Search results for "high"
showing 10 items of 25798 documents
High-Power Multicarrier Generation for RF Breakdown Testing
2017
Testing of satellite components for high RF power breakdown effects, such as multipactor and corona or passive-intermodulation, is a topic of growing interest in the aerospaceindustry. Switching fromthe classical single carrier approach to the more realisticmulticarrier scenario is very challenging from the experimental point of view. Themulticarrier signals, amplifiedby several RF power amplifiers, need to have controlled phase, amplitude, and frequency in each carrier. Fine tuning of the signal generator phases is required in order to compensate the phase drift occurring in the active elements of the test bed. This paper presents an efficient and low-cost technique to generate multicarrie…
Space charge behavior of different insulating materials employed in AC and DC cable systems
2017
In this work, the space charge accumulation in three different XLPE based material has been carried out by using the PEA (Pulsed Electro-Acoustic) method. The specimens provided by a cables industry have been subjected to the same DC stress during polarization time at environment temperature. Afterwards, the high voltage generator has been turned off and the amount residual charge has been evaluated. The space charge profiles during polarization and depolarization have been carried out and compared. Finally, the distribution of electric field within the samples has been reported. In particular, the maximum distortion of electric field has been calculated by taking into account the distribut…
Luminescence of divalent lanthanide doped BaBrI single crystal under synchrotron radiation excitations
2020
Abstract Luminescence excitation spectra of BaBrI single crystals doped by divalent lanthanide ions are studied using synchrotron radiation excitations from the MAX IV 1.5 GeV storage ring. The energy of the edge and the formation of core cation exciton as well as the energy threshold of the multiplications of electronic excitations is found. It was clearly established the energy transfer from intrinsic luminescence centers to Sm2+ and Eu2+ ions.
Systematic and statistical uncertainties of the hilbert-transform based high-precision FID frequency extraction method.
2021
Abstract Pulsed nuclear magnetic resonance (NMR) is widely used in high-precision magnetic field measurements. The absolute value of the magnetic field is determined from the precession frequency of nuclear magnetic moments. The Hilbert transform is one of the methods that have been used to extract the phase function from the observed free induction decay (FID) signal and then its frequency. In this paper, a detailed implementation of a Hilbert-transform based FID frequency extraction method is described, and it is briefly compared with other commonly used frequency extraction methods. How artifacts and noise level in the FID signal affect the extracted phase function are derived analytical…
SIC based solid state protections switches for space applications
2017
Development and technology maturation of Silicon Carbide (SiC) power transistors over the last 15 years has motivated its study in aerospace systems. When compared with Si devices, superior voltage blocking capacity and the capability of operation at higher temperatures, give important advantages in space power electronics applications, similar to what happens in terrestrial electronics. This paper discusses the use of SiC power transistors for Solid State Power Switches especially addressed to the space segment. Two applications will be covered, the first is the Solid State Shunt Switch, widely used in high power Direct Energy Transfer (DET) photovoltaic power regulators and the second is …
Contributed Review: Review of thermal methods for space charge measurement.
2016
The space charge accumulation phenomenon has garnered great interest over the last two decades because of the increased use of direct current in high voltage electrical systems. In this context, a significant relevance has been achieved by the thermal methods, used for solid dielectrics. This paper presents a review of this non-destructive measurement system used for the measurement of space charge. The thermal pulse method, the thermal step method, and the laser intensity modulation method are described. For each configuration, the principle of operation, the thicknesses analyzed, and the spatial resolution are described, reporting also the main related applications
Flash annealing influence on structural and electrical properties of TiO2/TiO/Ti periodic multilayers
2014
Abstract Multilayered structures with a 40 nm period composed of titanium and two different titanium oxides, TiO and TiO 2 , were accurately produced by DC magnetron sputtering using the reactive gas pulsing process. These multilayers were sputtered onto Al 2 O 3 sapphire to avoid substrate compound diffusion during flash annealing (ranging from 350 °C to 550 °C). Structure and composition of these periodic TiO 2 /TiO/Ti stacks were investigated by X-ray diffraction, X-ray photoemission spectroscopy and transmission electronic microscopy techniques. Two crystalline phases α-Ti and fcc-TiO were identified in the metallic-rich sub-layers whereas the oxygen-rich ones were composed of a mixture…
A multilayer model for self-propagating high-temperature synthesis of inter-metallic compounds
2007
International audience; Self-propagating high-temperature synthesis of intermetallic compounds is of wide interest. We consider reactions in a binary system in which the rise and fall of the temperature during the reaction is such that one of the reacting metals melts but not the other. For such a system, using the phase diagram of the binary system, we present a general theory that describes the reaction taking place in a single solid particle of one component surrounded by the melt of the second component. The theory gives us a set of kinetic equations that describe the propagation of the phase interfaces in the solid particle and the change in composition of the melt that surrounds it. I…
Space Charge Measurement under DC and DC Periodic Waveform
2018
In High Voltage systems, Partial Discharges (PDs) monitoring are one of the main diagnostic instrument to evaluate the reliability of the apparatus. Under Alternating Current (AC) stress, PDs detection and recognition techniques are well consolidated. On the contrary, the monitoring of PDs under Direct Current (DC) stress is difficult due to complexities related to the nature of the phenomenon, which cause the beginning of PDs events in proximity of the dielectric breakdown. This problem has been partially overcome by using a continuous Periodic waveform (DCP) with positive average value, as described in a recent published work. Under DC stress, another degradation factor is the Space Charg…
Structural characterization of TiO2/TiN O (δ-doping) heterostructures on (1 1 0)TiO2 substrates
2003
Abstract TiO2/TiNxOy δ-doping structures were grown on the top of (1 1 0)TiO2 rutile substrates by low pressure metal-organic vapor phase epitaxy (LP-MOVPE) technique at 750 °C. The samples were analyzed by high resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS) and X-ray diffraction techniques (rocking curves and φ-scans). The presence of satellites in the (1 1 0)TiO2 rocking curve revealed the epitaxial growth of 10 period δ-doping structures. The thickness of the TiO2 layers, 84 nm, was deduced from the satellites period. HRTEM observations showed around 1.5 nm thick δ-doping layers, where the presence of nitrogen was detected by EELS. The analy…