Additional X3 power
Experimental evidence shows that installed X3 power level of 1.5MW is marginal for high density H-modes plasmas with central densities above the X2-cutoff.
It is foreseen to inject an additional 2 MW of X3 power in the top-launch at 126GHz, with the installation of 2 new gyrotrons. The existing X3 (118GHz) gyrotrons are planned to be injected from the ‘low field side’ (by sharing the X2 launchers).
For the 2 MW of additional power injected at 126GHz, it is planned to use a slightly modified version of the existing 140GHz/1MW/CW gyrotron developed for the W7-X stellarator.
A preliminary study has shown that by passing from a diode electron gun of this existing gyrotron to a triode electron gun, not only one can reach the required parameters for the X3 upgrade in TCV, but also extend the operation of this same modified gyrotron to 1MW at 168.5GHz (TE35 ,9) near the ITER frequency (170GHz).
A system designed for fast variation of the microwave beam polarization and with real-time feedback control capability is planned to be installed in one of the transmission lines of the TCV ECRH-ECCD system.
For this purpose, two fast-acting polarizer mirrors were acquired and underwent performance and control tests.
Each polarizer consists in a grating mirror housed in a transmission line mitre bend, controlled by a direct drive programmable servo-motor.
This upgrade will allow:
- studies of methods for real-time feedback control of the polarization of the injected beams
- test calculations of power coupling optimization
- test methods for wrong mode detection (e.g., O-mode for X-mode injection).