Speaker
Prof.
Yousuke Nakashima
(Plasma Research Center, University of Tsukuba)
Description
The divertor simulation research has been started by making use of high heat-flux plasma flow from the large tandem mirror device GAMMA 10/PDX in Plasma Research Center [1-2]. A crucial advantage of using large tandem mirror is a capability of generating ion flux with high temperature (100$\sim$ 400 eV) comparable to SOL plasma parameters and its controllability.$\\$
In GAMMA 10/PDX, high-power plasma heating systems are installed such as ion cyclotron range of frequency (ICRF) heating, electron cyclotron heating (ECH) and neutral beam injection (NBI). By using above systems, high heat/particle-flux generation and divertor simulation experiments under similar circumstances of actual fusion devices have been performed [3]. So far the heat flux ${\it P_{Heat}}$ of $\geq$ 1 MW/m$^{2}$ and the particle flux ${\it \Gamma_{ion}}$ of 3.3$\times$ 10$^{23}$ particles/s•m$^2$ were achieved.
Recently divertor simulation experiments toward the realization and characterization of detached plasma were extensively started using a divertor simulation experimental module (D-module) in the west end-cell [4-5]. In D-module V-shaped two tungsten plates are mounted together with gas injection and diagnostic systems. On the V-shaped target and behind the gap at the V-shaped corner, array of Langmuir probe and calorimeter are installed for evaluation of radiation cooling and plasma detachment. In order to investigate the behavior of impurities and to capture the 2-D visible image of light emission in front of the V-shaped target, visible spectrometers and high-speed camera are installed.
In detached plasma formation experiments from high temperature plasma (${\it n_e}$ $\sim$ 2 $\times$ 10$^{18}$ m$^{-3}$, ${\it T_{i//}}$
$\sim$150 eV and ${\it T_e}$ $\sim$ 30 eV), the dependences of gas injection on the reduction of $\it T_{e}$, $\it\Gamma_{ion}$ and $\it P_{Heat}$ near the target plate were investigated using H$_2$ and noble gases injection into D-module. In cases of noble gases, the above plasma parameters decreased with the increase of the gas throughput. It was found that Xe gas was most effective on electron cooling and reduction of particle and heat fluxes down to less than 10 $\%$. The above results are almost consistent with the observation from an absolutely calibrated visible spectrometer viewing the inside of D-module. Furthermore, in the case with a simultaneous injection of H$_2$ and Xe, the ion flux was almost fully suppressed, which indicates the existence of Molecular Activated Recombination in D-module.$\\$
In this paper, detailed results of characterizing the plasma detachment are described and the physical mechanism of the plasma detachment will be discussed.$\\$
[1] Y. Nakashima, et al., Fusion Eng. Design **85** issue 6 (2010) 956. $\\$
[2] Y. Nakashima, et al., J. Nucl. Mater. **415** (2011) S996. $\\$
[3] Y. Nakashima, et al., J. Nucl. Mater. **438** (2013) S738. $\\$
[4] Y. Nakashima, et al., J. Nucl. Mater. **463** (2015) 537. $\\$
[5] Y. Nakashima, et al., Fusion Sci. Technol. **68** No.1 (2015) 28.
Primary author
Prof.
Yousuke Nakashima
(Plasma Research Center, University of Tsukuba)
Co-authors
Mr
Akihiro Terakado
(Plasma Research Center, University of Tsukuba)
Dr
Isao Katanuma
(Plasma Research Center, University of Tsukuba)
Dr
Junko Kohagura
(Plasma Research Center, University of Tsukuba)
Mr
Kazuma Fukui
(Plasma Research Center, University of Tsukuba)
Dr
Kazuya Ichimura
(Plasma Research Center, University of Tsukuba)
Mr
Keita Shimizu
(Plasma Research Center, University of Tsukuba)
Mr
Kunpei Nojiri
(Plasma Research Center, University of Tsukuba)
Mr
MD SHAHINUL ISLAM
(Plasma Research Center, University of Tsukuba)
Dr
Mafumi Hirata
(Plasma Research Center, University of Tsukuba)
Dr
Makoto Ichimura
(Plasma Research Center, University of Tsukuba)
Mr
Masato Ohuchi
(Plasma Research Center, University of Tsukuba)
Dr
Masayuki Yoshikawa
(University of Tsukuba)
Mr
Md. Maidul Islam
(Plasma Research Center, University of Tsukuba)
Prof.
Mizuki Sakamoto
(Plasma Research Center, University of Tsukuba)
Dr
Naomichi Ezumi
(Plasma Research Center, University of Tsukuba)
Dr
Ryutaro Minami
(Plasma Research Center, University of Tsukuba)
Dr
Ryuya Ikezoe
(Plasma Research Center, University of Tsukuba)
Mr
Takayuki Yokodo
(Plasma Research Center, University of Tsukuba)
Dr
Tomoharu Numakura
(Plasma Research Center, University of Tsukuba)
Prof.
Tsuyoshi Imai
(Plasma Research Center, University of Tsukuba)
Dr
Tsuyoshi Kariya
(Plasma Research Center, University of Tsukuba)
Dr
Xiaolong Wang
(Plasma Research Center, University of Tsukuba)
