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Saturday, August 8, 2020 | History

2 edition of study of impregnated cathodes by scanning and emission electron microscopy found in the catalog.

study of impregnated cathodes by scanning and emission electron microscopy

Rolf S. Vatne

study of impregnated cathodes by scanning and emission electron microscopy

by Rolf S. Vatne

  • 83 Want to read
  • 8 Currently reading

Published .
Written in English

    Subjects:
  • Cathode rays.

  • Edition Notes

    Statementby Rolf S. Vatne.
    The Physical Object
    Paginationvii, 78 leaves :
    Number of Pages78
    ID Numbers
    Open LibraryOL16428898M

    Various scandate cathodes have been developed, including impregnated [24–26], pressed [27,28], and top-layered types [29–31]. Of these, scandate cathodes fabricated from starting powders of micron-scale tungsten (W) and nanoscale scandia (Sc2O3) are reported to exhibit the most promising emission characteristics and have been widely.   The proposed methods of fabricating electron emission cathodes using vertically aligned CNTs include The cathode morphology was evaluated by field-emission scanning electron microscopy (FE-SEM; SU, Hitachi High-Technologies Corp., Japan). The results obtained in this study show that the time-averaged power consumption for driving a.

    Scanning electron microscope From Wikipedia, the free encyclopedia Not to be confused with Scanning tunneling microscope. A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons. The electrons interact with atoms in the. This retrospective sketches the evolution of emission electron microscopy, low energy electron microscopy and related methods from the early stages up to the present state and gives a brief outlook on the future possibilities of these cathode lens electron microscopy techniques.

    Deerinck T. J. et al. Enhancing serial block-face scanning electron microscopy to enable high resolution 3D nanohistology of cells and tissues. Microsc. Microanal. 16, – (). Tapia J. C. et al. High-contrast en bloc staining of neuronal tissue for field emission scanning electron microscopy. Nat Protoc. 7, – (). A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons interact with atoms in the sample, producing various signals that can be detected and that contain information about the sample's surface topography and composition. The electron beam is generally scanned in a raster scan pattern.


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Study of impregnated cathodes by scanning and emission electron microscopy by Rolf S. Vatne Download PDF EPUB FB2

Scanning electron microscopy was used for investigating surface microstructures of both kinds of cathodes and the results show that the emitting surface of the cathode with Os-W alloy after ageing. adshelp[at] The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86AAuthor: Rolf Steinar Vatne.

A procedure for preparing field emission cathodes of single-crystal tungsten for CWIKSCAN/50() scanning electron microscopes to replace expensive imported cathodes is described.

Particular attention was paid to making the conical part of the emitter short in order to increase its operational stability and service life. Through careful study [3,5,9,10,[13][14] [15] [16], researchers have found that uneven electron emission from scandate cathodes could be attributed to the non-uniformity of scandium or scandium.

Scanning electron microscopy and spatially resolved cathodoluminescence were used to study porous silicon prepared by electrochemical degradation in aqueous HF of epitaxial p-type silicon grown on {} silicon substrates. Scanning electron microscopy revealed the porous silicon to be non-uniform.

The evolution of the electron emission of impregnated cathodes has been measured over many thousands of hours of operation at various temperatures in diodes and traveling‐wave tubes.

Certain physical methods were used to investigate the correlation between these results and the mechanisms of cathode operation: X‐ray fluorescence electron microprobe analysis has given a new access to the. Scanning electron microscopy Electron micrographs of typical IDC surfaces were taken for each variety of cathode being investigated.

The instrument used was an AMR scanning electron microscope with a specified resolution of A. Samples were viewed normal to the surface in most cases and no additional conductive surface coating was used. In this study, the stoichiometric mixture of barium carbonate, calcium carbonate, and aluminum oxide with ratio of was produced by two individual methods: sol-gel combustion and ball-milling method used as a precursor of electron emissive material on impregnated cathodes which make up high power vacuum microwave tubes such as klystrons.

particle size of emissive materials affect the electron emission properties of impregnated cathodes. In this study, dry gel and heat treated powder at °C are investigated by thermal analysis (TG/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X.

Hollow cathodes with impregnated tungsten and tungsten-iridium emitters were operated with ppm of oxygen in the xenon gas flow for and 80 hours, respectively. Chemical and morphological changes were studied using scanning electron microscopy, energy dispersive spectroscopy, and. A scanning electron microscope (SEM) is an instrument for imaging topography and for obtaining material information of conductive specimen using a focused beam of high-energy electrons.

The electron beam is deflected in a magnetic field and performs a scanning movement in a raster pattern to capture the specimens’ surface. The morphology and microstructure were observed by the scanning electron microscopy (SEM, Hitachi SU), the field emission scanning electron microscopy (FESEM, JSMF, and TEAM Octane Plus), and transmission electron microscopy (TEM, JEM, and X.

Field Emission Scanning Electron Microscopy: New Perspectives for Materials Characterization Nicolas Brodusch, Hendrix Demers, Raynald Gauvin (auth.) This book highlights what is now achievable in terms of materials characterization with the new generation of cold-field emission scanning electron microscopes applied to real materials at high.

A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons interact with atoms in the sample, producing various signals that contain information about the surface topography and composition of the sample.

The electron beam is scanned in a raster scan pattern, and the position of. An efficient method is used to improve the emission stability and uniformity of the field emission from a carbon nanotube (CNT) cathode.

In this method, a fully sealed device with CNTs cathode is exhausted by a pumping system. At the same time, this device is baking at a temperature about degC and maintains for a few minutes, and an overload current is applied.

A field emission study by scanning anode field emission microscopy was performed to evaluate the field emission properties. The effective work function is about 1 eV, the threshold of the macroscopic field F app is about 6 V/μm for a current density J FE equal to A/m 2, which is a rather low field.

Then the mixed matrices of Sc 2 O 3-W were impregnated with standard 4BaOCaOAl 2 O 3 () impregnant to produce the dispenser cathodes. Typical results of scanning electron microscope (SEM) images of these four kinds of matrices and EDS spectra of the Sc-3 and Sc-4 matrices are shown in Fig.

A scanning transmission electron microscope (STEM) is a type of transmission electron microscope (TEM). Pronunciation is [stɛm] or [ɛsti:i:ɛm]. As with a conventional transmission electron microscope (CTEM), images are formed by electrons passing through a sufficiently thin specimen.

However, unlike CTEM, in STEM the electron beam is focused to a fine spot (with the typical spot size SEM was invented by Max Knoll in in Germany [1, 2] to study the targets of television instrument consisted of electron-beam deflection coils that scan the beam on a plate as the sample in a cathode ray tube (CRT) and an amplifier that boosts the plate current to display the signal on another CRT (Fig.

1a).Two years later, Manfred von Ardenne built an electron microscope with a. Scandate cathodes that were fabricated using the liquid-solid process and that exhibited excellent emission performance were characterized using complementary state-of-the-art electron microscopy techniques.

Sub-micron BaAl2O4 particles were observed on the surfaces and edges of tungsten particles, as seen in cross-section samples extracted from the scandate cathode surface regions. "The go-to resource for microscopists on biological applications of field emission gun scanning electron microscopy (FEGSEM) The evolution of scanning electron microscopy technologies and capability over the past few years has revolutionized the biological imaging capabilities of the microscope - giving it the capability to examine surface structures of cellular membranes to reveal the.An experimental study of the intense current electron beam diode with a foil-free annular C–C composite material cathode is carried out, the attenuation process of cathode carbon ions at different axial magnetic fields is acquired using an ultrahigh speed 12 framing camera, and the attenuation characteristics of cathode plasma under different discharging voltage waveforms have also been studied.Get this from a library!

Biological low voltage field emission scanning electron microscopy. [Heide Schatten; James B Pawley;] -- Field-emission, low-voltage scanning electron microscopy (LVSEM) is a field that has grown tremendously in recent years because is offers the optimal method for viewing complex surfaces at high.