(SG2, TC) Session Report

June 06, 2024 (H. Nakano)

Date: June 06, 2024
Time: 10:30 – 16:45
Shot#: 192731 – 192841 (90 shots)
Prior wall conditioning: HeDivertor pump: On
Gas puff: H2, Ar, CH4
Pellet: no
NBI#(1, 2, 3, 4, 5) = gas(H, H, H, H, H)=P(4.5, 4.1, 4.0, 3.3, 4.0) MW
ECH(77GHz) = ant(1.5-Uo, 5.5-U, 2-OUR)=P(-, 0.70, 0.38) MW
ECH(154GHz) = ant(2-OLL, 2-OUL, 2-OLR)=P(0.71, 0.81, 0.98) MW
ICH(3.5U, 3.5L, 4.5U, 4.5L) = P(-, -, -, -) MWTopics
1. Relation between plasma profile corrugations including transport barrier and magnetic field configurations (M.
Sasaki (Nihon Univ.))
2. Electron-scale turbulence on zero gradient (T. Nasu (SOKENDAI))
3. Investigation of the central negative diffusivity during the density modulation (Y. Ohtani (QST))o (Piggyback) Effect of a mixed-ion plasma on impurity transport in NBI heated plasmas (D. Damaskopoulos(Univ. Wisconsin-Madison))Relation between plasma profile corrugations
including transport barrier and magnetic field configurations
M.Sasaki, T.Kobayashi, Y.Kawachi, K.Ozawa

Experimental conditions: (Rax, Polarity, Bt, γ, Bq) = (1.375 T, 3.6 m, 1.2538, 100%)
Goal of this experiment:• Understanding the relation between the dynamics of plasma profile corrugations including the transport barrier
and the rational surface is investigated.

Results:•••

Position of the rational surface iscontrolled by the plasma current
induced by NBI and ECH.
The time scale of the change of iota
profile is compared in cases of NBI
current drive and NBI + ECCD current
drive.

Turbulence is measured by HIBP,and Back scattering, at
rho=0.2~0.7 by the shot-to-shotmanner.

PNB,perp
PNB,coPECH

PNB,ctr

IP-neWPElectron-scale turbulence on zero gradient (T. Nasu, T. Tokuzawa, and M. Nakata et al. )Experimental conditions: (Rax, Polarity, Bt, γ, Bq) = (3.60 m, CW, 2.75 T, 1.2538, 100.0%)
Goal of this experiment:• Investigating electron-scale turbulence
characteristics on flat Te profile,mainly turbulence propagation.
Results:• The flat Te profiles were attained by
combination between perp. NBI andoff-axis ECH.
• MECH was used to inject pulse
heating to raise center Te.
• center Te was successfully raised
locally on flat Te profile withoutchanging Ti and ne.
• BS data observed at reff/a99 ~ 0.1,0.3, 0.5, 0.7, 1.0 shot by shot.
• BS data will be analyzed to investigate
turbulence propagation on flat Teprofile.

nb5
on-axisoff-axis @ reff/a99 ~ 0.8TeneInvestigation of the central negative diffusivity during the density modulation.
Y. Ohtani (QST), K. Tanaka (NIFS), D. Damaskopoulos (WU-Madison)• Motivation
Understanding particle transport in the core region is one of the important issues for the profile control, the fusion power output.
However, during gas modulation, the modulation transported from core to edge is observed. This phenomenon cannot bepredicted by the previous method based on Fick's low with positive diffusivity. From this experiment, the relation between thisphenomenon and the turbulence and whether this phenomenon is predicted by simulation are investigated.
• MethodologyDensity scan (1 - 2.5 x 1019 m-3) were performed at Rax = 3.75 m, Bt = 2.64 T with 0.5 Hz density modulation. (#192836 - 42)• Result
As the previous experiments showed, the phase reversal in the core region is observed in high density case.
Phase reversal is observed in the high density discharge.
In preliminary analysis...
(however in low density cases, small phase reversal are observed.) Blue Dmod < 0In high density case,RedD>
0modDensity modulation component
Dmod in core region is#192842
negative.
19-3
ne=1.5x10 m
However, Dmod issometimes negative inlow density case.
#192840
ne=2.5x1019 m-3Comparison with ...
Turbulence
ProfilesandSimulation