Design and development of the edge Thomson scattering system in ITER

Hatae, Takaki; Yatsuka, Eiichi; Shimada, Takahiko; Ishikawa, Masao; Itami, Kiyoshi

JAEA has been developing the edge Thomson scattering system (ETS) in ITER, and the preliminary design phase has already started. The ETS is a primary diagnostic system for measuring electron temperature and electron density profiles in ITER. We present three current topics: collection optics, laser beam dump, and YAG laser. Collection optics, which is a key component of ETS, is installed in a diagnostic port connected to ITER vacuum vessel, and this optics collects extremely feeble light of Thomson scattering. From the neutron shielding point of view, the collection optics must have labyrinth-like optical path built by shielding material and mirrors, and the volume of optical path must be minimized. On the other hand, labyrinth-like optical path deteriorates optical performance. Balance of neutron shielding and optical performance are crucial for the burning plasma diagnostics. We found that a collection optics design satisfies required performances both optical design and neutron shield by the optimization of optical design and shielding design. In this design, shut-down dose rate as required a neutron shield performance is less than 100 Sv/h at the interspace just after the diagnostic port. And spatial resolution is 5 mm.