1. Asdex Upgrade Seminar
IPP Garching, 16th November 2011
Divertor Da-Light Profiles in AUG - First Results of New Strike Point Observation Diagnostics -
Arthur Weller
IPP Garching
Acknowledgments for substantial assistance to:
T. Lunt, A. Mayer, P. Bischoff, B. Kurzan, Ch. Veth, and the ASDEX Upgrade Team
A. Weller, Garching 2011

2. Introduction Connection Lengths (EMC3/EIRENE)
T.Lunt,
ASDEX Upgrade
Major goals of Strike Point Observation (SPO) diagnostics
● Measure light intensities of Ha(Da) & CIII
across divertor plates
● assess particle fluxes of H(D) and C
by normalizing measured intensities with data
predicted by edge model (e.g. EMC3/Eirene)
● characterize footprints of particle interaction
with divertor including effects of ELMs
and of ELM RMP coils
T.Lunt,
ASDEX Upgrade
A. Weller, Garching 2011

3. Outline Experimental Setup  Optics, CMOS Camera
 Laboratory Measurements, Calibration
 Arrangement on AUG
Initial Measurements on AUG
 Analysis Tool
 Camera Images & Intensity Histograms
 Da Light Profiles & Time Traces
 Effect of ELMs and RMP coils
Summary
A. Weller, Garching 2011

4. Introduction - diagnostics needed refurbishments (new camera & fibres) -
● 2 fibre arrays monitoring
light emission across inner
and outer divertor plates
● beams splitted into Da- and CIII
components
● measured by fast
CCD/CMOS camera
old system (until end of 2009)
A. Weller, Garching 2011

5. Phantom Miro eX4 (VisionResearch) - some data -
resolution [pixel]
800x600
pixel size [mm2]
22x22
sensor size [mm2]
17.6 x 13.2
sensitivity
[ASA] mono.
4800
ADC [Bit]
12 (real)
frame rate [fps]
1265
f. r. (reduced) [fps]
16100 (512x64)
memory (GB) 2
interface
(data & control)
Ethernet (10/100BASE-T)
min. shutter [ms]
A. Weller, Garching 2011

6. Phantom Miro 4 vs. Phantom 7.3 - both cameras use 12-bit ADCs -
Ha + grey-filter 12
(attenuation 1:1640)
Ha + grey-filter 13
(attenuation 1:3610)
Intensity Histograms
Miro 4
Miro 4
Miro 4
structure due
to pixel
calibrations ?
average over
100 frames
Phantom 7.3
Phantom 7.3
Phantom 7.3
A. Weller, Garching 2011

7. Tests and Calibration ● Assembly without filters
● 2 fibre bundles (100 m fibres)
● 85 mm Nikkor object lens towards fibre bundle,
50 mm Nikkor lens on camera  light points fit into 256 x 128 pixel frame
● Homogenous illumination of fibres with calibrated Ulbricht sphere
A. Weller, Garching 2011

8. Tests and Calibration ● 2 fibre bundles : - good old bundle (LWL_old)
test_spo_lwlalt+lwlneu1-ulb_half+grey13_c3_256x128_8000mues_b2_8_calib-6.cine
LWL_old CIII
LWL_old Ha + grey
LWL_new-1 Ha + grey
LWL_new-1 CIII
broken fibre
● 2 fibre bundles :
- good old bundle (LWL_old)
- new bundle (LWL_new-1)
but fibres disordered
(to be replaced again !)
● SPO optics generates
4 rows of fibre light spots
(each bundle split into
Ha - and C III - light
● Ha - channel attenuated
by additional grey filter
● light profile shows vignetting
vignetting effect
A. Weller, Garching 2011

9. Vignetting Correction (optional)
Low field side divertor Ha profiles 2.0 s)
raw data
corrected
A. Weller, Garching 2011

10. Calibration of Ha Intensities
● absolutely calibrated
Ulbricht sphere used
● transmittance of grey filter,
Ha-filter and dichroic beam splitters
measured
A. Weller, Garching 2011

11. Calibration of Ha Intensities
calibration with Ulbricht sphere
(distance to fibre head ≈ 20 cm)
Ha channel,
low field side
divertor fibres
edge fibres
not illuminated
A. Weller, Garching 2011

12. Determination of Regions of Interest (ROI) - to be used for online image analysis -
low field side
high field side + reflexes
CIII – channel removed in present setup,
but still reflexes from hf-side fibres
A. Weller, Garching 2011

13. Experimental Setup - LOS directed to gap between sectors 12 and 13 (f = 270°) -
Optical heads mounted underneath
lower divertor viewing through gaps
● toroidal alignment of LOS into
gap between adjacent tiles
to reduce light reflection
fibres (100 mm) arranged
in 2 bundles (2 x ~65 fibres)
A. Weller, Garching 2011

14. Neutral Penetration, Neutral Decay Length - neutral density across divertor gap ? -
according to Goldston, Plasma Physics
(including e--impact ionization and CX)
● no significant change of neutral density expected across gap
A. Weller, Garching 2011

15. Neutral Penetration, Ha Emissivities - Te and ne dependency -
neutral profiles according to Goldston, Plasma Physics
● line of sight integrated intensity only weak dependence on Te
● Expected Ha intensity roughly consistent with measured values
A. Weller, Garching 2011

16. Experimental Setup - Line of Sight Geometry -
Div II d
Light Spots from Fibre Illumination
inner divertor
target plate
TPi
TPic
● spatial resolution ~ 3-4 mm
● S-coordinate of spots measured (backward illumination)
● R-z coordinates of spots calculated
A. Weller, Garching 2011

17. New SPO Line of Sight Geometry - S-coordinates and R-z coordinates -
A. Weller, Garching 2011

18. axial tilt angle adjustment
Experimental Setup - assembly of adjustable support & magnetic shielding -
axial tilt angle adjustment
for optics & camera
horiz. & vert.
camera shift
interface to flange
of fibre outlet window
soft iron
camera shield
fibre outlet
in port 13Du
(sector 13)
A. Weller, Garching 2011

19. SPO Data Acquisition - Fast Camera TooL (Ch. Veth) -
● Shot synchronized DAQ
● SPO C++ software using
Phantom toolkit routines for
camera control & data transfer
● black balance before shot
● image processing:
- mean intensities (t),
(reduced frame rate)
- intensity profiles (t) from ROI
processing (not yet used)
● video stored in .cin format
in requested time interval
(optional)
A. Weller, Garching 2011

20. Data Analysis (Stored Video Processing)
● image display (single
frame, aver. frames,
contrast optimization)
● full image histogram
● profiles along line
● ROI generation
● intensity calibration
● S-coordinate transf.
● time resolved intens.
A. Weller, Garching 2011

21. Ha Signal from SPO - compared with ELM Ha signal ELMa-Han -
(4000 fps, averaged over profile)
A. Weller, Garching 2011

22. SPO Data in AUG DL Discharge - shift of strike point (outer divertor plate) -
#26901
Ha-Emission
across
Outer Divertor
A. Weller, Garching 2011

23. SPO Data in ELM and Inter-ELM Phases - low field side Ha profiles, #27028 -
A. Weller, Garching 2011

24. SPO Raw Data in ELM and Inter-ELM Phases - low field side Ha profiles, #27028
klick in frame to start movie …
low field side fibres
high field side fibres (disordered)
#27028, 3.25 – 3.50 sec, 4000 fps, 304 x 104 pixels
● Vibrations during shot  shift of light pattern on CMOS chip
● poloidal movement of strike point during ELM, field perturbation ?
A. Weller, Garching 2011

25. Single ELM Profile Evolution - low field side Ha profiles, #27028 -
● ELM induced particle fluxes
strongly peaked on target plate
● poloidal movement of strike point
during ELM, field perturbation ?
A. Weller, Garching 2011

26. SPO Data in AUG ELM Mitigated Discharge - low field side Ha profiles, #26853
A. Weller, Garching 2011

27. SPO Data in AUG ELM Mitigated Discharge - low field side Ha profiles, #27076
A. Weller, Garching 2011

28. SPO Data in AUG ELM Mitigated Discharge - low field side Ha profiles, #26840 -
residual ELMs at lower density
ELM-free phase
#26840
A. Weller, Garching 2011

29. First EMC3/EIRENE Modelling - ELM mitigated shot 26081@4.9 s -
Tilmann Lunt
no RMP coils
with RMP coils
SPO
plane
ion flux across div.
along toroidal angle
SPO
plane
electron density ne
A. Weller, Garching 2011

30. Conclusions & Outlook
 SPO (Strike Point Observation Diagn.) operational again (not fully)
new camera (Phantom Miro 4eX), new support & magn. shielding
 Issues with inner divertor fibre bundle, window light reflexes
and port movements / vibrations to be resolved
 pre-processing of ROIs by Fast Camera Tool requires
vibrationless recording, not yet realized; videos stored
 first experimental data (low field side):
- light emission during ELMs strongly localized in poloidal direction,
poloidal movement during ELMs
- very broad in inter-ELM and ELM-mitigated phases
- no distinct strike line splitting observed so far
(structures smoothed by LOS integration effects ?)
- changes of equilibrium seen by strike point movements
 calibrations to be checked by comparison
with other measurements and with edge modelling,
high spatial resolution desirable
A. Weller, Garching 2011

31. Conclusions & Outlook
 SPO (Strike Point Observation Diagn.) operational again (not fully)
new camera (Phantom Miro 4eX), new support & magn. shielding
 Issues with inner divertor fibre bundle, window light reflexes
and port movements / vibrations to be resolved
 pre-processing of ROIs by Fast Camera Tool requires
vibrationless recording, not yet realized; videos stored
 first experimental data (low field side):
- light emission during ELMs strongly localized in poloidal direction,
poloidal movement during ELMs
- very broad in inter-ELM and ELM-mitigated phases
- no distinct strike line splitting observed so far
(structures smoothed by LOS integration effects ?)
- changes of equilibrium seen by strike point movements
 calibrations to be checked by comparison
with other measurements and with edge modelling,
high spatial resolution desirable
A. Weller, Garching 2011