Speaker
Mr
Kunpei Nojiri
(Plasma Research Center, University of Tsukuba)
Description
$\quad$In GAMMA 10/PDX tandem mirror, divertor simulation experiments have been carried out by using a divertor simulation experimental module (D-module) installed in the west end region. To understand characteristics of plasma detachment in the module, electron temperature and density distributions of the divertor simulation plasma have been measured by Langmuir probes. The D-module consists of a cuboid box made of stainless steel and a V-shaped target. The size of the D-module is 500 mm x 700 mm x 480 mm. The width of the target is 300 mm and its depth is 350 mm. The surface of the V-shaped target is covered with tungsten plates with the thickness of 0.2 mm. In this study, the open angle of the V-shaped target was 45 degrees. Thirteen Langmuir probes are installed on the upper target and two probes are installed near the inlet of the D-module.
$\quad$The electron temperature near the corner of the target decreased to about 2 eV with increase in the neutral pressure in the D-module by the additional hydrogen gas injection. The electron density first increased from an order of 10$^{16}$ m$^{-3}$ to 10$^{17}$ m$^{-3}$ with increase in the neutral gas pressure and then decreased, indicating that the plasma was detached. The detachment seems to be caused by molecular activated recombination (MAR) from the spectroscopic measurement of the Balmer lines of hydrogen. When the plasma was detached, the electron density in the D-module measured along an axial direction decreased toward the corner of the target plate. And the position of the peak density moved to upstream of the plasma. This result indicates that the recombination region expanded to upstream with increase in the neutral gas pressure. On the other hand, increasing the gas pressure changed the horizontal distribution of the plasma density near the target plate from the peaked profile to the flat one, although the electron temperature distribution was almost flat.
Primary author
Mr
Kunpei Nojiri
(Plasma Research Center, University of Tsukuba)
Co-authors
Mr
Akihiro Terakado
(Plasma Research Center, University of Tsukuba)
Dr
Junko Kohagura
(Plasma Research Center, University of Tsukuba)
Dr
Kazuya Ichimura
(Plasma Research Center, University of Tsukuba)
Dr
Masayuki Yoshikawa
(University of Tsukuba)
Prof.
Mizuki Sakamoto
(Plasma Research Center, University of Tsukuba)
Dr
Naomichi Ezumi
(Plasma Research Center, University of Tsukuba)
Prof.
Yousuke Nakashima
(Plasma Research Center, University of Tsukuba)
