Simultaneous evaluation of potential fluctuation from the core plasma to the end region in GAMMA 10

Abstract

A correlation between drift-type fluctuations and anomalous radial transport was observed in GAMMA 10, and these fluctuations were suppressed by the electron-cyclotron-heating-driven radial electric field. We developed new diagnostics to conduct these studies: a simultaneous two-point-measurement gold neutral beam probe (GNBP) for the radial electric field and potential fluctuations, and a high-speed end-plate potential fluctuation measurement system. The electric field and its fluctuations were successfully obtained in a single plasma shot for the first time. Coherence between the drift-type potential fluctuations measured in the core plasma by the GNBP and those obtained by end-plate measurements was clearly observed. These potential and electric field fluctuations were clearly suppressed by the positive electric fields measured by two-point potential measurements using the GNBP and the end-plate system. We can obtain a powerful tool for probing the radial electric field and potential fluctuations in the core plasma because the end-plate potential fluctuation is the same as that in the core plasma measured using the new GNBP.

Direct Observation of Electron Heating by Electron Landau Damping of Alfvén Ion Cyclotron Waves Using Thomson Scattering System in the Tandem Mirror GAMMA 10/PDX

“…Detailed description of GAMMA 10/PDX has been provided elsewhere [1][2][3][4][5][6][7][8][9][10][11][12]. The magnetic field strength at the midplane of the central cell is 0.405 T, and the mirror ratio of the central cell is 5.…”

Doppler Reflectometer System for Measuring Rotation Velocity of Fluctuation in GAMMA 10

“…GAMMA 10 [8,9] is a tandem mirror device consisting of an axisymmetric central cell for confining main plasma, minimum-B field anchor cells for stabilizing MHD instabilities, and axisymmetric end mirrors. In the central cell, cylindrical plasma with a length of 5.6 m is formed by solenoid with a uniform magnetic field strength 0.4 T at the midplane.…”

“…At r ∼18 cm where the limiter is installed, the rotation velocity becomes very small in either case. Figure 4 (b) shows the potential profile of the central cell measured by a heavy ion beam probe (HIBP) [9] in the ICRF phase (squares) and in the ICRF+ECH phase (circles). Parabolic potential profile shown as the curves is assumed to fit the data in Fig.…”

“…In the GAMMA 10 tandem mirror device [8,9] a author's e-mail: kohagura@prc.tsukuba.ac.jp * ) This article is based on the presentation at the 25th International Toki Conference (ITC25).…”

Suppression of flute-like fluctuation by potential formation in GAMMA 10/PDX

“…The density fluctuation is observed using microwaves, such as the interferometer, reflectometry and Fraunhofer diffraction method, and electrostatic probes [1][2][3]5,6]. The potential fluctuation is observed by the gold neutral beam probe (GNBP) and the end plates [4,[15][16][17][18][19]. In the former experiments, we studied the drift-type fluctuation suppression by applying the P-ECH [5,6,[15][16][17][18][19].…”