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NSTX-U MHD Instability Diagnostic Measurement
Capabilities – January 2015
(black – available
for experiments, blue – under active development)
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Physics
Measurement
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Typical range
and coverage
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Spatial;
Temporal Resolution
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Typical
Precision
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Available
Diagnostic Techniques
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Comment
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Contact
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Low (m,n) MHD modes, sawteeth, locked modes, and disruption precursors
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DB/B = 10-4 – 10-1,
(0,0)<(m,n) < (5,10)
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2 MHz
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Mirnov coils outside plasma, known as the “high-n” array
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12 toroidal
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E. Fredrickson, S. P. Gerhardt - PPPL
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n=1,2&3 RWM Detection
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Toroidal
arrays of BP and BR sensors inside the vessel.
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Used for both n=1 RWM feedback and Dynamic Error
Field Correction, and offline analysis
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C. Myers-PPPL
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5 cm; < 300kHz bw
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Filtered
poloidal SXR arrays
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2 arrays (32 ch); discrete AXUV diode arrays
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K. Tritz, J. M. Burgos – JHU
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1
cm, < 10 kHz
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5%
(rel)
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Tangential
multi-color SXR arrays
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5 color/ 20 spatial channels, AXUV diode arrays
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K. Tritz, J. M. Burgos – JHU
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>2x1011 cm-2
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4MHz
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2x1011
cm-2
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Tangential
interferometry, polarimetry (FIReTIP)
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FIR laser with retroreflector in 1 tangential
chord at RTAN=0.64 m
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C. Domier – UC Davis, Y. Ren - PPPL
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Cut-off
1.1-7.0 x1013cm-3
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2.5 MHz BW
Dr ~ 1cm
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Quadrature reflectometer
(MHD density fluctuation)
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30-75 GHz, 16 channels
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S. Kubota - UCLA
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250 kHz
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Neutron scintillator array
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Plastic scintillators with PM tubes 1-
ZnS; 3 BC400
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D. Darrow - PPPL
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High frequency instabilities (MHD, fast ion modes)
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DB/B ≥ 10-3 to 10-7,
n
= 0 – 30
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5 MHz
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Toroidal
and poloidal
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Mirnov
coils outside plasma, known as the “high-f” array
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3-BT in toroidal array, and 8-BP in Toroidal array,
4-BP in poloidal array
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E. Fredrickson – PPPL
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5 cm; < 300kHz BW
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Filtered
poloidal SXR arrays
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2 horizontal arrays (32 ch); discrete AXUV diode
arrays
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K. Tritz, J. M. Burgos – JHU
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1.1-7.0 x1013cm-3
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2.5 MHz BW
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Quadrature reflectometer
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30-75 GHz, 16 channels
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S. Kubota - UCLA
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>2x1011 cm-2
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500 kHz
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2x1011 cm-2
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Tangential interferometry, polarimetry (FIReTIP)
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FIR laser with retroreflector in 1
tangential chord
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C. Domier – UC Davis, Y. Ren - PPPL
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Magnetic field pitch angle fluctuations
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3 cm core, 2 cm edge, 5 ms
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>0.2°
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Motional Stark effect based on collisionally-induced-
fluorescence (MSE/CIF)
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18 channels implemented,
presently applies correction for toroidal rotation, requires heating beam
source A.
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Y. Sechrest, F. Levinton – Nova Photonics
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Disruption Halo Currents
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0-1000 A
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~10x~20cm tiles, 0.1 msec resolution
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Shunt Tile Arrays
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10 tiles in outboard divertor and 18
on center column
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S.P. Gerhardt, PPPL
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