Low frequency fluctuation study using a microwave interferometer and Hα line emission measurement systems in the Pilot-PSI device

Abstract

A frequency multiplied microwave interferometer, a Hα line emission measurement system, and a high speed camera system were installed on the Pilot-PSI device for low frequency fluctuation study in the detached plasma condition. The two dimensional Hα line emission and its fluctuation were monitored with a fast visible camera with Hα filter. The coherent low frequency fluctuations of frequency of approximately 13 kHz were measured by all measurement systems. The stronger fluctuation intensities were observed in the downstream of the ionization front region in the detached plasma condition. Moreover, we show the clear difference between the strong fluctuation regions of the electron line density and Hα line emission for the first time. This means that the fluctuations of Hα line emissions was caused by not only electrons but also by hydrogen ions.

Effects from the Target Plate Geometry on Fluctuations of Helium Plasma in the Linear Divertor Simulator Magnum-PSI

“…Stronger oscillations in the ionization zone and/or recombination front region were observed in hydrogen plasmas in Pilot-PSI in earlier studies of linear divertor plasmas [6,7]. In an area that was axially localized and where pure He plasmas in NAGDIS-II experienced high volume recombination, the cross-field transport was enhanced [9][10][11].…”

“…The radiation zone, ionization region, recombination region, and momentum loss region are thought to make up the plasma conditions along the magnetic field to the diverter plate [1][2][3][4]. In addition, in some linear plasma simulators, including NAGDIS-II, Pilot-PSI, and Magnum-PSI [5][6][7][8][9][10][11][12][13][14][15], and the SOL of the tokamak plasma of ASDEX Upgrade [16], low-frequency fluctuations around the recombination front region have been observed in the detached plasma conditions. These fluctuations result in radial particle losses across the magnetic field.…”