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This study developed a prototype of a wire-plate air bubbling plasma reactor that can be easily scaled up for wastewater treatment. The electrical characteristics, including the discharge current and average power consumed, of the developed reactor were deeply investigated at different operating parameters and solution conductivities. The performance of the reactor was examined on the basis of energy efficiency and methylene blue (MB) decoloration efficiency. Moreover, the removal of the total organic carbon and the changes of the physicochemical properties of solution, including pH, conductivity, and temperature, were evaluated. The analysis of current discharge and average power consumed showed that the discharge mode in the present reactor is a filamentary streamer. Interestingly, the solution conductivity had no effect on the average power consumed at low applied voltages, due to confinement of the discharge in a small area surrounding the discharge electrode in the gas phase. However, at relatively high voltages, the effect of conductivity on the average power consumed was noticeable, yet it had no effect on the decoloration efficiency at the same average power. The present reactor showed a high energy-efficiency value of 42 g/kWh at 50% decoloration of 30 mg/l MB solution, but it dropped to 14 g/kWh at 97% decoloration. A first-order kinetics model described well the decoloration reaction rates and the overall rate constant correlated linearly to the average power. [ABSTRACT FROM AUTHOR]

The lower hybrid current drive (LHCD) plays an important role in the long pulse and high performance experiments on the EAST Tokamak, using LHW systems with frequencies of 2.45 GHz and 4.6 GHz. With the initial parallel refractive index mostly peaking at n ∥ ∼ 1.8 − 2.1 , it is difficult to have on-axis LHCD due to the accessibility conditions which prevents the LHW from propagating into the plasma core. However, according to the investigation of HXR diagnostics, LHW did provide an on-axis current drive in an EAST experiment. To interpret this on-axis LHCD phenomenon, various physics effects that give rise to variations in parallel wave numbers, thus influencing the propagation and the absorption of the LHW, have been taken into account, such as toroidal effects, full wave effects with focusing and diffraction, and scattering effects due to density fluctuations. Numerical tools including ray-tracing and full wave codes that contain one or two of the above physics effects have been used to model the heating and current drive of the LHW on EAST. Linear Landau damping and quasi-linear Landau damping have been compared by using the coupling between ray-tracing and the Fokker-Planck codes. Convergence studies have been performed for the full wave modeling, the maximum poloidal modes in the full wave have been scanned, and the results are compared with each other. The factors that characterize the amplitude, the radial thickness, and the location of the density fluctuations have been studied and scanned. The measurement of HXR diagnostics has been compared with synthetic diagnostics by reconstructing the HXR data from both the standard GENRAY/CQL3D LHCD modelling and the modeling taking the scattering effects into account. [ABSTRACT FROM AUTHOR]

In this paper, we report the results of ion cyclotron resonance frequency (ICRF) heating in the central cell of a fully axisymmetric tandem mirror. With a total power of 100 kW radiated by double half-turn and half-turn antennas, the plasma diamagnetism increases by 15-fold, with a corresponding peak β ⊥ ∼2%, density ∼ 1.5 × 10 18 m − 3 , and total temperature ∼60 eV. The effects of the magnetic configuration on resonance heating and wave emission are studied by varying the magnetic fields at the midplane and at the location of the antennas, respectively; the results confirm that the magnetic beach configuration is key to successful ICRF heating. The axial phase speed measurements suggest that the excited wave is a slow wave in the plasma core and a fast wave at the edge. [ABSTRACT FROM AUTHOR]

A systematic investigation of the expansion dynamics of plasma plumes generated by two Q-switched Nd:YAG lasers at 1064 nm wavelength operating on a silicon target was undertaken for the inter-pulse delay times of 0, 100, 200, and 400 ns using a technique involving fast-gated intensified charge-coupled device imaging. Our results indicate that the plasmas exhibit free expansion in a vacuum environment at an inter-pulse delay time of 0 ns. With increasing inter-pulse delay time, the plasma front becomes sharpened and an interaction boundary is formed. Moreover, using the radiation intensity distribution along the plasma axis of symmetry, the formation and evolution mechanism of the plasmas generated by the double pulses was analyzed at different inter-pulse delay times. Finally, the experimental results of the expansion of the plasma core and front were compared with a radiation hydrodynamics model and a drag model, and were found to be generally in good agreement. [ABSTRACT FROM AUTHOR]

We have developed and fielded x-ray penumbral imaging on the National Ignition Facility in order to enable sub-10 μm resolution imaging of stagnated plasma cores (hot spots) of spherically shock compressed spheres and shell implosion targets. By utilizing circular tungsten and tantalum apertures with diameters ranging from 20 μm to 2 mm, in combination with image plate and gated x-ray detectors as well as imaging magnifications ranging from 4 to 64, we have demonstrated high-resolution imaging of hot spot plasmas at x-ray energies above 5 keV. Here we give an overview of the experimental design criteria involved and demonstrate the most relevant influences on the reconstruction of x-ray penumbral images, as well as mitigation strategies of image degrading effects like over-exposed pixels, artifacts, and photon limited source emission. We describe experimental results showing the advantages of x-ray penumbral imaging over conventional Fraunhofer and photon limited pinhole imaging and showcase how internal hot spot microstructures can be resolved. [ABSTRACT FROM AUTHOR]

By arranging the particle first banana orbits to pass near a distant detector, the light ion beam probe (LIBP) utilizes orbital deflection to probe internal fields and field fluctuations. The LIBP technique takes advantage of (1) the in situ, known source of fast ions created by beam-injected neutral particles that naturally ionize near the plasma edge and (2) various commonly available diagnostics as its detector. These born trapped particles can traverse the plasma core on their inner banana leg before returning to the plasma edge. Orbital displacements (the forces on fast ions) caused by internal instabilities or edge perturbing fields appear as modulated signal at an edge detector. Adjustments in the q-profile and plasma shape that determine the first orbit, as well as the relative position of the source and detector, enable studies under a wide variety of plasma conditions. This diagnostic technique can be used to probe the impact on fast ions of various instabilities, e.g., Alfvén eigenmodes (AEs) and neoclassical tearing modes, and of externally imposed 3D fields, e.g., magnetic perturbations. To date, displacements by AEs and by externally applied resonant magnetic perturbation fields have been measured using a fast ion loss detector. Comparisons with simulations are shown. In addition, nonlinear interactions between fast ions and independent AE waves are revealed by this technique. [ABSTRACT FROM AUTHOR]

Plasmas with internal transport barriers (ITBs) are a potential and attractive route to steady-state operation in ITER. These plasmas exhibit radially localized regions of improved confinement with steep pressure gradients in the plasma core, which drive large bootstrap current and generate hollow current profiles and negative magnetic shear. This work examines the formation and sustainment of ITBs in ITER with electron cyclotron heating and current drive. The time-dependent transport simulations indicate that, with a trade-off of the power delivered to the equatorial and to the upper launcher, the sustainment of steady-state ITBs can be demonstrated in ITER with the baseline heating configuration. [ABSTRACT FROM AUTHOR]