1. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 20081 Rotation inversion vs density and current, in limited and diverted L-mode plasmas on C-MOD Basil P. DUVAL, Alessandro Bortolon Centre de Recherches en Physique des Plasmas, EPFL J. Rice, A. Ince-Cushman, B. LaBombard et al. MIT Presentation, bpd

2. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 20082 Introduction…Polemic ?  Intrinsic Rotation- Absence of External Torque- Is this closer to the ITER situation ? (Doyle et al 2007 ?) –Passive measurement (as far as our efforts are concerned) –TCV-DNBI… MIT- passive spectroscopy… Others ?  Other Definitions… Are these closer to ITER ? –Balanced Torque (DIII-D…) –Modulated Torque (JT60, JET) –Assuming you know everything.. (Fast Ions… ICH… ECH…)  Methods rely on –Knowing torque –Torque not affected by heating, braking, shaping….

3. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 20083 Goal- Can you see reversal elsewhere?  Use C-Mod’s rotation profile diagnostics to reproduce the TCV rotation scaling and reversal observations  Extend the published C-Mod data to lower plasma densities to seek correspondence with TCV data  If successful, see if any of the C-Mod diagnostics can provide some further clues in indentifying the momentum generation and transport mechanisms for rotation reversal…  Central Rotation with multichord X-ray spectroscopy Edge Rotation with DNBI HFS working gas rotation with GasJet

4. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 20084 TCV- Slightly increase ne: Velocity Inversion For n e0 >6x10 19 m -3 and I p >290kA Co-Current rotation profile  Similar core velocity u  0 ~10-15 km/s  Similar sawteeth effect (still “bulged” in the co-current direction)  Similar u  (0.85)  Small change in T e and T i profiles I p =340 kA,  =0.3,  =1.4, B  =1.4T A. Bortolon et al, Phys. Rev. Lett. 97, 235003 (2006) #28355 q e ~3.4 Counter-Current rotation observed  Core region (  <  inv ): convex u  (r) from sawteeth (  ST  ~ 5 ms)  Intermediate region (  inv <  <0.85): u   T i (  )  Edge region (  >0.85): u  

5. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 20085 Résumé of TCV observations  L-mode discussed here  Configuration:Limited Counter-Current toroidal rotation Diverted Co-Current toroidal rotation  Max toroidal velocity scales linearly with T i and 1/I p.Ip scaling partially due to toroidal profile flattening in core by sawteeth.  Toroidal velocity “reversal” events observed Limited Counter -> Co Diverted Co -> Counter, with increasing density  Toroidal rotation inversions when q e approaches ~3 (limited configurations)  3 zones: (more about this next time….) Core – flat toroidal profile within sawtooth inversion radius Intermediate zone Edge Zone: Limited ~0 km/s, Diverted freer to evolve

6. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 20086 C-Mod results 2005 (Diverted)

7. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 20087 Time-line  Velocity “reversal” a severe conundrum for theory- see Diamond, Peeters, Hahm, Gurcan, Callen….  Following APS07, suggested trying to reproduce TCV results on C-MOD  Finally accepted for operation in Feb 2008  Scheduled ITPA- one session May 2 2008 (morning !)  One session, 12 discharges (12:30 Boston time), then PS- failure until the end of the day- (we call this research)  Goal Kappa ~1.5, Delta ~0.4, q~3 (see Duval et al POP- 2008 & EPS 2008)  (Breakdown at 5T, q~3 (Bphi 3T) only reached @ 0.8s)

8. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 20088 Shot-Plan  Discharges 1080502#004 -010 Diverted-Lower, qedge ~3.2, Bphi 3T (breakdown @5T, 3T only @0.5s)  Nothing really happened- Core rotates Co-current, decreasing with core density (Ne-av 1.2-0.3 e20)  Moved to limited (same kappa ~1.5, Delta ~0.4)  Density too high (1.1e20)  Lower slowly, finally reached low enough densities (much more difficult than for diverted configurations)

9. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 20089 Limited results

10. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 200810 Reconstruction (EFIT)

11. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 200811 Rotation (Only From X-ray (Ar))

12. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 200812 Core Rotation, decreasing ne Lower ne, transition later Even Lower ne, transition absent ! Change in core rotation observed

13. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 200813 Compare with TCV-results  As on TCV –“transition” depends V.Strongly on Density –Edge rotation does not change much –Toroidal rotation changes inside q~1.5 –Even at 3T, density at transition is not far from that seen on TCV  However ! –Rotation goes more “co-current” with decreasing Density –If we can believe zero-reference (from discharge #1080502003 with an induced locked-mode), not symmetrical across Vphi=0 –Their definition of “limited” and “diverted” may require some complementary TCV experiments (lift config off central column)

14. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 200814 So…  Really Promising !  Analysis still very rudimentary- Hope to complete a more detailed analysis before end of 2008-  Bphi, as for TCV, does not appear to have too strong an effect..  Can we operate at 5T ?

15. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 200815 Full Bphi (5T) #1080520026

16. EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, presentation@ITPA, Milan, October 200816 EFIT Bphi (5T) #1080520026