Preliminary conceptual design of the DTT EC heating system

The Divertor Tokamak Test (DTT) facility has been proposed in the European roadmap to study solutions to mitigate the issue of power exhaust in conditions relevant for DEMO. The Italian DTT tokamak [1] is being designed to reproduce the optimal divertor magnetic configuration and test a prototype under reactor relevant power flow in the scrape off layer (PSEP/R>15 MW/m). A mix of three heating systems will equip the machine to reach the target value of 45 MW delivered at plasma: Electron Cyclotron Heating (ECH), Ion Cyclotron Heating (ICH) and Negative Neutron Beam Injector (NNBI). The present reference design considers a capability of 20-30 MW of ECH power at plasma to support and assist different tasks. The gyrotron sources (1 MW/170 GHz/100 s) will be based on the depressed collector technology with >40% efficiency and will exploit the experience gained from the solutions developed for ITER. A Transmission Line (TL) with 90% efficiency and >1 MW/beam power handling is being considered, using Quasi-Optical (QO) multi-beam mirrors. The conceptual design of equatorial and upper launchers based on the front steering concept is being developed to reach the required deposition locations for the given application. The EC wave absorption efficiency has been investigated and is presented here with dedicated beam tracing calculations using the GRAY code [2].