Some preliminary results of plasma rotations in a linear plasma experiment device, Peking University Plasma Test (PPT) device, are reported in this paper. PPT has a cylindrical vacuum chamber with 500 mm diameter and 1000 mm length, and a pair of Helmholtz coils which can generate cylindrical or cusp magnetic geometry with magnitude from 0 to 2000 G. Plasma was generated by a helicon source and the typical density is about 10 cm for the argon plasma. Some Langmuir probes, magnetic probes, and one high-speed camera are set up to diagnose the rotational plasmas. The preliminary results show that magnetic fluctuations exist during some plasma rotation processes with both cylindrical and cusp magnetic geometries, which might be related to some electromagnetic processes and need further studies.
Based on large energy spread of laser-driven ion beam (LIB), a new method, the Laser-driven Ion-beam Trace Probe (LITP), was suggested recently to diagnose the poloidal magnetic field (B) and radial electric field (E) in toroidal devices. Based on another property of LIB, a wide angular distribution, here we suggested that LITP could be extended to get 2D B profile or 1D profile of both poloidal and radial magnetic fields at the same time. In this paper, we show the basic principle, some preliminary simulation results, and experimental preparation to test the basic principle of LITP.
We report the first experimental observation of zonal flow (ZF) formation through phase patterning. Here the ‘phase’ refers to the eikonal phase carried by streamer-like mode. It is observed that the phase-gradient profile tends to form ‘shock’ layer structures in regions where there are strong streamer-ZF interactions. The emergence of phase-gradient shock layers invalidate the constant-phase-gradient hypothesis, which is frequently employed in the modulational instability models of ZF generation, and is consistent with a recent theoretical work (Guo et al 2016 Phys. Rev. Lett. 117 125002), which predicts that the phase-curvature (gradient of the phase-gradient) can produce a new Reynolds force and accelerate the ZF. By decomposing the Reynolds’ force of the tilted streamers into a phase curvature driven piece and an amplitude inhomogeneity driven one, it is found that inside the shock layers the phase curvature plays a prominent role in accelerating the ZF. We also explore the formation mechanism of the phase pattern and its consistent dynamics with phase-curvature-driven ZF. These findings potentially open a new way to understand the various elusive self-organization phenomena in plasma turbulence.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.