TY  - JOUR
AU  - Reinke, M. L.
AU  - Meigs, A.
AU  - Delabie, E.
AU  - Mumgaard, R.
AU  - Reimold, F.
AU  - Potzel, S.
AU  - Bernert, M.
AU  - Brunner, D.
AU  - Canik, J.
AU  - Cavedon, M.
AU  - Coffey, I.
AU  - Edlund, E.
AU  - Harrison, J.
AU  - LaBombard, B.
AU  - Lawson, K.
AU  - Lomanowski, B.
AU  - Lore, J.
AU  - Stamp, M.
AU  - Terry, J.
AU  - Viezzer, E.
TI  - Expanding the role of impurity spectroscopy for investigating the physics of high-Z dissipative divertors
JO  - Nuclear materials and energy
VL  - 12
SN  - 2352-1791
CY  - Amsterdam [u.a.]
PB  - Elsevier
M1  - FZJ-2017-06371
SP  - 91-99
PY  - 2017
AB  - 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.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000417293300012
DO  - DOI:10.1016/j.nme.2016.12.003
UR  - https://juser.fz-juelich.de/record/837458
ER  -