7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Effect of global field perturbations on fast ion redistribution and losses intoroidal plasmas
G.Z. Hao1, Y.Q.Liu2, G.Q. Dong1, G.M. Yang1, Y.F. Zhao3 ,S.Wang1 and Y. Q. Wang1
1
Southwestern Institute of Physics, Chengdu, China
2
General Atomics, San Diego, CA, USA
3Dalian University of Technology, Chinae-mail (speaker): haogz@swip.ac.cn
The confinement of fast ions is very important forachieving and maintaining high performance of tokamak
plasma, However, the global field perturbations, such as
the MHD instabilities and the externally applied resonant
magnetic perturbation, degrade the fast ion confinement,
and induce fast ion losses [1]. However, the dependenceof fast ion redistribution and losses on the mode structure,
frequency and amplitude is not yet clear, and requires
more investigations. In this presentation, we briefly
introduce recent progress of numerical studies on theeffects of global field perturbations on fast ion
redistribution and losses in toroidal plasmas, carried outin SWIP.
The kinds of perturbations include resistive wall mode
(RWM), fishbone-like mode (FLM), fishbone mode andexternally applied resonant magnetic perturbations(RMP) [2]. The main conclusions are shown below. (i)As the amplitude of FLM increases, the loss mechanism
converts from convective type to diffusion one. The fast
ion loss rate is sensitive to the mode frequency. The
numerical results agree well with the experimental
measurements from DIII-D [3]. (ii) The resistive RWM
significantly enhances the fast ion losses, compared withthe case of ideal RWM. (iii) For ITER device, theinternal kink or fishbone mainly induces the fast ion
redistribution and has neglectable effect on fast ion
losses. (iv) A threshold of RMP coil current for fast ion
losses is predicted. In addition, the mixed dominantcomponent and secondary sideband of RMPs greatly
enhances the fast ion losses, compared with that for thedominant harmonic alone. The results are in good
agreement with the experiment results on ASDEX-U andKSTAR.
This work is supported by the National Magnetic
Confinement Fusion Energy R&D Program (No.
2022YFE03060002), Youth Science and technology
innovation teamofSichuanprovince (No.
2022JDTD0003), CNNC Research Program (No.
CNNC-JCYJ-202236). The work is also supported byUS DoE Office of Science under Contract
DE-FG02-95ER54309 and DE-FC02-04ER54698.
References[1] Y.Q.Liu et.al., Nucl. Fusion 62, 066011 (2022)[2] G.Z.Hao et.al., Nucl. Fusion 61, 126031 (2021).
[3] Y.Q. Wang et.al., Nucl. Fusion, 63, 026003, (2023)[4] G.M.Yang et.al., Plasma Sci. Technol, 25, 055102,(2023)

IFigure 1. The defined fast ion redistribution factor I
versus the external kink perturbation amplitude with(solid curve) and without (dashed curve) pitch angle
scattering induced by the Coulomb collision. Thefilled dots show the calculated results, while thecurves are the fitting results. Linear and secondary
polynomial fittings are applied in the regions 0 <𝛿𝐵𝑟/𝐵 < 0.007 and 0.01 < 𝛿𝐵𝑟/𝐵 < 0.02,respectively.

Figure 2. Loss rate of fast ions as a function of theinitially launched radial position for the case with
only 𝑛 = 2 component (in blue) and with both the𝑛 = 2 and 𝑛 = 6 components (in red). Here, adouble-null reference equilibrium for the HL-2M
device is adopted. The resistive plasma response isincluded in the computation of total RMP fields. A
10 kAt RMP coil current with coil phasing between
the upper and lower rows of RMP coils being −90◦
for the n = 2 RMP component is assumed.