The systematic investigation of energetic particle driven geodesic acoustic mode channeling using MEGA code

P2-14

* FHF . F - F , FH E -,G B @ ,BFG GHG : E HF B B G B @ ,BFG GHG F : GHE @ B FA @ I B B :F D

Introduction• EGAM is an Energetic Particle Driven Geodesic Acoustic Mode• EGAMs are observed in many devices including JET, DIII-D, LHD,

AUG, HL-2A, EAST, KSTAR et al.• EGAM channeling is investigated experimentally and

theoretically. [M. Osakabe FEC2014] [M. Sasaki PPFC 2011]• The hybrid code MEGA is used to simulate the EGAMs. Both

the energetic particles and bulk ions are described by kinetic equations.

Energy Transfer [H. Wang et al NF 2019]

• EGAM channeling is reproduced using MEGA code. From 0.1 ms to 0.15 ms, the average bulk ion heating power is 96.1 kW, or, 3.2 kW/m3.

• The sideband resonance is dominant during the energy transfer from EGAM to the bulk ions, and the transit frequencies of resonant bulk ions are half EGAM frequency.

Energy Transfer and Growth Rate

• Left: frequency chirps up as shown in the left column of poster.• Right: frequency roughly keeps constant.• During the chirping EGAM activities, EGAM channeling occurs

continuously in both linear growth stage and nonlinear saturated stage; while during the non-chirping EGAM activities, EGAM channeling occurs in the linear growth stage but terminates in the nonlinear saturated stage.

Energy Transfer Efficiency: Ph and ENBI

• The energy transfer efficiency increases with energetic particle pressure, but decreases with NBI velocity.

• Lower mode frequency makes higher energy transfer efficiency, because there is stronger interaction between lower frequency mode and bulk ions.

Energy transfer Efficiency: T and η

• The energy transfer efficiency does not change with temperature, because the ratio of ftr/fEGAM keeps constant.

• The energy transfer efficiency decreases with the increase of dissipation coefficient, because more energy dissipates by dissipation coefficient.

Isotope Effect

• The energy transfer efficiency of deuterium is less than that of hydrogen.• The possible reason: orbit width is changed by the factor of 2, and thus,

many basic properties are changed. Then, it is not appropriate to directly compare the energy transfer efficiency.

• The mode width becomes larger.

Summary• The properties of EGAM channeling are systematically investigated for

the first time.• During the chirping EGAM activities, EGAM channeling occurs

continuously in both linear stage and nonlinear stage; while in the non-chirping cases, EGAM channeling occurs only in the linear stage.

• Lower mode frequency makes higher energy transfer efficiency, because there is stronger interaction between lower frequency mode and bulk ions.

• The energy transfer efficiency does not change with temperature, because the ratio of ftr/fEGAM keeps constant.

• The energy transfer efficiency decreases with the increase of dissipation coefficient.

• The energy transfer efficiency of deuterium is less than that of hydrogen.

1018

1019

1020

1021

1022 b) 0.9keV1.3keV

2.4keV1.9keV

Neut

ralF

lux

[a.u

.]

-3-2-10123

a)δB

θ

δBθ [

x10-

6 T]

0

0.2

0.4

0.6

0.8

1

4.9 4.95 5 5.05

c)

Ti

eff.

T ief

f. [ke

V]

time[sec]

~7.5msDecay time = ~79.3ms

0.43keV

0.26keV

Experiment:Osakabe et al

Model: Todo et al

Energy transferFreq. spectrum

0

0.2

0.4

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0 1 2 3 4 5 6 7 0

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24

36

48

60

E ion

/EEP

Freq

uenc

y [k

Hz]

Te [keV] 0

0.2

0.4

0.6

0.8

1

0 4x10-7 8x10-7 0

0.0006

0.0012

0.0018

E ion

/EEP

Ampl

itude

[a.u

.]

resistivity [a.u.]