TF2: Active control of RFP and tokamak plasmas Report on experimental proposals

1. TF2: Active control of RFP and tokamak plasmasReport on experimental proposals L. Zanotto, P. Piovesan, A. Soppelsa L. Zanotto – 10 February 2011 – RFX-mod programme workshop

2. Main areas covered by proposals • Tokamak scenarios • 3D magnetic field effects on flow • RWM in RFP • m=0 control and understanding • Active control of RFP plasmas • Optimisation L. Zanotto – 10 February 2011 – RFX-mod programme workshop

3. Main areas covered by proposals L. Zanotto – 10 February 2011 – RFX-mod programme workshop

4. Tokamak scenarios • Scenario development • H-mode (from DIIID) • Density limit • New states (helical boundaries) • Additional heating (DNBI) • Active control of Tokamak discharges • Active rotation • Sidebands studies • RWM control • Control of m=2, n=1 and error fields • Pellet injection and MHD control • RFA studies • Comparison between RFX-mod Tokamak and RFP discharges • Tokamak H-mode vs RFP high edge temperature gradient plasmas • Spontaneous rotation • Flow in Tokamaks • Effects of magnetic field perturbation on flow profile • RMP effects on zonal flows and edge L. Zanotto – 10 February 2011 – RFX-mod programme workshop

5. 3D effects on flow in RFPs • Effect of the 1/-7 flow on the penetration of magnetic field errors • External magnetic perturbation effect on plasma flow (T2R team) •  comparison with T2R results L. Zanotto – 10 February 2011 – RFX-mod programme workshop

6. Resistive Wall Modes in RFP • Model validation experiments • Expand the benchmark of existing and new numerical models • Test of innovative control schemes • Reconfigured sensor system • Resilience to magnetic noise and disturbances • RWM in high current helical plasmas L. Zanotto – 10 February 2011 – RFX-mod programme workshop

7. m=0 control and understanding • Control of m=0 by means of saddle coils • Imposing m=0, n=7 (n = 14) harmonic to vary the island amplitude and study PWI • High gains for m=0, n<7 @ F<=-0.1 • Study of the toroidal field ripple by imposing stationary m=0, n=12,16, 24 • Development of new feedback control scheme for low order m=0 harmonics • Can benefit from optimisation experiments on toroidal power supply • Study of toroidal field ripple • Imposing stationary m=0, n=12,16, 24 • Excluding some toroidal field coils L. Zanotto – 10 February 2011 – RFX-mod programme workshop

8. Optimisation • Power supplies • Optimisation of toroidal inverter gains • Voltage control of TFAT converters • Enhancement of toroidal power supply control • Upgrade of the Plasma Current Control System • Optimisation of the feedback regulator • Implementation of automatic plasma current ramp-up • Improve controller awarness of machine operative conditions • Correction of local toroidal field measurement • Slight misalignment due to mechanical tolerance  pick-up of poloidal field • Can provide a reduction of the heating observed at the same two toroidal position L. Zanotto – 10 February 2011 – RFX-mod programme workshop

9. Active control of RFP plasmas • Innovative schemes and advanced concepts • Modal Dynamic Decoupler • System Identification (T2R proposal) • Independent B and Br feedback • Feedback on plasma response • Control of the m=1, n=-7 at the resonance • Active control • DRE pacing • Different toroidal flux conserving boundaries • Test of a different decoupling matrix • 3D boundary conditions at high plasma current • Study of plasma-shell proximity effect L. Zanotto – 10 February 2011 – RFX-mod programme workshop

10. Main constraints to be considered • Many proposals involve Tokamaks • Need to develop a reliable scenario (not an easy task with X-point) • Check feasibility of single null X-point configurations (asap) • Check availability of diagnostics and/or additional heating (DNBI, NBI) • New control hardware and software architecture is being developed (see A. Barbalace’s talk) • Integration and interaction with the experimental programme must be assessed as soon as possible • An experimental proposal clearly stating the plan for integration is needed • Ready this year? • Some proposals require work/modifications to be carried out on the control system and on the power supplies • Collaboration between TF2 and Operation Support will be essential • Availability of proposers external to the laboratory • Various constraints to be considered L. Zanotto – 10 February 2011 – RFX-mod programme workshop

11. Experimental programme GDC commissioning Restart RFP plasma commissioning Restart TOK plasma Commissioning Test TOK with SN X-point GDC GDC aprile First TF2 experiments will be devoted to tokamak. The aim is only to test present capabilities after a long time without tokamak discharges. Operation Support to check technical feasibility of SN X-point. Shut-down L. Zanotto – 10 February 2011 – RFX-mod programme workshop

12. TF2 commitments for 2011 • Tokamak operation • Re-establish reliable operation to be able to perform proposals on active control, flow and edge studies • Try to develop the H-mode scenario • Improve tools for control and understanding of m=0 modes • Optimisation toroidal power supply • Implementation of a new m=0 controller • Integration of the new control system architecture • Major issue • Test innovative control and identification concepts • Modal Decoupler and/or others L. Zanotto – 10 February 2011 – RFX-mod programme workshop

13. Missing • Proposals taking advantage from the new control system • Optimisation and setup of diagnostics • Proposals dealing with plasma shape • Comparison with MST (maybe in TF1?) L. Zanotto – 10 February 2011 – RFX-mod programme workshop

14. Discussion • Is there any other area not covered by proposals? • Integration of the new control system: we should really identify when we want the new system to be in operation • the availability of the new system may lead to a substantial revision of the proposals ( overall re-optimisation of the control gains is probably necessary) • a clear path to the new system should be established now • Do we have enough tools to develop H-mode in RFX-mod tokamaks? It is not simply a matter of producing a Single-Null X-point in vacuum… Experience is needed directly in the control room. L. Zanotto – 10 February 2011 – RFX-mod programme workshop