High-k Scattering Diagnostics for EAST and NSTX-U tokamaks

• Datum: 25.09.2024
• Uhrzeit: 15:30 - 16:30
• Vortragende(r): Xianzi Liu
• (UC Davis)
• Ort: Seminarraum D3 / Zoom

A 693 GHz, 8-channel high-wavenumber scattering system is under development for NSTX-U (C.W. Domier et al 2022 JINST 17 C01018) and a 270 GHz, 4-channel high-wavenumber scattering system is being installed on the EAST tokamak. The systems aim to study high-k electron density fluctuations, by providing a measurement of the k spectrum of the electron temperature gradient (ETG) mode (Y. Ren et al., Rev. Mod. Plasma Phys. 8, 5 (2024)). ETG is important to plasma transport since anomalous electron thermal transport is the dominant transport channel in NSTX and GS2 linear analysis inside EAST ion internal transport barrier (ITB) also suggests that the ETG modes are robustly unstable.

The entire system, including the optical and electronics parts are presented. The challenge in the optical design lies in achieving strict wavenumber alignment and large r/a coverage, thus the optical design is carefully developed and evaluated. A beam tracing code accounting for refraction and diffraction has been developed and implemented for NSTX-U and EAST high-k scenarios. This code more accurately determines the location of the interaction region and the scattering volume and serves as a basis for the development of the synthetic high-k system.