高速度カメラを用いた不純物ガス入射時のGAMMA 10/PDX ダイバータ模擬プラズマの4波長同時観測
Simultaneous 4-wavelength observation of spatio-temporal changes in
GAMMA 10/PDX divertor simulated plasmas during impurity gas seeding

7P81

髙橋理志 1)、江角直道 1)、東郷訓 1)、坂本瑞樹 1)、杉山吏作 1,2)、蒲生宙樹 1)、
重松直希 1)、瀬戸拓実 1)、岡本拓馬 1)、高梨宏介 1)
TAKAHASHI Satoshi 1), EZUMI Naomichi 1), TOGO Satoshi 1), SAKAMOTO Mizuki, 1),
SUGIYAMA Tsukasa 1,2), GAMO Hiroki 1), SHIGEMATSU Naoki 1), SETO Takumi 1),
OKAMOTO Takuma 1), TAKANASHI Kosuke 1)1) 筑波大、2) 総研大1) Univ. Tsukuba, 2) SOKENDAIIntroduction
Reduction of intense heat load on a divertor is one of
the critical challenges in magnetic confinement fusion.
One promising solution is seeding impurity gases in thedivertor region to cause reduction of the particle/heatfluxes. So far, in previous researches conducted on
Divertor simulation experimental module (D-module) ofGAMMA 10/PDX, we have found that when N2 is
injected in conjunction with H2, the electron density andthe ion flux synergistically decrease while emissions fromNH radicals increase, correlated with increased N2 ratio[1,2]. These studies suggest the importance of thecontribution of N-MAR (Nitrogen Molecular Assisted
Recombination), which has higher reaction rate even in
relatively higher temperature compared to HydrogenMAR(H-MAR).
Hence,
understanding
thespatiotemporal behavior of the N-MAR in the divertor
region is important for suitable control of plasma
detachment. In this study, we measured emission profilesof Hα, Hβ, N-atom, and N2-1st Pos. in D-module using ahigh-speed camera with novel 4-branch optical system.
1.

Experimental setup
This study uses a high-speed camera ACS-1 with aprism named ‘Arbaa prism’ [3]. Schematics of the opticalsystem and D-module are shown in Fig. 1(a) and (b),respectively. This new setup allows us to simultaneously
obtain spatial profiles of four different wavelengths in thesame field of view which enables a more precise
evaluation between them.
2.

shown in Fig. 2. The input beam to the Arbaa prism is split
into four beams and each of them passes through different
band-pass filters then formed on the image sensor of thecamera. Each channel’s band-pass filters have 10 nm in
FWHM. Our new camera setup allowed us a 10-foldenhancement in temporal resolution as well as minor
improvement in spatial resolution.

Fig. 2: An example of raw data

Fig. 3: Change of I(Hα)/I(Hβ)
profiles in seeding gas(a) H2 only, (b) H2+N2

Fig. 3(a) shows an example of the spatial profiles of theratio of I(Hα)/I(Hβ), which is an indicator of H-MAR, with
H2 injection. Fig. 3(b) is the result with N2 injection inaddition to H2. In case of N2 seeding, it seems like thedominant region of H-MAR shifted toward upstream.
In this presentation, we will discuss the spatiotemporalchanges of emissions as well as comparison with otherimpurities, Neon and Argon.
High-speed camera ACS-1 and Arbaa prism are both provided by nac
Image Technology Inc. This work is partly supported by JSPS
KAKENHI Grant Number 19K03790, 22H01198 and NIFS
Collaboration
Researchprogram(NIFS19KUGM137,NIFS19KUGM146 and NIFS20KUGM148).

Fig. 1 (a) D-module, (b) Arbaa prism

3.

Results
An example of raw data acquired by the system is[1] N. Ezumi et al., Nucl. Fusion 59 (2019) 06630.
[2] H. Gamo, et al., Plasma and Fusion Research 16 (2021) 2402041.
[3] E. Shoji et al., Exp. Thermal and Fluid Science 60 (2015) 231-240.