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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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slide1
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

Fastimaging of GyM plasmas

Reconstruction of the emissivity profiles

Fluctuations profiles

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

Summary

motivations
Motivations

Basic understanding of fluctuations and turbulence in magnetized plasmas is an important issue for magnetic fusion, as they cause a high degree of particle and energy losses.

A full spatio-temporal imaging system with reasonable resolution in time and space is needed to study plasma turbulence .

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

Fast imaging is often used in fusion devices however detailed comparisons with other diagnostics are needed for justification.

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

  • 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

slide7

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

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

g(t):

Reconstructed emissivity profile at time t

I=T*g

T=U*S*V ,

U*U =V*V = unitary

V*S *U *I=g

T

T

T

-1

T

75000 fps, 4 us exposure time

NR~ 0.05

Z

r

B

slide11

Plasma structures in reconstructed profiles (fluctuations)

~

g(t)=g(t)-<g(t)>

Fluctuation profile of reconstructed emissivity at time t

  • Individual structures can be distinguished
  • Structures appear rotate, merge and split after a while

Z

r

B

slide12

Fluctuations

Fluctuations level

PSD of the MFL signal

Maximum fluctuations level (MFL)

slide13

Fluctuations

Z-Scan of PSD

r-Scan of PSD

Z

r

B

slide14

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

slide15

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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