Title: Alfvén eigenmode stability and critical gradient energetic particle transport using the Trapped-Gyro-Landau-Fluid model

Abstract

The Trapped-Gyro-Landau-Fluid (TGLF) transport model is a physically realistic and comprehensive theory based on a local quasilinear transport model fitted to linear and nonlinear GYRO gyrokinetic simulations [Staebler et al., Phys. Plasmas 14, 55909 (2007)]. This work presents the first use of the TGLF model to treat low-n Alfvén eigenmode (AE) stability and energetic particle (EP) transport. TGLF accurately recovers the local GYRO toroidicity-induced AE (TAE) and energetic particle mode (EPM) linear growth and frequency rates for a fusion alpha case. With a very high grid resolution, TGLF can quickly find the critical EP pressure gradient profile for stiff EP transport based on an AE linear threshold given the background thermal plasma profiles in DIII-D. The TGLF critical gradient profile using the recipe γ_AE=0, that is the linear AE growth rate without additional driving rates from the background plasma gradients, matches the more expensive linear GYRO results with a single worst toroidal mode number n. TGLF can easily find the minimum critical gradient profile with testing multiple ns. From a database of runs using a newly developed TGLFEP code, a rough but insightful parametric “power law” scaling for critical EP beta is demonstrated. An important toroidal stabilization condition on the EP pressure gradient p_EP/L$$EP\atop{p}$$ drive is isolated: R/L$$EP\atop{p}$$ > C_R ~ 3, where L$$EP\atop{p}$$ is the EP pressure gradient length and R is the tokamak major radius. This paper also demonstrates that relaxation of the fixed slowing down EP profile shape approximation often used to find the critical EP density profile has little effect on the resulting EP transport. The single EP species critical gradient model is generalized to handle two EP species.

Authors:

Sheng, He ^[1]; Waltz, R. E.  ^[2];

• Search DOE PAGES for author "Waltz, R. E."
• Search DOE PAGES for ORCID "0000-0002-5203-4830"

Staebler, G. M.  ^[2]

• Search DOE PAGES for author "Staebler, G. M."
• Search DOE PAGES for ORCID "0000-0002-1944-1733"

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+ Show Author Affiliations

1. Peking Univ., Beijing (China). School of Physics, State Key Lab. of Nuclear Physics
2. General Atomics, San Diego, CA (United States)

Publication Date:

Thu Jun 29 00:00:00 EDT 2017

Research Org.:

General Atomics, San Diego, CA (United States)

Sponsoring Org.:

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

OSTI Identifier:

1474303

Alternate Identifier(s):

OSTI ID: 1367361

Grant/Contract Number:  

FG02-95ER54309; FC02-08ER54977

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 24; Journal Issue: 7; Journal ID: ISSN 1070-664X

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY