Power Absorption Efficiency Research Articles

Characteristic of VHF plasma produced by balanced power feeding

The characteristics of a VHF hydrogen plasma produced by a balanced power feeding method were examined using a two-dimensional hybrid model. The simulation results showed that the electron density peaks at a certain pressure inside the discharge electrodes and significantly decreases outside the electrodes for high gas pressure. In addition, the power absorption efficiency inside the electrodes was improved by increasing the gas pressure. On the other hand, the plasma was produced within the electrodes for low applied voltages.

Very High Absorption of Traveling Wave Photodetectors in Superconducting Fiber Plasmon–Polariton Optical Waveguides

By using a finite element method, we investigate a new, very sensitive, superconducting traveling wave photodetector made by an optical fiber, which includes a high index layer (LaAlO3) with small losses, a number of metallic (gold) cylinders, and a single active superconducting layer (YBCO). Although in our structure of the fiber with 32 smaller gold cylinders, the number of the modes is large (3 nondegenerate modes and 16 twofold degenerate modes), the imaginary parts of the HE11, TM01, HE12, and higher order plasmon modes and also the power absorption (0.93 for HE11,0.91 for HE12,0.95 for TM01 and larger than 0.93 for all higher order plasmon modes) in the active superconducting layer are larger in comparison with that of a fundamental mode from a LaAlO3–YBCO–Au planar waveguide or with that of the HE11, TM01, HE12 modes from a model previously published where the gold cylinders are replaced with a single gold layer. The nondegenerate HE11 mode and the highest nondegenerate plasmon mode are highly confined in the YBCO layer in the space between the neighboring gold cylinders. Also, the plasmon mode TM01 is highly confined in the YBCO layer but on the exterior surface of the gold cylinders. The HE12 and the higher plasmon modes are highly confined in the YBCO layer in the space between the neighboring gold cylinders or very close to their exterior surface. The confinement regimes of the light and the power absorption efficiency in the superconducting layer can be optimized by only acting on the fiber geometry.

Power absorption efficiency of a new microstructured plasmon optical fiber

The propagation in a new microstructured plasmon optical fiber specifically designed for sensing of water dissolved chemicals is investigated using a finite element method. The fiber is made by a silica core with a small air hole in the center of the structure, surrounded by six air holes placed at the vertices of a hexagon, and further enclosed by gold and water layers. In order to enhance the sensitivity, the structure is designed to have the phase matching point corresponding to the maximum of the power fraction for a core guided mode in the water and gold layers and to a minimum in the glass layer, and vice versa for the plasmon mode. This way, near the phase matching point there is a strong interaction between the core and plasmon modes, causing a splitting in the real part of the propagation constant and also a shift of the imaginary part of the effective index toward the higher wavelengths. The real part of the group refractive index shows a minimum (maximum for the group velocity) and a very small value of the imaginary part of the group refractive index near the phase matching point for the degenerate core mode. When the analyte refractive index is increased by 0.001 RIU, the phase matching point is shifted by 4 nm toward longer wavelengths, with a corresponding sensitivity better than 2.5×10−5  RIU.

Absorption Efficiency of Traveling Wave Photodetectors in Superconducting Fiber Plasmon–Polariton Optical Waveguides

By using an analytical model and a finite element method, we investigate a new, very sensitive, superconducting traveling wave photodetector made by an optical fiber, which includes a high index layer (LaAlO3) with small losses, a metallic (gold) layer, and two active superconducting layers (YBCO). While the fundamental guided degenerate mode HE11 is highly confined in the interior YBCO layer, the plasmon non-degenerate mode TM01 and plasmon degenerate mode HE12 are tightly confined in the exterior superconducting layer. In our structure of the fiber with five layers (without a buffer layer), the imaginary parts of the HE11, TM01, HE12 modes and the power absorption efficiency in superconducting layers are larger in comparison with that of a fundamental mode from a LaAlO3–YBCO–Au planar waveguide. The confinement regimes of the light and the power absorption efficiency in superconducting layers can be optimized by only acting on the fiber geometry.

Sensitivity of Traveling Wave Photodetectors in Superconducting Fiber Plasmon–Polariton Optical Waveguides

By using an analytical model and a finite element method, we investigate a new, very sensitive, superconducting traveling wave photodetector made by a fiber waveguide, which includes a high index layer, a metallic layer, and an active superconducting layer. A comparison with the corresponding superconducting box shaped waveguide shows that a larger number of modes (HE11, TM01 and HE12) are obtained in optical fiber due to the surface plasmon–polariton modes at the interfaces between gold and air layers or between gold and YBCO layers. The radial component of the electric field is perpendicular to the metal surface and has sign changes at the gold boundaries as in the simple case of surface plasmon polaritons on metal cylinder with dielectric core. In a structure of the fiber with six layers, the imaginary parts of the TM01, HE12 modes, and the power absorption efficiency in superconducting layer are larger in comparison with that of the fiber with five layers. The confinement regimes of the light and the power absorption efficiency in superconducting layer can be optimized by only acting on the fiber geometry.

Power Absorption Efficiency in Superconducting Fiber Optical Waveguides

By using an analytical model and a finite element method, we investigate a new, very sensitive, superconducting traveling wave photodetector made by a fiber waveguide, which includes two high index layers and an active superconducting layer. A comparison with the corresponding superconducting box shaped waveguide shows that a larger width of the superconducting layer can be used to obtain single degenerate hybrid mode HE11. The real part of the propagation constants in the fiber is smaller in comparison with that of the box-shaped waveguide with similar dimensions but the imaginary part of the propagation constant and the power absorption efficiency in superconducting layer are comparable with those of the corresponding box-shaped waveguide. The confinement regimes of the light and the power absorption efficiency in superconducting layer can be optimized by only acting on the fiber geometry.

Dependence of EC-Driven Current on the EC-Wave Beam Direction in LHD

Electron cyclotron current drive (ECCD) experiments were conducted in the Large Helical Device to investigate the characteristics of EC-driven current and its profile and the possibility of controlling current and rotational transform profiles by ECCD. Successful ECCD helps prevent magnetohydrodynamic instabilities in plasmas. Scanning the EC-wave beam direction with a long pulse width of 8 s revealed a systematic change in the plasma current. The current's direction was reversed by a reversal of the beam direction. The direction agrees with the prediction of Fisch-Boozer theory regarding EC-wave beam injection from low-field side. The maximum driven current is 9 kA with an EC-wave power of 100 kW. The optimum beam direction that maximizes the driven current is investigated with the help of ray-tracing code. This direction depends on the magnetic field, efficiency of power absorption, and fraction of the power absorbed by trapped electrons.

Efficiency of Traveling-Wave Photodetectors in Superconducting Box-Shaped Metamaterial Optical Waveguides

Using finite element simulations we investigate a new, very sensitive, superconducting traveling-wave photodetector made from a modified box-shaped waveguide, which includes a high-index layer, a metamaterial layer and an active superconducting layer. The maximum of the electric field is shifted from the middle of the waveguide towards an interface which includes the active YBCO layer for an optimum imaginary part of the refractive index of the metamaterial. For some values of the refractive index of metamaterial and an optimized geometry of the waveguide, the power absorption efficiency in superconducting layer is comparable with or better than that of the plasmon–polariton optical waveguide.

Sensitivity of Traveling Wave Photodetectors in Superconducting Box-Shaped Plasmon-Polariton Optical Waveguides

A new, very sensitive, superconducting traveling-wave photodetector made by a modified box-shaped waveguide, which includes a high-index layer, a metallic layer, and an active superconducting layer, is studied. The light confinement regimes and the power absorption efficiency in superconducting layer can be maximized by optimizing only the waveguide geometry.

Oscillating water column at a coastal corner for wave power extraction

We extend the analytical theories by Martin-Rivas and Mei 1 1 In J. Fluid Mech. 2008 and Ocean Engineering 2009. to examine a large circular oscillating water column (OWC) installed at the tip of a coastal corner. Under the assumption of irrotational flow, a linear theory is employed. The sea depth is assumed to be constant everywhere. The diffraction and radiation problems are solved by eigenfunction expansions for an arbitrary apex angle. After calculating certain hydrodynamic coefficients, the power-absorption efficiency is obtained for two special geometries: a convex and a concave corner of right angle. For an OWC of given dimensions, the optimum efficiency is first examined by assuming that the extraction parameter can be controlled for all wave frequencies. The effects of column radius and height, the size of the submerged opening and the angle of incidence are studied. Comparisons are made between the two cornered coasts and with a thin breakwater and a straight coast studied before. Finally a simpler scheme of letting the extraction parameter be piecewise constant is shown to be a practical alternative.

Power Absorption Efficiency in Superconducting Box-Shaped Optical Waveguides

A very sensitive superconducting traveling wave photodetector made of a modified box-shaped waveguide, which includes two high index layers and an active superconducting layer, is studied. The optical propagation constants and the power absorption efficiency for guided modes are determined using the finite element method; the results show that by acting only on the waveguide geometry, different confinement regimes of the light in the absorption superconducting layer can be achieved and optimized.

Brownian rotational relaxation and power absorption in magnetite nanoparticles

We present a study of the power absorption efficiency in several magnetite-based colloids, to asses their potential as magnetic inductive hyperthermia (MIH) agents. Relaxation times τ were measured through the imaginary susceptibility component χ ″ ( T ) , and analyzed within Debye's theory of dipolar fluid. The results indicated Brownian rotational relaxation and allowed to calculate the hydrodynamic radius close to the values obtained from photon correlation. The study of the colloid performances as power absorbers showed no detectable increase of temperature for dextran-coated Fe 3O 4 nanoparticles, whereas a second Fe 3O 4-based dispersion of similar concentration could be heated up to 12 K after 30 min under similar experimental conditions. The different power absorption efficiencies are discussed in terms of the magnetic structure of the nanoparticles.

振動水柱型波力発電装置の一次変換効率に関する基礎的研究

It is presented how to calculate the efficiency of wave power absorption by oscillating water column type wave power devices installed to breakwaters. Experimental results and theoretical calculation results on amplitude of pressure and water lever in air chambers are shown. The theoretical calculation results, in which the compressibility of air is taken account and the pressure surface condition on water surface is strictly satisfied within the range of liner theory, are good agreement with experimental ones in the case when the period of incoming wave is long. In the case of wave length being short, the agreements are improved by taking the energy loss due to vortex shedding under the edge of curtain wall into consideration. The energy absorption characteristics of the chamber partitioned into two regions by a vertical or horizontal plate are shown. Such cambers have two resonant period corresponding with the dimensions of each partitioned region . The wave power device partitioned by a vertical plate is considered to have more applicable characteristics of wave power absorption as compared with the one by a horizontal plate.

Effects of assistant anode on planar inductively coupled magnetized argon plasma in plasma immersion ion implantation

The enhancement of planar radio frequency (RF) inductively coupled argon plasma is studied in the presence of an assistant anode and an external magnetic field at low pressure. The influence of the assistant anode and magnetic field on the efficiency of RF power absorption and plasma parameters is investigated. An external axial magnetic field is coupled into the plasma discharge region by an external electromagnetic coil outside the discharge chamber and an assistant cylindrical anode is inserted into the discharge chamber to enhance the plasma discharge. The plasma parameters and density profile are measured by an electrostatic Langmuir probe at different magnetic fields and anode voltages. The RF power absorption by the plasma can be effectively enhanced by the external magnetic field compared with the nonmagnetized discharge. The plasma density can be further increased by the application of a voltage to the assistant anode. Owing to the effective power absorption and enhanced plasma discharge by the assistant anode in a longitudinal magnetic field, the plasma density can be enhanced by more than a factor of two. Meanwhile, the nonuniformity of the plasma density is less than 10% and it can be achieved in a process chamber with a diameter of 600 mm.

Experimental investigation of discharge characteristics of a surface‐wave‐produced planar plasma

AbstractExperimental investigations of the discharge characteristics of planartype surfacewaveproduced plasmas (SWP) have been carried out. On this apparatus, the efficiency of microwave power absorption into the plasma depends strongly on the thickness of the dielectric window. Especially at a thickness of 12 mm, it has been found that more than 80% of microwave power is absorbed into the plasma. In order that the uniform power absorption is brought about effectively in a wide range of gas pressures, the dielectric waveguide that is placed above the dielectric window needs the air gap between them. These experimental results will enable us to improve the apparatus configuration to achieve better operational performances of surface wave plasmas. © 2001 Scripta Technica, Electr Eng Jpn, 138(3): 9–18, 2002

Ion and electron heating in ICRF heatingexperiments on LHD

The ICRF heating experiments conducted in 1999 in the third experimental campaign on LHD are reported, with an emphasis on the optimization of the heating regime. Specifically, an exhaustive study of seven different heating regimes was carried out by changing the radiofrequency relative to the magnetic field intensity, and the dependence of the heating efficiency on H minority concentration was investigated. It was found in the experiment that both ion and electron heating are attainable with the same experimental set-up by properly choosing the frequency relative to the magnetic field intensity. In the cases of both electronheating and ion heating, the power absorption efficiency depends on the minority ion concentration. An optimum minority concentration exists in the ion heating case while, in the electron heating case, the efficiency increases with concentration monotonically. A simple model calculation is introduced to provide a heuristic understanding of these experimental results. Among the heating regimes examined in this experiment, one of the ion heating regimes was finally chosen as the optimized heating regime and various high performance discharges were realized with it.

A ferrite core/metallic sheath thermoseed for interstitial thermal therapies.

An alternative form of ferromagnetic seed for thermal therapy has been developed following Matsuki, Murakami, and their colleagues [1]-[4]. A nearly lossless ceramic ferrite core (FC) is surrounded by an electrically conductive sheath. The FC has a high relative intrinsic permeability, typically 3000 at low magnetic field strengths, and a sharp transition from the ferrimagnetic state to the nonmagnetic state. The sheath is either a metallic tube or coating on the core. When this composite seed is excited with a radiofrequency magnetic field, large eddy currents are induced in the metallic sheath (MS) due to the concentrated magnetic flux in the core leading to Joule heating. Advantages of this configuration are that this ferrite core/metallic sheath (FC/MS) thermoseed has high power absorption efficiency and a sharp transition compared to ferromagnetic alloy systems; means of optimizing efficiency are apparent from simple expressions; the outer sheath can be of any biocompatible metal; the production method for the ferrites leads to large quantities of seeds with reproducible properties. The FC/MS configuration solves many of the technical problems that have hindered the clinical implementation of thermally regulating ferromagnetic implants for thermal therapies.

Characteristics of ECR plasmas for weakly resonant conditions

We investigated the characteristics of microwave plasmas in various magnetic field strengths. It was found by controlling the magnetic field strength that plasmas produced at 100 Gauss have higher plasma parameters and better homogeneity than plasmas which satisfy the electron cyclotron resonance (ECR) condition ( B = 875 Gauss). The efficiency of microwave power absorption into the plasma is better at weak magnetic field strengths than that under the ECR condition because the absorption of microwaves occurs in the whole vacuum chamber at weak magnetic field strengths. From the point of view of device and power efficiency, plasmas obtained at weak magnetic field strengths are considered to be very useful for plasma processing.

Laser-sustained plasmas in forced argon convective flow. I - Experimental studies

The results of an experimental investigation of the properties of laser-sustained plasmas in argon at forced convective flow speeds of 0.4-4.5 m/s are reported in this paper. At these speeds, the incident flow rate has a significant effect on the shape, size, and position of the plasma, which in turn affect the power absorption, thermal radiation, and total energy conversion efficiency of the plasma. In addition to the incident flow rate, the focusing geometry, chamber pressure, and laser power were varied as parameters in the experiments. The thermal conversion efficiency was found to range 9-38%, depending on the various parameters.

Wave power extraction at coastal structures by means of pendulor system. The first experimental Operation of the plant at Muroran-Port.

The authors reported on a 5kW wave power plant previously, which was deigned and installed by us. The plant consists of caisson which has two open water chambers faced to the offshore, and a wave pendulor in hung down in the pendulor drives an energy converter. Since April in 1983, the plant has been examined at Muroran-Port about 13 months. Through the experimental Operation, followings have been proved. 1. The plant is durable against to the rough sea. 2. Optimal efficiency of the wave power absorption is about 40∼50%. 3. The measured out put of oil motor is 16∼24 kW under 250% of rating wave power.