Search results for "Conde"
showing 10 items of 14592 documents
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…
Injected 1+ ion beam as a diagnostics tool of charge breeder ECR ion source plasmas
2015
International audience; Charge breeder electron cyclotron resonance ion sources (CB-ECRIS) are used as 1+ →n+ charge multiplication devices of post-accelerated radioactive ion beams. The charge breeding process involves thermalization of the injected 1+ ions with the plasma ions in ion–ion collisions, subsequent ionization by electron impact and extraction of the n+ ions. Charge breeding experiments of 85Rb and 133Cs ion beams with the 14.5 GHz PHOENIX CB-ECRIS operating with oxygen gas demonstrate the plasma diagnostics capabilities of the 1+ injection method. Two populations can be distinguished in the m/q-spectrum of the extracted ion beams, the low (1+ and 2+) charge states repres…
Topological insulator nanoribbon Josephson junctions: Evidence for size effects in transport properties
2020
We have used Bi$_2$Se$_3$ nanoribbons, grown by catalyst-free Physical Vapor Deposition to fabricate high quality Josephson junctions with Al superconducting electrodes. In our devices we observe a pronounced reduction of the Josephson critical current density $J_c$ by reducing the width of the junction, which in our case corresponds to the width of the nanoribbon. Because the topological surface states extend over the entire circumference of the nanoribbon, the superconducting transport associated to them is carried by modes on both the top and bottom surfaces of the nanoribbon. We show that the $J_c$ reduction as a function of the nanoribbons width can be accounted for by assuming that on…
Silicon Surface Passivation by ALD-Ga2O3: Thermal vs. Plasma-Enhanced Atomic Layer Deposition
2020
Silicon surface passivation by gallium oxide (Ga2O3) thin films deposited by thermal- and plasma-enhanced atomic layer deposition (ALD) over a broad temperature range from 75 °C to 350 °C is investigated. In addition, the role of oxidant (O3 or O-plasma) pulse lengths insufficient for saturated ALD-growth is studied. The material properties are analyzed including the quantification of the incorporated hydrogen. We find that oxidant dose pulses insufficient for saturation provide for both ALD methods generally better surface passivation. Furthermore, different Si surface pretreatments are compared (HF-last, chemically grown oxide, and thermal tunnel oxide). In contrast to previous reports, t…
Polarity conversion of GaN nanowires grown by plasma-assisted molecular beam epitaxy
2019
International audience; It is demonstrated that the N-polarity of GaN nanowires (NWs) spontaneously nucleated on Si (111) by molecular beam epitaxy can be reversed by intercalation of an Al-or Ga-oxynitride thin layer. The polarity change has been assessed by a combination of chemical etching, Kelvin probe force microscopy, cathodo-and photoluminescence spectroscopy and transmission electron microscopy experiments. Cathodoluminescence of the Ga-polar NW section exhibits a higher intensity in the band edge region, consistent with a reduced incorporation of chemical impurities. The polarity reversal method we propose opens the path to the integration of optimized metal-polar NW devices on any…
Object size effect on the contact potential difference measured by scanning Kelvin probe method
2010
International audience; Contact potential difference (CPD) was measured by macroscopic Kelvin probe instrument and scanning Kelvin probe microscope on Al, Ni and Pt on ITO substrates at ambient conditions. CPD values measured by scanning Kelvin probe microscope and macroscopic Kelvin probe are close within the error of about 10-30% for large studied objects, whereas scanning Kelvin probe microscope signal decreases, when the object size becomes smaller than 1.4 m. CPD and electric field signals measured using many-pass technique allowed us to estimate the influence of electrostatic field disturbance, especially, in the case of small objects.
Determination of Contact Potential Difference by the Kelvin Probe (Part I) I. Basic Principles of Measurements
2016
Abstract Determination of electric potential difference using the Kelvin probe, i.e. vibrating capacitor technique, is one of the most sensitive measuring procedures in surface physics. Periodic modulation of distance between electrodes leads to changes in capacitance, thereby causing current to flow through the external circuit. The procedure of contactless, non-destructive determination of contact potential difference between an electrically conductive vibrating reference electrode and an electrically conductive sample is based on precise control measurement of Kelvin current flowing through a capacitor. The present research is devoted to creation of a new low-cost miniaturised measuremen…
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…
Laser Ultrasonics Inspection for Defect Evaluation on Train Wheel
2019
Abstract Passengers’ safety and in-service life of wheelset axles play an important role in railway vehicles. For this reason, periodic inspections are necessary. Among non-destructive techniques, ultrasonic ones are widely applied in this field. The main disadvantage of conventional ultrasonic techniques is that the overall inspection of wheels requires the train to be put out-of-service and disassembly each part, which is time-consuming and expensive. In this paper, a non-conventional non-contact laser ultrasonic inspection for train wheels is proposed. The proposed method uses a laser interferometer to receive the ultrasonic wave without contact. The receiving system allows choosing the …