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ECRH for JET: Microwave system design

ECRH for JET: Microwave system design. M. Lennholm on behalf of the E4J team Special thanks to: G. Denisov, C. Sozzi, A. Moro, A. Bruschi, G. Granucci, S. Garavaglia. Power into plasma: 10MW (12 MW plant) Power Sources: Gyrotrons from GYCOM – (EU – Russia collaboration)

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ECRH for JET: Microwave system design

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  1. ECRH for JET:Microwave system design M. Lennholm on behalf of the E4J team Special thanks to: G. Denisov, C. Sozzi, A. Moro, A. Bruschi, G. Granucci, S. Garavaglia

  2. Power into plasma: 10MW(12 MW plant) Power Sources: Gyrotrons from GYCOM – (EU – Russia collaboration) Dual frequency – 150GHz/113GHz or Single frequency - 170GHz Launcher Real Time Poloidal steering – range: 30° Inter pulse Toroidal Steering -30° -> +30° Use ITER upper launcher steering mechanism for poloidal steering Transmission Allow Tritium containment Compatible with JET environment (can it fit?) Minimise Transmission losses Main Design Criteria

  3. Gyrotrons IAP RAS GYCOM INF Gyrotron options

  4. Gyrotrons INF GYCOM IAP RAS Development in Russia of 170 GHz Gyrotron for ITER Operating mode Output wave beam Superconducting magnets in cryostat Field ~ 5.5T TE 25.10

  5. Gyrotrons Development in Russia of 170 GHz Gyrotron for ITER INF GYCOM IAP RAS ITER Gyrotron parameters

  6. Gyrotrons Development in Russia of 170 GHz Gyrotron for ITER INF GYCOM IAP RAS 0.1 s-pulse test: Output power & efficiency vs. beam current at beam energy of 76keV Without energy recovery With energy recovery, I = 46A Urec , 1V => 10kV Ucath , 1V => 20kV URF_det

  7. Gyrotrons Development in Russia of 170 GHz Gyrotron for ITER Poutput = 1MW , 0.6 MW Pabsorbed~ 1kW Air forced cooling Temperature rise, 0K INF GYCOM Pulse duration, s IAP RAS Long-pulse test: Air forced cooling of DC-break ceramic insulator Cooling system with liquid manufactured. Gyrotron tests – 2009.

  8. Launcher ITER-UL steering mechanism for poloidal steering Size of this mechanism => Maximum 2 such mechanisms => 6 Beams per poloidal steering mirror • To avoid sticking and backlash: • Pneumatic actuator • Flexi-pivots • Range +/- 7.5deg • Tested to 1 million cycles 8 8 8

  9. Launcher Limiter Two options • Both options: • ITER mechanism allows real time variation of poloidal angle • Rotation of ITER mechanism around vertical axis for Toroidal steering Option 1: Steering mirrors in the front of the port, near the plasma Option 2: Steering mirrors at the back of port, far from plasma, beam reflected 0,1 or 2 times on sides of port • Advantages: • Focusing mirrors near plasma -> • small spot size in plasma - 40 mm • Only 2 mirrors -> lower losses and cost • Full coverage of all desired injection angles • Disadvantages: • Very tight fit –> • little space for toroidal steering mechanism • Large disruption forces on mobile mirror • Modification of ITER mechanism needed • Disadvantages: • Focusing mirrors far from plasma -> • larger spot size in plasma – 55 mm • 3-4 mirrors -> Higher Losses and Cost • Gaps in reachable toroidal range • Advantages: • Ample space for toroidal mecnanism • Smaller disruption forces on mobile mirrors • ITER mechanism can be used unmodified

  10. Option 1 Launcher Required modification of ITER steering Mirror: ITER: Mirror mounted on Steering mechanism axis JET Option 1: Mirror mounted tangential to Steering mechanism -> Moment of inertia increased by factor 4

  11. Option L2 Launcher Chosen as the prefered option! • Metal plates can be parallel, converging, symmetric or asymmetric (different options studied) • This option leaves angular windows around 2 or 3 preferred toroidal injection angles: • With some optimisation: Possible Toroidal Steeing solution: Circular rail with centre on toroidal steering axis. port expansion could allow optimal distance from waveguides tofocusing mirrors. (Larger distancewouldrequire dog-leg in beam path) • More optimisation to be done

  12. Option 2 ComputedBeam footprints on the steering mirror Launcher mirror aiming for perpendicular injection (radial propagation) Mirror aiming for injection at β=23°, z=-80 (q=2 surface). • Axis units in mm. The pink contour corresponds to the spot size. • Minimum size of Steering Mirror: about 280x280 mm (OK)

  13. toroidal mechanism Large required angular range (~40° deg for option 1, ~75° for option 2). This could be: Gaseous helium pneumatic actuator (as poloidal actuator but with gears to achieve the needed range) Push-pull rod system with bellows and external actuator (similar system already installed in JET) Cable system with bellows and external actuator (similar system already installed in JET) Water for mirror cooling and Pneumatic Gas (Helium) need to be brought to poloidal mechanism Flexible pipes (probably spirals as on Poloidal mechanism) Launcher

  14. Catia model for Option 2 Preliminary introduction into CATIA reduction of 30 mm of the distance between side reflectors to accommodate 30 mm thick side reflectors, (impact on steering range to be assessed) After this - only marginal interferences remain Launcher Waveguides Side mirrors Steering mechanism

  15. Possible variant of option 2Use one of side mirrors to vary toroidal angle Launcher • Advantages: • No need to rotate (heavy) ITER mechanism toroidally • No need to bring pneumatic gas and cooling water for ITER mechanism through flexible connections. • Toroidal steering mirror is vertical -> reduced disruption forces. • (potentially) full toroidal coverage • Rotation angle of toroidal mirror limited to 30deg for +/-30 deg toroidal steering • Disadvantages • Limited space above and below toroidal steering mirror • Fixed mirror must be installed before rest of launcher (not really a plug in) I think this looks promising but it remains preliminary. Need to be verified using same tools as the other options to see if it is feasible

  16. Transmission 2 options Quasi Optical : W7X Evacuated Waveguide:TCV, TS, DIII-D, LHD, JT-60, ITER • Can use (test) all components developed for ITER • Evacuated corrugated aluminium Waveguide (63.5 inner diameter) -> No stray RF power • -> Good for Tritium containment • HE11 mode – couples directly to Gaussian beam in antenna. • 12 lines fit in 1 x 1. 2 m crossection • Once in place Evacuated Waveguides do not require routine maintenance. This solution, has been designed in an integrated way with W7-X system. Not feasible to find a routing on JET!!

  17. Transmission line components DC Break Pumping T Corrugated waveguide (63.5 mm i.d.): aluminium + INCONEL section connected to the launcher 90º Mitre bend (MB): with plane mirrors Beam Switch to direct the power in the load, can be integrated in the MOU Polarizer: 2 MBs equipped with corrugated mirrors remote controlled Power monitor: a MB with detectors in both directions Sliding joints (bellows): to compensate thermal variations DC break Gate valve (GV): one before vessel, one after gyrotron+load Pumping unit: to evacuate WG to 10-5 mBar through Pumping Tees Load: 1MW/20s (cw equivalent) EWG Miter bend with polarizing mirror Bellow PowerMonitor DC Break Load Beamswitch

  18. Double Barrier for Tritium Transmission Line Two separate Windows Alows use of ITER window Safer – reduce risk of damaging both windows in one incident How to detect if a window is broken Standard JET procedure (Neon at 0.5 bar in interspace) cannot be used Alternative idea: Look continuously for T and/or He between the windows (Detects Leak from Torus continuously) . Fill inter-space at 0.5 bar during the night and leak test (Checks both window) Gate Valve Gyrotron JET MOU Single disk Diamond Window Load

  19. Gyrotrons: GYCOM 170GHz ITER gyrotrons: Proven performance:1.05MW for 200s Can Produce 4 per year with first delivery 12 month after order Antenna: 10MW through 1 Main Horizontal port Two ITER steering mechanisms at back of port each steering 6 beams for poloidal control Mirrors on sides of port to allow toroidal steering Stering range: Toroidal: +/- 26 deg, Poloidal:30 deg A few options are being pursued aiming to converge on single conceptual design by September Transmission: Evacuated waveguide allows use (test) of ITER components Two separate ITER CWD diamond windows per line Need to find way to detect if one window is damaged Conclusions

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