Instability & Anisotropy (IA) Session Report
Date: Mar. 26, 2024
Time: 10:30 – 16:45
Shot#: 188135 – 188254 (120 shots)
Prior wall conditioning: None
Divertor pump: ONGas puff: H2
Pellet: None
NBI#(1, 2, 3, 4, 5)=gas(H, H, H, H, H)=P(3.9, 3.7, 3.9, 4.0, 5.5) MWECH(77GHz)=ant(5.5U-Out, 2O-UR)=P(0.698, 0.380) MW
ECH(154GHz)=ant(2-OLL, 2-OUL, 2-OLR)=P(0.705, 0.889, 0.858) MW
Topic:
1. Understanding Energetic Particle Distribution during Helically-Trapped Energetic-IonDriven Resistive Interchange Mode (EIC) in LHD Using Newly Developed Imaging
Neutral Particle Analyzer (INPA) (W. Paenthong)
2. Degradation of fast-ion confinement without EP-driven instability (H.Nuga)
3. Fast ion and impurity measurements in sawtoothing stellarator plasmas (D. Moseev)
4. Anomaly detection of radiation profile in radiative collapse K. Mukai

Understanding Energetic Particle Distribution during
Helically-Trapped Energetic-Ion-Driven Resistive Interchange Mode (EIC)in LHD Using Newly Developed Imaging Neutral Particle Analyzer (INPA)
Proponent: Worathat Paenthong(SOKENDAI)Co-authors: Kunihiro Ogawa(NIFS), Mitsutaka Isobe(NIFS), Siriyaporn Sangaroon(MSU), Xiaodi Du(GA), Apiwat Wisitsorasak(KMUTT)

Conceptof INPA

Schematic view of INPA

Energetic ion

An energetic neutral passing through the aperture is ionized by a thin carbon foil.
The energetic ion is deflected by LHD magnetic field and then strikes the scintillator.
The scintillation position provides information about the energy and radial position of the ion.
INPA in LHD has two apertures for measurement in CW and CCW Bt configurations andmeasures energetic neutral passively.

Design to measure helically-trapped beam ion
injected by NBI#4 and NBI#5 or ICRH tail ions

Understanding Energetic Particle Distribution during
Helically-Trapped Energetic-Ion-Driven Resistive Interchange Mode (EIC)in LHD Using Newly Developed Imaging Neutral Particle Analyzer (INPA)
Proponent: Worathat Paenthong(SOKENDAI)
Co-authors: Kunihiro Ogawa(NIFS), Mitsutaka Isobe(NIFS), Siriyaporn Sangaroon(MSU), Xiaodi Du(GA), Apiwat Wisitsorasak(KMUTT)

Experimental conditions: (Rax, Polarity, Bt, γ, Bq) =N-NB injection phase

Shot: #188145(3.6 m, CCW, 2.75 T, 1.2538, 100.0%) Shots: #188135 - #188155#188145t=4.0 sMotivation & Objectives

Results• We successfully observed a scintillation spot correlatedwith perpendicular neutral beam (P-NB) injection.
• The direction of Bt from the top is CCW-> Beam ions hit the lower side of scintillator.
• We will check the result in CW-Bt configuration in this Friday.
• We will investigate EIC effect of energetic ion behavior.
[1] X. D. Du, et al., Nuclear Fusion, 56, 016002 (2016).

N-NB and P-NB injection phaseEnergy• We newly installed INPA as part of a collaboration
between Japan, Thailand, and the US to gain a deeper
understanding of energetic particle behavior in thepresence of EIC [1].
• In this experiment, we mainly focused on checking
whether the INPA image was reasonable or not.

#188145t=5.0 sRadial position
ECRH phase#188145
t=5.5 sDegradation of fast-ion confinement without EP-driven instability (H.Nuga)
Shot #:188156-188192

Results in the previous cycle (24th)

Experimental conditions:(Rax, Polarity, Bt, γ, Bq) = (3.6, CCW, 2.75, 1.2538, 100)

Background and motivation:•The degradation of the NB fast-ion confinement
without EP-driven instabilities were observed after NB
superpose through the neutron measurement.
• FIDA signal also showed the confinement
degradation after NB superpose.
•The mechanism is still unclear.

Summary:••

To investigatate the mechanism, the similar
experiments with hydrogen plasma were performed.
Data in 7 beam patterns and 3 densities scan weretaken to show FIDA signal before/after NB superpose.

Fig.1 Confinement degradation
appeared in Sn/PnbFig.2 FIDA also showed thedegradation after NB superpose.

Interaction of fast ions and impurities with sawteeth
Experimental conditions:(Rax, Polarity, Bt, γ, Bq) = (3.6 m, CCW, 2.75 T, 1.254, 100.0%)

Objective and method:Ø Fast ion transport and impurity
transport due to sawtooth crashes
Ø FI sources: NBI1,4,5. Impurity sources(F, Fe, W) - TESPELResults:
Ø Very reliable sawtooth generation byCCW NBCD and CW ECCDØ NBI3 and NBI1, though similar,
produce different plasmas and differentsawteeth
Ø No clear sign of F redistribution due tothe crashØ More analysis neededAnomaly detection of radiation profile in radiative collapse
Shot #: 188227 - 188254 (28 shots)Experimental condition- (Rax, Bt, γ, Bq) = (3.75 m, -2.64 T, 1.2538, 100%)- NBI #1, 2, 3
- ne, bar: 4 x 1019 m-3- Divertor pumping: ON- Gas: H (5.5-L)

6.5-U IRVB#188236 4.96 s

5.00 sK. Mukai

Background and objective- In the 24th campaign, radiative collapse in the Rax = 3.6 m configuration
could be detected from radiation images measured with an IRVB at 6.5-U
as an increase of abnormality using autoencoder (AE).
- To investigate the effect of magnetic configuration on the radiation
structure to trigger radiative collapse
Results- 2-D radiation profiles were obtained in the Rax = 3.75 m configuration
using IRVBs at 6.5-U (100 Hz) and 6.5-L (50 Hz).
- Anomaly detection will be conducted using AutoEncoder.
- Similar experiment in CW polarity will be conducted on Mar. 29.

5.04 s5.08 s5.12 s

5.16 s

6.5-L IRVB

6