Study of Fluctuation Suppression during Potential Formation in the Tandem Mirror GAMMA 10

Abstract

In the tandem mirror GAMMA 10, plasma confinement is achieved by not only a magnetic mirror configuration but also high potentials in both end regions. Before plug electron cyclotron resonance heating (P-ECH) was applied, drift-type fluctuations were observed in potential and density measurements. Potential and density fluctuation suppression during potential formation by the application of P-ECH was clearly observed using a gold neutral beam probe (GNBP) system. We study the relationship between the suppression levels of potential fluctuations and the effects of the produced potentials by varying the applied ECH power. Moreover, the particleflux-related values obtained by the phase difference between the potential and density fluctuations are measured using the GNBP. We can clearly show that radial anomalous transport induces radial particle transport, which decreases the plasma stored energy.

Density fluctuation measurements by using the Fraunhofer diffraction method in GAMMA10

“…The radial electric field E r arising from the potential causes the E r × B plasma rotation in the direction of the ion diamagnetic drift velocity, which may enhance instabilities, such as rotational flute and drift-wave modes, and degrade radial confinement. However, present study shows that the suppression of drift type fluctuation in the potential and density fluctuations with producing axial confining potential in GAMMA 10 [1]. GAMMA10 is a minimum-B anchored tandem mirror with thermal barrier.…”

23rd IAEA Fusion Energy Conference: summary of sessions EX/C and ICC

“…The radial particle flux is calculated from the measured phase difference between the potential and density fluctuations. The application of P-ECH is correlated with a significant reduction in the radial particle flux [8].…”

Measuring Electron Temperature in the Tandem Mirror GAMMA 10 Plasma Using a Yttrium-Aluminum-Garnet Thomson Scattering System

“…An electron temperature increase from 40 eV to 80 eV was observed with application of electron cyclotron heating to plug/barrier cells. GAMMA 10 is the world largest tandem mirror machine with which plasma confinement is achieved not only by a magnetic mirror configuration but also high potentials at both end regions [1][2][3]. The main plasma is produced and heated by ion-cyclotron range of frequency waves.…”

“…Thus far, direct electron heating by ECH experiments have been conducted in the central cell. In addition, density and potential fluctuation suppressions during the formation of confinement potential have been studied using a gold neutral beam probe system [1][2][3]. After the aforementioned problems with the ruby-laser TS system, we planned to install a neodymiumdoped, yttrium-aluminum-garnet laser (Nd:YAG) TS system to measure electron temperature directly in the central cell of GAMMA 10.…”