Hydrodynamic behaviors accompanied by a pulsed thin wire discharge in water have been observed via a fast framing/streak camera, together with the basic electric characteristics. Results show that the discharge plasma is tamped and stabilized by the surrounding water and it evolves through a warm dense state with high degree of symmetry and reproducibility up to a 2 μs discharge time. Numerical simulations show that the shock wave trajectories driven in the water are strongly dependent on equation of state (EOS) models of the plasma. Those results indicate that a semiempirical fitting of the shock traces to the experimental observation is a useful method for studying the EOS models of matter in a warm dense state.
Edge MHD modes are excited with an appreciable amplitude by the rise of the edge pressure gradient in the Large Helical Device (LHD), where the related rational surfaces are located near the last closed flux surface (LCFS). Internal structure of these edge MHD modes in high beta plasmas was measured by using a set of soft X-ray (SX) diode arrays. The relative amplitude of SX fluctuations related to these MHD modes increases rapidly toward the LCFS. The phase relation among SX fluctuation signals obtained by the SX-diode array clearly indicates the poloidal mode structure.
Alfévn ion-cyclotron (AIC) waves of various frequencies have been measured in the central cell of a tandem mirror, excited due to non-isotropic ion heating. Differential frequencies of the AIC waves were observed by analyzing the fluctuations of the end-loss ion current. From the analysis of both the frequency and intensity of the fluctuations, it was found that the differential frequencies are generated by the beat phenomenon caused by the AIC waves. The AIC waves affect the ion transport in the velocity space, and this phenomenon can be used to investigate the ion transport from the trapped region to the loss region in the tandem mirror.
An overview of the theory of zonal flows is presented. The contents include description of the mechanism by which zonal flows are generated, there relation between turbulence and zonal flows, and transport in drift wave-zonal flow turbulence. The physics of zonal flows is a prototypical example of a paradigm shift from the linear-local-deterministic view to the nonlinear-nonlocal-statistical view of structure formation in plasmas. Research regarding the turbulence-zonal flow system in laboratory plasma will deepen our understanding of this aspect of nature.
Zonal flows are now widely recognized to be a key phenomenon for understanding of fluctuation-induced transport in magnetically confined plasmas. The existence of the zonal flows has been directly identified by the measurement of electric-field fluctuations as well as of bicoherence of drift-wave turbulence which introduces the energy transfer from drift waves to zonal flows via three-wave interactions. The appropriate diagnostic methods for these subjects are introduced.
This report presents the recent identification of stationary zonal flow in CHS plasma using twin heavy ion beam probes and describes the general diagnostics principle used. The heavy ion beam probe measurement reveals that electric field fluctuation at low frequencies less than ˜1 kHz exhibits the characteristics of zonal flow, i.e., toroidal symmetry and a finite radial wavelength of the fluctuation.
The Heavy ion beam probe (HIBP) is a powerful tool to investigate the potential and density fluctuation of high temperature plasmas. The observations using HIBPs have contributed substentially to the recent rapid progress in the study of zonal flow. In this article, the characteristic of the Geodesic Acoustic Mode (GAM), which is a type of the zonal flow, is introduced on the basis of experimental results using HIBPs. The observed frequency and space structure are quite similar to the theoretical predictions. The influence of the GAM flow on the back ground fluctuation, including the causality, is also observed.
The collisionless time evolution of zonal flows is described based on gyrokinetic theory. The validity of theoretical predictions regarding geodesic acoustic modes and residual zonal flows is verified by gyrokinetic Vlasov simulation.
This article introduces the fundamental principles governing zonal flows for researchers who are engaged in experiments. The mechanism of the Geodesic Acoustic Mode (GAM) is first introduced for a simple tokamak having a circular cross section. The theoretical basis of which was described a rather long time ago. The theory is then extended to include helical systems based on the perspective that the geodesic curvature of the confining magnetic field plays an essential role. It is found that a short connection length in helical systems lends GAM oscillations different features from those in tokamaks. Special attention is paid to the low frequency range and a new branch is analyzed, which is referred to in this article as low frequency GAM. The zonal flow in the lowest frequency range is known as stationary zonal flow and known to have weak damping. Finally, an attempt is made to unify the theories of these two different frequency ranges.
EUV lithography with a 13.5nm EUV (Extreme ultra-violet) light source is the strongest candidate of the next generation lithography for LSI. EUV is obtained from a high temperature and high density plasma by DPP (Discharge Produce Plasma) and LPP (Laser Produced Plasma).
Light Emitting Diode (LED) is now one of the most popular and expected light sources after the bright blue light emitting LED was released on the market by Nichia Co. Ltd. This article describes basic concepts of light emitting diode and the features of white light emitting LED.
There are many lamp applications according to each spectrum characteristics. Ultraviolet radiation lamp is used for lithography, curing and medicals. In this paper, Excimer lamp is introduced and its applications are described.
At the end of the series of “Invitation to the World of the Plasma for Light Sources”, the author reviews the vista on the future of light sources considering recent advance and development of solid state lighting and its advantage and disadvantage. Finally it is concluded that discharge light sources will be staying as main light sources due to their higher energy capacity (high-wattage). “Bright future of the world is brought by plasma.”