Title: Central ion cyclotron emission in the DIII-D tokamak

Abstract

Collective ion cyclotron emission (ICE) at the ion cyclotron frequency and its harmonics is a potential passive diagnostic of the fast-ion distribution in fusion reactors. ICE is observed in most plasmas in the DIII-D tokamak and is most strongly excited by the fast ions from neutral beam injection. The conventional outboard-edge ICE is detected in H-mode plasmas. However, weaker centrally-localized ICE is measured in L-mode plasmas, including those with negative triangularity shapes. Similar ICE spectra are found with both ICE diagnostics systems, the dedicated magnetic probes and the instrumented antenna straps. Many differences in the behavior of this central ICE are generated by varying the deuterium beam injection angle into deuterium plasmas. The co-current 'near-perpendicular' beam excites the most central ICE from the co-current beams, with this emission detected from the fundamental to the fifth ICE harmonic. However, the counter-current 'near-tangential' beam destabilizes the highest amounts of centrally-localized ICE. This emission is spectrally broader than that driven by the co-current beams and is observed up to its seventh ICE harmonic. The central ICE excited by this co-current beam correlated strongly on the local electron density and related parameters (plasma current and neutron rate) and increased with deeper fast-ion loss boundariesmore » towards the magnetic axis. This was also the case with second harmonic ICE driven by the counter-current beam but not with its stronger third harmonic emission. The central ICE harmonics destabilized by both beams are observed to have different temporal dynamics. The central ICE amplitude responds rapidly to transient MHD events; it dropped and recovered in less than a millisecond at each sawtooth event. ICE frequency splitting is triggered by both the co-current and counter-current 'near-tangential' beams. The data presented provide opportunities to test and validate models of excitation of ICE by energetic ions.« less

Authors:

Thome, K. E.  ^[1];

• Search DOE PAGES for author "Thome, K. E."
• Search DOE PAGES for ORCID "0000-0002-4801-3922"

Pace, D. C.  ^[1];

• Search DOE PAGES for author "Pace, D. C."
• Search DOE PAGES for ORCID "0000-0002-7039-0011"

Pinsker, R. I.  ^[1];

• Search DOE PAGES for author "Pinsker, R. I."
• Search DOE PAGES for ORCID "0000-0003-2683-9480"

Van Zeeland, M. A.  ^[1];

• Search DOE PAGES for author "Van Zeeland, M. A."
• Search DOE PAGES for ORCID "0000-0002-7911-2739"

Heidbrink, W. W.  ^[2];

• Search DOE PAGES for author "Heidbrink, W. W."
• Search DOE PAGES for ORCID "0000-0002-6942-8043"

Austin, M. E.  ^[3]

• Search DOE PAGES for author "Austin, M. E."
• Search DOE PAGES for ORCID "0000-0002-0017-8605"

---

+ Show Author Affiliations

1. General Atomics, San Diego, CA (United States)
2. Univ. of California, Irvine, CA (United States)
3. Univ. of Texas, Austin, TX (United States). Inst. for Fusion Studies

Publication Date:

Fri May 10 00:00:00 EDT 2019

Research Org.:

General Atomics, San Diego, CA (United States); Univ. of Texas, Austin, TX (United States)

Sponsoring Org.:

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

OSTI Identifier:

1542180

Grant/Contract Number:  

FC02-04ER54698; FG03-97ER54415

Resource Type:

Accepted Manuscript

Journal Name:

Nuclear Fusion

Additional Journal Information:

Journal Volume: 59; Journal Issue: 8; Journal ID: ISSN 0029-5515

Publisher:

IOP Science

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY