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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 1

Rotation inversion vs density and current, in limited and diverted L-mode plasmas

on C-MOD

Basil P. DUVAL, Alessandro BortolonCentre de Recherches en Physique des Plasmas, EPFL

J. Rice, A. Ince-Cushman, B. LaBombard et al.MIT

Presentation, bpd

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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 2

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….

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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 3

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 spectroscopyEdge Rotation with DNBIHFS working gas rotation with GasJet

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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 4

TCV- Slightly increase ne: Velocity Inversion

For ne0>6x1019 m-3 and Ip>290kA

Co-Current rotation profile

Similar core velocity u0~10-15 km/s

Similar sawteeth effect (still “bulged” in the co-current direction)

Similar u(0.85)

Small change in Te and Ti profiles

Ip=340 kA, =0.3, =1.4, B=1.4T

A. Bortolon et al, Phys. Rev. Lett. 97, 235003 (2006)

•#28355 qe~3.4

Counter-Current rotation observed

Core region (<inv):

convex u(r) from sawteeth (ST~ 5 ms)

Intermediate region (inv<<0.85):

u Ti()

Edge region (>0.85): u

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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 5

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 Ti and 1/Ip.Ip scaling partially

due to toroidal profile flattening in core by sawteeth. Toroidal velocity “reversal” events observed

Limited Counter -> CoDiverted Co -> Counter, with increasing density

Toroidal rotation inversions when qe approaches ~3 (limited configurations)

3 zones: (more about this next time….)Core – flat toroidal profile within sawtooth inversion radiusIntermediate zoneEdge Zone: Limited ~0 km/s, Diverted freer to evolve

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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 6

C-Mod results 2005 (Diverted)

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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 7

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)

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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 8

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)

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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 9

Limited results

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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 10

Reconstruction (EFIT)

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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 11

Rotation (Only From X-ray (Ar))

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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 12

Core Rotation, decreasing ne

Lower ne, transition later

Even Lower ne, transition absent !

Change in core rotation observed

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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 13

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)

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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 14

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 ?

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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 15

Full Bphi (5T) #1080520026

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Basil P. DUVAL MIT, presentation@ITPA, Milan, October 2008 16

EFIT Bphi (5T) #1080520026