Search results for "Secondary emission"
showing 10 items of 16 documents
Study of the Secondary Electron Yield in Dielectrics Using Equivalent Circuital Models
2018
[EN] Secondary electron emission has an important role on the triggering of the multipactor effect; therefore, its study and characterization are essential in radio-frequency waveguide applications. In this paper, we propose a theoretical model, based on equivalent circuit models, to properly understand charging and discharging processes that occur in dielectric samples under electron irradiation for secondary electron emission characterization. Experimental results obtained for Pt, Si, GaS, and Teflon samples are presented to verify the accuracy of the proposed model. Good agreement between theory and experiments has been found.
Surface hysteresis curves of Fe(110) and Fe(100) crystals in ultrahigh vacuum — evidence of adsorbate influences
1992
Abstract We have investigated hysteresis curves of silicon-stabilized Fe(100) and Fe(110) crystals using Polarized Secondary Electron Emission (PSEE) for surface magnetization processes and Magneto-Optical Kerr Effect (MOKE) for bulk hysteresis curves. In particular, the influence of adsorbates (oxygen and sulphur) and surface roughness on the magnetization reversal has been studied. For surface hysteresis curves we found adsorbate-induced reductions of coercive force of up to 50%; the bulk hysteresis curves showed significantly smaller deviations. Similar changes were caused by surface disorder on an atomic scale induced by ion bombardment. The results agree qualitatively with a previous e…
Electron beam induced optical and electronical properties of SiO 2
2000
Abstract Ionizing radiation in dielectric and optically transparent silica as well as thin SiO 2 layers produces defect luminescence as well as charge storage. A comparison of different excitation–relaxation processes like cathodoluminescence, charge injection and trapping, secondary electron field emission, and exoelectron emission leads to a generally similar excitation dose behaviour described by an electron beam saturation dose of 0.01–0.1 C/cm 2 . This suggests a correlation of these four electron excitation mechanisms likely related to the same kind of defect in glassy SiO 2 , the 2-fold-coordinated silicon Si: centre with typical electronic singlet–singlet and singlet–triplet transit…
Analysis of Multipactor Effect in a Partially Dielectric-Loaded Rectangular Waveguide
2019
This paper 1 presents a study of the multipactor 2 effect in a partially dielectric-loaded rectangular waveguide. 3 To obtain the simulations presented in this paper, a detailed 4 analysis of the dynamics of the electron inside this waveguide 5 has been performed, taking into account the radio frequency 6 electromagnetic fields propagating in the waveguide and the dc 7 electric field that appears because of the charging of the dielectric 8 layer. This electrostatic field is obtained by computing the electric 9 potential produced by an arbitrary charge distribution on the 10 dielectric layer in a dielectric-loaded waveguide. The electron 11 trajectory is then found by numerically solving the…
Multipactor Discharges in Parallel-Plate Dielectric-Loaded Waveguides Including Space-Charge Effects
2008
[EN] The objective of this paper is to study the time evolution of multipactor discharges in a parallel-plate dielectric-loaded waveguide. The electron discharge phenomena investigated in this paper include the effects of space charge, as well as the presence of time varying static fields. In order to perform the simulations presented in this paper, an approach considering simultaneously multiple effective electrons has been used. The results obtained demonstrate that multipactor discharges do turn off by themselves under certain circumstances when they occur in such dielectric-loaded structures.
Time evolution of an electron discharge in a parallel-plate dielectric-loaded waveguide
2006
The objective of this letter is to study the time evolution of a multipactor discharge in a simple dielectric waveguide structure. In particular, the investigation is performed on the case of a parallel-plate waveguide structure partially filled with a dielectric layer. The main consequence of the specific case studied in this letter is the fact that the dielectric layer charges negatively, allowing a negative static field to build up. This dc field eventually leads to a single-surface multipactor in the metallic surface before finally turning off the electron discharge.
Untersuchung der Feldelektronenemission und ihrer Temperaturabh�ngigkeit bei Stromst�rken zwischen 10?14 und 10?19 A
1964
The field emission of a tungsten point cathode at very low emission currents was investigated by means of a secondary emission multiplier. The validity of the Fowler-Nordheim equation was experimentally confirmed within the range from 10−8 to 10−19 A. The dependence of the total emission current on temperature and electrical field strength was measured in the transition region between thermionic and field emission. A comparison is drawn with the theory ofMurphy andGood.
Preservation of quantum coherence after exciton-exciton interaction in quantum wells
2003
The dynamics of exciton-exciton interaction in quantum wells has been investigated by monitoring the time-resolved resonant secondary emission that follows excitation with linearly and circularly polarized light. Preservation of quantum beating in the cross-polarized emission demonstrates that spin relaxation can take place, for some scattering channels, without total quantum coherence loss. Interexciton electron exchange is the scattering mechanism that explains the persistence of the beating and, since it is sensitive to the fine structure of excitons, the shift by pi in the phase of the beating observed in the experiment.
Energy- and time-resolved microscopy using PEEM: recent developments and state-of-the-art
2008
Two novel methods of spectroscopic surface imaging are discussed, both based on photoemission electron microscopy PEEM. They are characterised by a simple electron-optical set up retaining a linear column. An imaging high-pass energy filter has been developed on the basis of lithographically-fabricated microgrids. Owing to a mesh size of only 7μm, no image distortions occur. The present energy resolution is 70 meV. The second approach employs time-of-flight energy dispersion and time-resolved detection using a Delayline Detector. In this case, the drift energy and the time resolution of the detector determine the energy resolution. The present time resolution is 180 ps, giving rise to an en…
Messungen zur Ansprechwahrscheinlichkeit und Impulshöhenverteilung eines Sekundärelektronenvervielfachers
1966
The pulse height distribution of a CuBe-secondary electron multiplier has been investigated under the action of single electrons. For an energy interval from 150 eV to 1000 eV the maximum pulse height increases with increasing electron energy (the energy corresponding to maximum yield being 365±10 eV). This shows the statistics of secondary electron emission as being dependant on primary electron energy.