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بسمه تعالی. Fast Imaging of turbulent plasmas in the GyM device D.Iraji , D.Ricci, G.Granucci, S.Garavaglia, A.Cremona IFP-CNR-Milan 7 th  Workshop on Fusion Data Processing Validation and Analysis Frascati-March 2012. Outlines. Motivations Fast imaging of GyM plasmas

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6723294
بسمه تعالی

Fast Imaging of turbulent plasmas in the GyM device

D.Iraji, D.Ricci, G.Granucci, S.Garavaglia, A.Cremona

IFP-CNR-Milan

7th Workshop on Fusion Data Processing Validation and Analysis

Frascati-March 2012


Outlines
Outlines

Motivations

Fast imaging of GyM plasmas

Reconstruction of the emissivity profiles

Fluctuations profiles

CAS for detection and visualization of plasma structures (a comparison with probe measurements)

Summary


Motivations
Motivations

A non perturbative approach is fast visible imaging of plasma turbulence. An ultimate goal of plasma imaging is extracting plasma characteristics as much as possible from images.

We need to reconstruct the plasma emissivity profiles in order to analyze plasma structures.


Fast visible imaging system
Fast Visible Imaging system

Camera Characteristics:

Photron ultima APX-RS

Full, 1024 by 1024 pixel resolution, up to 3,000 fps, 10-bit monochrome CMOS sensor with pixels in dimension of 17×17µm

Top recording speed is 250,000 fps

Image memory can be expanded to

facilitate 6 second recordings at 1,000 fps

And 4.2 seconds at 250,000 fps.

Capability of synchronization with the

Other diagnostics such as probes

(error < 100nsec)


Fast visible plasma imaging
Fast visible plasma imaging

CSDX, G.Antar

TORPEX D.Iraji

NSTX, S.Zweben

Camera + GP

Camera +Image Intensifier

  • ELMs

  • Blobs/Filaments

  • Modes


High speed gated image intensifier
High Speed gated Image Intensifier

Hamamatsu C10880-03

Max. gain 10000

Spectral response 185-900 nm

Gating 10ns-10ms

Repetition rate 200kHz

Resolution 38 lp/mm


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GyM

Electron density profile

Electron Temperature profile

Modular device in which the magnetic

field configuration can be easily modified.

# of Coils 10

Max current 1000 A

Max magnetic field 0.13 T

Cooling water rate 22 l/min

Power supply (d.c.) 1000A/50V

Vacuum chamber (m):

Length 2.11

Diameter 0.25

B average ~ 80 mT

Langmuir probe

2.45 GHz source

Hot filament source


Line integrated images raw data h 2 rf power 1500 w
Line integrated images (raw data)H2, RF power: 1500 W

I(t):

Camera image frame at time (t)

75000 fps, 4 us exposure time


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Reconstruction of the emissivity profile

Z

r

B

and g >=0

1cm×1cm

I =T g

Solving least square using SVD approach

N

M

MN


Reconstruction
Reconstruction

  • Calculation of the Transformer Matrix T :

  • Triangulation of reference images to find the camera pixels positions related to the machine coordinates (P)

  • Length of the intersection of LOS corresponding to each camera pixel (i) with plasma pixel (j) is Tij

I ref

P

T

Triangulation

LOS

g

Reconstruction

NR < 5%

I exp


Reconstructed emissivity profiles h 2 rf power 1500 w
Reconstructed emissivity profilesH2, RF power: 1500 W

g(t):

Reconstructed emissivity profile at time (t)

75000 fps, 4 us exposure time

Each frame Cnsums ~ 2 s of

Four 2.4 GHz CPUs, NR < 5%


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Fluctuations

Fluctuations level

PSD of the MFL signal

Maximum fluctuations level (MFL)


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Fluctuations

Z-Scan of PSD

r-Scan of PSD

Z

r

B


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Conditional Average Sampling (CAS)

E×B rotation and Te

Probe measurement

-1

2 L = FWHM

V E×B ~ 1km/s, B~80 mT: E~80 V/m

L ~5.5cm, Te~ E L ~ 4.4 eV

-1

-1


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E×B rotation and B

.

×

E

E

B

B

E×B is responsible for the rotation of the plasma column


Summary
Summary

The intensified fast camera is able to image plasma with spatial resolution of 2cm and temporal resolution of 4µs.

.Plasma emissivity profiles are reconstructed using pixel methode and singular value decomposition approach.

Fourier analysis of the reconstructed images show presence of a distinct mode at ~4 kHz which is radially extended between -3cm<r<2 cm and vertically located at the bottom.

CASed images show rotation of the structures associated with the mode due to E×B drift.


Outlooks

Outlooks

Structural analysis of the reconstructed emissivity profiles to estimate plasma transport.

The establishment of comparisons between the experimental plasma transport related to the plasma structures with theoretical predictions and confirmation using probe data.





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Tomographic reconstruction of the plasma emissivity profile in TORPEX

Before reconstruction

After reconstruction


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