Recent advances in cathode-ray-tube display devices
CRT display devices and R and D, discussing electron generation, luminescent materials, resolution, brightness, etc
Davis, J. A.↗
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Results for “electron tubes”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Development of a 25 - 50 watt high efficiency, X-band, traveling wave tube Quarterly report, Nov. 1970 - Jan. 1971
Computer design technique of electron gun for use in spacecraft transmitters
Knight, R. I.↗
Measurement and calculation of the Stark-broadening parameters for the resonance lines of singly ionized calcium and magnesium.
The electron-impact-broadened profiles of the resonance lines of singly ionized calcium and magnesium have been measured using an electromagnetically driven shock tube and a rapid-scanning Fabry-Perot spectrometer. For an electron density of 10 to the 17th power per cu cm and a temperature of 19,000 K, we found the Lorentzian half-width of the Ca+ line to be 0.086 A plus or minus 10% and of the Mg+ line to be 0.044 A plus or minus 10%. Using the quantum-mechanical theory of Barnes and Peach and our semiclassical calculation for the calcium lines, we found that the temperature dependence of the theoretical curves is close to that measured, although both theories predict actual values which are somewhat large.
Jones, W. W.↗
Carbon Nanotubes: Molecular Electronic Components
The carbon Nanotube junctions have recently emerged as excellent candidates for use as the building blocks in the formation of nanoscale molecular electronic networks. While the simple joint of two dissimilar tubes can be generated by the introduction of a pair of heptagon-pentagon defects in an otherwise perfect hexagonal graphene sheet, more complex joints require other mechanisms. In this work we explore structural characteristics of complex 3-point junctions of carbon nanotubes using a generalized tight-binding molecular-dynamics scheme. The study of pi-electron local densities of states (LDOS) of these junctions reveal many interesting features, most prominent among them being the defect-induced states in the gap.
Srivastava, Deepak↗
Low Temperature Regenerators for Zero Boil-Off Liquid Hydrogen Pulse Tube Cryocoolers
Recently, a great deal of attention has been focused on zero boil-off (ZBO) propellant storage as a means of minimizing the launch mass required for long-term exploration missions. A key component of ZBO systems is the cooler. Pulse tube coolers offer the advantage of zero moving mass at the cold head, and recent advances in lightweight, high efficiency cooler technology have paved the way for reliable liquid oxygen (LOx) temperature coolers to be developed which are suitable for flight ZBO systems. Liquid hydrogen (LH2) systems, however, are another matter. For ZBO liquid hydrogen systems, cooling powers of 1-5 watts are required at 20 K. The final development from tier for these coolers is to achieve high efficiency and reliability at lower operating temperatures. Most of the life-limiting issues of flight Stirling and pulse tube coolers are associated with contamination, drive mechanisms, and drive electronics. These problems are well in hand in the present generation coolers. The remaining efficiency and reliability issues reside with the low temperature regenerators. This paper will discuss advances to be made in regenerators for pulse tube LH2 ZBO coolers, present some historical background, and discuss recent progress in regenerator technology development using alloys of erbium.
Salerno, Louis J.↗
Jovian S-burst observations at 32 MHz
Drift rates for S-burst emissions from Jupiter are studied. The burst spectra, recorded in the frequency range near 32 MHz, provide a qualitative illustration of the behavior of electron bunches shortly after injection into the Io-associated magnetic flux tube. The morphology of the spectra may be taken as support for the hypothesis of an ionospheric acceleration mechanism influencing the flow of electrons.
Desch, M. D.↗
The Conductance of Nanotubes Deformed by the AFM Tip
The conductance drop under AFM-tip deformation can be explained by stretching of the tube length. NT sensors can be built utilizing uniform stretching. Single sp3 bond cross section cannot block electrons, because another conducting path may exist. AFM tip which forms sp3 bonds with the tube will decrease conductance. In the "table experiment" a conductance drop of 2 orders of magnitude happened only after some bonds were broken.
Svizhenko, Alexei↗
Shock tube study of ionization rates of NaCl-contaminated argon
Spectrally resolved radiometry and a microwave technique were used to measure the electron density, electron temperature, and concentration, and the concentration of sodium atoms in the weakly ionized region behind a shock wave in an argon shock tube. It is shown that the observed increase in the ionization rate is due to electron detachment of negative chlorine ions produced from sodium chloride vapor contained as an impurity in the argon gas. The observed behavior of the electron temperature in time and the reactions controlled by the electron temperature are analyzed in the light of the impurity reaction scheme.
Scheneider, C.-P.↗
ELECTRON BOMBARDMENT INDUCED CONDUCTIVITY INCLUDING ITS APPLICATION TO ULTRAVIOLET IMAGING IN THE SCHUMAN REGION
Electron bombardment induced conductivity - ultraviolet imaging in the schuman region
INTELLECT↗
Electron and metastable density measurements in argon with a laser heterodyne interferometer
Electron and metastable density measurements in argon discharge tube using laser heterodyne interferometer
Cotman, R. N.↗
Electrofluoroplanigraphy.
The authors describe a fluoroplanigraphic method of synthesizing single-plane sections of any desired layer within the body. This is done by appropriate positioning of the individual images obtained at various locations of the X-ray tube during a single tomographic motion, followed by electronic summation of each roentgenogram. A TV image of any desired body section is available within seconds of the original recording sequence.
Baily, N. A.↗
Large area double scattering telescope for balloon-borne studies of neutrons and gamma rays
A large area double scattering telescope for balloon-borne research is described. It measures the flux, energy and direction of 2-100 MeV neutrons and 0.5-30 MeV gamma rays. These measurements are made using time-of-flight and pulse height analysis techniques with two large tanks of mineral oil liquid scintillator. Results from Monte Carlo calculations of the efficiency, energy resolution and angular resolution are presented and the electronics implementation for the processing of 80 photomultiplier tubes signals will be discussed. The detector weighs 800 kg with a large part of this weight being the liquid scintillator (320 kg). It will be flown at 3 mbars for flight durations up to 40 hours. The first flight is planned for Spring, 1975.
Zych, A. D.↗
Thermionic cathode life-test studies
A NASA-Lewis Research Center program for life testing commercial, high-current-density thermionic cathodes has been in progress since 1971. The purpose of the program is to develop long-life power microwave tubes for space communications. Four commercial-type cathodes are being evaluated in this investigation. They are the 'Tungstate', 'S' type, 'B' type, and 'M' type cathodes, all of which are capable of delivering 1 A/ sq cm or more of emission current at an operating temperature in the range of 1000-1100 C. The life test vehicles used in these studies are similar in construction to that of a high-power microwave tube and employ a high-convergence electron-gun structure; in contrast to earlier studies that used close-space diodes. These guns were designed for operation at 2 A/sq cm of cathode loading. The 'Tungstate' cathodes failed at 700 h or less and the 'S' cathode exhibited a lifetime of about 20,000 h. One 'B' cathode has failed after 27,000 h, the remaining units continuing to operate after up to 30,000 h. Only limited data are now available for the 'M' cathode, because only one has been operated for as long as 19,000 h. However, the preliminary results indicate the emission current from the 'M' cathode is more stable than the 'B' cathode and that it can be operated at a true temperature approximately 100 C lower than for the 'B' cathode.
Forman, R.↗
Long-Life/Low-Power Ion-Gun Cathode
New cathode has form of hollow tube through which gas enters region of high electron density, produced by electric discharge with auxiliary electrode referred to as "keeper." Ion-gun cathode emits electrons that bombard gas in chamber. Ions accelerated out of source are used to dope semiconductor material.
Fitzgerald, D. J.↗
Calculation of resolution for a windowless charge coupled device (CCD)-Digicon
A new version of an intensified charge-coupled device (ICCD) system, which is based on the incorporation of a CsI mesh photocathode and a thinned backside-illuminated CCD into a Space Telescope design Digicon tube, is being developed for future use in space-based observations in the Extreme Ultraviolet waveband. In this paper, a report is presented of the results of computer simulations involving the effects of the non-uniform electrostatic field near the mesh photocathode on imaging properties (especially, the spread function and modulation transfer function) of the detector system. The results are of importance in the design of the front end of the tube and the selection of optimum tube operating conditions. The overall resolution characteristics of the tube, including the effects of the mesh, the electron optics of the region between the mesh photocathode and the CCD target, and the structure of the CCD itself, are estimated.
Jia, X. Z.↗
Photon counting image sensor development for astronomical applications
Specially built intensified CCD (ICCD) detector tubes were purchased and the performance of the electron bombardment process was investigated. In addition to studying the signal characteristics of the photoevents, there was interest in demonstrating that back-illuminated chips were not susceptible to radiation damage to their clocking electrodes. How to perform a centroid analysis for a 2-dimensional Gaussian distribution of charge is described. Measurement of the projection (along columns or rows) of the average charge spread profile is discussed. The development and flight of the Interstellar Medium Absorption Profile Spectrograph (IMAPS) is discussed.
Jenkins, Edward B.↗
Preliminary results from a subsonic high angle-of-attack flush airdata sensing (HI-FADS) system: Design, calibration, and flight test evaluation
A nonintrusive high angle-of-attack flush airdata sensing (HI-FADS) system was installed and flight-tested on the F-18 high alpha research flight vehicle. The system is a matrix of 25 pressure orifices in concentric circles on the nose of the vehicle. The orifices determine angles of attack and sideslip, Mach number, and pressure altitude. Pressure was transmitted from the orifices to an electronically scanned pressure module by lines of pneumatic tubing. The HI-FADS system was calibrated and demonstrated using dutch roll flight maneuvers covering large Mach, angle-of-attack, and sideslip ranges. Reference airdata for system calibration were generated by a minimum variance estimation technique blending measurements from two wingtip airdata booms with inertial velocities, aircraft angular rates and attitudes, precision radar tracking, and meteorological analyses. The pressure orifice calibration was based on identifying empirical adjustments to modified Newtonian flow on a hemisphere. Calibration results are presented. Flight test results used all 25 orifices or used a subset of 9 orifices. Under moderate maneuvering conditions, the HI-FADS system gave excellent results over the entire subsonic Mach number range up to 55 deg angle of attack. The internal pneumatic frequency response of the system is accurate to beyond 10 Hz. Aerodynamic lags in the aircraft flow field caused some performance degradation during heavy maneuvering.
Whitmore, Stephen A.↗
Computer Analysis of Spectrum Anomaly in 32-GHz Traveling-Wave Tube for Cassini Mission
Computer modeling of the 32-GHz traveling-wave tube (TWT) for the Cassini Mission was conducted to explain the anomaly observed in the spectrum analysis of one of the flight-model tubes. The analysis indicated that the effect, manifested as a weak signal in the neighborhood of 35 GHz, was an intermodulation product of the 32-GHz drive signal with a 66.9-GHz oscillation induced by coupling to the second harmonic'signal. The oscillation occurred only at low- radiofrequency (RF) drive power levels that are not expected during the Cassini Mission. The conclusion was that the anomaly was caused by a generic defect inadvertently incorporated in the geometric design of the slow-wave circuit and that it would not change as the TWT aged. The most probable effect of aging on tube performance would be a reduction in the electron beam current. The computer modeling indicated that although not likely to occur within the mission lifetime, a reduction in beam current would reduce or eliminate the anomaly but would do so at the cost of reduced RF output power.
Dayton, James A., Jr.↗