Overview of Physics Advances in MSTicc2006.ph.utexas.edu/uploads/43/craig_poster.pdf · 2006. 2....
1
D C P P A k 0 5 5 H S Q m , 1 = n 6 = 4 5 0 5 1 9 0 5 0 1 # s m 0 0 2 3 . 6 1 = t 0 . 1 - 5 . 0 - 0 . 0 5 . 0 0 . 1 ) m ( R 0 . 1 - 5 . 0 - 0 . 0 5 . 0 0 . 1 Z (m) T e ) V e ( 0 0 2 0 9 2 1 8 3 2 7 4 2 6 5 3 5 6 4 4 7 4 3 8 5 2 9 6 1 0 1 7 0 1 1 0 1 2 1 4 1 6 1 8 1 0 2 ) s m ( e m i t 0 2 4 6 8 0 1 2 1 4 1 mode amplitude (Gauss) 6 = n 5 = n 7 = n 8 = n 0 200 400 600 0 2x10 12 6x10 12 1x10 13 0 12.5 25 8 10 12 14 16 18 20 22 -10 -5 0 5 10 PPCD shot 2005/9/2 52 0.0 0.2 0.4 0.6 0.8 1.0 r/a 0 500 1000 1500 Te (eV) shot 2005/9/2 86 0.0 0.2 0.4 0.6 0.8 1.0 r/a 0 500 1000 1500 Te (eV) Plasma Current Density Magnetic Fluctuations 30-sep-2005 -1.0 -0.5 0.0 0.5 1.0 time relative to sawtooth crash (ms) 0 600 1000 1400 r/ a = 0.0 r/ a = 0.19 r/ a = 0.37 r/ a = 0.55 0.0 0.2 0.4 0.6 0.8 1.0 r/a 0 200 400 600 800 1000 r/ a ~ 0.8 (line-integrated) 200 400 800 1200 30-sep-2005 numbers are time relative to sawtooth crash (all data 0.1 ms averaged) -0.50 0.0 +0.25 +0.50 +0.95 200 400 600 800 200 400 600 800 1000 r/a = 0.0 r/a = 0.37 r/a = 0.55 r/a = 0.75 Localized temperature (eV) time (ms) 13 14 15 16 17 14 15 16 17 m=0 burst m=0 burst m=0 burst m=0 burst 0 -10 -20 0 -10 -20 0 -10 -20 0 -10 -20 Time relative to event (ms) -0.5 V/m V/m V/m V/m 0.0 +0.5 r/a=0.92 r/a=0.88 r/a=0.85 r/a=0.81 <v x b> || ηJ || - E || MHD Dynamo in the edge balances Ohm’s law at some radii but is insignifigant at others Overview of Physics Advances in MST D. Craig 1,2 , A.F. Almagri 1,2 , J.K. Anderson 1 , F. Bonomo 3 , D.L. Brower 4 , B.E. Chapman 1 , S.H. Choi 1,2 , D.J. Clayton 1 , H.D. Cummings 1 , B.H. Deng 4 , D.J. Den Hartog 1,2 , W.X. Ding 4 , D.A. Ennis 1,2 , G. Fiksel 1,2 , P. Franz 3 , S. Gangadhara 1,2 , M. Gobbin 3 , J.A. Goetz 1 , B. Hudson 1 , R.M. Magee 1 , L. Marrelli 3 , P. Martin 3 , V.V. Mirnov 1,2 , R. O’Connell 1 , P. Piovesan 3 , S.C. Prager 1,2 , J.A. Reusch 1 , J.S. Sarff 1,2 , G. Spizzo 3 MHD and Hall Dynamo 1 University of Wisconsin - Madison, 2 Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, 3 Consorzio RFX - Associazione Euratom - ENEA Padova, Italy, 4 University of California - Los Angeles 0.0 0.2 0.4 0.6 0.8 1.0 r/a 0.2 ms before crash at crash 0 100 200 300 400 500 Te (eV) Edge Parallel Electric Field Quasi-Single Helicity Ion Heating R = 1.5 m a = 0.52 m I p = 0.2-0.6 MA n e ~ 10 19 m -3 T e = 0.1-1.5 keV τ E = 1-10 ms β tot ~ <p>/B 2 (a) = 5-15% The Madison Symmetric Torus Reversed Field Pinch Magnetic Topology B 26 28 30 32 time (ms) -0.3 -0.2 -0.1 0.0 0.1 0.2 impact parameter (m) SXR Tomography t = 25.5ms -0.4 -0.2 0.0 0.2 0.4 R (m) -0.4 -0.2 0.0 0.2 0.4 Z (m) t = 31.5ms -0.4 -0.2 0.0 0.2 0.4 R (m) -0.4 -0.2 0.0 0.2 0.4 Z (m) ABSTRACT MST continues to be a fruitful device for plasma physics, particularly for studies of magnetic fluctuations and their effect on transport, the current profile, and ion heating. Multi-point Thomson scattering measurements of the electron temperature profile highlight the dramatic improvement in electron energy confinement during periods of reduced fluctuations with current profile control and the equally dramatic degradation of confinement during increased fluctuations at a sawtooth crash. In quasi-single helicity plasmas (where one magnetic mode dominates the spectrum) double filter SXR tomography has been used to infer temperature profiles and observe an enhancement of temperature inside the dominant island. Hard X-Ray measurements also show evidence for generation of a confined high energy population when a large island is present. The current profile is strongly modified by both single and two-fluid effects arising from magnetic fluctuations. Fast Charge Exchange Recombination Spectroscopy measurements of velocity fluctuations yield information on the MHD dynamo <v x b> and fast FIR Faraday rotation measurements of current density fluctuations yield information on the Hall dynamo <j x b>/en. Both are important in balancing Ohm’s law. The current density fluctuations also induce a significant non- ambipolar charge flux during reconnection events. Ion heating accompanies bursts of magnetic fluctuations and is measured to be a global effect, present at all radii during a sawtooth crash. Spatially non-uniform features can exist, however, when edge resonant modes burst during periods of improved confinement. Here, a more edge localized heating is measured. Magnetic fluctuations which grow in time cause magnetic reconnection in MST. Measurements have also been made of the origin of impulsive reconnection, particularly from m=0 modes, and the importance of multi-site reconnection for obtaining the strongest effects of fluctuations on the plasma. This work is supported by U.S.D.O.E. and the N.S.F. Electron Confinement 0.0 0.2 0.4 0.6 0.8 r/a 0 1 2 3 4 m=1, n=6 m=1, n=7 m=1, n=8 m=1, n=9 m=1, n=10 m=1, n=11 m=1, n=12 6 7 8 9 10 11 12 n Mode Number (m=1) r/a=0.55 e (m 2 /s) r/a r/a PPCD Standard 1 10 100 1000 0 0 1 1 t s t s m=0 fluctuation amplitude Heating is more edge localized during small events where m=0 dominates Ti (eV) Ti (eV) Ion heating during a sawtooth crash appears at all radii power balance Stochasticity and energy transport are reduced in PPCD Measured thermal diffusivity is comparable to calculated one assuming transport is dominated by stochastic magnetic field: Stochastic transport does not have to be large χ st = v th D m PPCD = Pulsed Poloidal Current Drive Edge inductive electric field is modified to support current in the outer part of plasma Magnetic fluctuations are reduced and confinement improves dramatically During a sawtooth crash, magnetic fluctuations are large and cause rapid energy loss -2 0 2 4 6 8 10 <v θ b r > ) r e t e m / s t l o V ( ~ ~ 0.00 0.20 0.15 0.10 0.05 -0.05 -0.10 0.0 0.2 0.4 0.6 0.8 1.0 n=6 9 10 7 8 q r/a Edge Modes (m=0; n=1,2,…) Core Modes (m=1; n=6,7,…) j || - E || =〈 ˜ v × ˜ B 〉 || − 1 en e 〈 ˜ j × ˜ B 〉 || η Fluctuating Poloidal Velocity (km/s) Localized v and spatial profile of MHD dynamo are being measured Hall dynamo is important at sawtooth crash in core and edge 60 40 20 0 -2 -1 0 1 2 Time relative to event (ms) E // <δJx δB> // /ne V/m core -0.5 0.0 0.5 Time relative to event (ms) -10 -5 0 5 10 15 20 V/m <δJx δB> // /ne edge MHD Dynamo Hall Dynamo 60 40 20 0 V /m 0.8 0.4 r/a < δJxδB> // /ne 0.0 Core 0.80 0.85 0.90 0.95 1.00 0 5 10 15 V/m r/a < δJxδB> // /ne Edge Hall dynamo is localized to mode resonant surfaces 1,6 resonance q=0 Current fluctuations that produce Hall dynamo also produce non-ambipolar charge flux HXR emission is observed in some QSH periods HXR emission is brightest when SXR tomography shows strong island also Secondary mode amplitudes matter Very hot islands can form in QSH with PPCD at high plasma current m=1, n=6 m=0, n=1 Stored magnetic energy (kJ) Toroidal flux (Wb) Ti (eV) Mode amplitudes (G) Multi-mode events give the strongest effects of fluctuations on the plasma -0.6 -0.4 -0.2 0.0 0.2 time (ms) -10 0 10 20 30 40 γ τ A (x 10 -3 ) Measured MHD linear drive term Instantaneous growth rates for both cases are similar -2 -1 0 1 2 time (ms) Gauss 0 50 100 150 200 250 300 stable mode (0,1) offset -1.0 -0.5 0.0 0.5 1.0 time (ms) 0 60 50 40 30 20 10 Gauss unstable mode (0,1) offset tesla 2 /sec -0.1 0.0 0.1 0.2 0.3 0.4 -0.10 -0.05 0.00 0.05 0.10 time (ms) linear drive > 0 unstable (spontaneous) tesla 2 /sec -0.20 -0.15 -0.10 -0.05 0.00 0.05 -1.0 -0.5 0.0 0.5 1.0 time (ms) linear drive < 0 stable (driven) ( ) n dissipatio nonlinear C C t + + + ⋅ × × ∇ = ∂ ∂ . . b B v b * k 0 k 2 k Impulsive Reconnection sawtooth crash m=0 burst Impulsive reconnection occurs both for stable and unstable (nonlinearly driven) modes
Transcript of Overview of Physics Advances in MSTicc2006.ph.utexas.edu/uploads/43/craig_poster.pdf · 2006. 2....
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shot 2005/9/2 52
0.0 0.2 0.4 0.6 0.8 1.0r/a
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500
1000
1500Te (eV)
shot 2005/9/2 86
0.0 0.2 0.4 0.6 0.8 1.0r/a
0
500
1000
1500Te (eV)
Plasma Current
Density
Magnetic Fluctuations
30-s
ep-2
005
-1.0 -0.5 0.0 0.5 1.0time relative to sawtooth crash (ms)
0
600
1000
1400 r/ a = 0.0r/ a = 0.19r/ a = 0.37r/ a = 0.55
0.0 0.2 0.4 0.6 0.8 1.0r/ a
0
200
400
600
800
1000
r/ a ~ 0.8(line-integrated)
200
400
800
1200
30-s
ep-2
005
numbers are time relativeto sawtooth crash(all data 0.1 ms averaged)
-0.50
0.0
+0.25
+0.50
+0.95
200400600800
200400600800
1000
r/a = 0.0 r/a = 0.37
r/a = 0.55 r/a = 0.75Loca
lized
tem
pera
ture
(eV
)
time (ms)13 14 15 16 17 14 15 16 17
m=0 burst
m=0 burst m=0 burst
m=0 burst
0
-10
-20
0
-10
-20
0
-10
-20
0
-10
-20
Time relative to event (ms)-0.5
V/m
V/m
V/m
V/m
0.0 +0.5
r/a=0.92
r/a=0.88
r/a=0.85
r/a=0.81
<v x b>||ηJ|| - E||
MHD Dynamo in the edge balancesOhm’s law at some radii but isinsignifigant at others
Overview of Physics Advances in MSTD. Craig1,2, A.F. Almagri1,2, J.K. Anderson1, F. Bonomo3, D.L. Brower4, B.E. Chapman1, S.H. Choi1,2, D.J. Clayton1, H.D. Cummings1, B.H. Deng4, D.J. Den Hartog1,2, W.X. Ding4, D.A. Ennis1,2, G. Fiksel1,2, P. Franz3,
S. Gangadhara1,2, M. Gobbin3, J.A. Goetz1, B. Hudson1, R.M. Magee1, L. Marrelli3, P. Martin3, V.V. Mirnov1,2, R. O’Connell1, P. Piovesan3, S.C. Prager1,2, J.A. Reusch1, J.S. Sarff1,2, G. Spizzo3
MHD and Hall Dynamo
1University of Wisconsin - Madison, 2Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, 3Consorzio RFX - Associazione Euratom - ENEA Padova, Italy, 4University of California - Los Angeles
0.0 0.2 0.4 0.6 0.8 1.0r/a
0.2 ms before crash
at crash
0
100
200
300
400
500
Te (e
V)
Edge Parallel Electric Field
Quasi-Single Helicity
Ion Heating
R = 1.5 ma = 0.52 mIp = 0.2-0.6 MAne ~ 1019 m-3
Te = 0.1-1.5 keVτE = 1-10 msβtot ~ <p>/B2(a) = 5-15%
The Madison Symmetric Torus
Reversed Field PinchMagnetic Topology
B
26 28 30 32time (ms)
-0.3
-0.2
-0.1
0.0
0.1
0.2
impa
ct p
aram
eter
(m)
SXR Tomography
t = 25.5ms
-0.4 -0.2 0.0 0.2 0.4R (m)
-0.4
-0.2
0.0
0.2
0.4
Z (m
)
t = 31.5ms
-0.4 -0.2 0.0 0.2 0.4R (m)
-0.4
-0.2
0.0
0.2
0.4
Z (m
)
ABSTRACTMST continues to be a fruitful device for plasma physics, particularly for studies ofmagnetic fluctuations and their effect on transport, the current profile, and ion heating.Multi-point Thomson scattering measurements of the electron temperature profilehighlight the dramatic improvement in electron energy confinement during periods ofreduced fluctuations with current profile control and the equally dramatic degradation ofconfinement during increased fluctuations at a sawtooth crash. In quasi-single helicityplasmas (where one magnetic mode dominates the spectrum) double filter SXRtomography has been used to infer temperature profiles and observe an enhancement oftemperature inside the dominant island. Hard X-Ray measurements also showevidence for generation of a confined high energy population when a large islandis present. The current profile is strongly modified by both single and two-fluid effectsarising from magnetic fluctuations. Fast Charge Exchange RecombinationSpectroscopy measurements of velocity fluctuations yield information on the MHDdynamo <v x b> and fast FIR Faraday rotation measurements of current densityfluctuations yield information on the Hall dynamo <j x b>/en. Both are important inbalancing Ohm’s law. The current density fluctuations also induce a significant non-ambipolar charge flux during reconnection events. Ion heating accompanies bursts ofmagnetic fluctuations and is measured to be a global effect, present at all radii during asawtooth crash. Spatially non-uniform features can exist, however, when edge resonantmodes burst during periods of improved confinement. Here, a more edge localizedheating is measured. Magnetic fluctuations which grow in time cause magneticreconnection in MST. Measurements have also been made of the origin of impulsivereconnection, particularly from m=0 modes, and the importance of multi-sitereconnection for obtaining the strongest effects of fluctuations on the plasma.
This work is supported by U.S.D.O.E. and the N.S.F.
Electron Confinement
0.0 0.2 0.4 0.6 0.8r/a
0
1
2
3
4m=1, n=6m=1, n=7m=1, n=8m=1, n=9m=1, n=10m=1, n=11m=1, n=12
6 7 8 9 10 11 12n Mode Number (m=1)
r/a=0.55
e
(m2/s)
r/a r/a
PPCDStandard
1
10
100
1000
0 01 1
ts
ts
m=0 fluctuation amplitude
Heating is more edge localized duringsmall events where m=0 dominates
Ti (e
V)
Ti (e
V)
Ion heating during a sawtooth crash appears at all radii
power balance
Stochasticity and energy transport arereduced in PPCD
Measured thermal diffusivity is comparableto calculated one assuming transport isdominated by stochastic magnetic field:
Stochastic transport does not have to be large
χst = vth Dm
PPCD = Pulsed Poloidal Current Drive
Edge inductive electric fieldis modified to support currentin the outer part of plasma
Magnetic fluctuations arereduced and confinementimproves dramatically
During a sawtooth crash,magnetic fluctuationsare large and cause rapidenergy loss
-2
0
2
4
6
8
10
<vθ
b r>
)retem/stloV(
~~
0.00
0.20
0.15
0.10
0.05
-0.05
-0.100.0 0.2 0.4 0.6 0.8 1.0
n=6
910
7 8
q
r/a
Edge Modes (m=0; n=1,2,…)
Core Modes(m=1; n=6,7,…)
j || - E || = ⟨ ˜ v × ˜ B ⟩|| −1
ene⟨ ˜ j × ˜ B ⟩||η
Fluc
tuat
ing
Polo
idal
Vel
ocity
(km
/s)
Localized v and spatial profile of MHD dynamo are being measured
Hall dynamo is important at sawtooth crash in core and edge60
40
20
0
-2 -1 0 1 2Time relative to event (ms)
E// <δJx δB>// /ne
V/m
core
-0.5 0.0 0.5Time relative to event (ms)
-10
-5
0
5
10
15
20
V/m
<δJx δB>// /ne
edge
MHD Dynamo Hall Dynamo
60
40
20
0
V/m
0.80.4r/a
< δJ xδB>// /ne
0.0
Core
0.80 0.85 0.90 0.95 1.000
5
10
15
V/m
r/a
< δJ xδB>// /ne
EdgeHall dynamo is localized to mode resonant surfaces
1,6 resonance
q=0
Current fluctuations that produceHall dynamo also produce non-ambipolar charge flux
HXR emission is observed in some QSH periodsHXR emission is brightest when SXRtomography shows strong island also
Secondary mode amplitudes matter
Very hot islands can formin QSH with PPCD athigh plasma current
m=1, n=6m=0, n=1
Storedmagnetic
energy (kJ)
Toroidalflux (Wb)
Ti (eV)
Modeamplitudes
(G)
Multi-mode events give the strongest effectsof fluctuations on the plasma
-0.6 -0.4 -0.2 0.0 0.2time (ms)
-10
0
10
20
30
40
γ τ A
(x 1
0-3)
Measured MHD linear drive term
Instantaneous growth ratesfor both cases are similar
-2 -1 0 1 2time (ms)
Gau
ss
0
50
100
150
200
250
300stable mode (0,1)
offset
-1.0 -0.5 0.0 0.5 1.0time (ms)
0
60
50
40
30
20
10
Gau
ss
unstable mode (0,1)
offset
tesl
a2/s
ec
-0.1
0.0
0.1
0.2
0.3
0.4
-0.10 -0.05 0.00 0.05 0.10time (ms)
linear drive > 0unstable
(spontaneous)
tesl
a2/s
ec
-0.20
-0.15
-0.10
-0.05
0.00
0.05
-1.0 -0.5 0.0 0.5 1.0time (ms)
linear drive < 0stable
(driven)
( ) ndissipationonlinearCCt
+++⋅××∇=∂
∂..bBv
b *k0k
2k
Impulsive Reconnectionsawtooth crash m=0 burst
Impulsive reconnection occurs both for stable and unstable (nonlinearly driven) modes
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