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Wednesday, August 5, 2020 | History

2 edition of Bulk effect photofield emission from tungsten. found in the catalog.

Bulk effect photofield emission from tungsten.

Paul John Donders

Bulk effect photofield emission from tungsten.

by Paul John Donders

  • 278 Want to read
  • 13 Currently reading

Published .
Written in English

    Subjects:
  • Physics Theses

  • Edition Notes

    Thesis (Ph.D.), Dept. of Physics, University of Toronto

    ContributionsLee, Martin (supervisor)
    The Physical Object
    Pagination186 p.
    Number of Pages186
    ID Numbers
    Open LibraryOL18380520M

    Field electron emission, also known as field emission (FE) and electron field emission, is emission of electrons induced by an electrostatic most common context is field emission from a solid surface into a r, field emission can take place from solid or liquid surfaces, into a vacuum, a fluid (e.g. air), or any non-conducting or weakly conducting dielectric.   With careful design, the interface polar effects can also work concurrently with bulk effects arising from inherent 7,8 or externally induced polarity by, for .

    Tungsten, chemical element that is an exceptionally strong metal. Occurrence, properties, and uses. The amount of tungsten in Earth’s crust is estimated to be parts per million, or about grams per ton of rock. China is the dominant producer of tungsten; in it produced over 80 percent of total tungsten mined, and it contained nearly two-thirds of the world’s reserves. Tungsten wire is arguably the key component of the incandescent lamp business. The emissivity of tungsten wire is therefore important in several ways. First of all, the higher the emissivity of the filament, the better the lamp performs: there is a direct correlation between emissivity and illumination.

      Books. Publishing Support. Login. Reset your password. If you have a user account, you will need to reset your password the next time you login. You will only need to do this once. Find out more. IOPscience login / Sign Up.   The secondary electron coefficient γ has been measured for singly charged hydrogen, helium, nitrogen, neon, oxygen, argon and krypton ions in the energy range keV incident on a tungsten surface. Measurements have been made within the monolayer adsorption time (similar 5 min) after production of an atomically clean surface.


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Bulk effect photofield emission from tungsten by Paul John Donders Download PDF EPUB FB2

Studies of photofield emission from surface states on W(), Mo(), and Ir() are reported. The yield of photofield electrons from the W() surface states are analyzed for photon energies.

Photofield emission characteristics from () face of tungsten for p-polarized light are measured. By differentiation of the true photocurrent curves Cited by: 6. Photofield emission characteristics from (0 0 1) face of tungsten for p-polarized light are measured.

By differentiation of the true photocurrent curves, after subtracting thermocurrents, energy. Photo-field emission current-voltage characteristics of the clean W () plane were measured.

From the observed knees the energies of two indirect transitions are derived and compared with the band structure and total energy distributions obtained by Venus and by: 4.

Using the photofield emission method, surface states and bulk excitations from clean and residual gas adsorbed () face of tungsten were measured.

Residual gas shaded the surface states and diminished photoemission from the bulk excitations. We present here the results of the calculations of photofield emission current by using the free electron model in which the appropriate wavefunctions are used.

The transmission probability had been calculated by solving the Airy’s equation. The model developed is used to calculate photofield emission current from tungsten. Abstract Measurements of the irradiance dependence of photofield emission from tungsten have been extended to GW m The photoyield (the photocurrent per unit irradiance) from the () crystal plane is found to be almost independent of irradiance.

3. Thermal photofield emission The departures from free electron behaviour observed in field emission from the () surface of tungsten, involving emission from thermally popu- lated electron states above the Fermi level, have also been studied in photo- field emission.

The separation of the observed photocurrent into bulk and surface contributions is therefore a matter of great importance, and has been a long-standing problem:n both photofield emission [] and photoemission [].

/88/$ Elsevier Science Publishers I3.V. (North-Holland Physics Publishing Division) G. Lopinski et al. A novel photofield emission spectrometer has been used to observe departures from free electron behaviour in the total energy distributions of photofield emission from the (), (), (   Surface Science () North-Holland Publishing Company LINEAR INTENSITY DEPENDENCE OF PHOTO-INDUCED FIELD EMISSION FROM TUNGSTEN D.

VENUS and M.J.G. LEE Department of Physics, University of Toronto, Toronto, Ontario, Canada M5S 1A7 Received 9 September ; accepted for publication 29 December As a first step in an. Part 1 Phenomenological description: introduction the photovoltaic effect and photoelectric phenomena linear and circular photovoltaic effects polarization aspects of the photovoltaic effect in some crystal types glass coefficients spatially oscillating and steady currents photoinduced fields experiment the magnetophotovoltaic effect conversion efficiency limits to the phenomenological.

In this thesis the efforts made to better understand the mech- anisms and to refine the apparatus of photofield emission are described. Photofield electron yield and photofield emission from surface electronic have been measured. Both demonstrate the surface sensitivity of this new technique.

Analyses of laser-induced thermal effects are also reported which allows the simultaneous. The effect of adsorbed oxygen on the photoelectron yield of bulk polycrystalline tungsten was studied at photon energies of, and eV. Use of ultrahigh vacua ∼3 × 10−10 tor. Books. Publishing Support.

Login. field emission from a tungsten nanotip enabled by local field enhancement. Flytzanis C, Elsaesser T and Woerner M High-field terahertz bulk photovoltaic effect in lithium niobate Phys.

Rev. Lett. Crossref Google Scholar. Fowler R H and Nordheim L Electron emission in intense. 5: Thermionic Emission Purpose While we think of quantum mechanics being best demonstrated in processes that show discontinuous change, historically quantum mechanics was first revealed in systems where a large number of particles washed out the jumps: blackbody radiation and thermionic emission.

Large single-crystal domains of WS2 are grown by chemical vapor deposition, and their photoluminescent properties under a lateral electric field are studied.

We demonstrate that monolayer and bilayer WS2 have opposite responses to lateral electric fields, with WS2 photoluminescence (PL) substantially reduced in monolayer and increased in bilayers with increasing lateral electric field strength.

However, the presence of tungsten in groundwater near background sources and anthropogenic sources suggests that under certain conditions, tungsten dissolves in water and is mobile in the environment.

Currently, limited information is available about the fate and transport of tungsten in the environment and its effects on human health. The total-energy distributions (TEDs) of the emission currents in field emission and surface photofield emission and the overlayer-induced modifications in the surface electronic structures from.

Photofield emission (PFE) measurements are employed to examine modifications of the surface electronic structure of the tungsten (1 1 1) facet upon deposition of thin films ( monolayers) of.

Tungsten has several properties that make it well suited for use as a PFM. Current technology employs W as a thin (1–3 mm) coating on graphite or carbon fiber com-posite tiles, but future PFCs might be composed simply of bulk W.2,5 Tungsten retains strength at high temperatures and can sufficiently conduct heat away from the surface.

To summarise the outer divertor case: ERO can reproduce in general well the large integral gross erosion of W, the low integral net erosion of W, and therefore the high re-deposition of W on the bulk W divertor observed experimentally by optical emission spectroscopy and post-mortem analysis in the H-mode plasmas of the quasi-steady-state.In most applications, welders use tungsten that contains an emission-enhancing oxide such as Thorium, Cerium, or Lanthanum.

These oxides naturally migrate from inside the tungsten to the heat at the point of the electrode, where they give off their oxide element in the .