image processing in magnetic fusion devices · 2019-06-23 · image processing in fusion 04.06.2019...

04.06.2019 1

Marcin Jakubowski

Max-Planck-Institut für Plasmaphysik, Greifswald, Germany

Image Processing in Magnetic Fusion Devices

Images in science

04.06.2019 IAEA Meeting on Fusion Data Processing, Validation and Analysis, 30th May 2019 2

• Visual information has always played an important role during the evolution of science.

• The advent of the imaging in science came with digital cameras, which allowed for easier, faster and more accurate detection of events in magnetic fusion devices.

C. Darwin, “Voyage of the Beagle”

C. D. Anderson, Phys. Rev. 43 (1933) 491

TFTR

Disruption caused by a locked mode at TFTR. Intensified image in the wavelength range of 440–700 nm, 2000 fps/30usec exposure, Each full image is composed of 239 ×192 pixels and the digitalization is 8 bit deep

R.J. Maqueda and G.A. Wurden, Nucl. Fusion, 39 (1999) 629

Challenging definition of an image


• In April of 2017, a global web of eight radio telescopes located in six places (Chile, Mexico, Spain, Hawaii, Arizona and the Antarctic), the collective network that makes up the EHT, began surveying the Messier 87 black hole, as well as the black hole at the center of our own Milky Way galaxy. → talk by S. Ohdachi

• An image is a 2D representation of electromagnetic waves either emitted or reflected by an object or set of objects

Infrared VUV Soft X-ray→ In this session

BöckenhoffPisano

Farley Ohdachi

Image processing starts with image acquisition and preparation

04.06.2019 4

Getting images

Acquiring images

Calibration of the images

Spatiotemporal interpretation

IAEA Meeting on Fusion Data Processing, Validation and Analysis, 30th May 2019


04.06.2019 5

Getting images

Acquiring images

R.J. Maqueda and G.A. Wurden, Nucl. Fusion, 39 (1999) 629

M. W. Jakubowski, et al., Review of Scientific Instruments 89, 10E116 (2018)

Instrumentation of next generation devices becomes challenging due to steady-state requirements and harsh conditions (ITER)Combination of large depth of field and high resolution challenging


04.06.2019 6

Getting images

Acquiring images

Calibration of the images

Spatiotemporal interpretation

W7-X

→ See talk by F. Pisano

Thermography Image Analysis Thermal Events Trackingand Characterization

Control, Safetyand Protection


In the case of infrared images by careful selection of observed wavelength range we can assure to observe an emission from surface of PFCs, which makes interpretation much easier

Image Processing in Fusion


Processing of physical information

Analysis

Interpretation

Extraction of the information





• Typical issue with an image is that it represents 3D objects on a 2D plane.

• In real life our brain has 3D models, which help us to interpret partially stereoscopic images.

• In fusion devices we interpret a 2D image, where the models are either non-existing or not accurate enough.

• Several methods are developed to the extract structural information from a visual scene to understand phenomena and even control the discharge





COMPASS

P. Hacek, et al., W

DS’1

4 (2

01

4) 2

21

-22

6

W7-X

T. Szepsi, et al., EP

S 20

17

P5

.11

9

• Assumption of thin emissive surface layer. • Identification of plasma boundary based

on the visible radiation belt at the edge with help of either equilibrium reconstruction (COMPASS) or field line tracing (W7-X).


04.06.2019 10IAEA Meeting on Fusion Data Processing, Validation and Analysis, 30th May 2019

S. Lisgo, et al., Jo

urn

al of N

uclear M

aterials 39

0–3

91

(20

09

) 10

78

–10

80

MAST

• For a quantitative comparison with the model, pixel-based tomographic inversion is used to reconstruct the Da emission profile in the poloidal plane.

• The algorithm is represented by Ax = b, where x is the poloidal emission profile and b is the camera data.

• A is the ‘geometry matrix’, which maps the line-of-sight camera view onto a poloidal mesh and is calculated using a ray tracing code.



Sparse modelling for tomographic reconstruction

• Expansion of the emission profile using orthogonal patters with the sparse modelling (e.g., L1 regularization) is promising for tomographic reconstruction even when the condition for the reconstruction is quite severe.

• Synthetic data analysis shows that, if we use two tangentially viewing camera data, island-like structure can effectively detected.

→ See talk S. Ohdachi

Reconstruction with L1

Assumed profile

W7-X

LHD



MARFE detection based on optical flow detection.




• The optical flow is the pattern of apparent motion of objects caused by the relative motion between an observer and a scene.

𝑓𝑠 ⋅ 𝑣 + 𝑓𝑡 = 0

• Method allows for motion detection. The optical flow is defined as the ‘flow’ of grey values at the image plane and it is an approximation of the motion field, i.e. of the real motion of the object in the 3D scene, projected onto the image plane.

JET

T. Craciunescu, et al. Plasma Phys. Control. Fusion 56 (2014) 114006A. Murari, et al., IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 38, NO. 12, DECEMBER 2010

Analysis

Analysis of Scrape-Off Layer Filament Properties Using Visual Camera Data

13

Camera frame Elzar tomographic inversion


Analysis


MAST

• Detection of filaments with neural networks from visual cameras has been developed at CCFE

• Application to experiments allows determining the statistics of the filaments with unique flexibility

• → see talk of Tom Farley


Interpretation of images



Analysis

Interpretation

Tore Supra

• Interpretation of surface temperature and heat flux to the carbon plasma components deduced from infrared images requires detailed knowledge of surface emissivity and presence of so-called surface layers (redeposited material)

• Temporal evolution of the infrared images allowed to identify areas affected by surface layers A. Ali, et al., Nuclear Materials and Energy 19 (2019) 335–339


Information required to understand an infrared image

15

• Layers of information for interpratationof an image

• Emissivity ε of the target material (not constant in time)

• Surface layers (not constant in time)

• Reflections map (dependent on scenario)

• Target distance D

• Angle α with normal to target surface

• 3D world coordinates: X,Y,Z, ϕ, θ

LoS

ϕ, θ

X,Y,Z

α

D

ε

PFC ID

CAD view


Analysis

Interpretation


Image changes properties during thedischarge

Thermographic image from W7-X divertor

Surface layer detection

A. Ali, et al., Nuclear Materials and Energy 19 (2019) 335–339

W7-X


Surface layers obtained withTHEODOR – 2D heat flux code

Automatic processing of large amount of data

04.06.2019 17


Analysis

Interpretation


• Any diagnostic data can be converted into electrical signal stored for offline use

• Present and future magnetic fusion experiments need to deal with petabytes of data, which cannot be processed in a typical approach.

• An automatic data processing is required.

• A promising approach to deal with large amount of data is shown in J. Vega et al., Rev. Sci. Instruments 81, 023505

• Universal Multi Event Locator allows for automatic detection of events in time traces (e.g. saw teeth) or IR data (hot spots).

• Works also on images with reduced resolution.

Plasma parameter reconstruction from divertor heat load with sparse data

04.06.2019 18

• Reconstruction of magnetic equilibrium parameters from infrared data with neural networks.

• Due to small data amount training set supported by simulated images.

• → see talk D. Böckhenhoff• ITER requires methods to train neural

networks w/o experimental data (e.g. avoidance of disruptions)



Analysis

Interpretation


Image analysis requires sophisticated software

04.06.2019 19

• WEST, W7-X: THERMAVIP – A. Puig-Sitjes, et al., Fusion Science and Technology, 74 (2017) 1–2, 116–124• JET: JUVIL - V. Huber, et al., Fusion Engineering and Design123(2017)979–985


Operating System

Qt

Acquisition Processing

ThermaVIP SDK

StorageTriggers

CameraLocal

storageGPU NetworkIO board

Camera driver

CUDAIO board driver

GUI

Acquisition and analysis

OS

Qt

ThermaVIPSDK

Network

GUI

DisplayWEST, W7-X

JET

04.06.2019 20

Thank you

image processing in magnetic fusion devices · 2019-06-23 · image processing in fusion 04.06.2019...

Documents