1 / 34

Tearing modes control in RFX-mod: status and perspectives

Tearing modes control in RFX-mod: status and perspectives. P.Zanca , R.Cavazzana, L.Piron, A.Soppelsa Consorzio RFX, Associazione Euratom-ENEA sulla Fusione, Padova, Italy. Milestones. Intelligent Shell: egde radial field control (2005)

nate
Télécharger la présentation

Tearing modes control in RFX-mod: status and perspectives

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Tearing modes control in RFX-mod: status and perspectives P.Zanca, R.Cavazzana, L.Piron, A.Soppelsa Consorzio RFX, Associazione Euratom-ENEA sulla Fusione, Padova, Italy

  2. Milestones • Intelligent Shell: egde radial field control (2005) • Clean Mode Control (de-aliasing of the measurement): TM wall-unlocking (2007) • Coils amplifiers improvements: maximum current and rensponse time (2008, 2010) • MHD model of the feedback (RFXlocking) (2007-2010)

  3. Optimizations • Edge radial field reduction: get closer to the ideal-shell limit (determined by vessel/copper shell) • Increase the QSH duration: non-zero reference for the dominant mode • m=2, n=1 control in tokamak dicharges

  4. Optimizations • Edge radial field reduction: get closer to the ideal-shell limit (determined by vessel/copper shell) • Increase the QSH duration: non-zero reference for the dominant mode • Control in tokamak dicharges

  5. Model-based optimizationfor m=1

  6. Latency reduction m=1,n=8-16 br(a) Empirical gains

  7. Latency reduction m=1, n=8-16 br(a) Empirical gains

  8. Latency reduction m=1, n=8-16 br(a) Empirical gains

  9. Derivative control • db/dtis currentlyobtained numerically from b • Acquisition of the derivative signal db/dt is preferable • This allows a better PD gains optimization

  10. m=1, n=-7 m=0, n=7 m=1, n=7 m=2, n=7 Brm,n (T) Icoilm,n (A) decoupler ON Dynamic decoupler • The dynamic decoupler reduces the side-harmonic components of the magnetic field produced • A “modal” decoupler could be designed considering a limited number of harmonics (i.e. only the poloidal sidebands)

  11. bφ systematic errors correction • Unavoidable misalignment of the pick-up coils determines a spurious Ip contribution to bφ • Real-time subtraction of this term Similar for m=±1,2

  12. M=0 control • Little affected by the feedback • High gains test on m=0, n<6 has not shown any improvement on F shallow discharges • m=0 control at deeper F still to be investigated • m=0 n≥7 spurious contribution should be removed by the dynamic decoupler

  13. M=0, n<6 feedback with the toroidal circuit • Enhance the natural reaction of the 12 toroidal sectors to the m=0 low n TM • Present circuit too slow to follow the m=0 dynamic (2.5ms delay according to 2006 experiments) • Upgrade of the internal circuit control by reducing the latency

  14. Independent feedback on br and bφ Iref = Kr br + Kφbφ • Suggested by J.Finn and co-workers • A more general control could allow finding a new optimum • Preliminary RFXlocking simulations are planned

  15. Feedback on the plasma response bplasma = br – bcoils(vacuum) • bcoils from the cylindrical model used in the de-aliasing or from a state-space model which includes the shell frequency response • The hope is to reduce the TM amplitude at the resonant surface • According to RFXlocking edge br is comparable to the standard feedback case upon PD gains optimization

  16. Synopsis • Control system upgrade • Latency reduction • db/dt acquisition • Improved toroidal circuit control • New algorithms • Dynamic decoupler • bφ sistematic errors removal • M=0 low n control with the toroidal circuit (partially developed) • Plasma response • Independent br bφ feedback • Other schemes • M=0 control at deep F • Non-zero reference control to sustain QSH } Gains optimization

  17. Spare

  18. RFXlocking • Semi-analitical approach in cylindrical geometry • Newcomb’s equation for global TMs profiles • Resonant surface amplitudes imposed from experiments estimates • Viscous and electromagnetic torques for phase evolution • Radial field diffusion across the shell(s) • Feedback equations for the coils current

  19. Model-based optimization

  20. Simulation of the derivative control

  21. Feedback limit Sensors Vessel Coils plasma

  22. Feedback limit Sensors Vessel Coils plasma

  23. Feedback limit Sensors Vessel Coils plasma br=0 everywhere: impossible

  24. Single-shell: discrete feedback Δt = latency of the system

  25. External coils: discrete feedback τw=100ms

  26. External coils: discrete feedback τw=10ms

  27. External coils: discrete feedback τw=1ms

  28. Edge radial field control by feedback

  29. RFXlocking simulation of the plasma response

  30. Toroidal circuit dynamic response Control system + internal control latency: 2.5 ms Power supply time constant: 3 ms

  31. Toroidal circuit dynamic response Simulation of power supply behaviour with latency = 1.6 ms - Kp = 0.04 Simulation of power supply behaviour with latency = 0.1 ms - Kp = 0.7

  32. br(rm,n) vs br(a) experimental

  33. Edge radial field .vs. current time constant

  34. Normalized edge radial field: no rf dependence m=1

More Related