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17–22 Oct 2016
Kyoto International Conference Center
Japan timezone

Bifurcation of Quiescent H-mode to a Wide Pedestal Regime in DIII-D and Advances in the Understanding of Edge Harmonic Oscillations

19 Oct 2016, 14:20
20m
Kyoto International Conference Center

Kyoto International Conference Center

Takaragaike, Sakyo-ku, Kyoto 606-0001 Japan
Oral EXC - Magnetic Confinement Experiments: Confinement Pedestal & ELM Physics

Speaker

Dr Xi Chen (General Atomics)

Description

In a recent discovery, the Quiescent H-mode (QH-mode) regime in DIII-D has been found to bifurcate into a new state at low torque in double-null shaped plasmas, characterized by increased pedestal height, width and global confinement [1, 2]. This provides an alternate path for achieving high performance ELM-stable operation at low torque, in addition to the conventional QH-mode operation sustained at low-torque with applied 3D fields [3]. Measurements and simulation indicate that in the wide pedestal state, the decreased ExB shear destabilizes broadband turbulence, which relaxes edge pressure gradients, improves peeling-ballooning stability and enables a wider and thus higher pedestal and enhanced confinement. In parallel, new experimental study and modeling [4] of low, experimentally-relevant toroidal mode number (n≤5) Edge Harmonic Oscillation (EHO), which regulates the standard QH edge, validate the proposed importance of rotational shear in exciting the EHO. The ability to accurately simulate the EHO and maintain high performance QH-mode at low torque is an essential requirement for projecting QH-mode operation to ITER. [1] K.H. Burrell, et al., Plasma Phys. (in press) [2] Xi Chen, et al., Nucl. Fusion (H-mode workshop, 2015) [3] A.M. Garofalo, et al., Nucl. Fusion 51, 083018(2011) [4] Xi Chen, et al., Nucl. Fusion (submitted)
Country or International Organization USA
Paper Number EX/3-2

Primary author

Dr Xi Chen (General Atomics)

Co-authors

Mr A. M. Garofalo (General Atomics) B. Tobias (Princeton Plasma Physics Laboratory) Mr B.A. Grierson (Princeton Plasma Physics Laboratory) Dr C. Craig Petty (General Atomics) Dr C.M. Muscatello (General Atomics) Dr George R. McKee (University of Wisconsin-Madison) J.C. Rost (Massachusetts Institute of Technology) Dr Keith H. Burrell (General Atomics) Dr Kshitish Kumar Barada (UCLA, Los Angeles, USA) L. Zeng (University of California, Los Angeles) Dr M. Ono (Sokendai (Graduate University for Advanced Studies), Toki, Gifu, Japan) Dr N.C. Luhmann, Jr. (University of California, Davis) Dr Nathaniel M. Ferraro (General Atomics) Dr Philip B. Snyder (General Atomics) Mr R.J. Groebner (General Atomics) Dr Raffi Nazikian (Princeton Plasma Physics Laboratory) Dr T.H. Osborne (General Atomics) Dr T.L. Rhodes (University of California, Los Angeles) Dr Wayne M. Solomon (Princeton Plasma Physics Laboratory) Dr X. Ren (University of California, Davis) Zheng Yan (University of Wisconsin- Madison)

Presentation materials