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A fast-sampling fast-ion D-alpha (F-FIDA) measurement has been developed in the large helical device in order to investigate fast ion dynamics associated with helically trapped fast-ion-driven Magnetohydrodynamic (MHD) bursts. F-FIDA consists of a multi-anode photomultiplier tube (PMT) and achieves a sampling rate of 10 kHz. During the deuterium experiment campaign in 2022, F-FIDA measured the spectrum of perpendicular fast ions, using perpendicular lines of sight. We compared F-FIDA with conventional FIDA, using an electron multiplying charge coupled device, and confirmed that the time-averaged images were generally consistent between the two. The statistical properties of the temporal evolution associated with MHD bursts were analyzed using a conditional sampling technique. The results showed that the PMT signal varied in different spatial and wavelength channels. Although the signal-to-noise ratio was poor and there was room for improvement, it could provide useful information for studies on the phase-space dynamics of fast ions. [ABSTRACT FROM AUTHOR]

Nonlinear fluid simulation of drift wave turbulence in the presence of symmetry breaking particle source is performed for the cylindrical magnetized plasmas. It is demonstrated that the symmetry breaking of the system directly affects the selection rule of structure formations, the streamers disappear, and the zonal flows are enhanced in the case with the symmetry breaking. The symmetry breaking is introduced in the flux-driven simulation by inducing the particle source whose amplitude depends on the azimuthal angle. The symmetry breaking mode is driven stationarily, and the nonlinear process of the drift waves is significantly modified. By scanning the amplitude of the symmetry breaking source, the structure formation processes are systematically investigated. In addition, the nonlinear forces of the turbulence show the relaxation of the density gradient and the drive of the perpendicular/parallel flows in a two-dimensional manner. [ABSTRACT FROM AUTHOR]

Fourier-rectangular function (FRF) transform [K. Yamasaki et al., J. Appl. Phys. 126, 043304 (2019)] is used to analyze the structure and dynamics of plasma with cylindrical symmetry. In this article, a new technique based on FRF transform is proposed to elucidate the polarization characteristics of azimuthal modes and fluctuations. The application results are shown for a two-dimensional tomography image of linear cylindrical plasma. The method successfully resolves the polarization characteristics of azimuthal modes and attributes the intermittent behavior of the m = 1 mode to its polarization characteristics. [ABSTRACT FROM AUTHOR]

We present the evidence that drift waves can develop into nonlinear breathers. The theoretical analysis predicts that drift waves with secondary flow can excite the nonlinear breather through modulational instability. It is found that the simultaneous modulation of both amplitude and phase is a relevant feature of breather excitation. These features are used to elucidate the excitation of drift breather in a linear plasma experiment. The drift breathers are found to be excited frequently and intermittently. The transient increase in the transport flux is also demonstrated. We argue that there exists a critical condition on the wave amplitude for breather excitation. [ABSTRACT FROM AUTHOR]

This paper presents the experimental identification of the dynamic interaction between three fluctuations excited by different thermodynamical forces in a linear plasma. The observed fluctuations are characterized as an axial symmetric mode, a drift wave, and an azimuthally symmetric potential fluctuation from the spatiotemporal structures measured with Langmuir probe arrays. The intermittent burst of the axial symmetric mode is observed by the instantaneous wave number spectrum. The energy transfer analysis revealed that the axially symmetric mode gains energy from the other mode during the burst while the drift wave loses energy. The intermittent burst synchronizes with the azimuthal symmetric potential fluctuation. [ABSTRACT FROM AUTHOR]

Interaction between drift wave turbulence and streamer flow in magnetized plasmas is investigated in the framework of wave-kinetic theory. By performing a wave-kinetic simulation of turbulence coupling with the streamer flow, the role of the phase-space dynamics of turbulence is clarified. Here, the phase-space consists of the real space and wavenumber space. As a consequence of the phase-space dynamics, the turbulence is trapped in the flow and propagates with the streamer. Because of the trapping, the asymmetry of the turbulence intensity with respect to the sign of the flow curvature appears. The trajectories of the turbulence wave-packet, which are the characteristic curves of the wave-kinetic solution, can be categorized by the trapping, passing, and scattering. Therefore, the obtained phase-space structure of the turbulence can be understood by their trajectories. The propagation direction and speed are found to be governed by the turbulence spectrum. The obtained characteristics can be explained by the theoretical analysis. [ABSTRACT FROM AUTHOR]

In order to explore the impact of the neutrals on the plasma turbulence, a new gas puff system is developed for a linear magnetized plasma column PANTA. Helium gas is injected into the argon plasma without changing the electron density profile. After the helium gas puff, the dominant fluctuation mode changes from the broadband m = 2 drift wave to the coherent m = 1 mode, where m is the azimuthal mode number. Accordingly, the property of the nonlinear coupling with other fluctuating modes changes from broadband couplings to coherent couplings. [ABSTRACT FROM AUTHOR]

The streamer-driven particle flux is evaluated experimentally in a linear cylindrical plasma. The streamers, a radially elongated and azimuthally localized structure created in turbulent plasma, really induce ballistic transport, and directly connect the plasma core to the edge within one order faster time scale than that of turbulence. The occurrence of large transport deviates from a Gaussian distribution and is likely to obey a power law. The fundamental plasma experiment clearly shows the significant and essential contributions of streamers to cross-field transport and structural formation of turbulent plasmas. [ABSTRACT FROM AUTHOR]