Comparison of radiating divertor behaviour in single-null and double-null plasmas in DIII-D

Journal Article · Tue Jan 01 04:00:00 EST 2008 · Nuclear Fusion

DOI:https://doi.org/10.1088/0029-5515/48/4/045010· OSTI ID:1014262

Petrie, T W ^[1]; Brooks, N. H. ^[1]; Fenstermacher, M. E. ^[2]; Groth, M. ^[2]; Hyatt, A. W. ^[1]; Isler, R. C. ^[3]; Lasnier, C. J. ^[2]; Leonard, A. W. ^[4]; Porter, G. D. ^[2]; Schaffer, M. J. ^[1]; Watkins, J. G. ^[5]; Wade, M R ^[1]; West, W. P. ^[1]

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1. General Atomics, San Diego
2. Lawrence Livermore National Laboratory (LLNL)
3. Oak Ridge National Laboratory (ORNL)
4. General Atomics
5. Sandia National Laboratories (SNL)

Puff-and-pump' radiating divertor scenarios, applied to both upper single-null (SN) and double-null (DN) H-mode plasmas, result in a 30-60% increase in radiated power with little or no decrease in tau(E). Argon was injected into the private flux region of the upper divertor, and plasma flow into the upper divertor was enhanced by a combination of deuterium gas puffing upstream of the divertor targets and particle pumping at the targets. For the same constant deuterium injection rate, argon penetrated the main plasma of SNs more rapidly and reached a higher steady-state concentration when the B x del B-ion drift direction was towards the divertor (V-del B up arrow) rather than away from the divertor (V-del B down arrow). We also found that the initial rate at which argon accumulated inside DN plasmas was more than twice that of comparable SN plasmas having the same B x del B-ion drift direction. In DNs, the radiated power was not shared equally between divertors during argon injection. Only when the B x del B ion drift direction was away from the divertor were both significant increases in divertor radiated power and an accumulation of argon in the divertor observed, based on spectroscopic measurements of Ar II. Our data suggest that an unbalanced DN shape where the B x del B-ion drift is directed away from the dominant divertor may provide the best chance of successfully coupling a radiating divertor approach with a higher performance H-mode plasma.

• Research Organization: Oak Ridge National Laboratory (ORNL)
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1014262
• Journal Information: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 4 Vol. 48; ISSN 0029-5515
• Country of Publication: United States
• Language: English