TCV heating and in-vessel upgrades for addressing DEMO physics issues

Abstract

TCV is presently undergoing major heating upgrades, installing a neutral beam for direct ion heating and increasing the electron cyclotron(EC) power injected in X-mode at the third harmonic(X3). The neutral beam is under construction at BINP-Plasma LLC(Russia), with energies of 18-35 keV and power up to 1 MW for 2 s. The injection of 1 MW 30 keV D-beam will allow access to regimes with T-i/T-e > 1 and beta(N) similar to 2.8 in L- and H-mode, with densities compatible with X3 EC heating. A lower energy and power(20 keV, 0.5 MW) D NBI is suitable for lower densities with X2 EC heating and current drive. The vacuum vessel has been modified to allow for the beam tangential injection, necessary for beam access and to minimize shine through and orbit losses. The X3 upgrade consists of adding two dual-frequency gyrotrons(X2/X3, 126 GHz/84 GHz) with a total power of 2 MW. In addition, to explore solutions to the exhaust problem in tokamaks and test innovative solutions like the snowflake divertor in the presence of a closed divertor chamber, we are considering inserting new in-vessel modular structures, generating a divertor aperture with variable closure.