Design of tangential viewing phase contrast imaging for turbulence measurements in JT-60SA

A tangential viewing phase contrast imaging system is being designed for the JT-60SA tokamak to investigate microturbulence. In order to obtain localized information on the turbulence, a spatial-filtering technique is applied, based on magnetic shearing. The tangential viewing geometry enhances the radial localization. The probing laser beam is injected tangentially and traverses the entire plasma region including both low and high field sides. The spatial resolution for an Internal Transport Barrier discharge is estimated at 30%-70% of the minor radius at k = 5 cm^-1, which is the typical expected wave number of ion scale turbulence such as ion temperature gradient/trapped electron mode.