Detection of Cascading in Drift Wave Turbulence Using Probe Array in Linear Plasmas

Abstract

Measurement of drift wave turbulence using multi-probe systems was performed in the Large Mirror Device-Upgrade linear plasma. We compared a drift wave's two-dimensional (poloidal wave number and frequency) power spectrum with its calculated linear dispersion relation. As a result, a few wave modes that satisfy the linear dispersion relation were observed. Moreover, cascades to non-mode peaks and broadband components that do not satisfy the dispersion relation were identified.

Experimental Study of Drift Wave Turbulence in Linear Plasmas

“…A 64-channel poloidal Langmuir probe array, which can measure the precise poloidal wave numbers of the fluctuations [16], obtained a highquality, two-dimensional (poloidal wave number k θ and frequency ω) power spectrum of drift wave turbulence. In drift wave turbulence, a number of fluctuation peaks and broadband components appeared in the two-dimensional power spectrum [17]. In this article, we present a change in the spatiotemporal behavior and two-dimensional power spectrum from a coherent to a turbulent regime.…”

Two-dimensional bispectral analysis of drift wave turbulence in a cylindrical plasma

“…32 A 64-channel poloidal Langmuir probe array 33 has been installed to take 2D measurements in poloidal wave number and frequency, in order to clarify the structure of nonlinear coupling in drift wave turbulence. The measurements have provided several interesting results, [34][35][36] such as the first experimental identification of streamers. In this paper, we present a full description of the results from the 2D bispectral analysis, e.g., the existence of nonlinear coupling between peaks and broadband fluctuations.…”

Spatiotemporal Behavior of Drift Waves in LMD-U

“…3 show the calculated linear dispersion relation of drift waves with a uniform rotation assuming a dc radial electric field. The value of the electric field (30 V/m) was selected as the strongest peak at (m, f ) = (1, 2.8 kHz) to match the eigenfrequency, and was within an error-bar of the potential profile measurement [19]. The peak at (m, f ) = (2, 3.2 kHz) also satisfies the dispersion relation.…”

“…The quasi-mode peaks and broadband components appear nearly on the line m ∝ f , and they are away from the linear dispersion relation curve of the drift wave, irrespective of the value of the radial electric field. Quasi-modes and broadband components are considered to be produced by nonlinear couplings of parent modes [19]. Figure 4 shows the logarithmic plots of power spectra S ( f ) and S …”

“…Moreover, in a drift wave turbulence regime, quasi-modes and broadband components that do not satisfy the dispersion relation were found. They were considered to be produced by nonlinear couplings of primary modes [19]. In the previous works, the details of the broadband components were not reported, while the quasi-modes were discussed in detail.…”