1. Lithiumization of Plasma-Facing components in Next-Gen Fusion reactors
October 7, 2011
Lithiumization of Plasma-Facing components in Next-Gen Fusion reactors
Talk about an area of plasma-material interactions research that can broadly be described as …
Anupama Khan

2. Why develop fusion energy?
Fusion energy deployment scenarios match long-term carbon mitigation projections.
First like to mention why I think fusion is an interesting topic to look at, especially since my summer was funded by PEI Energy Grand Challenges.

3. Fusion Development Plan
If we look at the global development plan for fusion energy, we can see that this is a project on science fiction novel timescales.
At the earliest, we can expect a net energy producing demonstration plant around 2040.
Though that seems a little late for our immediate carbon mitigation/environmental concerns…
Goldston, R. “Fusion Development Path Panel: Preliminary Report.” Report to the Fusion Sciences Advisory Committee (2002).
Demo of commercial fusion energy by 2040.

4. Projected Emissions Reductions
IMAGE/MESSAGE series of models from Energy Modeling Forum 21st report, released in 2006, by Stanford University. Total reductions the same, but differ in where the reductions will come from. MESSAGE puts the greatest emphasis on nuclear development.
Prepared for the IPCC Special Report on Emissions Scenarios (SRES)
Metz, B. et al (eds). Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press (2007).
IPCC predicts 95% of reductions made after 2030.

5. Materials Challenges
High power flux from radiation and particles
Erosion of structural materials
Pumping/gettering impurities (N, H2O, CO)
Hydrogen recycling and retention
Goal: Choose multi-functional materials that resist erosion and improve plasma performance over extended periods of time.

6. Why use liquid lithium PFCs?
Liquid lithium PFCs have been shown to improve several plasma performance parameters, though the mechanisms remain poorly characterized.
Melting T of Li is 180 C

7. Observed Benefits of Liquid Lithium
Limited Li sputtering
Suppresses off-normal events
Reduced D,T recycling
Surface chemistry?
Li doesn’t sputter, tends to redeposit on walls; potential to be self-healing, self-cooling
Kugel, H., et al. “Lithium coatings on NSTX plasma-facing components.” Fusion Engineering and Design. 85 (2010)

8. Imaging exposed LLD samples Mapping damage patterns
Two-Fold Approach
Surface Chemistry of PFCs
Observation
Imaging exposed LLD samples
Mapping damage patterns
Experiment
Lithiated ATJ graphite
Boron pre-conditioning on Mo alloys
Distinction between looking at samples that have been damaged in reactor or reactor-like conditions; vs. in-house exp.

9. Why study damaged surfaces?
Li predicted to protect porous Mo from neutral beam bombardment, prolong lifetime of structural materials in NSTX.
Predicted to get more even heat distribution instead of localized melting.

10. Narrow Band of Damage
Intuitive result given a semi-quantitative treatment
Abrams, T. “Investigation of LLD Test Sample Performance under High Heat Loads.” Unpublished data. (2010).

11. SEM: No Beam Exposure

12. SEM: Beam Exposure
Formation of small crystal-like structures. Further characterization.

13. SEM: Lithium and Beam Exposure

14. Current Work
Stitch together “panorama” sweeping length of sample to identify changes in morphology
Energy-dispersed X-ray spectroscopy for analysis of elemental composition in Li’ized samples
Determine changes in crystal structure after beam exposure in samples with and without lithium
Remove lithium and image underlying Mo structures

15. Summary
Fusion has the potential to significantly impact global energy consumption over the next 100 years
Liquid lithium is a multi-functional material that has been shown to improve plasma performance
SEM to study heat diffusion in Li on porous Mo
XPS to study interactions between O-B-Li

16. Acknowledgements Prof. Bernasek Steve Wulfsberg Prof. Rob Goldston
Matt Frith
Dr. Bob Kaita
Sean Edington
Conor Thomas
Chemistry Department
Pearl Dickerson
PEI Grand Challenges
Amber Hibberd
PPPL
Esther Frederick

17. Thank You!
Questions?