Variable Frequency Doppler and cross-polarization scattering Systems for MAST-U*

A new variable frequency Doppler and cross-polarization scattering system (V-DBS) is being developed for the Mega Ampere Spherical Tokamak – Upgrade (MAST-U). This system will provide localized density turbulence, flow velocities, and magnetic turbulence measurements in the core of higher density MAST-U discharges. The V-DBS will be integrated into the existing Q-band DBS/CPS quasi-optical system which has remote aiming and polarization selection capability. Within a single shot, the VDBS can launch a frequency sweep at 10 – 20 Hz increment ranging from 50 GHz to 75 GHz. Tunability will allow for higher spatial resolution of the plasma properties to be captured. The higher V-band frequencies will enable data collection much deeper into the plasma core of the MAST-U chamber. Both the Q and V-band systems will be capable of launching in either X or O-mode as well as being able to select DBS or CPS operation independently of each other. A full-scale mockup will be fabricated and optimized prior to installation on the MAST-U tokamak. The design, tests, etc. will be reported on.