Optical design for divertor Thomson scattering system for JT-60SA

• A detailed designing for collection optical system of divertor Thomson scattering system in JT-60SA is conducted.
• The assessment of the density and temperature errors of the measurement system is conducted.
• It is shown that the measurement could be done with the temperature error of 50% when the density was 1020 m−3.
• The availability of the laser transmission mirrors for the measurement system is discussed.
• Several guidelines to improve the measurement system are discussed.

Optical design for divertor Thomson scattering system in JT-60SA has been conducted. The measurement system will use a Nd:YAG laser at 1064 nm, and scattered photons are collected by a collection optical system. The collection optics consists of primary mirror, secondary mirror, relay optics, and fiber collection optics. The laser transmission mirror and collection optics were designed to be installed in a slender lower port of JT-60SA. The assessment of the measurement errors in temperature was conducted for the designed collection optical system. Because of spatial limitation, the solid angle from the measurement points would be small especially for the measurement points in high field side, and consequently, the temperature errors in the high field side would be considerably large. The effects of several improvements on the error are discussed. Moreover, an assessment for the in-vessel laser transmission metallic mirrors is conducted for the present design.