%0 Journal Article
%A Reinke, M. L.
%A Meigs, A.
%A Delabie, E.
%A Mumgaard, R.
%A Reimold, F.
%A Potzel, S.
%A Bernert, M.
%A Brunner, D.
%A Canik, J.
%A Cavedon, M.
%A Coffey, I.
%A Edlund, E.
%A Harrison, J.
%A LaBombard, B.
%A Lawson, K.
%A Lomanowski, B.
%A Lore, J.
%A Stamp, M.
%A Terry, J.
%A Viezzer, E.
%T Expanding the role of impurity spectroscopy for investigating the physics of high-Z dissipative divertors
%J Nuclear materials and energy
%V 12
%@ 2352-1791
%C Amsterdam [u.a.]
%I Elsevier
%M FZJ-2017-06371
%P 91-99
%D 2017
%X 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.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000417293300012
%R 10.1016/j.nme.2016.12.003
%U https://juser.fz-juelich.de/record/837458