Speaker
Mr
Gary L. Jackson
(USA)
Description
Long duration plasmas, stable to m/n=2/1 tearing modes (TM), with an ITER similar shape and an ITER similar value of I_p/aB_T have been demonstrated in DIII-D, evolving to stationary conditions with the most stable operating point at beta_N approximately 2. Lower beta_N, corresponding to an ITER baseline scenario 2 value of 1.8, led to a higher probability of m/n=2/1 tearing modes modes, which is the opposite of predictions from neoclassical tearing mode theory. These plasmas (delta t_duration less equal 7.5 s and less equal 11tau_R), without electron cyclo¬tron current drive (ECCD) for TM mitigation, have extended shorter pulse experiments in which the internal inductance was continually evolving [1] often until rotating m/n=2/1 TMs or locked modes occurred, which are a concern for ITER operation.
Although long-pulse plasmas have reached sta¬tionary conditions, in some cases with similar programming m/n=2/1 TMs and locked modes limited the duration, indicating operation near stability limits. In addition to the plasmas described above, the use of ECCD, broadly deposited near q=3/2, allowed stable operation in plasmas with reduced torque which were otherwise found to be 2/1 TM unstable. We note that direct stabilization of 2/1 TMs was not attempted in these experiments.
With one toroidal row of the DIII-D internal coil set (n=3 configuration) and broad ECCD for 2/1 TM mitigation, edge localized mode suppression with periods up to 1 s was observed (q_95=3.15) in plasmas with an ITER similar shape.
This work was supported by the US Department of Energy under DE-FC02-04ER54698, DE-AC02-09CH11466, DE-FG02-04ER54761, and DE-FG02-08ER54984.
[1] F. Turco and T.C. Luce, Nucl. Fusion 50 (2010) 095010.
Country or International Organization of Primary Author
USA
Primary author
Mr
Gary L. Jackson
(USA)
Co-authors
Mr
Alan W. Hyatt
(General Atomics)
Dr
Edward J. Doyle
(University of California Los Angeles)
Ms
Francesca Turco
(Columbia University)
Dr
John R. Ferron
(General Atomics)
Dr
Mickey R. Wade
(General Atomics)
Dr
Peter A. Politzer
(General Atomics)
Dr
Richard J. Buttery
(General Atomics)
Dr
Robert J. La Haye
(General Atomics)
Dr
Timothy C. Luce
(General Atomics)
Dr
Wayne M. Solomon
(Princeton Plasma Physics Laboratory)
