Goals of experiment: document and study

iITB formation and evolution in H-mode plasmas on NSTX/MAST

Dependence of driven and ExB flow shear on input momentum

Flow shear and q-profile effects on iITB and low-k turbulence

Motivation: turbulence suppression & microinstability drive

Zone (i ~ NC) starts deeper (r/a ~ 0.5) and moves out

Evolves to broader Ti profile (r/a 0.7 – 0.9!), sustained

Strong coupling to high toroidal flow shear, already verified in ‘04

Produced on August 8, 2005, via 116318 long-pulse H-Mode:

NBI energy and power varied: 100 – 65kV, 7 – 3MW; & step down

11 in 23 shots with: >1s, low MHD duration = 0.2-0.5s >

Good documentation: CHERS, MSE; MHD, NPA spectra, EFITs

Results useful to other ISD, T&T, energetic ion mode, JNB studies

XP513: NSTX/MAST Identity Experiments on iITB Formation and Evolution: ITPA TP-8.1 (Peng, Field, R Bell, Menard, etc)

iITB-like behavior remains

New stationary V profile, MHD-quiescent plasma for ~ 200 ms

Data analysis and modeling underway

Long-Pulse Results Are Consistent with Earlier Suspicion of Mechanisms That Limit Maximum Rotation

Limiting Velocity?

Long

-Pul

se T

oroi

dal R

otat

ion

Vel

ocity

,

V

@ 1

10 c

m (

km/s

) Lower EB & P

B Higher EB &

P B

Increasing n

Time (s)

Global MHDLocked Mode

Energetic Ion MHD & Possible Depletion

MHD-Quiet

D

CAE/GAE (kHz)117532

TAE/EPM-“Fishbone” (kHz)

Neutron Rate, Sn

(Rec = reconnection)(T = tearing mode)

EPM T T T EPM Rec Rec Rec D D D D D D D D Spikes

Coincidental Events of EPM, TM, Reconnection, D

Spikes with Vt and Sn are Cataloged in the Study of

iITB Evolution and Momentum Transport

• Identified changes in momentum source & sink

• “Stationary” plasma should reveal intrinsic momentum transport () mechanisms, affecting iITB.

• Need to map out regime of stationary plasma as part of momentum transport study.

“Stationary”Plasma

Ti (R)

Vt (R)

1.5

R(m)

1.0

D

CAE/GAE (kHz)117532

TAE/EPM-“Fishbone” (kHz)

Neutron Rate, Sn

(Rec = reconnection)(T = tearing mode)

EPM T T T EPM Rec Rec Rec D D D D D D D D Spikes

Coincidental Events of EPM, TM, Reconnection, D

Spikes with Vt and Sn are Cataloged in the Study of

iITB Evolution and Momentum Transport

• Identified changes in momentum source & sink

• “Stationary” plasma reveals intrinsic momentum transport () mechanisms, affecting iITB.

• Need to map out regime of stationary plasma for momentum transport study.

“Stationary”Plasma

Vt (R)

1.5

R(m)

1.0

Tearing Mode Near Edge Restrains Outward Evolution of iITB-Like Region (B1) toward the H-mode edge (B2) – Located by nC-VI Profile (LCFS to be Determined)

LCFS? LCFS?

New stationary regime in NSTX in 2005: Sustained H98 > 1 for ~ 4E; other cases only for ~ E [TRANSP, Te()]

Stationary *AE spectrum, small ELMs, Vt(R), Sn, no MHD [MHD stability]

Stationary energetic ion distribution including *AE-induced loss [Medley, Fredrickson]

Hints of stationary oscillations at f ~ 10, 20, 30 kHz [USXR spectrum analysis] Strong candidate plasmas for detailed transport analysis, including ITB,

Transitions in and out of this regime: Entered regime following EPM, with coincidental fast ion loss & D spike

Exited regime following fast reconnection (q-related); fast ion loss & D spike

ITB evolution, profiles: Identified role of periphery tearing mode (TM) in determining “foot point” of V

shear (which dominates Er shear and determines iITB region)

Transition coincidental with disappearance of TM, allowing iITB to nearly reach “ETB,” which also shows increased Ti-ped (~250eV)

Back-transition linked to reconnection-induced loss of fast ions and Potential physics interests

Broadest pressure profile for H98 ~ 1 so far only in ST

Mechanism may shed light on similar regimes in tokamaks

Discussion and Needed Analysis for Publication