Modeling Helium-­Hydrogen Plasma Mediated Tungsten Surface Response to Predict Fusion Plasma Facing Component Performance in ITER

PI Name: 
Brian Wirth
PI Email: 
bdwirth@utk.edu
Institution: 
University of Tennessee
Allocation Program: 
ALCC
Allocation Hours at ALCF: 
70 Million
Year: 
2016
Research Domain: 
Materials Science

The purpose of this project is to develop high performance materials suitable for a future fusion power plant. The performance demands on plasma-­facing components (PFCs), first wall and blanket systems of future fusion power plants are beyond the capability of current materials,  which  is  one  of  the  reasons  that  the  United  States  National  Academy  of  Engineering  has  ranked  the  quest  for  fusion  as  one  of  the  top  grand  challenges  for engineering in the 21st Century. Furthermore, it is clear that of this list, the plasma surface interactions  (PSIs)  occurring  in  the  divertor  and  PFCs  pose  a  critical  scientific  challenge  that  limits  our  ability  to  achieve  electricity  production  from  fusion.  Gaining  physical understanding  and  predictive  modeling  capability  in  this  critical  PSI  area  requires  simultaneously  addressing  complex  and  diverse  physics  occurring  over  a  wide  range  of lengths (Ångströms to meters) and times (femtoseconds to seconds, days to years), as well as  integrating  extensive  physical  processes  across  the  plasma-­surface-­bulk  materials  boundaries. It is now well established that He and H plasma exposure with ion energies in the  range  of  10  to  100  eV  and  for  implanted  gas  fluences  around  1E25  per  m2  can  have  profound  effects  on  the  metallic  surface  morphology  and  on  the  quantity  of  retained  gas atoms. The extent to which both surface morphology and sub-­surface defect creation and evolution  processes  driven  by  neutron-­induced  damage  influence  the  diffusion,  trapping  and  precipitation  of  hydrogen  isotopes  into  gas  bubbles  is  an  outstanding  question  that impacts  the  tritium  permeation,  retention  and  near-­surface  saturation  levels;  and  will  definitely influence the operation of the ITER fusion experimental reactor. The outcome of this proposal will be a better understanding of the materials and properties necessary to serve as walls of a future fusion power plant.