Integration of Diagnostics into the ITER Machine

This paper defines and discusses the integration of diagnostics systems into the ITER machine. For each machine region, the key constraints and solutions adopted are discussed, and illustrated with selected examples. 1. THE INTEGRATION PROCESS In order to meet the ITER programmatic and operational goals it is necessary to measure a wide range of plasma parameters as well as the condition of the first wall and divertor target plates [1]. Thus there is a need for an extensive collection of individual measurement systems (diagnostics) which together form the ITER diagnostic system. Integration of this system into the ITER machine is the iterative process of allocating space for each diagnostic following a set of priorities, and resolving all the interface issues between the diagnostic and other machine systems (including other diagnostics) or operations (including maintenance). Priorities for the diagnostics largely follow the categorisation of measurements [2]: these are 1a) those necessary for machine protection and basic control; 1b) advanced control; and 2) physics understanding. Interface issues [3] dominate the integration process, making it natural to discuss integration by location [4]. There are four main areas where diagnostic components are installed: a) equatorial port: LIDAR Thomson scattering, wide angle viewing in visible and IR, radial neutron camera, bolometers, polarimeter, tangential interferometer/polarimeter, ECE, edge reflectometers, X-ray crystal spectroscopy, vacuum-UV spectroscopy, active spectroscopy (MSE and CXRS), neutral particle analyser; b) back plate and vacuum vessel (VV): Magnetic pick up coils and flux loops, bolometers, soft x-ray diodes, position reflectometers, high-field side profile reflectometers; c) vertical port: bolometers, impurity monitors, edge Thomson Scattering, neutron activation, vertical neutron camera, wide angle viewing in visible and IR, In Vessel Inspection (IVI); d) divertor cassette: Impurity spectroscopy, target IR viewing, reflectometry, Langmuir probes, pressure gauges, magnetic pick up coils, bolometers. The integration of diagnostics must be consistent with the number of ports allocated, the design of the port plugs and in-vessel machine components, nuclear shielding requirements, tritium containment and vacuum requirements, as well as maintainability with remote handling equipment both in the vacuum vessel and in the Hot Cell. The main shielding requirements are met by labyrinthine access penetrations, while materials survivability is met by the choice of materials for the exposed front end components [5]. Thus the above requirements which arise in an ITER like machine serve as the primary design drivers, posing a new design challenge.