Speaker
Dr
Naomichi Ezumi
(Plasma Research Center, University of Tsukuba)
Description
Ion sensitive probe (ISP) is an electrical probe used for measuring ion temperature (Ti) in magnetized plasmas [1]. Simultaneously, electron temperature (Te) and plasma space potential (Vs) are also available. Recently, the ISP was installed in the divertor simulation module (D-module) of the largest tandem mirror plasma device GAMMA 10/PDX in order to evaluate the property of the high temperature end loss plasmas which are equivalent of the edge and divertor plasmas in tokamak and helical devices. These measurements are expected to contribute to realizing the important physics in handling extremely high heat and/or particle load to the plasma facing components of magnetic fusion devices.
The installed ISP consists of two electrodes that an ion collector and electron guard electrode. The ion collector only collects ions at positive potential higher than Vs. This behavior is based on the difference of the gyro radius between the ion and the electron in a magnetic field. A recess distance of the ion collector (h) is one of the important parameters for the probe design. Then the h-parameter was optimized by using the typical experimental conditions of the probe position in the D-module.
So far, we have tested the ISP measurement for several discharge and neutral gas pressure conditions. For example, in the case of hydrogen gas pressure range < 2 Pa, Ti evaluated by using the ion collector of the ISP shows about 6 eV which corresponds to the perpendicular component of Ti in principle. On the other hand, parallel Ti estimated by using ion saturation current on the electron guard electrode of the ISP shows almost ten times higher than the perpendicular one. This result is qualitatively consistent with the existence of strong temperature anisotropy in the open magnetic field, because the ions of the end loss plasma in the GAMMA 10/PDX usually have a few hundred eV as parallel Ti. In this paper, we show the detail of the newly designed ISP for open magnetic field plasma in GAMMA 10/PDX and discuss the validity of the measurement. Furthermore, the influence of high ion temperature on probe current will be discussed.
This work is performed with the support of JSPS KAKENHI Grant Number 25420888 and NIFS Collaborative Research Program (NIFS13KLPP027).
[1] I. Katsumata, Contrib. Plasma Phys., 36 (1996) S, 73.
Primary author
Dr
Naomichi Ezumi
(Plasma Research Center, University of Tsukuba)
Co-authors
Mr
Akihiro Terakado
(Plasma Research Center, University of Tsukuba)
Dr
Kazuya Ichimura
(Plasma Research Center, University of Tsukuba)
Mr
Kunpei Nojiri
(Plasma Research Center, University of Tsukuba)
Prof.
Mizuki Sakamoto
(Plasma Research Center, University of Tsukuba)
Prof.
Yousuke Nakashima
(Plasma Research Center, University of Tsukuba)
