Theoretical analysis of key factors achieving reversed magnetic shear q-profiles sustained with lower hybrid waves on EAST

Zhai, X. M.; Xiang, N.; Chen, J. L.; Bonoli, P. T.; Shiraiwa, S.; Garofalo, A. M.; Yang, C.; Li, M. H.; Qian, J. P.; Li, G. Q.; Li, K.; Liu, H. Q.; Lyu, B.; Zang, Q.

doi:10.1088/1361-6587/aaffe5

Theoretical analysis of key factors achieving reversed magnetic shear q-profiles sustained with lower hybrid waves on EAST

Journal Article · Fri Feb 15 00:00:00 EST 2019 · Plasma Physics and Controlled Fusion

DOI:https://doi.org/10.1088/1361-6587/aaffe5· OSTI ID:1611429

^[1]; Xiang, N. ^[2]; ^[2]; Bonoli, P. T. ^[3]; Shiraiwa, S. ^[3]; ^[4]; Yang, C. ^[2]; ^[2]; Qian, J. P. ^[2]; ^[2]; Li, K. ^[2]; Liu, H. Q. ^[2]; ^[2]; Zang, Q. ^[2]

Chinese Academy of Sciences (CAS), Hefei (China); University of Chinese Academy of Sciences, Beijing (China); OSTI
Chinese Academy of Sciences (CAS), Hefei (China)
Massachusetts Institute of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
General Atomics, San Diego, CA (United States)

The phase space analysis technique is applied to provide new insights into the fully non-inductive lower hybrid current driven (LHCD) discharges on EAST. The analysis shows that there are bounded and unbounded topologies of lower hybrid (LH) waves in phase space. For typical parameters on EAST, the propagation domain for 4.6 GHz LH waves is bounded, while unbounded for 2.45 GHz LH waves and one of the conditions is recognized to be good for achieving an off-axis current profile driven by 4.6 GHz LH waves on EAST. The parametric analysis on the potential power deposition (PPD) region for those experiments demonstrates that the reversed magnetic shear dominates the wave behavior, and confines the LH power absorption to the far off-axis region as long as it occurs in the 4.6 GHz dominated LHCD discharge. GENRAY/CQL3D simulations also confirm this effect of reversed shear on the power absorption of 4.6 GHz waves. A bounded propagation domain and a positive feedback loop between magnetic shear reversal and off-axis LHCD profile could explain the LH-only-sustained strong reversed magnetic shear observed in experiments on multiple machines. In contrast, there is no such effect for 2.45 GHz waves on EAST since the PPD region is less sensitive to the change of reversed shear due to the unbounded propagation domain.

View Accepted Manuscript (DOE)

Research Organization:: Massachusetts Institute of Technology (MIT), Cambridge, MA (United States)

Sponsoring Organization:: National ITER program of China; National Key R&D Program of China; National Natural Science Foundation of China; USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: SC0010492

OSTI ID:: 1611429

Alternate ID(s):: OSTI ID: 23002119

Report Number(s):: PPCF-102064

Journal Information:: Plasma Physics and Controlled Fusion, Journal Name: Plasma Physics and Controlled Fusion Journal Issue: 4 Vol. 61; ISSN 0741-3335

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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