Speaker
Mr
Keith H. Burrell
(USA)
Description
Recent DIII-D results demonstrate that quiescent H-mode (QH-mode) sustained by magnetic torque is a promising operating mode for future burning plasmas. We have produced steady, edge localized mode (ELM)-free, QH-mode plasmas with co-I_p neutral beam torque at reactor relevant levels. This was achieved by replacing the counter-I_p torque from neutral beam injection (NBI) with the torque due to neoclassical toroidal viscosity [1] produced by non-axisymmetric, non-resonant external magnetic fields. In addition, QH-mode plasmas have simultaneously demonstrated the reactor requirements of steady operation at the maximum stable pedestal pressure, ELM-free operation and rapid particle transport for helium exhaust in discharges which operate with constant density and radiated power [2]. Using n=3 non-resonant magnetic fields (NRMF) from two sets of non-axisymmetric coils, recent experiments have achieved long duration QH-modes with co-I_p NBI torque up to 1–1.3 Nm. Scaling from ITER, this co-I_p torque is 3 to 4 times the NBI torque that ITER will have [1]. These experiments utilized an ITER-relevant lower single-null plasma shape and were done with ITER-relevant values of nu_ped^*~0.1 and beta_T^ped~1%. The discharges exhibited confinement quality H_98y2=1.3, in the range required for ITER. In preliminary experiments only using n=3 fields from a coil outside the toroidal coil, QH-mode plasmas with low q_95=3.4 have reached normalized fusion gain values of G= beta_N H_89/q_95^2= 0.4, which is the desired value for ITER. Shots with the same coil configuration also operated with net zero NBI torque. The limits on G and co-I_p torque have not yet been established for this coil configuration. Peeling-ballooning stability calculations utilizing the EPED1 model predict that the H-mode edge pedestal in ITER will be in the stability region required for QH-mode operation [3].
[1] A.M. Garofalo, et al., Nucl. Fusion 51, 083018 (2011).
[2] K.H. Burrell, et al., Phys. Plasmas 12, 056121 (2005).
[3] K.H. Burrell, et al., Phys. Plasmas 19 (2012) to be published.
Work supported by the US Department of Energy under DE-FC02-04ER54698, DE-AC02-09ER54698 and DE-AC02-09CH11466.
Country or International Organization of Primary Author
USA
Primary author
Mr
Keith H. Burrell
(USA)
Co-authors
Dr
Andrea M. Garofalo
(General Atomics)
Dr
J.-K. Park
(Princeton Plasma Physics Laboratory)
Dr
Max E. Fenstermacher
(Lawrence Livermore National Laboratory)
Mr
Michael J. Schaffer
(General Atomics)
Dr
Philip B. Snyder
(General Atomics)
Dr
Tom H. Osborne
(General Atomics)
Dr
Wayne M. Solomon
(Princeton Plasma Physics Laboratory)
