(MAP) Session Report
Date: June 11, 2024
Time: 10:30 – 16:45
Shot#: 192929 – 193032 (104 shots)
Prior wall conditioning: None
Divertor pump: OffGas puff: H2, Ne
Pellet: None

June 12, 2024 (K. Mukai, M. Shoji)

NBI#(1, 2, 3, 4, 5) = gas(H, H, H, -, -)=P(1.8, 2.1, 2.3, 3.3, 2.8) 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. Long-pulse steady-state shots in the 3.55 m configuration (U. Wenzel (IPP))
2. Exposure of material samples into the LHD edge plasma by means of the manipulator (C.P. Dhard)
3. Development of steady-state detachment scenarios at LHD (M. Jakubowski)

1Long-pulse steady-state shots in the Rax = 3.55 m configuration(U. Wenzel (IPP), G. Motojima)ü Experimental conditions:#192932-192953&#192968-192974:
Rax=3.55m, CCW, B=2.78T, g=1.254, Bq=100%#192711-192728: Rax=3.53m, CCW, B=2.804T, g =1.254, Bq=100%

ü Motivationv In the 24th LHD campaign, very high neutral pressures were measured in
the sub-divertor region(Wenzel et al., Nuclear Fusion 2024).
The divertor went into a low temperature mode (LTM).
v It is proposed to1) Verify the result and determine the threshold for the transition
2) Generate a steady-state shot for long pulse dischages.

Rax=3.55m (#192969)
Rax=3.53m (#192964)
Rax=3.55m
Rax=3.53m

ü Experiments
vDensity ramp up for confirmation of reproducibility
vDensity steady state (8-11x1019 m-3)

ü Results
vHigh neutral pressure (~1Pa) is successfully observed in density steadystate of R=3.55m, CCW condition for long pulse NBIs.
vMore inward (R=3.53 m) the effect was also observed but neutral pressure
was lower compared to R=3.55 m.

ßTe0

Rax=3.55m
Rax=3.53m

ne0 à
Rax=3.55m
Rax=3.53m

Exposure of material samples into the LHD edge
plasma by means of the manipulator

C.P. Dhard, D. Naujoks (IPP), S. Masuzaki

Shot #: 192975 – 192991, Cycle: 3 min. 30s.

(Rax, Bt, γ, Bq) = (3.6 m, - 2.75 T, 1.2538, 100.0%) , Working gas: H2
PECH～0.4 MW, Pt-NBI~7MW (pulse length:4s),Pp-NBI~3MW (modulated, pulse length:12s
Objectives•

To form FUZZ-like nanostructure on surfaces of W alloy samples by
exposing to He plasma.

•The samples with the FUZZ-like structure will be exposed to H
plasma in the next experiment to investigate the change of surface
morphology.

Method•Three sets of W-alloy samples (W95NiFe, W97NiFe), and one setof W samples were installed to the position of the divertor strike
point by using the manipulator at 10.5L port.

•The W-alloy samples had been exposed to He plasma in 25s.
Discharge sustained by ECH and ICH on 15 April.

Results•

Samples were exposed to H plasma from 192981 to 192991 (11 shots)•

Surface analysis will be conducted.

Typical time evolutions of heating power, ne,gas puffing, Te in this experiment (#192988)

Development of steady-state detachment scenarios at LHD

20240611

Marcin Jakubowski (IPP), Masahiro Kobayashi (NIFS)
Motivation & Objectives:• Based on the previous experiments at LHD and W7-X scenarios for steady-state detachment with seeding low-Z species (Ar orNe) will be developed.
• The optimum scenario: highest radiation levels without core contamination. Detachment will be stabilized with RMP coils.
• The scenario will be prolonged in time to explore the compatibility of such scenarios with time scales of wall recycling.
Results:
Rax = 3.90m, B=2.54T, CCW, =1.254, Bq=100%.
NBI ~ 2MW with 4 sec pulse in train. IRMP = 2.8 and2.0 kAThe discharge is extended to 12 sec with 3 NBIs intrain. The Ne was seeded from 5.5L valve at 2.0s(12ms), 4.5s (4ms), 8.0s (2ms), 10 s (2 ms). Thedetachment was sustained from t = 2.0 to 12.3 sec.
The duration is longer than wall recycling time.
The divertor particle flux was decreased at least in
all measured toroidal section with divertor probearray.
IRMP and power was scanned. The data will beanalyzed to investigate dependence on power andIRMP, and to be compared with W7-X.