very long period of operation, high radiation and neutron fluxes, very strong magnetic fields and low or zero access to certain parts of diagnostics. This is a major challenge for manufacturers and teams involved in developing new far infrared diagnostics and devices.