1. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 p 1 Corsica free-boundary scenario and controller studies for ITER 12th ITPA Confinement Database and Modelling Topical Group Meeting EPFL, Lausanne May 7--10, 2007 L. L. LoDestro, T. A. Casper, W. H. Meyer, and L. D. Pearlstein Ackn: A. Portone, EFDA-CSU Barcelona Work supported by the U.S. DOE Contract W-7405-48.

2. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 p 2 Recent Corsica ITER modelling is focussed on free-boundary predictive simulation: ITER scenarios: Assess VS consumption, PF-coil currents, strike- point locations. Verify the equilibria pass through the fiducial shapes. Test the plasma shape-and-position controller. We are developing code capability. Physics results here are illustrative.

3. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 p 3 Outline Start-up simulations for ITER and DIII-D ITER scenario studies ITER controller studies Corsica and Corsica/Simulink Summary/Conclusions

4. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 p 4 ITER start-up experiments at DIII-D will be used for code validation EFIT01 shapes Corsica computed Ip equilibria EFIT boundaries at selected times provide “fiducial” shapes Corsica evolves internal flux/current densities using N,T measurements

5. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 p 5 sawteeth Corsica is also being used to design and model the DIII-D experiments simulating ITER DD  DIII-D ITER  Ip 1st day of expt’s. Without trying very hard, q0 & li come close. sawteeth q0 li Ref. 2 with faster Ip ramp. L-mode . More expt.’s to follow.

6. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 p 6 Simulations of ITER scenarios (following) employ a special free-boundary technique Prescribed shape scenario technique: –Developed for Snowmass –Plasma boundary is linearly interpolated between fiducials –Coil currents and Volt-seconds (VS) are backed out –Result is similar to that with a perfect controller Faster and simpler than using a controller.

7. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 p 7 Simulation of ITER reference scenario 2 finds PF-coil currents and VS are within limits Simulation includes  neo,  neo, GLF23, analytic P aux,  heating & diffusion. n is prescribed.

8. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 p 8 Ref. 2 simulation indicates J BS has a significant impact on the plasma boundary (preliminary result). Divertor strike-points were not prescribed here. When they are prescribed along with the boundary and JBS is included, the plasma shape can not be held “close” to the fiducials--- suggesting control might be problematic. Note increased range of divertor strike-points and limiter point with JBS. With J BS Without J BS

9. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 p 9 ITER reference scenario 2, no J BS, cont. Simulation includes coil ramp-down through return of VS.

10. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 p 10 Two implementations for simulating control with Corsica Corsica solves circuit equations –Can run with implicit time-step  speed Corsica is coupled to Mathworks Matlab/Simulink ($$$) –Circuit eqn’s solved by Simulink -- state-space controllers, explicit –Modular Rapid installation of new controllers Entire coil description can reside outside the 1&1/2D code –Corsica can serve as the plasma model in D. Humphrey’s (GA) PCS, continue collaboration on devel. of Simulink environment. Can split the control: fast (VS) with Corsica, slow (shape) with Simulink

11. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 Corisca/Simulink simulation is distributed over network Corsica on beowulf cluster Matlab node MDSPlus server Xwindows and jScope X mdsip Rpc & mdsip

12. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 p 12 We have successfully controlled VDEs & MD1,2 in Corsica/Simulink with the JCT Feb 2001 controller Ohm’s law transport only. Inputs to controller: Vertical Stability: d Z CS /dt Shape: gaps, I p, I PFC Outputs: VS: voltage to PFC2--5 Shape: CS and PF voltages Delays, etc., included Tested 0 ok (nec for implicit) Linear plasma model tests were successful

13. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 Corsica – JCT/Feb 2001 controller during Vertical Displacement Event

14. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 Minor Disruptions: MD1 Instantaneous li drop of 0.2(li -0.5) and  p drop of 0.2  p followed by a 3s exponential recovery. MD2 Instantaneous  p drop of 0.2  p followed by a 3s exponential recovery. Corsica models the large-scale plasma disturbances Corsica  p drop Prescribed  p drop Corsica li drop

15. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 Corsica – JCT/Feb 2001 Controller during MD1 Graphics produced with MDSPlus jScope

16. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 Corsica – JCT/Feb 2001 Controller during MD2 Graphics produced with MDSPlus jScope

17. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 p 17 Controlled simulations with T e,i transport are being carried out with Corsica performing the control Capability was developed for original ITER-EDA –Exercised with Ohm’s law only –ITER-FEAT results agree with Corsica/Simulink Here we include J BS. Other transport and sources as before. Plasma bulges toward the upper x-point.

18. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 p 18 Summary and conclusions Physics conclusions: –Reasonable VS & PF currents found for ITER reference scenario 2 (Ohm’s law + T e,i transport). –Large edge bootstrap current is an issue affects shape & divertor strike-points –The ITER-FEAT controller successfully controls 1cm VDE’s and MD1, MD2 minor disruptions tested with Ohm’s law only, without large edge J BS –Location of upper control point cf. upper X-point with large edge J BS is an issue

19. LoDestro, ITPA CDBM, Lausanne, May 7--10, 2007 p 19 Summary and conclusions, cont. Code status: –Two types of predictive free-boundary simulation are available: backing out PF currents (ready); and solving circuit equations with controllers. –Two environments for plasma control simulations are available (same physics): Corsica/Simulink code-coupling; or all Corsica. Ohm’s law: working well. Ohm’s law plus T e,i transport: minor warts. Not in this talk: alternative start-up and performance scenario simulation; profile control; synthetic diagnostics.