Recent updates on the Thomson scattering diagnostic for the SMall Aspect Ratio Tokamak (SMART)

We present recent developments on the installation of the Thomson scattering (TS) diagnostic on the SMall Aspect Ratio Tokamak (SMART) [1]. The SMART TS diagnostic is designed to operate at high spatial resolution – 6 mm scattering length in the low-field side and 9 mm in the high-field side regions – and a wide dynamic range [2]. It measures electron temperature (T_e) from 1 eV to 1 keV and density (n_e) from 0.5 – 10 × 10¹⁹ m⁻³, allowing characterization of steep plasma edge gradients across varying triangularities. A 2 J, 1064 nm laser is installed, and TS light is collected from 28 mid-plane radial points using custom collection optics. The lenses are built, and their housing is under fabrication along with a custom alignment setup. TS light will be transmitted via fourteen Y-branched unequal-length fiber bundles, currently under construction. We installed fourteen (duplexed) polychromators to extract T_e profiles and an additional unit to monitor in situ laser alignment. The TS data is recorded on a 250 MHz 14-bit acquisition system, undergoing remote testing. Raman calibration is planned for later this year after the remaining components are installed.



References:

[1] D. Cruz-Zabala et al., Nucl. Fusion 64, 126071 (2024).

[2] M. Kaur et al., Rev. Sci. Instrum. 95, 093508 (2024).