Heating Issues G.Granucci on behalf of the project team EURO fusion DTT Workshop Frascati, Italy, 19-20 June 2017
Summary Physical Requirements DTT Heating Mix ECRH System ICRH System Auxiliary Heating Systems Installation Timing Conclusion The NNBI System will be described in next presentation by P. Sonato
Physical Requirements for DTT Heating Systems The main tasks for DTT Heating System are to supply the power to reach the prescribed P sep /R of 15 MW/m and to sustain a robust H- mode. This requires a reference amount of ~45 MW of P AUX. Three Heating system are considered: ICRH, ECRH and NNBI Main Physical requirements are: Bulk electron/ion heating for H-mode: Current profile tailoring with localized CD: Pulse extension by assisting current ramp-up: Avoid central impurity accumulation: Sawtooth and NTM control: Plasma Current Sustainment: Fast particle simulation: NNBI, EC, IC EC EC EC, IC EC NNBI, EC IC, NNBI
DTT Heating Mix The required 45 MW at plasma can be assured in different ways, depending on different considerations as: performances, costs, availability, engineering compatibility The Report Scenario was in two steps (installed power): 1 st 24 MW* of IC and 12 MW of EC; full available in 2 years 2 nd - 15 MW of NNBI to be decided after 1 year A New Scenario is : 1 st - 24 MW* of IC and 16 MW of EC full available in 2 years 2 nd -15 MW of NNBI + 12 MW of EC in 5 year from plasma start * 10 MW at plasma or up to 17 MW in case of positive tests on EBG antenna.
EC System Main Features Cluster approach (4 gyrotron for single HVPS) Multi Beam Quasi optical Transmission line: 6 beams x line Dedicated (straight) layout to access to DTT CD Efficiency vs deposition Upper Launcher GRAY code Two different plug-in in launchers: 1 RT front steering launcher (4MW) from upper port for NTM stabilization and control; 3 Simplified Front Steering launchers (4MW) from Equatorial Ports; In the Report EC Launchers were at fixed toroidal direction, in case of more CD flexibility required, symmetric solutions will be studied
ECRH System: Source Issue Reference Gyrotron: 170 GHZ, 1 MW, cw already developed for ITER with High reliability and efficiency (~50%) The EU 170 GHz gyrotron at SPC test-bed For more flexibility in magnetic field a double frequency gyrotron can be considered: 140 GHz and 170 GHz The ECRH system will be designed using same concepts under study for DEMO EC system (WPHCD) applying a similar simplicity and the high reliability required.
Concepts for EC Systems 3 plug-in EC equatorial launchers 4 open-ended waveguides launch to individual ellipsoidal focusing movable mirrors Multi Beam Quasi Optical Evacuated TL Up to 6 beams are transmitted by set of focussing + plane mirrors (see W7-X) eventually under vacuum (as for DEMO) 1 plug-in EC Upper Launcher Concepts Toroidal steering
ICRH System Characteristics Heating scheme for H-mode reference 6 T scenario: H minority heating ω c ~ 90 MHz at plasma centre, 3 He minority heating ω c ~ 60 MHz at plasma centre. 16 transmitters based on a 3-stage amplification TH526 by Thales Electron Devices, able to deliver: 24 MW at 60 MHz or 21 MW at 90 MHz for 100s of pulse. A factor 1.3 can be applied in case of pulse < 30 s ~32 MW @ 60MHz Transmission lines and matching: Matching circuit based on external conjugate-t junctions 3-dB hybrid couplers as possible future upgrade. Coaxial lines with 50(30) Ω impedance before(after) conjugate-t and 13.4 Ω antenna feeders 4 Antennas Baseline design: shimming port-plugged antenna, 2(H) x 4(V) straps fed by 8 coaxial through ~ 0.65m x 1.1m port. Coupled power limited by voltage standoff according to TOPICA simulations Conservative 4 MW /m 2 assumed ~11 MW coupled to plasma
ICRH alternative antenna designs Three-strap (AUG-like) antenna to balance image currents: requires wider antenna P_central / P_outer = 1.5 TOPICA code improvement to 4 MW feasible with optimization EBG antenna concept: periodic structures (Electromagnetic Band Gap ) behind the straps, acting as high impedance surfaces lead to reflected power < -10 db and low standing wave ratios in the feeders Thermo-mechanical analyses is required Possible first demonstrative test on EAST. If positive EBG will be adopted in DTT h=12 cm h=11 cm h=10 cm h=9 cm h strap Resonance frequency tuneable in 60 90 MHz by varyng h
RF System Timeline EC IC
Conclusion DTT RF Heating Systems will exploit R&D already done for ITER and W7-X Some R&D activity (double frequency gyrotron and EBG antenna) will be addressed quickly in order to avoid delay in procurement The Power installation will be articulated in two steps: First 5 years : from 26 MW to 33 MW depending on EBG From 6 Th year : extra 10 MW of NNBI and 10 MW of EC and pulse length Present stage is a pre-conceptual phase: new input can be easily included and/or power mix modified