1 c. e. bush (ornl), b. c. stratton, s. von goeler, j. robinson, l. e. zakharov, e. fredrickson...
TRANSCRIPT
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C. E. Bush (ORNL), B. C. Stratton, S. von Goeler,J. Robinson, L. E. Zakharov,
E. Fredrickson (PPPL)D. Stutman and K. Tritz (JHU)
and the NSTX Team
17th Topical Meeting on theTechnology of Fusion Energy
November 12-16, 2006Albuquerque, New Mexico
Investigation of MHD Phenomena in NSTX Using a Fast Soft X-ray
Imaging Camera
ORNL PPPL
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
Goal, Motivation and Outline
•Goal: MHD physics studies on NSTX using fast soft x-ray camera imaging.
•Knowledge of fast particle behavior important in NSTX and ITER
•SXR camera obtains a snapshot of mode and structure of MHD
•Rich variety of MHD observed on NSTX: EPMs, NTMs and ELMs.
— Important to ITER and future STs•Tools are available for effective data analysis and physics modeling.
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
The Camera System is Optimized for Time and Spatially Resolved Observation of
MHD•State of the Art PSI5 CCD Camera.— 300 frames of 64x64 pixel at up to 500 kHz— Image allows fast ID of mode and structure Important for NSTX, future STs and ITER.
•Fast conversion of 1-5 keV soft X-ray to visible light
— Uses P47 phosphor (plus signal gain)•Electrostatic image intensifier and lenses— demagnify image by 6:1; couples light to CCD
•Pinhole camera for wide-angle tangential view— Remotely selectable pinholes: 1-5 mm dia
•Remotely selectable beryllium foils.
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
The Horizontal Field-of-View of the Camera Includes Nearly the Full Minor Cross-
Section of Plasma
• Optical axis inclined at 9º downward angle with respect to midplane• Full spatial structure of MHD Mode captured in each frame.
Remotely SelectableSize: 1-5 mm
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
System Installed on NSTX
CCD camer
a
Image intensifierinside magnetic shield
Pinholes andBe foils
NSTXbay Kport
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
Example of SXR Images of m/n=1/1 Mode
t0=175.060 ms t0+90 s
• Camera frame rate= 100 kHz
• Mode frequency: ~2.5 kHz
• Images show 4 times during one mode period
• m/n=1/1 mode character clearly seen
• Shot #113778t0+180 s t0+270 s
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
SXR Diode Traces for a m/n = 1/1 mode Shot 113778
Time (s)
Shot 113778
Ip(kA)
Wtot(kJ)
ISXR-
center(arb)
ISXR-above-
mid(arb)
0 0.1 0.2 0.3 0.40
200
0
1000
0
0
10
20
400
600
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
SXR Diode Traces for a Tearing Mode
Ip(kA)
ISXR-
center(arb)ISXR-below-
mid(arb)
ISXR-above-
mid(arb)
0
400600
8001200
Time (s)
400
200
8001200
400
800
4000.1770.173 0.175 0.179
3 ms Time ofFSXIC Camera
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
Camera Images Clearly Show m/n = 1/1 Mode
for Shot 113778
• Camera frame rate: 100 kHz (for 3 ms)
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
Singular Value Decomposition (SVD) of the Camera Data Separates Coherent Fluctuations in Space and
Timefrom Background Noise
• SVD identifies major components
• 300 frames are recorded per shot, N = 300
• Matrix A(MxN) of N time series of M frames is decomposed into 3 matrices
— A(MxN) = UWVT
• Where:
— U(MxN) - columns are spatial vectors (topos)— V(NxN) - columns are temporal vectors (chronos)
— W(NxN)- a diagonal matrix (of weights)
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
SVD for a m/n = 1/1 mode113778
0 10 20 30 40 5010
3
10
4
10
5
10
6
10
7
0
-0.2-0.10.00.10.2
1
-0.2-0.10.00.10.2
2
-0.2-0.10.00.10.2
3
-0.2-0.10.00.10.2
4
0.175 0.176 0.177 0.178
-0.2-0.10.00.10.2
0.175 0.176 0.177 0.178
103
105
107
113778
Time (s)
U1
U0
U2
U3
U4
V0
V1
V3
V4
V2
The Singular ValueDecomposition (SVD) yields the coherent fluctuaions in space“topos” U0-U4and time“chronos” V0-V4within a background of noise.
U0, V0 => globaltime evolution of thePlasma
Ref. S. Ohdachi et al.Rev. Sci. Instrum., 742136 (2003)
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
Time Evolution of m/n=1/1 Mode from Soft
X-ray Diode Shows Mode Slowing Down
• Signal from conventional soft x-ray diode with radial midplane view shows time evolution of m/n=1/1 mode (Shot 113355).• Later, will show of reconstruction of a camera image late in the evolution of the mode (247.0 ms).
Time (s)
SXR Signal
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
Shot 113355: Tearing Mode
• Camera frame rate: 10 kHz
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
SVD Shows the m/n = 1/1 mode
0.22 0.23 0.24 0.26
103
105
107113355
Time (s)
U1
U0
U2
U3
U4
V0
V1
V3
V4
V2
The Singular ValueDecomposition (SVD) yields the coherent fluctuaions in space“topos” U0-U4and time“chronos” V0-V4within a background of noise.
U0, V0 => globaltime evolution of thePlasma
Ref. S. Ohdachi et al.Rev. Sci. Instrum., 742136 (2003)
113355
0 10 20 30 40 50
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
SXR Camera Image and Reconstruction at t=247.0 ms
(shot=113355) using Cbbst Code
Camera Image Reconstruction
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
Example: Multi-Mode (shot 113384)072 122 139
227 232244
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ORNL PPPL
C. Bush, ANS-TOFE 17-2006
Summary• A state of the art fast soft X-ray imaging camera has been successfully used for MHD physics on NSTX
— 300 frames at up to 500 kHz— Full cross sectional structure with excellent time resolution
— Several MHD phenomena have been observed and studied
— tearing mode, fishbones, sawteeth— m/n = 1:1 and higher observed
• Tools for analysis and physics modeling are providing consistent results
• Plan to use thicker foils for hotter NSTX Plasmas
• Plan to study more complex MHD phenomena
This work was supported by the US DOE, Contract No. DE-AC02-76-CHO-3073.
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EXTRAS