Transient heat load tests with Nd:YAG laserMain results of
EFDA TW3-TPP/ERCARPWI Task Force meeting – CEA Cadarache
17-19 October 2005
Douglas d’Hulst, Jaap G. van der Laan and Friso Schmalz
Objectives
Study of power handling characteristics of CFC tiles exposed to plasmas for high fluences and repetitive power fluxes.
The goal is to understand if plasma erosion changes the thermal properties of the tile surface for power loads typical of ~ 10 MW/m², that is, far away from any material ablation limit. Secondly the effect of repetitive power fluxes on the material micro-structure is to be examined.
Experiments
1. Determining the effusivity of samples from AUG exposed CFC tiles (< 0.5 MJ/m²).
2. Investigate the influence of repetitive heat loads on NB-31 (± 2.5 MJ/m²), special emphasis on fibre-matrix debonding.
100
1000
10000
0,1 1 10 100
big particles
small and medium particles
no particle emission
2 3 4 5
absorbed peak power density (MW/m²)
pulse duration (ms)
Brittle destruction analysis, J. Linke (Feb. 04)
VDEs 60 MJm-2
disruptions10 MJm-2
safe operation regime
ELMs 1 MJm-2
Effusivity 0.5 MJm-2
Repetitive heat load2.5 MJm-2
Test facilitiesNd:YAG laser & HV chamber
– t = 0.2-20 ms
– E = 2 – 70 J (– 25 J for 5 ms)
Specimen holder with HF heating
Fast IR-pyrometer
Effusivity measurements
ASDEX Upgrade samples
Effusivity measurements
* Pulse energy 12 – 18 J* Pulse length 3 – 6 ms* Spot size 30 – 40 mm²* Sample temperature 530°C
* Absorbed energy density ± 0.5 MJ/m²* Absorbed power density ± 100 MW/m²
Effusivity measurements
0
500
1000
1500
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2500
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Time (ms)
Pyr
om
eter
tem
per
atu
re (
°C)
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1
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Las
er P
ow
er (
A.U
.)
Deposition 1 Deposition 2 Erosion 1 Erosion 2 Reference Laser Power
Effusivity measurements
0
500
1000
1500
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2500
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Time (ms)
Pyr
om
eter
tem
per
atu
re (
°C)
0
1
2
3
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5
Las
er P
ow
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A.U
.)
Deposition 1 Deposition 2 Erosion 1 Erosion 2 Reference Laser Power
Repetitive heat loads
Repetitive heat loads
* Pulse length 5 ms* Pulse energy 22 J* Spot size 7.5 mm²* Pulse frequency 3 Hz* Amount of pulses 1000* Sample temperature 300°C ( - 750°C)
* Absorbed energy density 2.5 MJ/m²* Absorbed power density 0.5 GW/m²
Repetitive heat loads
Effects of repetitive heat loads difficult to detect
* No effects on surface detected with SEM* No effects visible on cross section with optical
microscopy* No effects visible on thermal diffusivity
measurements* No effects visible on effusivity measurements
Advantages of Tomography
* 3-D data set * Ability to visualise internal
features non-destructively* Characterise structures
– “Virtual” metallography
* Study deformation processes
Paul Mummery, Manchester Materials Science Centre
Graphite Applications
* 3-D distribution of porosity
* Can analyse data set to give spatially-resolved density distribution
Pore distribution in UCAR CPaul Mummery, Manchester Materials Science Centre
Cracking in UCAR C
1mm
Paul Mummery, Manchester Materials Science Centre
Fibre composite pore structure
Paul Mummery, Manchester Materials Science Centre
Conclusions
* No influence of erosion on power handling characteristics of CFC
* Deposited layers show a low thermal contact with the original sample surface
* No effects detected of repetitive heat loads* Recommendation to try to detect effects with
X-ray tomography
Additional remarkNRG is involved in an EFDA-task with TNO on explosively bonded structures of solid W on Cu or W.
low temperature joint of 0.2- 0.3 mm plate, on possibly curved surfaces; promise for thick and dense W on heat sinks