E. D. Fredrickson, D. Darrow, N. N. Gorelenkov, S. Medley, J. Menard, L. Roquemore 45 th Annual Meeting of Division of Plasma Physics American Physical Society MHD-induced Fast Ion Losses on NSTX Supported by Columbia U Comp-X General Atomics INEL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics NYU ORNL PPPL PSI SNL UC Davis UC Irvine UCLA UCSD U Maryland U New Mexico U Rochester U Washington U Wisconsin Culham Sci Ctr Hiroshima U HIST Kyushu Tokai U Niigata U Tsukuba U U Tokyo JAERI Ioffe Inst TRINITI KBSI KAIST ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching U Quebec
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E. D. Fredrickson, D. Darrow, N. N. Gorelenkov, S. Medley, J. Menard, L. Roquemore
Supported by. Columbia U Comp-X General Atomics INEL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics NYU ORNL PPPL PSI SNL UC Davis UC Irvine UCLA UCSD U Maryland U New Mexico U Rochester U Washington U Wisconsin Culham Sci Ctr Hiroshima U HIST Kyushu Tokai U - PowerPoint PPT Presentation
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E. D. Fredrickson, D. Darrow,
N. N. Gorelenkov, S. Medley, J. Menard, L. Roquemore
45th Annual Meeting of Division of Plasma PhysicsAmerican Physical Society
October 27 – 31, 2003Albuquerque, New Mexico
MHD-induced Fast Ion Losses on NSTX
Supported by
Columbia UComp-X
General AtomicsINEL
Johns Hopkins ULANLLLNL
LodestarMIT
Nova PhotonicsNYU
ORNLPPPL
PSISNL
UC DavisUC Irvine
UCLAUCSD
U MarylandU New Mexico
U RochesterU Washington
U WisconsinCulham Sci Ctr
Hiroshima UHIST
Kyushu Tokai UNiigata U
Tsukuba UU Tokyo
JAERIIoffe Inst
TRINITIKBSI
KAISTENEA, Frascati
CEA, CadaracheIPP, Jülich
IPP, GarchingU Quebec
Will fast ion driven instabilities be important in the NSST, CTF?
• Fast ion instabilities important for fusion reactors;– Fast ion losses raise ignition threshold, first wall damage
– Potentially beneficial (alpha-channeling)?
• ST's, with intrinsic low field, are particularly susceptible to fast ion driven instabilities.– Vfast ion / Valfvén>1; fast ion energy available to drive modes
– fi/aplasma; sets mode structure scale, fast ion transport
– Also affected by q and density profiles, thermal ion/electron .
• Need to understand instability drive, loss mechanisms.– Result important for conventional aspect ratio reactors (ITER).
10
100
1000
0.1 0.2 0.3TIME (s)
FR
EQ
UE
NC
Y (
kHz)
“fishbones”
TAE
CAE/GAE
108170
A broad spectra of kinetic instabilities are seen on NSTX
“mostly harmless”
Usually do not result in large fast ion losses.
However, in some cases…
Gorelenkov - GI2.001, Taylor - QP1.048, Fu - QP1.122
Neutron rate drops, D bursts imply fast ion loss in some shots
• Neutrons are beam-target; drops mean fast ion loss– S nfi
• D bursts probably due to fast ions hitting wall or divertor plates– Can be confused with ELMs
• In L-mode, sometimes correlated with D drops.
• Loss also seen in iFLIP, redistribution in NPA.
H-alpha (a.u.)
Plasma Current (MW)
Pnbi (MW)
0.8
0.4
0.0
1.0
0.01.0
0.06
0
-6
shot 108530
4
00.2 0.30.0 0.1 0.4
TIME (s)0.20 0.25 0.30
Neutrons (1014/s)
Mirnov Coil (a.u.)
TAE bursts responsible for most of fast ion loss here
• Neutron drops ≈ 10-15 %.• Period is ≈ 10 ms.• In steady-state, predicted
reduction in fast ion beta of 40 %.
• TAE have strong bursting character with multiple modes present.
• Fishbones have small neutron drops
black n=1 red n=2 green n=3 blue n=4 yellow n=5
FR
EQ
UE
NC
Y (
kHz)
200
150
100
50
0
108530
fTAE= VA(0)/4qR0 + n “frot”
0.20 0.300.22 0.24 0.26 0.28
1.0
0.0
Neutrons (1014/s)
TIME (s)
Large fast ion losses also with " fishbones”
• Up to 20% drops in the neutron rate, with f.b. periods of ≈ 10 ms; steady-state reduction in fast ion population of ≈50%.
• Why do some fishbones cause neutron drops, others no drop?
• Even no-drop f.b.'s affect CAE.• Do CAE trigger f.b.’s?• Correlation of (large) fishbones
with H-mode transitions?
Ip = 0.8 MA, Pb = 3.4 MW, tor = 16%)
CAE (0.5-1.2MHz)
FR
EQ
UE
NC
Y (
kHz)
TIME (s)0.15 0.20 0.25 0.30 0.35
1.41.0
0.00.4
(x10
14/s
)
0.80.6
0.0
0.40.2
D-alpha
150
100
50
0
“TAE”
“Fishbone”
108170
Neutron Rate
3
2
1
050
0
fishbone (10-90 kHz)
(mG
)(G
)
Strong frequency chirping correlated
with fast ion loss
• In this case, multiple modes also seem to co-exist.
• Lack of neutron drop may mean loss of lower energy ions; but not according to NPA.
• It would be very nice to have good internal data.
S. Medley - NPAIp = 0.8 MA, Pb = 6 MW, tor = 18%)
0.3 0.35 0.40 0.45
0
20
40
60
80109022
TIME (s)
5
04
2
032
10
5
0
n = 1 n = 2 n = 3 n = 4
FR
EQ
UE
NC
Y (
kHz)
SN
PA
(10
5 /s)
(10
13/s
)(G
)
NEUTRON RATE
ED = 50 keV
ED = 10 keV
5 - 50 kHz, 0.45 - 1.2 MHz (x100)
TAE, f.b. and CAE/GAE interact
• TAE bursts precede fishbones.
• TAE-induced fast-ion losses don't affect CAE.
• Fishbone-induced bursts cause drops in CAE amplitude, small effect on neutron rate.
H-alpha (a.u.)
Plasma Current (MW)
Pnbi (MW)
0.8
0.4
0.0
1.0
0.01.0
0.0
shot 108530
4
00.2 0.30.0 0.1 0.4
TIME (s)0.20 0.25 0.30
Neutrons (1014/s)
~rm
s(B
)
103
102
101
103
102
101
100
102
101
100
10-1CAE 500 - 1500 kHz
TAE 70 - 150 kHz
f.b. 10- 40 kHz
Ip = 0.65 MA, Pb = 3.6 MW, tor = 10%)
"Not your typical fishbones…"
• Retain strong frequency chirping and periodic bursting character.
• Toroidal mode numbers up to n=5 have been seen.
• Often with q(0) > 1 and m >1• Onset frequency well above