Shunjiro Shinohara

Bio: Shunjiro Shinohara is an academic researcher from Tokyo University of Agriculture and Technology. The author has contributed to research in topics: Plasma & Helicon. The author has an hindex of 22, co-authored 171 publications receiving 2124 citations. Previous affiliations of Shunjiro Shinohara include Kyushu University & Tokai University.

Space micropropulsion systems for Cubesats and small satellites: from proximate targets to furthermost frontiers

Abstract: Rapid evolution of miniaturized, automatic, robotized, function-centered devices has redefined space technology, bringing closer the realization of most ambitious interplanetary missions and intense near-Earth space exploration. Small unmanned satellites and probes are now being launched in hundreds at a time, resurrecting a dream of satellite constellations, i.e., wide, all-covering networks of small satellites capable of forming universal multifunctional, intelligent platforms for global communication, navigation, ubiquitous data mining, Earth observation, and many other functions, which was once doomed by the extraordinary cost of such systems. The ingression of novel nanostructured materials provided a solid base that enabled the advancement of these affordable systems in aspects of power, instrumentation, and communication. However, absence of efficient and reliable thrust systems with the capacity to support precise maneuvering of small satellites and CubeSats over long periods of deployment remains a real stumbling block both for the deployment of large satellite systems and for further exploration of deep space using a new generation of spacecraft. The last few years have seen tremendous global efforts to develop various miniaturized space thrusters, with great success stories. Yet, there are critical challenges that still face the space technology. These have been outlined at an inaugural International Workshop on Micropropulsion and Cubesats, MPCS-2017, a joint effort between Plasma Sources and Application Centre/Space Propulsion Centre (Singapore) and the Micropropulsion and Nanotechnology Lab, the G. Washington University (USA) devoted to miniaturized space propulsion systems, and hosted by CNR-Nanotec—P.Las.M.I. lab in Bari, Italy. This focused review aims to highlight the most promising developments reported at MPCS-2017 by leading world-reputed experts in miniaturized space propulsion systems. Recent advances in several major types of small thrusters including Hall thrusters, ion engines, helicon, and vacuum arc devices are presented, and trends and perspectives are outlined.

Anatomy of plasma turbulence

Abstract: Detailed analysis of multiscale structures and the identification of long-lived streamer-like wavemodes in a magnetically confined plasma provides new insight into the physics of plasma turbulence.

Development of Electrodeless Plasma Thrusters With High-Density Helicon Plasma Sources

Abstract: Helicon plasma sources are very useful in many aspects and are applicable to many fields across science and technology, as they can supply high-density $({\sim}10^{13}~{\rm cm}^{-3})$ plasmas with a broad range of external operating parameters. In this paper, developed, featured sources with various sizes are characterized along with discussions on their particle production efficiency. This paper aims to develop systems that can realize schemes with completely electrodeless plasma production and acceleration. This is expected to mitigate the existing problems of the finite lifetimes inherent in electric plasma propulsion tools. Experimental and theoretical approaches that implement such schemes are presented.

Development of high-density helicon plasma sources and their applications

Abstract: We report on the development of unique, high-density helicon plasma sources and describe their applications. Characterization of one of the largest helicon plasma sources yet constructed is made. Scalings of the particle production efficiency are derived from various plasma production devices in open literature and our own data from long and short cylinder devices, i.e., high and low values of the aspect ratio A (the ratio of the axial length to the diameter), considering the power balance in the framework of a simple diffusion model. A high plasma production efficiency is demonstrated, and we clarify the structures of the excited waves in the low A region down to 0.075 (the large device diameter of 73.8 cm with the axial length as short as 5.5 cm). We describe the application to plasma propulsion using a new concept that employs no electrodes. A very small diameter (2.5 cm) helicon plasma with 1013 cm−3 density is produced, and the preliminary results of electromagnetic plasma acceleration are briefly de...

Helicon high-density plasma sources: physics and applications

Abstract: Helicon high-density (up to ~1013 cm−3) plasma sources using a radio frequency wave in the presence of a magnetic field under a low pressure are very promising for various application fields owing ...

Fast-wave heating of a two-component plasma

Abstract: The use of the compressional hydromagnetic mode (also called the magnetosonic or, simply, the fast wave) is examined in some detail with respect to the heating of a tritium plasma containing a few percent deuterium. Efficient absorption of wave energy by the deuteron component is found when ω = ωC (deuterons), with Qwave 100. Reasonable efficiencies are found also for electron heating, but coherence effects between transit-time and Landau damping for electrons reduce the total absorption for both processes to one-half of the transit-time power, calculated separately.The fusion output of a two-component neutral-injected plasma can be enhanced by selective heating of the injected deuterons. Also, selective deuteron absorption may be used for ion-tail creation by radiofrequency excitation alone, as an alternative to neutral injection. The dominant behaviour of the high-energy deuteron distribution function is found to be f(v) ~ exp[(3/2)∫vdv / ], where is the Chandrasekhar-Spitzer drag coefficient, and is the Kennel-Engelmann quasi-linear diffusion coefficient for wave-particle interaction at the deuteron cyclotron frequency. An analytic solution to the one-dimensional Fokker-Planck equation, with r.f.-induced diffusion, is developed, and using this solution together with Duane's fit to the D-T fusion cross-section, it is found that the nuclear-fusion power output from an r.f.-produced two-component plasma can significantly exceed the incremental (radiofrequency) power input.

Convective transport by intermittent blob-filaments: Comparison of theory and experiment

Abstract: A blob-filament (or simply “blob”) is a magnetic-field-aligned plasma structure which is considerably denser than the surrounding background plasma and highly localized in the directions perpendicular to the equilibrium magnetic field B. In experiments and simulations, these intermittent filaments are often formed near the boundary between open and closed field lines, and seem to arise in theory from the saturation process for the dominant edge instabilities and turbulence. Blobs become charge-polarized under the action of an external force which causes unequal drifts on ions and electrons; the resulting polarization-induced E × B drift moves the blobs radially outwards across the scrape-off-layer (SOL). Since confined plasmas generally are subject to radial or outwards expansion forces (e.g., curvature and ∇B forces in toroidal plasmas), blob transport is a general phenomenon occurring in nearly all plasmas. This paper reviews the relationship between the experimental and theoretical results on blob form...

A review of zonal flow experiments

Abstract: The present status of zonal flow experiments is reviewed with the historical process to attain the concept of zonal flows, which provides a new framework for understanding turbulence and transport in toroidal plasmas. The existence of zonal flows is experimentally confirmed to present a new paradigm of plasma turbulence. The paper presents contemporary experiments on zonal flows as major topics with a brief presentation of the zonal flow theories, the diagnostics and data processing techniques for turbulence and zonal flows and the peripheral issues of zonal flow physics. The accumulated experimental results introduced in this review include identification of zonal flows (both stationary zonal flows and geodesic acoustic modes), nonlinear interactions between zonal flows and turbulence, quantification of turbulent Reynolds stress, flow dynamics, energy transfer dynamics between turbulent wave components and the effects of zonal flows on plasma transport. These results have given rise to a new paradigm, namely, that the plasma turbulence is a system of zonal flows and drift waves, with an emphasis on the interaction between the disparate scale structures, e.g. zonal flows (mesoscale) and turbulence (micro-scale).

Electric probes for plasmas: The link between theory and instrument

Abstract: Electric probe methods for diagnostics of plasmas are reviewed with emphasis on the link between the appropriate probe theories and the instrumental design. The starting point is an elementary discussion of the working principles and a discussion of the physical quantities that can be measured by the probe method. This is followed by a systematic classification of the various regimes of probe operation and a summary of theories and methods for measurements of charged particle distributions. Application of a single probe and probe clusters for measurements of fluid observables is discussed. Probe clusters permit both instantaneous and time-averaged measurements without sweeping the probe voltage. Two classes of applications are presented as illustrations of the methods reviewed. These are measurements of cross sections and collision frequencies (plasma electron spectroscopy), and measurements of fluctuations and anomalous transport in magnetized plasma.