Search results for "aw"

XUV diagnostic to monitor H-like emission from B, C, N, and O for the W7-X stellarator

2019

The “C/O Monitor” system for the Wendelstein 7-X (W7-X) stellarator is a dedicated spectrometer with high throughput and high time resolution (order of 1 ms) for fast monitoring of content of low-Z impurities in the plasma. The observed spectral lines are fixed to Lyman-α lines of H-like atoms of carbon (3.4 nm), oxygen (1.9 nm), nitrogen (2.5 nm), and boron (4.9 nm). The quality of the wall condition will be monitored by the measurements of oxygen being released from the walls during the experiments. The strong presence of carbon is an indication for enhanced plasma-wall interaction or overload of plasma facing components. The presence of nitrogen (together with oxygen) may indicate a poss…

X-ray diffraction Warren–Averbach mullite analysis in whiteware porcelains: influence of kaolin raw material

2018

ABSTRACTCompositional and microstructural analysis of mullites in porcelain whitewares obtained by the firing of two blends of identical triaxial composition using a kaolin B consisting of ‘higher-crystallinity’ kaolinite or a finer halloysitic kaolin M of lower crystal order was performed. No significant changes in the average Al2O3 contents (near the stoichiometric composition 3:2) of the mullites were observed. Fast and slow firing at the same temperature using B or M kaolin yielded different mullite contents. The Warren–Averbach method showed increase of the D110 mullite crystallite size and crystallite size distributions with small shifts to greater values with increasing firing temper…

3D magnetic and thermal fields for in the transformer with homogenised amorphous C-core under high frequency

2017

Current Spreading Length and Injection Efficiency in ZnO/GaN-Based Light-Emitting Diodes

2019

We report on carrier injection features in light-emitting diodes (LEDs) based on nonintentionally doped-ZnO/p-GaN heterostructures. These LEDs consist of a ZnO layer grown by chemical-bath deposition (CBD) onto a p-GaN template without using any seed layer. The ZnO layer (~1- $\mu \text{m}$ thickness) consists of a dense collection of partially coalesced ZnO nanorods, organized in wurtzite phase with marked vertical orientation, whose density depends on the concentration of the solution during the CBD process. Due to the limited conductivity of the p-GaN layer, the recombination in the n-region is strongly dependent on the spreading length of the holes, ${L}_{h}$ , coming from the p-contact…

A new Collinear Apparatus for Laser Spectroscopy and Applied Science (COALA).

2020

We present a new collinear laser spectroscopy setup that has been designed to overcome systematic uncertainty limits arising from high-voltage and frequency measurements, beam superposition, and collisions with residual gas that are present in other installations utilizing this technique. The applied methods and experimental realizations are described, including an active stabilization of the ion-source potential, new types of ion sources that have not been used for collinear laser spectroscopy so far, dedicated installations for pump-and-probe measurements, and a versatile laser system referenced to a frequency comb. The advanced setup enables us to routinely determine transition frequenci…

Guiding and splitting Lamb waves in coupled-resonator elastic waveguides

2018

Abstract We investigate experimentally Lamb wave propagation in coupled-resonator elastic waveguides (CREWs) formed by a chain of cavities in a two-dimensional phononic crystal slab with cross holes. Wide complete bandgaps, extending from 53 to 88 kHz, are first measured in a finite phononic crystal slab sample. A straight waveguide and a wave splitting circuit with 90° bends are then designed, fabricated and measured. Elastic Lamb waves are excited by a piezoelectric patch attached to one side of the phononic slab and detected using a scanning vibrometer. Strongly confined guiding and splitting at waveguide junctions are clearly observed for several guided waves. Numerical simulations are …

Determination of refractive index of submicron-thick films using resonance shift in a four-layer slab waveguide

2017

The measurement of refractive index of very thin films at the order of ten to hundred nanometers is cumbersome and usually requires employing sophisticated techniques such as the spectral ellipsometry. In this paper we describe a simple contact method for measuring the refractive index of thin films. Here we have used the prism-coupling technique for characterizing samples prepared as four-layer slab waveguides. The waveguide resonance condition can be calculated by solving simple analytic transcendental equations for the slab waveguide. Then the captured mode position as a function of cladding thickness is used for probing the refractive index of cladding layer. We used indium-tin-oxide la…

Multi-pulse characterization of trapping/detrapping mechanisms in AlGaN/GaN high electromobility transistors

2019

GaN high-electro mobility transistors (HEMTs) are among the most promising candidates for use in high-power, high-frequency, and high-temperature electronics owing to their high electrical breakdown threshold and their high saturation electron velocity. The applications of these AlGaN/GaN HEMTs in power converters are limited by the surface trapping effects of drain-current collapse. Charge-trapping mechanisms affect the dynamic performance of all GaN HEMTs used in power switching applications. This study analyzes the dynamic resistance of GaN HEMTs and finds that the effects of dynamic resistance can be suppressed by controlling switching conditions and on-off cycles.

Crystalline phase detection in glass ceramics by EPR spectroscopy

2018

The advances of EPR spectroscopy for the detection of activators as well as determining their local structure in the crystalline phase of glass ceramics is considered. The feasibility of d-element (Mn2+, Cu2+) and f-element (Gd3+, Eu2+) ion probes for the investigation of glass ceramics is discussed. In the case of Mn2+, the information is obtained from the EPR spectrum superhyperfine structure, for Gd3+ and Eu2+ probes – from the EPR spectrum fine structure, whereas for Cu2+ ions the changes in the EPR spectrum shape could be useful. The examples of EPR spectra of the above-mentioned probes in oxyfluoride glass ceramics are illustrated. ----/ / /---- This is the preprint version of the fol…

Power efficiency improvements with the radio frequency H− ion source

2016

CW 13.56 MHz radio frequency-driven H(-) ion source is under development at the University of Jyväskylä for replacing an existing filament-driven ion source at the MCC30/15 cyclotron. Previously, production of 1 mA H(-) beam, which is the target intensity of the ion source, has been reported at 3 kW of RF power. The original ion source front plate with an adjustable electromagnet based filter field has been replaced with a new front plate with permanent magnet filter field. The new structure is more open and enables a higher flux of ro-vibrationally excited molecules towards the plasma electrode and provides a better control of the potential near the extraction due to a stronger separation …