(IA) Session Report

May 28, 2024 (M.Goto)

Date: May 24, 2024
Time: 10:25 – 14:45
Shot#: 191878– 191965 (88 shots)
Prior wall conditioning: No
Divertor pump: Off
Gas puff: H2, Ar
Pellet: No
NBI#(1, 2, 3, 4, 5) = gas(H, H, H, H, He)=P(4.0, 2.1, 2.0, 3.5, max 3.8) MW
ECH(77GHz) = ant(1.5-Uo, 5.5-U, 2-OUR)=P( -, 0.698, 0.38) MW
ECH(154GHz) = ant(2-OLL, 2-OUL, 2-OLR)=P(0.70, 0.806, 0.980) MW
ICH(3.5U, 3.5L, 4.5U, 4.5L) = P(-, -, -, -) MWTopics
1. Sub-Alfvenic harmonic ICEs modulated by He beam injection (G. Yun(POSTECH), H. Igami)
2. Excitation of ultra higher harmonic ICEs with MHD instabilities during He beam injection (H. Igami)
3. Comparison of turbulent transport between LHD and W7-X (H. Sakai (Kyushu U.), K. Tanaka)

-Sub-Alfvenic harmonic ICEs modulated by He beam injection-Excitation of ultra higher harmonic ICEs with MHD instabilities during He beam injection
G. Yun, S. Hong, H. Igami

Shot #: 191879-191965 Magnetic configuration: (Rax, Polarity, Bt, γ, Bq) = (3.60, CW, 2.75, 1.2538, 100),
Background and motivation:

Control parameters:- background density- beam energy of BL5 (45, 53, 60 and 65 keV)- number of ion sources of BL5* Plasma sustained by tangential NBs and 5 ECH

Energetic ions can transfer energy to waves, which isan important dissipation mechanism in plasma andcan be utilized for diagnostics of fusion-born alphaparticles and beam ions.
We investigate the bursts of sub-Alfvenic harmonic
ICEs and very high order harmonic ICEs driven by He
beam ions, as a proxy to fusion-born alpha particles.
We aim to find the conditions of ICE burst events bychanging the position of the superposition resonance.

PatternABCDEFGH# of Ion Sources

2

2

2

2

1

1

3

4BL5(He)
Beam Energy (keV)

6560

53

45

45

60

4545

Sub-Alfvenic harmonic ICEs modulated by He beam injection
Excitation of ultra higher harmonic ICEs with MHD instabilities during He beam injection
G. Yun, S. Hong, H. IgamiResults• At the same beam energy, larger RF burst occurred at lower density even with lower
number of the ion sources• At the same energy and same density, the peak intensities and RF bursts are larger withlarger number of ion sources

45keV BL5 He beam
E 45keV, 1sources.
ne :1.5e19 vb/vA : 0.45
BL4(H)
BL5(He)As the density decreases, the ratio of V_beam/V_A decreases.
D 45keV, 2sources.
ne :2.5e19, vb/vA : 0.58

G 45keV, 3 sources
ne :2.5e19 vb/vA : 0.58

H 45keV 4 sources
ne :3e19 vb/vA : 0.64

Sub-Alfvenic harmonic ICEs modulated by He beam injection
Excitation of ultra higher harmonic ICEs with MHD instabilities during He beam injection
G. Yun, S. Hong, H. Igami

Results• RF bursts were prominent for 𝑣beam Τ𝑣𝐴 < 0.65 with beam energies 45, 53, 60, and 65 keV• With the same injection power, RF bursts were more prominent at larger beam energy• Chirping-up were observed for high beam energy and low density cases (e.g. 65keV, 2e19m^-3).

H 45keV 4 sources
ne :3e19 vb/vA : 0.64

C 53keV, 2sources.
n_e:2.5e19, vb/vA : 0.63

Same injection power

B 60keV, 2sources.
n_e:2e19, vb/vA : 0.60

A 65 keV, 2sources.
n_e:2e19, vb/vA : 0.62

Chirping-up

Sub-Alfvenic harmonic ICEs modulated by He beam injection
Excitation of ultra higher harmonic ICEs with MHD instabilities during He beam injection
G. Yun, S. Hong, H. Igami

Results• RF bursts were not observed 𝑣beam Τ𝑣𝐴 > 0.8
A 65 keV, 2sources.
B 60keV, 2sources.
C 53keV, 2sources.
n_e:4e19, vb/vA :0.88
n_e:4e19, vb/vA : 0.84
n_e:4e19, vb/vA : 0.80

Conclusion • Prominent RF bursts were observed for 𝑣beam Τ𝑣𝐴 < 0.65 for each scanned beam energy• RF intensities are stronger with higher beam energy and lower density.
• We plan to analyze spectra of RF signals in detail to identify the condition of ICE bursts.

Comparison of turbulence driven transport between LHD and W7-X (He/H-case as piggy-back)H. Sakai (Kyushu Univ.), K. Tanaka

Turbulence level [a.u.]
ne_turb/ne_bar

0.40:He:H20123450.15
0.10.05
06:He:H20.20123

ne_barne_bar [1019 m-3]

✓ High bulk ion purity could be realized in the density range
between 1.2x-5.0x in He and 0.6x-4.8x in H. The fine density
scan was successful and turbulence transition was observedin both cases (It should be noted that the ECH power wasdifferent).

✓ Detail analyses, e.g. turbulence analysis on PCI and heattransport analysis will be performed.

>70%0.2Result456[1019 m-3]

ECH power: 2MW, ne_bar: 1.5x in W7-X, 1.59x in LHD
276

1.5

ne [1019 m-3]

✓ Comparative data on ne and Te profiles by TS could beobtained between two devices in similar line-averaged
electron density and heating power.

0.6

14
3
2:W7-X:LHD

0.5

0:W7-X:LHD5

Te [keV]At 4/19, our experiment was not conducted well due to ECH
trouble. Therefore, the experiment was re-conducted as piggyback at 5/23 and 24, in Masuzaki-san(for He-rich) and Igamisan(for H-rich)’s machine time respectively. Flat-top electron
density was scanned shot-by shot between 0.5x to 5.0x.

Bulk ion purity

Shot No: #191770~191813 (piggy-back, 5/23), #191880~191959 (piggy-back, 5/24)
Experimental conditions: (Rax, Polarity, Bt, γ, Bq) = (3.6 m, CCW(5/23)/CW(5/24), 2.75 T, 1.2538, 100 %)0.3
1
Gas-puff: He(5/23), H2(5/24)
0.25
0.8
Approach

1000.2

0.4

0.6

reff/a99

0.8

100.2

0.4

0.6

reff/a990.81