Conceptual design of laser transfer system of the JT-60SA Thomson scattering diagnostic

This paper provides a conceptual design of the laser transfer system to be installed for the JT-60SA Thomson scattering system. The optical design newly permits transferring two wavelength lasers, i.e., YAG (1064 nm) and ruby (694 nm) lasers, so that an in situ relative calibration for high-field edge measurements, where the scattering angle is close to 90◦, is possible under severe radiation condition. Stray light generated from scattering at a vacuum window can be suppressed using multiple baffles. It is newly found that the baffles spaced at a geometric series, i.e., 40% of unit length, is an effective way and reduces the stray light. The amount of stray light can be reduced to ∼6% using only three baffles compared with the case of no-baffles