Conceptual design of microwave interferometric system for high densities on the COMPASS-U tokamak

0552328 - ÚFP 2022 RIV US eng A - Abstract
Varavin, Mykyta - Varavin, A.V. - Zadvitskiy, Georgiy - Tomeš, Matěj - Žáček, František - Zajac, Jaromír - Naydenkova, Diana - Bílková, Petra - Weinzettl, Vladimír - Nanobashvilil, S. - Král, Miroslav - Havránek, Aleš - Hron, Martin - Jaulmes, Fabien
Conceptual design of microwave interferometric system for high densities on the COMPASS-U tokamak.
The sub-mm unambiguous interferometer concept for COMPASS-Upgrade. La Canada Flintridge: The International Society of Infrared, Millimeter, and Terahertz Waves, 2021.
[31st Symposium on Fusion Technology. 20.09.2020-25.09.2020, Dubrovník]
Institutional support: RVO:61389021
Keywords : COMPASS-U * tokamak * METIS
OECD category: Fluids and plasma physics (including surface physics)

The COMPASS-U tokamak is under construction in the Institute of Plasma Physics in Prague. Expected high plasma densities in COMPASS-U up to 5x1020 m-3 and a high magnetic field up to 5 T require a new design of a sub-mm interferometer. The proposed solution for real-time line-integrated electron density measurements is based on an ”unambiguous” channel.
The introduced design of the microwave interferometric system will allow precise measurements in a wide density range as well as its use for a real-time density feedback. The technical solution of the interferometer is based on solid-state element technology. Among main features of this system there is a use of two microwave transceivers at close frequencies and a principle of the „unambiguous” channel. Conceptual design of the quasi optic focusing system including the in-vessel reflection mirror placed on the central column is also introduced.
The study of both vertical and horizontal orientations of the interferometer with respect to an influence of different plasma shapes, plasma density profiles and possible mechanical vibrations to the density measurement is presented.
Ray tracing simulations done by the FIESTA-8, TORE beam, Zemax and Cherab codes are shown and demonstrate propagation of the probing waves through COMPASS-U plasmas. The plasmas (equilibrium, profiles) are simulated using METIS.
Calculations of the coefficient for correction of a non-linear dependence of the refraction index on plasma density were done using the WKB and Full wave methods. Coefficients for real-time correction were calculated using numerical methods already tested on the COMPASS tokamak.
Permanent Link: http://hdl.handle.net/11104/0327461