The radial phase variation of reversed-shear and toroidicity-induced Alfvén eigenmodes in DIII-D

Heidbrink, W. W.; Hansen, E. C.; Austin, M. E.; Kramer, G. J.; Van Zeeland, M. A.

doi:10.1088/1741-4326/ac5109

Title: The radial phase variation of reversed-shear and toroidicity-induced Alfvén eigenmodes in DIII-D

Journal Article · Tue Apr 05 00:00:00 EDT 2022 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/ac5109· OSTI ID:1873489

^[1]; Hansen, E. C. ^[2]; Austin, M. E. ^[3];

^[4];

^[5]

Univ. of California, Irvine, CA (United States)
Univ. of California, Irvine, CA (United States); Univ. of Texas, Austin, TX (United States)
Univ. of Texas, Austin, TX (United States)
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
General Atomics, San Diego, CA (United States)

The eigenfunction of an instability contains information about energy flow in the wave. Here, the amplitude and phase of electron cyclotron emission radiometer data from hundreds of DIII-D reversed shear Alfvén eigenmodes (RSAE) and toroidicity-induced Alfvén eigenmodes (TAE) are analyzed along the outboard horizontal midplane. The radial phase profile can be flat, linearly rising or falling, convex or concave; in other words, a wide variety of shapes is observed. For a particular mode, often the radial phase profile remains approximately constant as the mode evolves in time but sometimes it changes rapidly. Many TAEs and some RSAEs have phase profiles that are rather flat where the mode amplitude is largest but rise steadily by ~2π at large major radius. Rapid phase changes are observed when the frequencies of an RSAE and TAE overlap and the modes couple. The phase profile depends weakly on the fast-ion gradient that would appear in the absence of wave-induced transport. Linear and quadratic fits to the phase profiles, together with many plasma parameters, are assembled into RSAE and TAE databases. In both cases, large variability is observed. For RSAEs, the strongest phase dependencies are on electron temperature T_e, RSAE mode frequency, and the density of carbon impurities. For TAEs, the strongest dependencies are on beam power and major radius of the mode. In general, the average RSAE radial phase profile is essentially flat but the TAE profile has non-zero slope and curvature.

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Research Organization:: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); General Atomics, San Diego, CA (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: FC02-04ER54698; SC0019352; SC0020337

OSTI ID:: 1873489

Alternate ID(s):: OSTI ID: 1877857

Report Number(s):: DOE-GA-54698; TRN: US2307042

Journal Information:: Nuclear Fusion, Vol. 62, Issue 6; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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Title: The radial phase variation of reversed-shear and toroidicity-induced Alfvén eigenmodes in DIII-D

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