goals of experiment: document and study
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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
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