Transcript Investigation of Collective Fast-ion Supported by

Supported by
Investigation of Collective Fast-ion
Redistribution or Loss in NSTX
S. S. Medley, D. S. Darrow, E. D. Fredrickson, J. Menard
and the NSTX Team
Princeton Plasma Physics Laboratory, PO Box 451, Princeton, NJ 08543 USA
IAEA 2006 Poster Outline
PPPL August 7, 2006
Columbia U
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Comp-X
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General Atomics
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Johns Hopkins U
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LANL
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LLNL
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Lodestar
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MIT
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NYU
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PPPL
PPPL
PSI
PSI
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SNL
UC Davis
UC Davis
UC Irvine
UC Irvine
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U Maryland
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Hiroshima U
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HIST
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Kyushu Tokai U
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Niigata U
Niigata U
Tsukuba U
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JAERI
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CEA, Cadarache
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CEA, Cadarache
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U Quebec
Categories of MHD-induced Redistribution/Loss
of Energetic Ions
•
Magnitude of the MHD-induced redistribution/loss has been based
almost entirely on volume-integrated neutron yield measurements.
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Investigation of Collective Fast-ion
Redistribution or Loss in NSTX: Poster Outline
•
Interpretation of Snpa(E, t, Rtan) NPA measurements (3 Vg):
- ‘line-integrated’ measurements are significantly localized by CX on
NB primary and halo neutrals (space and field pitch)
- outer gap (plasma volume) excursions, gap, give false loss signals
- CX production/attenuation (emissivity) is co-mingled with MHD-induced loss
•
Interpretation of Sn(t) volume-averaged neutron rate (1 Vg):
- Sn(t) affected by gap(t), Zeff(r,t), edge neutral density
•
Interpretation of sFLIP measurements (1 Vg + movie)
•
Procedure to correct NPA measurements for emissivity effects (1 Vg):
- TRANSP NPA simulation and halo neutral computational issue
•
Anomalous fast ion diffusion (AFID) model in TRANSP(1 Vg):
- space, time and energy selection criteria for matching Sn(t), Snpa(E, t, Rtan)
•
Results for different categories of MHD-induced redistribution /loss:
- bursting activity - Fredrickson (2 Vg)
- continuous MHD mode - ala Menard using 117449 (3 Vg)
- continuous EPM/TAE activity - ? (3 Vg)
3
Backup
4
The Neutral Particle Analyzer (NPA) on NSTX Scans Horizontally
Over a Wide Range of Tangency Angles on a Shot-to-Shot Basis
Source C: RNB = 48.7 cm
B: RNB = 59.2 cm
Neutral Beam
A: RNB = 69.4 cm
Injector
Neutral Particle
Analyzer
Rtan = 125cm
Rtan = -75 cm
• Covers Thermal (0.1 - 20 keV) and Energetic Ion (≤ 150 keV) Ranges
5
Overview of Diagnostics for Evaluation of
MHD-induced Energetic Ion Redistribution/Loss
•
Mirnov, USXR, FireTip…characterize MHD activity (mode, amplitude, localization)
•
Sn(t)…volume-averaged neutron rate
•
Snpa(E, t, Rtan)…line-integrated charge exchange neutral efflux
• Both the volume-averaged Sn(t) and line-averaged Snpa(E, t, Rta)
show MHD-induced fast ion depletion, but cannot distinguish
between redistribution and loss effects .
•
sFLIP Imaging (Darrow)…identifies energetic ion loss to the outer wall
•
MSE (Levinton) + LRDFIT (Menard)…identifies redistribution because
outward displacement of the core-peaked energetic beam ions
modifies the beam-driven current profile and hence the core q-profile [1]
[1] “Observation of Instability-induced Current Redistribution in a Spherical Torus Experiment,”
J. E. Menard, et al. PPPL-4160 (May, 2006). Submitted to PRL
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NPA Measurements are Localized
in Pitch and Space by Beam Injected Neutrals
1.0
NB Source
Minimum
A
0.5
0
1.0
5
0.9
4
0.8
3
0.7
0.6
0.5
-0.5
-50
0
Total Beam
Neu tral
Den sity
2
Em iss ivity
@ ED = 60 ke V
1
0
100
150
200
250
Distance Along NPA Sightline (cm)
50
100
NPAem iss(x1 06 eV-1cm-3s-1)nb0 (x1 08 cm-3)
C
Pitch Angle, v| |/v
Pitch Angle, v||/v
B
NPA Intercept with NB, Rint(cm)
A
B
C
100
NSTX M ajor
Radius = 85 cm
50
0
150
100
95
90
85
80
NPA R tan = 25 - 100 cm
150
75
NPA Tangency Radius, Rtan (cm)
100
50
NPA Tange ncy Radius, Rtan(cm)
Snpa Signal Decrease at NB Notch(%)
Maximum
Source
150
0
20
40
60
80
100
Ene rgy (ke V)
• Dominance of charge exchange emissivity by beam neutrals results in
both field pitch and spatial localization of NPA measurements.
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NPA R tan = 125 cm
t = 20 mse c
SN115776
18
80
16
14
200 ms
380 ms
12
0%
De ple tion
10
8
0
20
40
60
80
100
Ene rgy (ke V)
ln(NPA Flux/Energy1/2)
(ster-1cm-2eV-3/2s-1)
NPA R tan = 88 cm
t = 20 mse c
SN115790
18
16
14
200 ms
380 ms
12
45%
De ple tion
10
8
0
20
40
60
80
100
ln(NPA Flux/Energy1/2)
(ster-1cm-2eV-3/2s-1)
Ene rgy (ke V)
70
60
50
40
30
20
10
0
-50
0
50
100
150
NPA Tangency Radius (cm)
NPA R tan = 75 cm
t = 20 mse c
SN115779
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NPA Spectrum Depletion @ 60 keV (%)
ln(NPA Flux/Energy1/2)
(ster-1cm-2eV-3/2s-1)
Depletion of the NPA Energetic Ion Spectra
Exhibits a Spatial Dependence
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• The left panels show spectra at various
14
200 ms
380 ms
12
Rtan preceeding (t = 200 ms) and following
(t = 380 ms) H-mode onset.
70%
De ple tion
10
• The right panel shows the spatial
8
0
20
40
60
Ene rgy (ke V)
80
100
dependence of the depletion at E = 60 keV.
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New Tool Enables Correlation of Energetic Ion Flux
with sFLIP and Mirnov Data
• D. Darrow is preparing an sFLIP image overlay to quantify gyroradius
centroid (energy) and pitch angle of the energetic ion loss.
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SN117449 Waveforms
Ip=0.75 MA, BT=4.5 kG, A&B@90 keV, C@80 keV
0.6
6
0.4
4
0.2
2
SN117449
0
PNB(MW)
Ip(MA)
0.8
0
Sn (x1013 s-1)
2.5
2.0
1.5
1.0
0.5
2.5
5
2.0
4
3
1.5
ED = 60 ke V
1.0
0.5
0
2
1
0
0
0.2
0.4
Time (s)
0.6
0.8
1.0
ne L(x1013 cm-2)
Snpa(x105 s-1)
0
•
Snpa depletion during ne rise (t = 0.20.6 s) is due to combined effects of
CX emissivity & Alfvén instabilities.
• TOI for TRANSP analysis is t = 0.61.0 s during an n=1, f<10 kHz kinktype MHD mode.
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Ip=0.75 MA, BT=4.5 kG, A&B@90 keV, C@80 keV
Sn (x1013 s-1)
1.0
2.0
1.5
1.0
0
0.8
6
117449M 08 w/o AFID
117449M 13 w AFID
M e asure d
0.5
0.9
0.2
0.7
5
)
(s
e
Snpa(x103 s-1)
0.4
3
0.3
2
1
0.2
0
0.1
0.0
0.5
1.0
Normalized Minor Radius
0.8
1.0
1.5
1.0
0.5
Normalization
0
0.2
Eb = 90 keV
0.4
0.6
Time (s)
22
20
0.6
0.4
E/3
0.2
0
1.0
2.0
1.0
0.8
0.8
2.5
0.5
m
4
0.4
0.6
Time (s)
3.0
0.6
Ti
Anomalous Fast Ion
Diffusion(m2s-1)
2.5
ln(Flux/Energy1/2)
(ster-1cm-2eV-3/2s-1)
AFID Multiplier
TRANSP Anomalous Fast Ion Diffusion (AFID) Model
E
E/2
18
16
14
12
t = 700 ms
10
0
20
40
60
Energy (keV)
80
100
20
40
60
Ene rgy(ke V)
80
100
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Summary
• Data mining for fast ion loss effects is complete for 2005 and in progress for 2006.
•
MSE/LRDFIT and sFLIP are being utilized to distinguish between energetic ion
redistribution and loss effects, respectively.
•
Both CX emissivity and MHD instability effects contribute to depletion of the Snpa.
•
Volume averaging of NB halo neutrals in TRANSP compromises analysis to separate
the CX emissivity and MHD instability effects.
•
R. Akers is applying the LOCUST code (that has proper halo neutral modeling) to
quantify the effect of halo neutrals on Snpa amplitude and time evolution.
•
If halo neutrals affect the evolution of Snpa, progress in the investigation reported here
will be severely impacted: options are to upgrade TRANSP or import LOCUST, both
requiring ~ 0.5-1.0 MY of manpower.
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