Expanding the role of impurity spectroscopy for investigating the physics of high-Z dissipative divertors

Reinke, M. L.; Meigs, A.; Delabie, E.; Coffey, I.; Stamp, M.; Lawson, K.; Harrison, J.; Terry, J.; Viezzer, E.; Edlund, E.; Mumgaard, R.; Brunner, D.; Cavedon, M.; Lore, J.; Reimold, F.; Lomanowski, B.; LaBombard, B.; Bernert, M.; Potzel, S.; Canik, J.

doi:10.1016/j.nme.2016.12.003

Journal Article

FZJ-2017-06371

Expanding the role of impurity spectroscopy for investigating the physics of high-Z dissipative divertors

Reinke, M. L. (Corresponding author) ; Meigs, A. ; Delabie, E.FZJ* ; Mumgaard, R. ; Reimold, F.FZJ* ; Potzel, S. ; Bernert, M. ; Brunner, D. ; Canik, J. ; Cavedon, M. ; Coffey, I. ; Edlund, E. ; Harrison, J. ; LaBombard, B. ; Lawson, K. ; Lomanowski, B. ; Lore, J. ; Stamp, M. ; Terry, J. ; Viezzer, E.

2017
Elsevier Amsterdam [u.a.]

Nuclear materials and energy 12, 91-99 (2017) [10.1016/j.nme.2016.12.003]

This record in other databases:

Please use a persistent id in citations: http://hdl.handle.net/2128/15892 doi:10.1016/j.nme.2016.12.003

Abstract: New techniques that attempt to more fully exploit spectroscopic diagnostics in the divertor and pedestal region during highly dissipative scenarios are demonstrated using experimental results from recent low-Z seeding experiments on Alcator C-Mod, JET and ASDEX Upgrade. To exhaust power at high parallel heat flux, q∥ > 1 GW/m2, while minimizing erosion, reactors with solid, high-Z plasma facing components (PFCs) are expected to use extrinsic impurity seeding. Due to transport and atomic physics processes which impact impurity ionization balance, so-called ‘non-coronal’ effects, we do not accurately know and have yet to demonstrate the maximum q∥ which can be mitigated in a tokamak. Radiation enhancement for nitrogen is shown to arise primarily from changes in Li- and Be-like charge states on open field lines, but also through transport-driven enhancement of H- and He-like charge states in the pedestal region. Measurements are presented from nitrogen seeded H-mode and L-mode plasmas where emission from N through N are observed. Active charge exchange spectroscopy of partially ionized low-Z impurities in the plasma edge is explored to measure N and N within the confined plasma, while passive UV and visible spectroscopy is used to measure N-N in the boundary. Examples from recent JET and Alcator C-Mod experiments which employ nitrogen seeding highlight how improving spectroscopic coverage can be used to gain empirical insight and provide more data to validate boundary simulations.

Classification: