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(EX6/6) Radiative Divertor and SOL Experiments in Open and Baffled Divertors on DIII-D

S. L. Allen, M. E. Fenstermacher, D. N. Hill, C. J. Lasnier, W. H. Meyer, D. G. Nilson, G. D. Porter, M. Rensink, N. Wolf, R. D. Wood

Lawrence Livermore National Laboratory, Livermore, California, USA

N. H. Brooks, T. E. Evans, G. L. Jackson, A. W. Hyatt, A. W. Leonard, M. A. Mahdavi, T. W. Petrie, M. J. Schaffer, J. Smith, G. M. Staebler, R. D. Stambaugh, D. M. Thomas, W. P. West, C. P. C. Wong, and the DIII-D Physics and Operations Teams

General Atomics, P.O. Box 85608, San Diego, California 92186-9784, USA

R. Bastasz, W. Wampler, J. G. Watkins

Sandia National Laboratories, Albuquerque, New Mexico, USA

J. A. Boedo, J. W. Cuthbertson, R. Lehmer, R. A. Moyer, D. G. Whyte

University of California, San Diego, La Jolla, California, USA

J. N. Brooks

Argonne National Laboratory, Argonne, Illinois, USA

D. L. Hillis, J. Hogan, R. C. Isler, T. Jernigan, R. Maingi, P. K. Mioduszewski, L. W. Owen, M. R. Wade
Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA

Abstract.  We present recent progress towards an understanding of the physical processes in the divertor and scrape-off-layer (SOL) plasmas in DIII-D. This has been made possible by a combination of new diagnostics, improved computational models, and changes in divertor geometry. We have focused primarily on ELMing H-mode discharges. The physics of Partially Detached Divertor (PDD) plasmas, with divertor heat flux reduction by divertor radiation enhancement using D₂ puffing, has been studied in 2-D, and a model of the heat and particle transport has been developed that includes conduction, convection, ionization, recombination, and flows. Plasma and impurity particle flows have been measured with Mach probes and spectroscopy and these flows have been compared with the UEDGE model. The model now includes self-consistent calculations of carbon impurities. Impurity radiation has been increased in the divertor and SOL with ``puff and pump'' techniques using SOL D₂ puffing, divertor cryopumping, and argon puffing. The important physical processes in plasma-wall interactions have been examined with a DiMES probe, plasma characterization near the divertor plate, and the REDEP code. Experiments comparing single-null (SN) plasma operation in baffled and open divertors have demonstrated a change in the edge plasma profiles. These results are consistent with a reduction in the core ionization source calculated with UEDGE. Divertor particle control in ELMing H-mode with pumping and baffling has resulted in reduction in H-mode core densities to n_e/n_gw = 0.25. Divertor particle exhaust and heat flux has been studied as the plasma shape was varied from a lower SN, to a balanced double null (DN), and finally to an upper SN.

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