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  • Other Sources  (7)
  • ELECTRONICS AND ELECTRICAL ENGINEERING  (5)
  • RESEARCH AND SUPPORT FACILITIES (AIR)  (2)
  • Chemistry
  • 1
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    Secondary electron emission from a charged dielectric (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Charges on the surface of fluorinated-ethylene-propylene affect its secondary electron emission coefficient. Measurements with impact energies exceeding that energy which causes peak emission have been made in regions where the local electric field produced by the surface charge is normal to the surface and in regions where it is oblique. The surface of the 6-mm wide specimen was charged to either 6 or 10 kV. Because the impinging primary beam was deflected by the charged specimen, numerical modeling was used to predict the beam's impact energy E, impact angle theta, and the impact point. The formula predicts the coefficient in the region of normal field up to 60 deg although E(0) depends upon the electric field and also on the history of the specimen. Near the edges where the field is oblique, the measured coefficient departs significantly from what the formula predicts.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEEE Transactions on Electrical Insulation (ISSN 0018-9367); EI-20; 485-491
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Charge distributions near metal-dielectric interfaces before and after dielectric surface flashover (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A technique was developed for measuring surface charge distribution near interfaces without placing any measuring apparatus near the face of the samples. The results of measurements which were made on FEP Teflon and Kapton dielectrics, before and after are given flashover, with various types of interfaces. Also given are data showing mean time between flashovers for various configurations exposed to a variety of environmental conditions. Several charge transfer mechanisms are considered as a means by which stable charge distributions may be maintained near interfaces.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA. Lewis Res. Center Proc. of the Spacecraft Charging-Technol. Conf.; p 503-717
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Structural modeling of high Reynolds number wind tunnel models (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A solid uninstrumented wing and a pressure instrumented wing having a tongue and groove type joint have been structurally modeled by using SPAR Structural Analysis System. The solid wing model can be analyzed by SPAR, using either solid elements or plate elements with reasonable accuracy. The instrumented wing models with tongue and groove joint can be modeled by using solid elements. A solid model representation for the wing with tongue and groove joint can be used for the cases where an error of 6 percent in deflections is acceptable.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: AIAA PAPER 82-0602 , In: Aerodynamic Testing Conference; Mar 22, 1982 - Mar 24, 1982; Williamsburg, VA
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Feasiblity study for a 34 GHz (Ka band) gyroamplifier (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The feasibility of using a gyroklystron power tube as the final amplifier in a 400 kW CW 34 GHz transmitter on the Goldstone Antenna is investigated. A conceptual design of the gyroklystron and the transmission line connecting it with the antenna feed horn is presented. The performance characteristics of the tube and transmission line are compared to the transmitter requirements for a deep space radar system. Areas of technical risk for a follow-on hardware development program for the gyroklystron amplifier and overmoded transmission line components are discussed.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA-CR-174439 , JPL-9950-961 , NAS 1.26:174439
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    NASA TECHNICAL REPORTS
  • 5
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    Surface charge kinetics near metal-dielectric interfaces exposed to kilovolt electron flux (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Interfaces between dielectric films and grounded metallic boundaries were exposed, in vacuum, to monoenergic electron fluxes having energies up to 22 keV. Two principal concerns were the measuring of the charge distributions on dielectrics and the determining of causes of flashovers, events where dielectric surface charges abruptly transfer to the metallic structures. Surface charges are perturbed within 10 mm of interfaces. Perturbations are relatively small except within about 3 mm of the interface. The probability of flashover was found to be related to microscopic imperfections in the interfaces. As flashovers occur in an exposed metal substrate, points become burned into the dielectric along the slit. As these points develop, the probability of flashover increases greatly. An interface which is highly immune to flashover was formed by covering a dielectric film with a 1.5-mm-thick aperture plate which exposes the film through a machined opening.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA-CR-155195
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Mapping of electrical potential distributions with charged particle beams (1982)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Methods for measuring electrostatic potentials on and near dielectric surfaces charged to several kilovolts are studied. Secondary emission from those charged dielectrics is measured. Candidates for potential measurement include the induced charge, from which potential is calculated; the trajectory endpoints of either high or low energy particles traversing the region near the surface; trajectory impact on the surface; and creating ions at points of interest near the surface. Some of the methods require computer simulations and iterative calculation if potential maps are to be generated. Several approaches are described and compared. A method using a half-cylinder as a test chamber and low-energy probing beams is adapted for the measurement of seconary emission.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA-CR-168556
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Analysis and design of a ceramic nozzle insert for the Langley 8-foot high temperature structures tunnel (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An analysis is presented of various ceramic design concepts intended to improve nozzle throat life and tunnel performance in the hypersonic Langley 8-Foot High-Temperature Structures Tunnel, which uses methane-air combustion products as the wind-tunnel test medium. Calculations of the axial pressure distribution and heating rates in the air-cooled nozzle throat are presented, and desirable characteristics of a ceramic material to be used in the nozzle throat are outlined, including high-temperature strength, thermal shock and erosion resistance, low conductivity and low thermal expansion. Ceramic nozzle throat design concepts are then examined, with attention given to monolithic and layered constructions of cast ceramics, reaction-bonded materials and a fiber-reinforced silica-silica ceramic. Results of a finite element analysis of the temperatures and stresses characteristic of the various concepts are then presented which indicate the monolithic silica-silica and the layered silica-silica/reaction bonded silicon nitride concepts to be the most promising of those investigated.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: Carbon-Carbon Nozzle Technology Meeting; Oct 22, 1980 - Oct 23, 1980; US Naval Postgraduate School, Monterey, CA
    Format: text
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    NASA TECHNICAL REPORTS
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