Millimeter wave system upgrades on TCV: Additional X3 power and fast ECE polarizers

In the foreseen upgrade of the Tokamak-à-Configuration-Variable (TCV) it is planned to add 3MW of additional RF power (3rd harmonic X-mode, X3, top-launch) to the present Electron Cyclotron (EC) system. With the upgrade of the EC-system, bringing the total EC power in X3-mode to 4.5MW, and the installation of 1 MW of neutral beam injection, a new avenue will be opened allowing the extensive study of H-mode physics in TCV. The envisaged new gyrotrons (1MW, 126 GHz) are based on a minimum redesign of the 140 GHz gyrotron that was developed within the European development program for W7-X [1,2]. The layout, the operational capabilities, and the TCV plasma parameter range that will be achievable with the upgraded TCV EC-system are discussed. Two fast-acting motorized grating polarizers, purchased from General Atomics to further improve the ITER relevancy of one TCV EC transmission line, have recently been installed, temporarily, in the TCV electron cyclotron emission (ECE) diagnostic. The goal is to optimize the receiver mode-coupling during oblique ECE studies that require fast polarization variations, and to allow correlation ECE studies with stepped frequency variation [3]. An overview of the design, installation, testing and integration of these fast polarizers is discussed.