Speaker
Dr
Thomas W. Petrie
(General Atomics)
Description
Results are reported and interpretation made of recent experiments on DIII-D that assess the effectiveness of three innovative tokamak divertor concepts under radiating divertor (RD) conditions: (1) high performance standard double-null divertor (DND) plasmas, (2) high performance double-null “snowflake” (SF-DN) plasmas, and (3) single-null H-mode plasmas with different parallel connection lengths between their X-points and outer divertor targets (L||-XPT). In general, all three concepts are attractive, with reduced heat flux and good H-mode confinement. Significant reductions in peak divertor heat flux (q⊥,P) of more than 50% and 85% at the outer and inner targets, respectively, were observed in DND plasmas under neon/deuterium-based RD conditions, and high performance metrics were maintained, e.g., βN ≅ 3.0 and H98(Y,2) ≅ 1.35. Under these RD conditions, <20% of the input power (≈10-13 MW) was radiated in the core, while >40% outside the main plasma. Impurity injection from poloidal locations other than the private flux region opposite the Bx∇B drift direction produced high levels of fuel dilution. High performance SF-DN plasmas mirrored the DND results under similar RD conditions. While the heat flux profiles at the inner target of the SF-DN and DND plasmas behaved similarly under comparable RD conditions, q⊥,P at its outer divertor target of the SF-DN cases was generally about a factor of two lower. Impurity build up in the main plasma, however, was 15%-20% higher in the SF-DN, due in part to difficulty in pumping the broad density profile under the outer divertor leg of the SF-DN. Plasmas with longer L||-XPT had lower q⊥,P than those with the shorter L||-XPT. SOLPS modeling has indicated that cross-field transport between the X-point and the divertor target resulted in broadened heat flux profiles and reduced q⊥,P. Under similar RD conditions, the longer L||,XPT cases maintained lower q⊥,P by at least 50%. Partial detachment at the outer divertor under RD conditions occurred at lower bar_ne in the longer L||,XPT cases. This study represents a first systematic step in examining three potential solutions to the excessive power loading expected in future generation high-powered tokamaks.
This work was supported in part by the US DOE under DE-FC02-04ER54698, DE-AC52-07NA27344, DE-AC05-00OR22725, DE-FG02-07ER54917, DE-FG02-04ER54541, and DE-AC04-94AL85000.
| Country or International Organisation | USA |
|---|---|
| Paper Number | EX/P2-26 |
Primary author
Dr
Thomas W. Petrie
(General Atomics)
Co-authors
Dr
Adam G. McLean
(Lawrence Livermore National Laboratory)
Dr
Al W. Hyatt
(General Atomics)
Dr
Anthony W. Leonard
(General Atomics)
Dr
Charles J. Lasnier
(Lawrence Livermore National Laboratory)
Dr
Christopher T. Holcomb
(Lawrence Livermore National Laboratory)
Dr
Egemen Kolemen
(PPPL)
Dr
Francesca Turco
(Columbia University)
John Canik
(Oak Ridge National Laboratory)
Dr
John Ferron
(General Atomics)
Dr
Jon G. Watkins
(Sandia National Laboratories)
Dr
Max E. Fenstermacher
(Lawrence Livermore National Laboratory)
Mr
R.J. Groebner
(General Atomics)
Dr
Rajesh Maingi
(Oak Ridge National Laboratory)
Dr
Richard Moyer
(University of California San Diego)
Dr
Robert J. La Haye
(General Atomics)
Dr
Steve L. Allen
(Lawrence Livermore National Laboratory)
Dr
Timothy C. Luce
(General Atomics)
Dr
Vsevolod Soukhanovskii
(Lawrence Livermore National Laboratory)
Dr
Wayne M. Solomon
(Princeton Plasma Physics Laboratory)
