This overview describes the confinement and structure of two-dimensional plasma crystals. Phonons and Mach cones in monolayer systems can be used for diagnostic purposes. Three-dimensional plasma crystals are found as multilayer systems or as Yukawa balls. The differences between Coulomb and Yukawa balls are described by means of a simple model. Optical diagnostic methods for studying dynamical phenomena in three-dimensional plasma crystals are discussed.

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In the fast ignition concept, assembled fuel is ignited through a separate high intensity laser pulse. Fast Ignition targets facilitate this ignition using a reentrant cone. It provides clear access through the overlaying coronal plasma, and controls the laser plasma interaction to optimize hot-electron production and transport into the compressed plasma. Recent results suggest that the cone does not play any role in guiding light or electrons to its tip, and coupling to electrons can be reduced by a small amount of preplasma. This puts stringent requirements on the ignition laser focusing, pointing, and prepulse.

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Astrophysical accretion is arguably the most prevalent physical process in the Universe; it occurs during the birth and death of individual stars and plays a pivotal role in the evolution of entire galaxies. Accretion onto a black hole, in particular, is also the most efficient mechanism known in nature, converting up to 40% of accreting rest mass energy into spectacular forms such as high-energy (X-ray and gamma-ray) emission and relativistic jets. Whilst magnetic fields are thought to be ultimately responsible for these phenomena, our understanding of the microphysics of MHD turbulence in accretion flows as well as large-scale MHD outflows remains far from complete. We present a new theoretical model for astrophysical disk accretion which considers enhanced vertical transport of momentum and energy by MHD winds and jets, as well as transport resulting from MHD turbulence. We also describe new global, 3D simulations that we are currently developing to investigate the extent to which non-ideal MHD effects may explain how small-scale, turbulent fields (generated by the magnetorotational instability — MRI) might evolve into large-scale, ordered fields that produce a magnetized corona and/or jets where the highest energy phenomena necessarily originate.

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A brief review is presented of transport in the boundary region of magnetized plasmas by blob-like filaments. Such structures have enhanced levels of particles and heat, are elongated along the magnetic field lines and are localized in the drift plane across the field. The motion of an isolated blob structure is described in some detail and the contribution of such filaments to turbulence-driven transport are discussed. Results are presented from numerical simulations and probe measurements in tokamak plasmas. An interpretation is given of the measured dependence of particle density and transport on experimental control parameters in the scrape-off layer.

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This review covers recent developments in multi-hundred-TW femtosecond laser systems and progress in intense laser-plasma interactions at the Institute of Physics, Chinese Academy of Sciences. The peak power of the institute's Xtreme Light III (XL-III) laser system has been upgraded from 350 to 725 TW, and the system used to observe the lateral transport of fast electrons due to magnetic and electrostatic fields at target surfaces. The surface fields cause fast-electron beams to be emitted along the front and rear target surfaces. Confinement and guiding of fast-electron propagation is demonstrated with wire- or wedge-shaped targets. Longitudinal transport is detected by optical and ion emission. Numerical simulations show that quasi-monoenergetic ion beams can be generated by collisionless electrostatic shock acceleration and phase-stable acceleration with a circularly polarized laser field. A new mechanism for high-power THz emission with plasmas as media is proposed; it can be used to obtain a single-cycle THz emission. The conversion efficiency from laser energy to K_α X-ray emission in a laser-copper target interaction is increased to 10^-4 using high-contrast laser pulses.

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Review of dusty plasma phenomena in application to geophysical problems is presented. Possible observational manifestations of dusty ionospheric plasmas during high-speed meteor showers are described. A unified explanation of ionization properties of the polar mesosphere under summer conditions is given. Dusty plasma processes are also considered in application to active geophysical rocket experiments which involve release of some gaseous substance in near-Earth space, the origin of the primary Earth's crust, hydrosphere, and atmosphere, and global electromagnetic Schumann resonances.

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We present a short review of recent developments in nonlinear quantum plasma physics, including quantum hydrodynamic and effective nonlinear shrödinger equation formalisms, for describing collective phenomena in quantum plasmas. As examples we discuss simulation studies of the formation and dynamics of dark solitons and vortices, and of nonlinear interactions between intense circularly polarized electromagnetic (CPEM) waves and electron plasma oscillations (EPOs) in dense in quantum electron plasmas. The electron dynamics of dark solitons and vortices is governed by a pair of equations comprising the nonlinear Schrödinger and Poisson equations. Both dark solitons and singly charged electron vortices are robust, and the latter tend to form pairs of oppositely charged vortices. The two-dimensional quantum electron vortex pairs survive during collisions under the change of partners. The dynamics of the CPEM waves is governed by a nonlinear Schrödinger equation, which is nonlinearly coupled with the Schrödinger equation of the EPOs via the relativistic ponderomotive force, the relativistic electron mass increase in the CPEM field, and the electron density fluctuations. The present governing equations in one spatial dimension admit stationary solutions in the form dark envelope solitons. The nonlinear equations admit the modulational instability of an intense CPEM pump wave against EPOs, leading to the formation and trapping of localized CPEM wave envelopes in the electron density holes that are associated with positive potential profiles.

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The next frontier for fusion science is the study of burning plasmas. The international ITER facility will advance research efforts into this new regime. In this paper we will first define burning plasmas and describe their distinctive features. One such feature is dominant self-heating (exothermic) by a large population of alpha particles, created from thermonuclear reactions. Next, we will briefly review how previous experiments on JET and TFTR to attain breakeven have laid the foundation for taking the present step to ITER. Then, we will describe various physics and technology issues that need to be addressed for burning plasmas. In addition to the scientific opportunities, we will also describe how ITER, being operated as a large-scale international project, is making progress in terms of organization, mission, funding, and programmatic coordination worldwide.

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This overview summarizes progress made to date on the Specially Promoted Research Project “Structure Formation and Selection Rule in Turbulent Plasmas.” Keys for the progress of the project are a change of view, from one that is linear, local, and deterministic to one that is nonlinear, nonlocal, and statistical, and the integration of theory, simulation, and experiment.

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At the LULI laboratory we developed since a few years a program on several topics related to laboratory astrophysics: high velocity jets, shock waves in density gradients, collisionless shocks, and radiative shocks (RS). In this paper, the latest experiments related to RS’s obtained on the new LULI2000 facility and on GEKKOXII are presented. In particular a strong radiative precursor was observed and its time evolution compared with 2D radiative simulations. The second topic developed at LULI is related to plasma jets which are often observed in Young Stellar Objects (YSO), during their phase of bulk contraction. They interact with the interstellar medium resulting in emission lobes, including the so-called bow shocks. The objective of our experiments was to generate plasma jets propagating through an ambient medium. To this aim, we developed a new target design (a foam filled cone ended with a “nozzle”) in order to generate a plasma jet. A jet-like structure was observed and its time evolution studied by varying the foam density. Interaction with ambient medium was recently performed showing growing instabilities for low density gas.

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Accelerator-based experiments have produced key breakthroughs in our understanding of the physical world. New accelerators, to explore the frontiers of Tera-scale Physics, appear possible, based on concepts developed over the last three decades in multi-disciplinary endeavors. The Plasma-Based Particle Accelerator is one concept that has made spectacular advances in the last few years. In this scheme, electrons or positrons gain energy by surfing the electric field of a plasma wave that is produced by the passage of an intense laser pulse or an electron beam through the plasma. This talk reviews the principles of this new technique and prognosticates how it is likely to impact science and technology in the future.

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Extreme ultraviolet lithography (EUVL) is a technology to be used in mass production of the next-generation semiconductor devices. Critical issues in the development of a Sn-based EUV source are in achieving a high conversion efficiency (CE) of incident laser energy into EUV light, reducing debris emanating from light source plasmas, and suppressing out-of-band radiation beside the EUV light. The minimum-mass target, which contains the minimum number of Sn atoms required for sufficient EUV radiation, is a solution to these critical issues. One practical-minimum mass target is a pure Sn microdroplet. Laser-driven expansion of a pure Sn microdroplet is proposed to solve the considerable mismatch between the optimal laser spot diameter (300 µm) and the diameter (20 µm) of microdroplets containing the minimum-mass Sn fuel for generating the required EUV radiant energy (10 mJ/pulse). An expanded microdroplet was irradiated with a CO₂ laser pulse to generate EUV light. A combination of low density and long scale length of the expanded microdroplet leads to a higher EUV energy CE (4%) than that (2.5%) obtained from planar Sn bulk targets irradiated by a single CO₂ laser pulse. This scheme can be used to produce a practical EUV light source system with an EUV CE of 3.9%.

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Interferometry for weakly relativistic plasmas is studied in this paper. It is shown that the phase difference in plasma and vacuum propagation becomes small due to the relativistic mass correction of electrons. The axisymmetric density profile obtained from the usual Abel inversion equation also becomes small by the correction factor, which is 1 ∼ 1.3 for T_e = 0 ∼ 60 keV. It is shown that we have to use the Abel inversion equation to take into account the relativistic mass correction of electrons in order to reconstruct the correct density profile.

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High power, single mode oscillations from a sub-terahertz gyrotron, at a second harmonic, were successfully demonstrated with pulse operation. A powerful electron gun was applied to attain high power oscillation. The resonant modes were selected carefully enough to oscillate singly and the cavity shape was optimized for the resonant modes to interact efficiently with an electron beam generated by the electron gun. Optimizing the operational parameters produced output powers of 33 and 27 kW, at frequencies of 349 and 389 GHz, respectively — the highest oscillation powers obtained to date in the sub-terahertz frequency region.

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An extension of geodesic acoustic mode (GAM) spectroscopy [Plasma Phys. Control. Fusion 49, L7 (2007)] is proposed. The ratio between the lowest frequency of the co-existing ion acoustic mode (IAM) and the frequency of GAM enables us to identify the safety factor of toroidal plasmas. The lowest frequency can be detected by bispectrum analysis when both GAM and IAM are excited. The possibility of measuring the safety factor is discussed.

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MHD instabilities followed by minor collapses in the TST-2 plasma are studied. Precursors with toroidal mode numbers n = 1 and n = 2 localized in the plasma's core become phase aligned so that their mode amplitudes strengthen each other at a certain spatial point. During phase alignment, the total mode amplitude on the soft X-ray radiation profile does not show significant change, and a minor collapse occurs but does not terminate the discharge. This behaviour is similar to the results during a non-linear growth phase in three-dimensional MHD simulations [N. Mizuguchi et al., Phys. Plasmas 7, 940 (2000)]. However, predicted pressure-driven modes are not confirmed in these experiments.

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Beam parameter requirements are estimated for generating warm dense matter (WDM) by means of an intense electron beam. An energy balance equation between input beam and energies distributed into a target is derived. Results show that a beam of lower kinetic energy has some advantages for WDM generation from the viewpoint of radiation loss and beam current. Results also indicate that WDM (2 mm × 2 mm) at 5000 K can be generated using an electron beam with parameters kinetic energy = 1 MeV, beam current = 2.3 kA, and pulse duration = 100 ns.

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Results from a scintillator-based lost-fast ion probe newly installed at the horizontally elongated outboard side of the Large Helical Device are presented. Correlating with bursts of toroidal Alfvén eigenmodes (TAEs) and energetic-particle continuum modes (EPMs), recurrent increases in beam ion losses were observed during co-neutral beam injections. Beam ion loss rate was also enhanced, correlating with low-frequency interchange modes driven by the bulk plasma pressure gradient near the plasma edge.

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To improve the accuracy of the magnetic field of Ring Trap-1 (RT-1), we have constructed a system of correction coils to cancel the geomagnetic field and control the attitude of the floating magnet. Without the geomagnetic field canccellation, the floating magnet tilts about 1.4 degrees. The previous prototype correction coils have been replaced by new coils that are much larger and farther from the chamber, so the error field due to the multipole components of the correction field is reduced by a factor of 30 (from 2.6% to 0.1% of the confinement field near the edge region). A significant improvement in plasma confinement has been observed (the stored energy of the plasma has been increased by a factor of 1.5).

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The collisional effects on the kinetics of interactions between a high-power subpicosecond laser and a solid-carbon thin film in a fast-ignition scenario are investigated by one-dimensional particle-in-cell simulations. Collisions are found to play an essential role in energy absorption and transport, compared to collisionless cases. In the collisional cases, the absorption at the heating edge, heat transport inside the thin film, and hot electron production are reduced in the early transient process.

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The axial profile of Balmer-alpha emission near a tungsten target has been measured in the compact plasma wall interaction (PWI) simulator Advanced PWI Simulation Experimental Device and Analysis System (APSEDAS). Axial H_α emission decreases toward the target at two levels, a steep gradient within 10 mm of the target and a shallow gradient more than 10 mm away. The structure of the H_α profile within 40 mm of the target is the same even though the electron density changes by one order of magnitude and the neutral pressure changes by a factor of three. On the other hand, the H_α profile more than 40 mm from the target gradually increases with increasing hydrogen filling pressure, although it does not change with the density in the case of constant filling pressure.

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A multi-hierarchy simulation model for magnetic reconnection studies is developed in which macroscopic and microscopic physics are expressed consistently and simultaneously. We are the first to have successfully demonstrated collisionless driven reconnection in the framework of a multi-hierarchy model. Magnetic reconnection is found to occur in a micro-hierarchy upon plasma injection from a macro-hierarchy.

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To acquire spatial profiles and energy spectra of hot electrons in ECH plasmas, we installed a soft x-ray pinhole camera in RT-1. In this publication, we compare the results of an initial experiment using a mechanically supported dipole field coil with the measurements of plasma pressure for different microwave frequencies. The results indicate that the coil support structure was the major loss channel for the high temperature electrons.

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Cryogenically cooled foam shells with deuterium and tritium fuels are expected to be utilized in the fast ignition realization experiment project of ILE, Osaka University, to demonstrate efficient heating of properly compressed fuel plasmas. These targets consist of a foam shell with solid fuel and a conical light guide for additional heating with an ultra-high intensity laser beam, in accordance with previous preliminary experiments [R. Kodama et al., Nature 412, 798 (2001).] Recent theoretical predictions and elemental experiments have suggested some advanced modifications to enhance the coupling efficiency of fast heating and improve implosion performance. The five major points of these improvements are as follows: 1) use of a low-Z foam layer on the inner surface of the cone; 2) use of a double-layered cone as a light guide; 3) use of a low-Z plastic layer on the outer surface of the cone; 4) adding a Br-doped plastic ablator to the fuel capsule; and 5) evacuation of the target center.

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In past years, the Research Center of Laser Fusion (RCLF) at the China Academy of Engineering Physics has developed many facilities and technologies in the field of ultrahigh-intensity lasers, physical diagnoses, and target fabrications for ICF experiments. This paper briefly reports some of the latest advances achieved and future plans at RCLF.

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An emulsion encapsulation method is applied to the fabrication of polymer capsules in inertial confinement fusion (ICF) experiments. Craters on the capsule surfaces make the capsules useless. This paper introduces the origins of the craters and focuses on ways to remove the craters from polymer capsules. Three origins are discussed and their influence can be restrained to reduce the cratering to meet the demand for mass production of targets.

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The focusing performance of a double magnetic lens and the delay in the arrival time at the shot point are presented for a Pb-coated superconducting inertial fusion energy target injection system. Magnets placed symmetrically in the injection path adjust the target trajectory and focus it toward the designated point. When the target passes through the magnetic lens, it receives deceleration and acceleration forces, producing a delay in the arrival time.

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In this paper, we report the progress made in fabrication of perdeuterated polymer foam materials such as deuterated polystyrene (d-PS), deuterated polyethene (d-PE), and deuterated divinylbenzene (d-DVB) based on the inertial confinement fusion (ICF) research in China. Perdeuterated DVB foams were fabricated using the high internal phase emulsion (HIPE) technique, and perdeuterated PS and PE foams were prepared via the thermally-induced phase separation (TIPS) of polymer solution and freeze-drying. As a result, foams with a deuterium/hydrogen (D/H) ratio of more than 95%, density of 10-200 mg/cm³ , and average porous sizes of 1-20 µm were obtained.

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Projectile-shooting experiments using a simple gas gun were carried out to address issues in target injection technology for fast-ignition-type inertial fusion energy. The gas gun consisted of a high-pressure gas reservoir, quick solenoid valve, and smooth-bore acceleration tube. Simple cylindrical projectiles were accelerated at room temperature by nitrogen gas and shot into a diagnostic chamber. In these experiments, we measured the flight speed, direction, and attitude of projectiles of different lengths. Longer projectiles showed better flight performance.

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One of the techniques to produce a uniform solid fuel layer for the Fast Ignition Realization EXperiment (FIREX) target is applying a solid fuel redistribution process. During the redistribution process, temperature control is essential for the FIREX target, because a cone guide, also called a conical laser guide, causes temperature non-uniformity. To minimize its temperature distribution, one possible procedure is temperature control at the cone guide. A radiation plate for indirect temperature control, installed next to the cone guide, is proposed. As the heat input to the radiation plate was varied, the temperature profile of the target was calculated using the ANSYS code. The optimal heat input was evaluated. The feasibility of using a radiation plate is discussed.

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N-doped diamond-like carbon (DLC) films were deposited on Si substrates by pulsed laser deposition (PLD) at varying N₂ pressure. The films were characterized by Raman spectroscopy and X-ray diffraction (XRD). Spectra show that the sp² hybridized carbon content increases with increasing N₂ pressure and that the films have a mainly amorphous structure. The residual stress of the films is reduced from 31.8 to −2.2 GPa by N-doping at appropriate N₂ pressure.

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In this study, colloidal crystal beads with controllable size, small-size dispersion, and good repeatability were fabricated. These beads have an optical stop-band and can be distinguished by their colors or spectra. Applications in genomics, proteomics, combinatorial chemistry, drug screening, and clinical diagnosis are anticipated.

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This article reports the latest progress in the manufacture of shell targets used for the first stage of the Fast Ignition Realization Experiment (FIREX-I). In the project, the targets are cooled to cryogenic temperature and filled with hydrogen isotope fuel through a gas feed tube. If the target has a leak or the gas feeder is blocked, the experiments cannot be carried out successfully and waste much time. The authors have developed a system to check integrity of the targets. SF₆ is used instead of H₂ or D₂ because of its high refractive index and low diffusivity. When SF₆ is loaded into the target, the optical path length that passes through a target is longer than that of an evacuated target. The difference can be measured with an interferometer. Analyzing the interference images, it is possible to know whether the gas feeder is blocked and a leak is present. The validity of the system was experimentally confirmed.

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Tin-doped resorcinol-formaldehyde (RF) aerogel was synthesized through immersion of tin (IV) alkoxide in RF gel and drying with supercritical carbon dioxide. The obtained density was 150-280 mg/cm³ , depending on the synthesis conditions. Despite the tin doping, the density is similar to that of undoped aerogel, implying that the shrinkage was suppressed. The cells were ∼50 nm in size, much finer than undoped RF. Such characteristics were discussed as they relate to chelate formation between tin (IV) and RF ligands.

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A target position measurement method using a compressed Arago spot image is presented for real time data processing. To decrease the amount of data of the Arago spot image, the image is optically compressed into a one dimensional line image by a cylindrical lens. The experimental results for a 5 mm diameter target demonstrated a measurement accuracy of 0.35 µm when the target was 10 m from a charge coupled device (CCD) camera.

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Ground penetrating radar (GPR) is a nondestructive sensor technology for detecting underground objects. GPR requires large-aperture antennas to survey a remote location precisely because of the expansion of microwaves. We propose a laser-driven GPR (LGPR) that uses microwave radiation from a laser plasma to achieve remote sensing. LGPR is expected to provide good spatial resolution with a small antenna. We selected a subnanosecond laser pulse as a suitable radiator for LGPR (L-S band). Experimental results show that the LGPR system can detect aluminum disks buried in sand.

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Details of the first repetitive operation of a 170 GHz long pulse gyrotron with quasi-CW (400 s pulse width) and high power are presented. The interval between pulses was 30 minutes, which matches the ITER operation scenario. The repetitive operation continued for 5 hours without problems and terminated as planned. The pressure inside the gyrotron returned to the original level after 20 minutes. This was the first operation for the high power gyrotron system applicable to ITER.

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The ascent velocity of long-lived plasmoids generated under atmospheric conditions to simulate ball lightning was estimated in [Fussmann et al., Phys. Unserer Zeit 39, 246 (2008) and Jegorov et al., Tech. Phys. 53, 688 (2008): Refs. 1 and 2 in the text, respectively], using a rigid sphere model with poor agreement with the experiment. The plasmoids were, however, deformed. Much better agreement is obtained using the Davies and Taylor formula, which describes the ascent velocity of large spherical-cap bubbles.

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In order to coat TiO₂ and TiN/TiO₂ films on glass over a large surface area for industrial application, plasma gun and magnetron sputtering processes were used. Also, nitrogen radicals were synthesized on the surface via the atmospheric plasma process. Hydrophilic characteristics were studied via water contact angle. Film adherence was tested via single stylus scratch tester. We also compared the XPS spectra between the nitrogen-synthesized and non-synthesized film and obtained the Ti2p peak shift towards the higher energy level proportional to film adherence. For photocatalytic film durability, the relationship best described, “the higher the critical load, the lower the contact angle, and the higher the binding energy” has become a unique interrelationship among the scratch tester, contact angle, and XPS spectra.

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In this paper we calculate and visualize the dynamics of an ensemble of electrons trapping in an electrostatic wave of slowly increasing amplitude, illustrating that, despite disordering of particles in angle during the trapping transition as they pass close to X-points, there is still an adiabatic invariant for the great majority of particles that allows the long-time distribution function to be predicted. Possible application of this approach to recent work on the nonlinear frequency shift of a driven wave is briefly discussed.

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Two types of solid hydrogen pellet injection systems have been developed, and plasma refueling experiments have been performed using these pellet injectors. One is an in-situ pipe-gun type pellet injector, which has the simplest design of all pellet injectors. This in-situ pipe-gun injector has 10 injection barrels, each of which can independently inject cylindrical solid hydrogen pellets (3.4 and 3.8 mm in diameter and length, respectively) at velocities up to 1,200 m/s. The other is a repetitive pellet injector with a screw extruder, which can form a 3.0 mmφ solid hydrogen rod continuously at extrusion rates up to 55 mm/s. This extruder allows consecutive pellet injection up to 11 Hz without time limit. Both of these pellet injectors employ compact cryo-coolers to solidify hydrogen; therefore, they can be operated using only electrical input instead of a complicated liquid helium supply system. In particular, using a combination of the repetitive pellet injector with cryo-coolers provides a steady-state capability with minimum maintenance.

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Laser-induced blow-off from a tungsten surface that was exposed to helium plasma is investigated experimentally in the divertor simulator NAGDIS-II. The pulse width of the laser is submillisecond and is similar to the duration of type-I edge localized modes in ITER. The temporal evolution of blow-off particles, which are visualized by the electron impact excitation in the surrounding plasma, is investigated by using filter spectroscopy. We demonstrate the effect of helium irradiation damages on the tungsten ejection behavior in response to a transient heat load.

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Aberrations due to the electrostatic lenses of a negative ion accelerator for a neutral beam injector and the space charge effect are theoretically investigated. A multi-stage extractor/accelerator is modeled and the aberration coefficients are numerically calculated using the eikonal method, which is conventionally used in electron optics. The aberrations are compared with the radii of a beam core with good beam divergence and a beam halo with poor beam divergence. H^- beamlet profile measurements give the 1/e radii of the beam core and beam halo of 5.8 mm (beam divergence angle: 6 mrad) and 11.5 mm (beam divergence angle: 12 mrad), respectively. When the beam divergence angle of the beam core is 5 mrad and the beam energy is 406 keV, the aberrations due to the electrostatic lenses are less than a few millimeters, thus are less than the radii of the beam core and beam halo. The geometrical aberrations due to the space charge effect (negative ion current density: 10 mA/cm² ), however, are estimated to be much larger than the radius of the beam halo. Although the aperture radii of the grids are not taken into account in this estimation, the results indicate that the space charge effect is an important factor in the aberration or beam halo in a negative ion accelerator.

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The energy dependence of the diffusion coefficients of α particles in rippled fields of tokamaks is numerically investigated with an orbit-following Monte Carlo code. The diffusion coefficients are enhanced around the ripple resonance energy while they are not so much enhanced in the neighborhood of it. Consequently, they have a local minimum near the resonance energy, and hence they have an M-shaped energy dependence. Ripple resonance is caused by a radial change of the toroidal precession of banana particles, and creates islands in (Nφ, ψ) phase space. Since particles outside the separatrix are the main contributors to diffusion enhancement, the M-shaped energy dependence is explained by the co-existence of open and closed orbits in the phase space. Ripple resonance diffusion is dominant for fusion-produced α particles since the resonance energy width occupies a large portion of the energy range in their slowing-down processes.

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Experiments at the microscopic scale show the shrinking and melting processes of porcelain by microwave and infrared heating. Microscopic in-situ observations reveal that the porcelain is sintered rapidly and volumetrically by microwaves. This experiment clarifies the differences between microwave and conventional heating.

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Recent experimental and theoretical studies of two-dimensional (2D) turbulence reveal that spectrally condensed turbulence which is a system of coupled large-scale coherent flow and broadband turbulence, is similar to plasma turbulence near the L-H transition threshold. Large condensate vortices fed via the turbulent inverse energy cascade, can control both the level of the broadband turbulence by shear decorrelation, and the energy injected into turbulence at the forcing scale via sweeping of the forcing-scale vortices. The interaction between these ingredients of spectrally condensed fluid turbulence is in many aspects similar to the interactions in the zonal flow-GAMs-turbulence system in plasma. In this paper we overview recent results on condensed 2D turbulence and present evidence of interaction between its three components: condensate structures, turbulence and forcingscale vortices. This is compared with the modifications in the spectra of plasma electrostatic potential during L-H transitions. It is shown that mean zonal flows are spatially and temporally correlated with both the broadband turbulence and with the narrow spectral range identified as the spectral range of the underlying instability.

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The propagation of small amplitude stationary profile nonlinear electrostatic excitations in a pair plasma is investigated, mainly drawing inspiration from experiments on fullerene pair-ion plasmas. Two distinct pair ion species are considered of opposite polarity and same mass, in addition to a massive charged background species, which is assumed to be stationary, given the frequency scale of interest. In the pair-ion context, the third species is thought of as a background defect (e.g. charged dust) component. On the other hand, the model also applies formally to electron-positron-ion (e-p-i) plasmas, if one neglects electron-positron annihilation. A two-fluid plasma model is employed, incorporating both Lorentz and Coriolis forces, thus taking into account the interplay between the gyroscopic (Larmor) frequency ω_c and the (intrinsic) plasma rotation frequency Ω₀. By employing a multi-dimensional reductive perturbation technique, a Zakharov-Kuznetsov (ZK) type equation is derived for the evolution of the electric potential perturbation. Assuming an arbitrary direction of propagation, with respect to the magnetic field, we derive the exact form of nonlinear solutions, and study their characteristics. A parametric analysis is carried out, as regards the effect of the dusty plasma composition (background number density), species temperature(s) and the relative strength of rotation to Larmor frequencies. It is shown that the Larmor and mechanical rotation affect the pulse dynamics via a parallel-to-transverse mode coupling diffusion term, which in fact diverges at ω_c → ±2Ω₀. Pulses collapse at this limit, as nonlinearity fails to balance dispersion. The analysis is complemented by investigating critical plasma compositions, in fact near-symmetric (T_- ≈ T₊) “pure” (n_- ≈ n₊) pair plasmas, i.e. when the concentration of the 3rd background species is negligible, case in which the (quadratic) nonlinearity vanishes, so one needs to resort to higher order nonlinear theory. A modified ZK equation is derived and analyzed. Our results are of relevance in pair-ion (fullerene) experiments and also potentially in astrophysical environments, e.g. in pulsars.

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An internal coil device called Ring Trap-1 (RT-1) has been constructed to explore an innovative concept for a high-beta plasma based on a new relaxation theory. A high-temperature superconductor (HTS) Bi-2223 tape is employed for the internal coil of RT-1. The coil is cooled to 20 K with helium gas supplied by G-M refrigerators, and charged to a magnetomotive force of 250 kA using an external power supply. For these cooling and charging methods, we have developed several innovative techniques such as a demountable transfer tube system, persistent current switch, detachable electrode, and others. In addition, we have paid much attention to the deterioration of the HTS tape during the fabrication of the internal coil. As a result, we have demonstrated that the decay of the persistent current of the internal coil is ∼1% during 8 h. The internal coil is lifted with a levitation coil located at the upper region of the vacuum vessel. The coil position monitored with laser sensors is feedback controlled through the regulation of the levitation coil current. Stable levitation for a few hours has been demonstrated for various plasma experiments.

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Significant progress has been made in understanding the scrape-off layer (SOL) mass transport along magnetic field lines — the SOL flow. Understanding the driving mechanisms of the SOL flow was summarized based on experiments in the JT-60U tokamak plasmas. Fast SOL flow with parallel Mach numbers of 0.2-1 was generated from the low magnetic field side (LFS) SOL to the high magnetic field side (HFS) divertor for the ion ∇B drift direction toward the divertor. The SOL flow pattern was formed mainly by the LFS enhanced in-out asymmetry in diffusion and by classical drifts in the torus. Detachment of the divertor plasma affected enhancement of the SOL flow at the HFS SOL. Dynamics of the SOL flow were measured during the transient event of edge localized modes (ELM), and the flow pattern of the plasma filaments was clarified at both SOLs. The radial movement of the ELM filaments at the LFS SOL was sometimes faster than the parallel convective transport to the divertor target, which caused the heat loading to the first wall. Filament structures with temporal peaks and flow velocities comparable to the ion sonic level were also determined in the HFS SOL, but they appeared only near the separatrix. The delay after start of the ELM was shorter than the parallel convection time from the LFS midplane, suggesting that part of the ELM filaments was ejected into the HFS SOL.

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A high poloidal beta, β_p, was achieved using pulsed poloidal current drive (PPCD) in a toroidal pinch experiment-RX (TPE-RX). The plasma electron density and temperature increased, hence improving β_p from 5 to 30% during PPCD. β_p is almost equal to the total beta in the reversed-field pinch (RFP). D-alpha emission from recycling deuterium by the plasma-wall interaction decreased during the PPCD. An improved particle confinement time was indicated by a ten fold increase in the ratio of the total number of particles to the D-alpha emission. Single pellet injection into the good particle confinement plasma, achieved by the PPCD, produced high density plasma with high beta values. The plasma electron density rapidly increased to triple that of standard plasma, and high density was maintained till the end of the PPCD period. The electron temperature was lower than that of PPCD without ice pellet injection, but β_p remained almost the same because the plasma electron density was higher with pellet injection.

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