Title: Modelling the Alfvén eigenmode induced fast-ion flow measured by an imaging neutral particle analyzer

Abstract

An imaging neutral particle analyzer (INPA) provides energy and radially resolved measurements of the confined fast-ion population ranging from the high-field side to the edge on the midplane of the DIII-D tokamak. In recent experiments, it was used to diagnose fast-ion flow in the INPA-interrogated phase-space driven by multiple, marginally unstable Alfvén eigenmodes (AEs). Here, the key features of this measured fast-ion flow are: (I) a fast-ion flow from q_min and the injection energy (81 keV) towards lower energies and plasma periphery.(II) A flow from the same location towards higher energies and the plasma core, (III) a phase-space 'hole' at the injected energy and plasma core and (IV) a pile-up at the plasma core at lower energies (~60 keV). Ad hoc energetic particle diffusivity modelling of TRANSP significantly deviates from the observation. Comparably, a reduced modelling, i.e. a combination of NOVA-K and ASCOT5 code with the measured mode structure and amplitude, generally reproduce some key features of the observed phase-space flow, but largely failed to interpret fast ion depletion near the plasma axis. At last, self-consistent, first-principle multi-phase hybrid simulations that include realistic neutral beam injection and collisions are able to reproduce most features of the time-resolved phase-space flow. Duringmore » consecutive hybrid phases, an RSAE consistent with the experiment grows and saturates, redistributing the injected fast ions. The resulting synthetic INPA images are in good agreement with the measurement near the injection energy. The simulations track the fast-ion redistribution within the INPA range, confirming that the measured fast-ion flow follows streamlines defined by the intersection of phase-space surfaces of constant magnetic moment μ and constant E' = nE + ωP_φ, where n and ω are the instability toroidal mode number and frequency, and E and P_φ the ion energy and toroidal canonical momentum. Nonperturbative effects are required to reproduce the depletion of fast ions near the magnetic axis at the injection energy.« less

Authors:

Gonzalez-Martin, J.  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-3237-5195"

Du, X. D.  ^[2];

• Search DOE PAGES for author "Du, X. D."
• Search DOE PAGES for ORCID "0000-0001-6127-2825"

Heidbrink, W. W.  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-6942-8043"

Van Zeeland, M. A.  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-7911-2739"

Särkimäki, K.  ^[3];

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• Search DOE PAGES for ORCID "0000-0001-9156-2559"

Snicker, A.  ^[4];

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• Search DOE PAGES for ORCID "0000-0001-9604-9666"

Wang, X. ^[3]; Todo, Y.  ^[5]

• Search DOE PAGES for author "Todo, Y."
• Search DOE PAGES for ORCID "0000-0001-9323-8285"

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+ Show Author Affiliations

1. Univ. of California, Irvine, CA (United States)
2. General Atomics, San Diego, CA (United States)
3. Max Planck Inst. for Plasma Physics, Garching bei Munchen (Germany)
4. Aalto Univ. (Finland)
5. National Inst. for Fusion Science, Toki (Japan)

Publication Date:

Thu Sep 29 00:00:00 EDT 2022

Research Org.:

General Atomics, San Diego, CA (United States); Univ. of California, Irvine, CA (United States)

Sponsoring Org.:

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

OSTI Identifier:

1894950

Grant/Contract Number:  

FC02-04ER54698; SC0020337; AC05-00OR22725; AC02-09CH11466; SC0015878

Resource Type:

Accepted Manuscript

Journal Name:

Nuclear Fusion

Additional Journal Information:

Journal Volume: 62; Journal Issue: 11; Journal ID: ISSN 0029-5515

Publisher:

IOP Science

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY