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

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.

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.

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.

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.

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

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) 865-873.

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.

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.

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).

SEM: No Beam Exposure

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

SEM: Lithium and Beam Exposure

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

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

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

Thank You! Questions?