Parameter dependencies of the experimental nitrogen concentration required for detachment on ASDEX Upgrade and JET

Henderson, Stuart S.; Bernert, M.; Giroud, C.; Brida, D.; Cavedon, M.; David, P.; Dux, R.; Harrison, J. R.; Huber, A.; Kallenbach, A.; Karhunen, Juuso; Lomanowski, Bart A.; Matthews, G.; Meigs, Andrew; Pitts, R. A.; Reimold, F.; Reinke, Matthew L.; Silburn, S.; Vianello, N; Wiesen, Sven; Wischmeier, M.

doi:10.1016/j.nme.2021.101000

Parameter dependencies of the experimental nitrogen concentration required for detachment on ASDEX Upgrade and JET

Journal Article · Tue May 25 04:00:00 EDT 2021 · Nuclear Materials and Energy

DOI:https://doi.org/10.1016/j.nme.2021.101000· OSTI ID:1844870

Henderson, Stuart S. ^[1]; Bernert, M. ^[2]; Giroud, C. ^[1]; Brida, D. ^[2]; Cavedon, M. ^[2]; David, P. ^[2]; Dux, R. ^[2]; Harrison, J. R. ^[1]; Huber, A. ^[3]; Kallenbach, A. ^[2]; Karhunen, Juuso ^[4]; ^[5]; Matthews, G. ^[1]; Meigs, Andrew ^[1]; Pitts, R. A. ^[6]; Reimold, F. ^[7]; ^[5]; Silburn, S. ^[1]; Vianello, N ^[8]; Wiesen, Sven ^[3] more »

Culham Science Centre, Abingdon (United Kingdom)
Max Planck Institute for Plasma Physics, Garching, Germany
Institute for Energy and Climate Research, Juelich (Germany)
Aalto Univ., Espoo (Finland)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
International Thermonuclear Experimental Reactor (ITER), Saint Paul Lez Durance (France)
Max Planck Institute for Plasma Physics, Greifswald, Germany
Univ. degli Studi di Padova (Italy)

While current tokamak experiments are beginning to use real-time feedback control systems to manage the plasma exhaust, future tokamaks still require validation of theoretical models used to predict the threshold impurity concentration required to sufficiently reduce the power and particle fluxes to the divertor. This work exploits new spectroscopic measurements of the divertor nitrogen concentration, c_n, in partially detached N₂-seeded H-mode plasmas on ASDEX Upgrade (AUG) and JET with the ITER-Like Wall (JET-ILW) to test the parameter dependencies of the power flowing to the outer divertor, P_div,outer , and the separatrix electron density, n_e.sep. A least-squares regression of the AUG measurements demonstrates that the threshold c_n required for detachment scales as $$c_n∝P^{1.19±0.32}_{div,outer}n^{-2.77±0.36}_{e,sep}$$. This scaling of n_e,sep is also consistent with the measurements from JET which, at constant P_div,outer, show $$c_n∝n^{-2.43±0.27}_{e,sep}$$. The dependencies of P_div,outer and n_e.sep is demonstrated over at least a factor of two change in both parameters and indicates a stronger dependence on n_e.sep in comparison to the Lengyel model, which could be due to the assumption in this model that the heat flux channel width is independent of density. This first assessment of detachment scaling with impurity seeding highlights the need for further analysis of the systematic uncertainties of the measurement and more consistent scenarios from more tokamaks to investigate the machine size scaling.

View Accepted Manuscript (DOE)

Research Organization:: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Organization:: USDOE Office of Science (SC); Euratom Research and Training Programme; Engineering and Physical Sciences Research Council (EPSRC)

Grant/Contract Number:: AC05-00OR22725

OSTI ID:: 1844870

Journal Information:: Nuclear Materials and Energy, Journal Name: Nuclear Materials and Energy Journal Issue: NA Vol. 28; ISSN 2352-1791

Publisher:: ElsevierCopyright Statement

Country of Publication:: United States

Language:: English

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