Development status of sub-mm unambiguous interferometer for COMPASS-Upgrade

0555634 - ÚFP 2024 RIV eng A3 - Přednáška/prezentace nepublikovaná
Varavin, Mykyta - Zadvitskiy, G. - Zajac, Jaromír - Shyshkin, Oleg - Preinhaelter, Josef - Bílková, Petra - Balner, Vojtěch - Veselovský, Viktor - Žáček, František - Nanobashvilil, S.
Development status of sub-mm unambiguous interferometer for COMPASS-Upgrade.
[32nd Symposium on Fusion Technology. Dubrovnik, 18.09.2022-23.09.2022]
Způsob prezentace: Poster
Institucionální podpora: RVO:61389021
Klíčová slova: COMPASS-Upgrade * interferometer * tokamak
Obor OECD: Fluids and plasma physics (including surface physics)

The COMPASS-U tokamak (ne=5x1020m-3, R = 0.9 m, a = 0.27 m, Bt = 5 T, Ip = 2 MA) is under construction in the Institute of Plasma Physics in Prague. Combination of high temperature vessel 300-500oC, high plasma densities, toroidal magnetic fields and plasma current is a big call for the diagnostic design. Based on simulation the differential (unambiguous) interferometer concept for real-time line-integrated electron density measurements was proposed.
Combination of simulation methods is used. Raw estimation was done based on WKB method and Helmholtz equation-based method. Ray tracing simulations by Matlab code based on 4th order Runge-Kutta method and 2D COMSOL simulations were done. As a precise method for wave propagation the 2D full-wave COMSOL simulation was chosen. The plasma profiles are simulated by METIS. Correction coefficient calculations for a non-linear dependence of the refraction index on plasma density were done. The unique study of phase measurement inaccuracy caused by O-X-mode parasitic interference was done. Method of correction such error was proposed.
The study of different plasma shapes, plasma density profiles and possible mechanical vibrations influence to the density measurement is presented. Based on these simulations the special cassette port-plug design was proposed. The technical solution of the interferometer based on the solid-state element technology is presented. Conceptual design of the quasi-optical focusing system including the in-vessel reflection mirror placed on the central column is also introduced. The introduced concept allows the precise phase measurements in a wide density range and compatible with a real-time density feedback system. A similar solution was successfully used on COMPASS tokamak.
Trvalý link: https://hdl.handle.net/11104/0343899