(IA) Session Report

June 11, 2024 (H. Funaba)

Date: June 7, 2024
Time: 10:25 – 16:45
Shot#: 192843– 192928 (86 shots)
Prior wall conditioning: No
Divertor pump: Off
Gas puff: H2
Pellet: No
NBI#(1, 2, 3, 4, 5) = gas(H, H, H, H, H)=P(4.6,2.9, 3.2, 3.5, 2.8) MW
ECH(77GHz) = ant(1.5-Uo, 5.5-U, 2-OUR)=P( -, 0.698, 0.380) MW
ECH(154GHz) = ant(2-OLL, 2-OUL, 2-OLR)=P(0.705, 0.806, 0.982) MW
ECH(116GHz) = ant(2-OLR)=P(0.629) MWICH(3.5U, 3.5L, 4.5U, 4.5L) = P(-, -, -, -) MW
Topics
1. Development of C-ECE for measuring temperature fluctuation inside/outside e-ITB (M. Gong (U. Tokyo),M. Nishiura))
2. MHD instability suppression by RMP field (S. Ito, K.Y. Watanabe)
3. Plasma shape effect on bootstrap current in high collisional regime in LHD (O. Mitarai, K.Y. Watanabe)data_oct24(shot-time)_local+global+2024
Resistive Interchange Instability suppression by Ext.-RMP(S.Ito[, K.Y.Watanabe])10

Background and motivation:
According to our previous work, RIC (Resistive InterChange) instability is
known to be suppreseed by external RMP, and the empirical scaling law of ext.
RMP amplitude to suppress the RIC completely was found as the following;

AdditionalDataset

1“Ext.-RMP amplitude to completely suppress RIC”
= 𝟐. 𝟑 × 𝟏𝟎𝟑 ・𝜷𝟏.𝟖 ・𝝂 ∗𝟎.𝟐𝟒 ・𝝆 ∗𝟎.𝟖𝟓
However, the exponent of β and ν* would not be accurate because the data, weused for our analysis, has high correlation between β and ν*. Now, we get theadditional dataset to decrease the correlation between β and ν* to improveaccuracy of the above scaling on β and ν*.
Experimental conditions:(Rax, Polarity, Bt, γ, Bq) = (3.75m, CW, 2T/1.5T/0.6T, 1.2538, 100%);#192872-88(2T), 192889-99(1T), 192900-12(0.6T)
Results:
The dataset is extended as shown in the right-top figure. Now we are improving
the scaling law of ext. RMP amplitude to suppress the RIC completely. However,the correlation between β and ν*.looks still high.
Next, we will check the correlation under the same normalized ion Lamour radius.

0.1A0.2F

0.4 0.6 0.8 1
192881-887_br.qpc

2<> %1.5

B0=2T<>~0.8%ei/*h~0.2

10.500<>~0.4%
ei/*h ~0.8200

400IRMP

600

800[A]results(tentative)

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2024June7-byOM_ne-Te0.qpc

Plasma shape effect on BSC in high collisional regime

3.75m/B 0%q
3.75m/B 100%
(O.Mitarai[, K.Y.Watanabe])q

Background and motivation:
2According to a helical fusion reactor design, there is a possibility the BSC(BootStrapCurrent) affect the MHD equilibrium and instability. We already investigated the BSC
13.75m/Bq0%
dependence on the magnetic axis location and the collisionality, and found that it is 2024June7-byOM_ne-Ip.qpc
3.75mBq100%
reduced in more torus-inward magnetic axis and in more collisional regime. Now, we
3.75m/Bq0%
0focus on the magnetic surface shape effect on the BSC. According to a theoretical
01233.75m/B
4
5 100%
67819 -3 q10n
[10 m ]
prediction, elongated deformation of the magnetic surface vertically(Bq0%) reducese-bar
the BSC comparing with quasi-circular shape(Bq100%) in a low collisional regime [N.
Nakajima et al., NF 29 (1989) 605, and K.C.Shaing et al., POF B1, (8) (1989) 1663]. 2024June7-byOM_ne-Isat.qpc
3.75m/B 0%
5q
Now we would like to confirm the plasma shape effect in the relatively high
3.75m/B 100%q
collisional plateau regime in LHD.
0
Experimental conditions:(Rax, Polarity, Bt, γ, Bq) = (3.75m, CW, 2.64T, 1.2538, 0%); #192913-917# Balanced NB(BL2+BL3) is injected for 3 second.
Results:We compare Ip(around the end of discharge) and central elec. temp. dependence inbetween Bq0% and Bq100% with almost same NBI power. Ip decreases with density inboth cases. In the same density, Ip in Bq0% is smaller than that in Bq100%, which isconsistent with the theoretical prediction in the low collisionality. However, plasma
volume of Bq0% is smaller than that of Bq100%, and the Te0 of Bq0% is lower thanthat in Bq100%. We should take them into account in near future.

012103ne-bar

4567819 -3
results(tentative)[10 m ]

500123ne-bar4
5619 -3[10 m ]

78Te0 and Ip at the end of discharge
dependence on density inbalance-injected NB discharges.
Isat(Ip in the steady state); ~BSC4