Haywood Shelton. / "March 21, 1957"--Cover. "Reprinted from The Physical review, vol. 107, no. 6, 1553-1557, September 5, 1957." / Includes bibliographical references. / Army Signal Corps Contract DA36-039-sc-64637

Andrew R. Hutson. / "January 13, 1955"--Cover. "Reprinted from The Physical review, vol. 98, no. 4, 889-901, May 15, 1955." / Includes bibliographical references. / Army Signal Corps Contract DA36-039 sc-42607 Project 132B Dept. of the Army Project 3-99-12-022

"December 11,1951." "This report is essentially the same as a doctoral thesis in the Department of Physics, Massachusetts Institute of Technology, 1950." / Bibliography: p. 25. / Army Signal Corps Contract No. DA36-039 sc-100. Project No. 8-102B-0. Dept. of the Army Project No. 3-99-10-022.

C.S. Hung. / "From a doctoral thesis submitted to the M.I.T. Department of Physics." "July 20, 1949." / Bibliography: p. 16. / Army Signal Corps Contract No. W36-039-sc-32037 Project No. 102B Dept. of the Army Project No. 3-99-10-022

A cathode structure was demonstrated that utilizes aligned carbon nanotubes (CNTs) to improve the thermionic electron emission by increasing the field enhancement of the cathode surface. Aligned CNTs were grown on the surface of a tungsten substrate by plasma enhanced chemical vapor deposition. The tungsten-CNT structure was further coated with a thin film of low work function emissive materials by magnetron sputtering. Numerous cathodes with varying CNT morphology and oxide layer thickness were created. The field and thermionic emission of the cathodes were tested in order to study the effects of the surface properties on the emission characteristics. It was observed that the introduction of CNTs into an oxide cathode structure improves both the thermionic and field emission, even in cathodes with relatively low field enhancement factors. Because of the high field enhancement factors that are available for CNTs, there remains a potential for dramatically improved electron emission. / Department of Physics and Astronomy

Thesis (Ph.D.)--McMaster University (Canada), 1996. / Source: Dissertation Abstracts International, Volume: 57-10, Section: B, page: 6328. Adviser: J. S. Preston.

We have developed a thermionic cathode capable of high emission currents. The structure of this cathode is oxide coated carbon nanotubes (CNTs) on a tungsten (W) substrate. This cathode was superior in emission due to the combination of the field enhancement effect from the CNTs and the lowered work function from the semiconducting oxide surface. Such oxide coated CNTs were excellent electron emitters. Conventional electron emission theories, such as Richardson's and Fowler-Nordheim's, did not accurately describe the field enhanced thermionic emission from such emitters. A unified electron emission theory was adopted and numerical simulations were performed to explain the deviation of electron emission from conventional field and thermionic emission theories. Also, the thermionic measurement system and measurement methods were improved in order to measure and characterize the strong electron emission from this new cathode. Large electron emission current from such structures also made a new thermionic cooling device a possibility. Cooling due to the electron emission was measured in terms of temperature drop, and a large temperature drop was observed from this cathode structure. Finally, applications of this cathode in plasma discharge devices were explored. This new cathode was tested in a plasma environment and initial results were obtained. / Department of Physics and Astronomy

GaSe thin films were deposited by thermal evaporation technique with and without Cd doping. X-ray analysis showed that the crystallinity increases in (1014) preferred orientation direction with annealing for doped and undoped films. The room temperature conductivity and mobility values of the samples were found to be for doped and undoped films in between 1.3&times / 101 - 3.4&times / 102 (&amp / #8486 / -cm)-1, 1.2&times / 10-6 - 1.5&times / 10-6 (&amp / #8486 / -cm)-1 and 5.9 &amp / #8211 / 20.9 (cm2/V.s) (for doped samples only), respectively. Due to the high resistivity of the undoped samples mobility measurements could not be performed. The dominant conduction mechanisms were determined to be thermionic emission in the high temperature region (250-400 K), tunneling in the range 160-250 K and between 100-150 K variable range hopping mechanism for the doped films. For the undoped films above 250 K thermionic emission was the dominant conduction mechanism. Space charge limited currents in parallel and perpendicular directions of the film surface showed two different localized energy levels with different concentrations for each case, namely, 99.8 meV with concentration 3.5&times / 1012 cm-3 and 418.3 meV with the concentration 2.2&times / 105 cm-3 for parallel direction and for perpendicular direction 58.3 meV with concentration 6.2&times / 1025 cm-3 and 486.1 meV with concentration 3.3&times / 1022 cm-3. Photocurrentillumination intensity dependences indicated that power exponent of illumination intensity with values n&gt / 1 implied two recombination centers exist in studied samples.

abstract: In this dissertation, combined photo-induced and thermionic electron emission from low work function diamond films is studied through low energy electron spectroscopy analysis and other associated techniques. Nitrogen-doped, hydrogen-terminated diamond films prepared by the microwave plasma chemical vapor deposition method have been the most focused material. The theme of this research is represented by four interrelated issues. (1) An in-depth study describes combined photo-induced and thermionic emission from nitrogen-doped diamond films on molybdenum substrates, which were illuminated with visible light photons, and the electron emission spectra were recorded as a function of temperature. The diamond films displayed significant emissivity with a low work function of ~ 1.5 eV. The results indicate that these diamond emitters can be applied in combined solar and thermal energy conversion. (2) The nitrogen-doped diamond was further investigated to understand the physical mechanism and material-related properties that enable the combined electron emission. Through analysis of the spectroscopy, optical absorbance and photoelectron microscopy results from sample sets prepared with different configurations, it was deduced that the photo-induced electron generation involves both the ultra-nanocrystalline diamond and the interface between the diamond film and metal substrate. (3) Based on results from the first two studies, possible photon-enhanced thermionic emission was examined from nitrogen-doped diamond films deposited on silicon substrates, which could provide the basis for a novel approach for concentrated solar energy conversion. A significant increase of emission intensity was observed at elevated temperatures, which was analyzed using computer-based modeling and a combination of different emission mechanisms. (4) In addition, the electronic structure of vanadium-oxide-terminated diamond surfaces was studied through in-situ photoemission spectroscopy. Thin layers of vanadium were deposited on oxygen-terminated diamond surfaces which led to oxide formation. After thermal annealing, a negative electron affinity was found on boron-doped diamond, while a positive electron affinity was found on nitrogen-doped diamond. A model based on the barrier at the diamond-oxide interface was employed to analyze the results. Based on results of this dissertation, applications of diamond-based energy conversion devices for combined solar- and thermal energy conversion are proposed. / Dissertation/Thesis / Ph.D. Physics 2013

The thesis deals with numerical simulations of a hairpin thermionic electron gun, an electron source of the electron-beam welding machine. Simulations showed that the space charge in the electron gun has a significant influence on the beam current and electron trajectories. Simulation outputs are in a sufficient agreement with the experimental measurements.