Conceptual design of JT-60SA edge Thomson scattering diagnostic

The mission of JT-60SA is to complement ITER in resolving key physics andengineering issues to finally decide an acceptable DEMO plasma design, includingpractical and reliable plasma control schemes suitable for a power plant. To thispurpose diagnostics play a key role. Electron temperature and density profiles willbe measured by Thomson scattering systems (TS). They are designed to achievehigh spatial resolution, required to identify the pedestal parameters and smallstructures.Two TS systems are being designed for JT-60SA, to be procured and installedwithin 2022. They both use a tangential Nd:YAG laser beam path on the plasmaequatorial plane. Tangential ports for injecting the laser beams are situated atPort-1 and Port-8 horizontal port sections. In accordance with this laser beamgeometry, Port-1 lower oblique and Port-2 horizontal ports are assigned for theoptics collecting the scattered light from the outer edge (low field side) and core ofthe plasma, respectively. Design of TS systems is carried out by a joint Japan-EU team. EU is contributingwith procurement of the edge TS collection optics and supporting structure, anedge dedicated laser, polychromators and optical fibres for both systems. Keyfeatures of the edge TS diagnostic setup and main components will be presented.The collection optics are specifically designed to fit in the port plug tube and toimage with suitable resolution the scattering volumes into an array of fibrebundles. The optics is held by a mechanical structure bolted on the floor,decoupled from the cryostat. A set of filter polychromators with APD detectorsdetect the scattered radiation: their specification and interference filter design willbe presented. Simulations of the TS signals provide the expected performance.