(MAP) Session Report
Date: Mar. 27, 2024
Time: 10:35 – 16:44
Shot#: 188257 – 188374 (117 shots)
Prior wall conditioning: He glow
Divertor pump: OffGas puff: H2
Pellet: None

Mar. 28, 2024 (C. Suzuki)

NBI#(1, 2, 3, 4, 5) = gas(H, H, H, H, H)=P(4.2, 4.0, 4.1, 3.3, 3.2) 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(0.92, 1.06, 0.98) MW
ICH(3.5U, 3.5L, 4.5U, 4.5L) = P(-, -, -, -) MW
Topics
1. The investigation of the impurity shielding performance of the LHD peripheral plasma using the Impurity
Powder Dropper (a low plasma density condition) (M. Shoji)
2. The evaluation of the toroidal uniformity of the boron deposition on the divertor plates for effective real-timeboronization using the impurity powder dropper (a low plasma density condition) (M. Shoji)
3. Spectroscopic studies of boron hydrides near plasma-facing materials during boron powder dropping
experiments (T. Kawate)Investigation of the impurity shielding performance of the LHD peripheral
plasma using the Impurity Powder Dropper (IPD)(M. Shoji)

Experimental conditions:(Rax, Polarity, Bt, γ, Bq) = (3.75 m, CW, 2.64 T, 1.2538, 100%), Shots: #188262 - #188271= (3.60 m, CW, 2.75 T, 1.2538, 100%), Shots: #188273 - #188281
ECH: only for start-up, NBI: BL1+BL2+BL3+BL4+BL5, IPD: Li, Si, B#188279 Rax=3.60 m

Objective:

LiThe shielding performance of the LHD peripheral plasma against
impurity dust particles was investigated by measuring the dust particletrajectories and the ablation positions using a fast-framing camera.

AH02-02

Experiment:
The ablation positions of impurity dust particles (Li, Si, B) dropped
from the IPD were observed with the fast-framing camera (installed
next to the IPD) in low-density plasma discharges (ne〜2×1019 m-3)
for two different magnetic configurations (Rax=3.60 m and 3.75 m).

Results:
The ablation positions of dropped Li dust particles (d=500 µm) for
both magnetic configurations were almost the same, which isdifferent from those in the high-density plasma discharges
performed on 19th March. It can be explained by the lower plasma
flow effect in the upper divertor leg on the dust trajectories.

Outboard
2000 fps#188265 Rax=3.75 m
AH02-02

LiAblation Position

Outboard
2000 fps

Evaluation of the toroidal uniformity of the boron deposition on the divertor
plates for effective real-time boronization using the Impurity Powder Dropper(M. Shoji)

Experimental conditions:(Rax, Polarity, Bt, γ, Bq) = (3.60 m, CW, 2.75 T, 1.2538, 100%), Shots: #188285 - #188330
ECH: only for start-up, NBI: BL1+BL2+BL3+BL4+BL5, IPD: Li, Si, B

10.5-U

Objective:
The toroidal uniformity of the boron deposition on divertor plates by boron powder
injection is investigated using two manipulators installed in different toroidal
positions for both low and high-density plasmas.

#188294
Target plate

Experiment:
Boron powders were dropped by the impurity powder dropper (IPD) in lowdensity plasma discharges (ne〜1.5×1019 m-3), in which carbon target plates
were exposed to the divertor plasma in two different toroidal positions (4.5-L
and 10.5-L) for Rax=3.60 m.

Results:
The target plates were successfully exposed to the divertor plasma for about
20 discharges. The deposited boron density profiles on the plates will be
investigated and compared to simulations which predict more toroidally
uniform boron deposition for low-density plasmas. The investigation of theablation positions of the impurity dust particles for medium-density plasma
discharges (ne〜3×1019 m-3 and 4×1019 m-3) was also performed.

Inboard#188294

4.5-U
Target plate

Inboard

Spectroscopic studies of boron hydrides near plasma-facing materials
during boron powder dropping experiments

Kawate et al.

Background: We confirmed real-time depositions of boron onto diverter regions during IPD via BH molecularspectroscopy. For investigation of formation processes of BH during boronization (i.e., validity of diagnostics ofboron deposition by BH molecular spectroscopy), we propose spectroscopic measurements of BH+ and BH2,
which can be reactant/product of BH molecules
Experimental conditions:(Rax, Bt, γ, Bq ) = (3.6 m, 2.75 T, 1.254, 100%), CW, H2 gas#188331 – 188374, IPD with B powder
Results:• We confirmed emissions from BH+ molecules around 379 nm duringboron powder injection. On the other hand, we cannot find BH2 ~330
nm emission (due to the low efficiency of the detector in UV or lessBH2 amount...?).
• We performed experiments with different amount of boron as well asdifferent NBI conditions (to compare different Te of diverter plasmas).
• We will investigate temporal evolutions/spatial distributions of BH,
BH+, B0, and B+ emissions to understand chemical kinetics of theseatoms and molecules during boron deposition onto plasma-facing
materials.