EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, Milan, October 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

EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, Milan, October 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….

EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, Milan, October 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

EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, Milan, October 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, (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  

EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, Milan, October 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

EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, Milan, October C-Mod results 2005 (Diverted)

EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, Milan, October 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 (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 & EPS 2008)  (Breakdown at 5T, q~3 (Bphi 3T) only 0.8s)

EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, Milan, October Shot-Plan  Discharges # Diverted-Lower, qedge ~3.2, Bphi 3T 3T  Nothing really happened- Core rotates Co-current, decreasing with core density (Ne-av 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)

EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, Milan, October Limited results

EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, Milan, October Reconstruction (EFIT)

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

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

EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, Milan, October 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 # 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)

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

EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, Milan, October Full Bphi (5T) #

EPFL, Lausanne, Switzerland Basil P. DUVAL MIT, Milan, October EFIT Bphi (5T) #