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MHD Instability Diagnostics

NSTX-U MHD Instability Diagnostic Measurement Capabilities – January 2015

(black – available for experiments, blue – under active development)

Physics Measurement

Typical range and coverage

Spatial; Temporal Resolution

Typical Precision

Available Diagnostic Techniques

Comment

Contact

Low (m,n) MHD modes, sawteeth, locked modes,  and disruption precursors

DB/B = 10-4 – 10-1,

(0,0)<(m,n) < (5,10)

2 MHz

 

Mirnov coils outside plasma, known as the “high-n” array

12 toroidal

E. Fredrickson, S. P. Gerhardt - PPPL

 

n=1,2&3 RWM Detection

 

Toroidal arrays of BP and BR sensors inside the vessel.

Used for both n=1 RWM feedback and Dynamic Error Field Correction, and offline analysis

C. Myers-PPPL

 

5 cm; < 300kHz bw

 

Filtered poloidal SXR arrays

2 arrays (32 ch); discrete AXUV diode arrays

K. Tritz, J. M. Burgos – JHU

 

1 cm, < 10 kHz

5% (rel)

Tangential multi-color SXR arrays

5 color/ 20 spatial channels, AXUV diode arrays

K. Tritz, J. M. Burgos – JHU

>2x1011 cm-2

4MHz

2x1011 cm-2

Tangential interferometry, polarimetry (FIReTIP)

FIR laser with retroreflector in 1 tangential chord at RTAN=0.64 m

C. Domier – UC Davis, Y. Ren - PPPL

Cut-off

1.1-7.0 x1013cm-3

2.5 MHz BW

Dr ~ 1cm

 

Quadrature reflectometer

(MHD density fluctuation)

30-75 GHz, 16 channels

S. Kubota - UCLA

 

250 kHz

 

Neutron scintillator array

Plastic scintillators with PM tubes 1- ZnS; 3 BC400

D. Darrow - PPPL

High frequency instabilities (MHD, fast ion modes)

DB/B ≥ 10-3 to 10-7,

n = 0 – 30

5 MHz

Toroidal and poloidal

Mirnov coils outside plasma, known as the “high-f” array

3-BT in toroidal array,  and 8-BP in Toroidal array, 4-BP in poloidal array

E. Fredrickson – PPPL

 

5 cm; < 300kHz BW

 

Filtered poloidal SXR arrays

2 horizontal arrays (32 ch); discrete AXUV diode arrays

K. Tritz, J. M. Burgos – JHU

1.1-7.0 x1013cm-3

2.5 MHz BW

 

Quadrature reflectometer

30-75 GHz, 16 channels

S. Kubota - UCLA

>2x1011 cm-2

500 kHz

2x1011 cm-2

Tangential interferometry, polarimetry (FIReTIP)

FIR laser with retroreflector in 1 tangential chord

C. Domier – UC Davis, Y. Ren - PPPL

Magnetic field  pitch angle fluctuations

 

3 cm core, 2 cm edge, 5 ms

>0.2°

Motional Stark effect based on collisionally-induced- fluorescence (MSE/CIF)

18 channels implemented, presently applies correction for toroidal rotation, requires heating beam source A.

Y. Sechrest, F. Levinton – Nova Photonics

Disruption Halo Currents

0-1000 A

~10x~20cm tiles, 0.1 msec resolution

 

Shunt Tile Arrays

10 tiles in outboard divertor and 18 on center column

S.P. Gerhardt, PPPL