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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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Woven electron emitters for high reliability.
Woven and knitted electron emitters noting reliability, mechanical stability, transparency and efficiency
Plasma-anode tube in metal-ceramic envelope
Plasma anode tube in metal-ceramic envelope with improved capabilities for electron emission studies, considering movable Langmuir probe
Use of photomultiplier tubes for photon counting
Critique on photomultiplier tube for photon counting, considering pulse height distribution, SNR and electron collection efficiency errors
Evaluation of some wide dynamic range readout systems for photoelectric integrating spectrometers
Five types of electronic circuits commonly used for readout of currents from photomultiplier tubes were evaluated. This evaluation was conducted to define the experimental limits of achieving the widest possible dynamic range of light detection and concentration measurements in spectrochemical analysis. The circuits evaluated included the photon-counting technique and four dc circuits. These circuits displayed a dynamic range from 3 to about 4.5 decades within a repeatability criterion of 1 percent, or better. The maximum dynamic range allowed by the photomultiplier tube in this application was estimated to be about 6 decades.
Fluorescence and phosphorescence of photomultiplier window materials under electron irradiation
The fluorescence and phosphorescence of photomultiplier window materials under electron irradiation were investigated using a Sr-90/Y-90 beta emitter as the electron source. Spectral emission curves of UV grade, optical grade, and electron-irradiated samples of MGF2 and LiF, CaF2, BaF2, sapphire, fused silica, and UV transmitting glasses were obtained over the spectral range of 200 nm to 650 nm. Fluorescence yields, expressed as the number of counts in a solid angle of 2 pi steradian per 1MeV of incident electron energy deposited, were determined on these materials utilizing photomultiplier tubes with cesium telluride, bialkali, and trialkali (S-20) photocathodes, respectively.
Development of a CCD for ultraviolet imaging using a CCD photocathode combination
CCD in the electron-in mode, coupled with a bi-alkali photocathode to produce UV photon conversion, provides the following desirable features: (1) high UV response of the bi-alkali photocathode; (2) excellent imaging quality of a CCD area array; and (3) high signal-to-noise ratio due to the EBS (electron bombarded silicon) gain of the CCD operating in a tube configuration. This paper describes the rationale and progress made in developing a CCD for use as an UV imager.
Multichannel electrochemical microbial detection unit
The paper describes the design and capabilities of a compact multichannel electrochemical unit devised to detect and automatically indicate detection time length of bacteria. By connecting this unit to a strip-chart recorder, a permanent record is obtained of the end points and growth curves for each of eight channels. The experimental setup utilizing the multichannel unit consists of a test tube (25 by 150 mm) containing a combination redox electrode plus 18 ml of lauryl tryptose broth and positioned in a 35-C water bath. Leads from the electrodes are connected to the multichannel unit, which in turn is connected to a strip-chart recorder. After addition of 2.0 ml of inoculum to the test tubes, depression of the push-button starter activates the electronics, timer, and indicator light for each channel. The multichannel unit is employed to test tenfold dilutions of various members of the Enterobacteriaceae group, and a typical dose-response curve is presented.
Atmospheric Emission Photometric Imaging on Spacelab (AEPI)
Two parallel detector systems are used for atmospheric emission photometric emission. The top system is a TV system using the image intensified S.E.C. tube as the detector. The bottom system, the photon counting array (P.C.A.), uses a microchannel plate intensified anode array tube and is equivalent to a 100 channel photomultiplier. For the television, the filters are selected by means of a filter wheel set. The field of view of the is interchangeable between 20 and 6 degrees, by means of a moveable prism. The quartz window mu channel plate intensifier is fiber optically coupled to a 40-25 demagnifying tube which is in turn coupled to the S.E.C. tube. The PCA channel has a fixed field of view of 4 deg and a remote control interchangeable photometric converter optics which converts the imaging array into a multichannel photometer. The mu channel plate array tube amplifies the photons into detectable counts for the PCA electronics. The entire system is pointed by a two axis gimbal. The flight equipment to be acquired consists of a gyro package and an interactive flight control unit panel. The gyro package is necessary because of the inadequate attitude reference supplied by the current Spacelab systems.
Low cost Get-Away-Special (GAS) furnace
A simple and inexpensive Space Shuttle experimental apparatus to conduct microgravity melting and solidification is presented. A GAS space furnace was initially developed as a student design project at the USAF Academy and further refined at NASA Lewis. The experiment package consists of a melting chamber, battery power system, temperature data recording systems, and electronic controller. The melting chamber is a thin-walled tube wrapped by heating resistance wire. Thermocouples are used to record the specimen thermal history. Power is supplied by 2-V batteries wired to produce 360 W. The mV output of the thermocouples is amplified, cold-junction compensated, and converted to a frequency which is then recorded on an off-the-shelf cassette tape recorder. A backup data recording system which digitizes the amplified signal and records the data on EEPROMs has also been included. This experimental device demonstrates that basic science research can be kept simple and inexpensive.
Scanning Tunneling Microscope For Use In Vacuum
Scanning tunneling microscope with subangstrom resolution developed to study surface structures. Although instrument used in air, designed especially for use in vacuum. Scanning head is assembly of small, mostly rigid components made of low-outgassing materials. Includes coarse-positioning mechanical-translation stage, on which specimen mounted by use of standard mounting stub. Tunneling tip mounted on piezoelectric fine-positioning tube. Application of suitable voltages to electrodes on piezoelectric tube controls scan of tunneling tip across surface of specimen. Electronic subsystem generates scanning voltages and collects data.
Force Balance and Substorm Effects in the Magnetotail
A model of the quiet time middle magnetotail is developed using a consistent orbit tracing technique. The momentum equation is used to calculate geocentric solar magnetospheric components of the particle and electromagnetic forces throughout the current sheet. Ions generate the dominant x and z force components. Electron and ion forces almost cancel in the y direction because the two species drift earthward at comparable speeds. The force viewpoint is applied to a study of some substorm processes. Generation of the rapid flows seen during substorm injection and bursty bulk flow events implies substantial force imbalances. The formation of a substorm diversion loop is one cause of changes in the magnetic field and therefore in the electromagnetic force. It is found that larger forces are produced when the cross-tail current is diverted to the ionosphere than would be produced if the entire tail current system simply decreased. Plasma is accelerated while the forces are unbalanced resulting in field lines within a diversion loop becoming more dipolar. Field lines become more stretched and the plasma sheet becomes thinner outside a diversion loop. Mechanisms that require thin current sheets to produce current disruption then can create additional diversion loops in the newly thinned regions. This process may be important during multiple expansion substorms and in differentiating pseudoexpansions from full substorms. It is found that the tail field model used here can be generated by a variety of particle distribution functions. However, for a given energy distribution the mixture of particle mirror or reflection points is constrained by the consistency requirement. The study of uniqueness also leads to the development of a technique to select guiding center electrons that will produce charge neutrality all along a flux tube containing nonguiding center ions without the imposition of a parallel electric field.
Signal-Induced Noise Effects in a Photon Counting System for Stratospheric Ozone Measurement
Signal-induced noise (SIN) is a common effect resulting when a photomultiplier tube (PMT) is saturated, for a brief moment, with a high intensity light pulse. After the laser pulse is sent into the atmosphere a very large light return, from either the near-field or a cloud, causes the PMT to momentarily saturate. The PMT is gated off at this time so no signal is seen at the anode. When the PMT gate is turned on, the far-field light return from the atmosphere is observed. This signal is distorted, however because of the addition of SIN to the received light signal causing a slower than expected decay of the atmospheric signal return. We have characterized SIN responses to varying parameters of the incident light on the PMT. These varied parameters included incident wavelength, PMT voltage, incident intensity, and tube type. We found that only the amplitude of the SIN was effected by varying PMT voltages and light intensities. The amplitude increased linearly as input light intensity increased. Different incident wavelengths at the same intensity did not effect the amplitude or the temporal behavior of the SIN response. Finally, different PMT tubes with similar physical structures exhibited similar SIN responses although with different amplitudes. The different amplitudes can be attributed to the different gains and operating voltages of each tube. These results suggest that SIN is caused by photocathode electron dynamics such as charge accumulation on internal PMT surfaces. These surfaces then emit the electrons slowly resulting in a long decay noise signal. With the SIN responses characterized we can now try to develop a method to reduce or eliminate SIN in DIAL systems.
Transport of Photoelectrons in the Nightside Magnetosphere
Kinetic modeling results are analyzed to examine the transport of photoelectrons through the nightside inner magnetosphere. A natural filter exists on the nightside for these particles, with Coulomb collisions eroding the distribution at low energies and low L shells, and magnetospheric convection compressing the flux tubes as they corotate towards dawn. This leads to an electron population with very distinctive features. It is shown that, for low activity levels, a band of photoelectrons forms between L=4 and 6 that extends throughout the nightside local times and into the morning sector. Modeled energy and pitch angle distributions are presented to show the development and features of this electron band, as well as their influences on the thermal plasma. Such a population should be observable in satellite spectrometer measurements.
Instrument Overview of the JEM-EUSO Mission
JEM-EUSO with a large and wide-angle telescope mounted on the International Space Station (ISS) has been planned as a space mission to explore extremes of the universe through the investigation of extreme energy cosmic rays by detecting photons which accompany air showers developed in the earth's atmosphere. JEM-EUSO will be launched by Japanese H-II Transfer Vehicle (HTV) and mounted at the Exposed Facility of Japanese Experiment Module (JEM/EF) of the ISS in the second phase of utilization plan. The telescope consists of high transmittance optical Fresnel lenses with a diameter of 2.5m, 200k channels of multi anode-photomultiplier tubes, focal surface front-end, readout, trigger and system electronics. An infrared camera and a LIDAR system will be also used to monitor the earth's atmosphere.
Space-Shuttle Emulator Software
A package of software has been developed to execute a raw binary image of the space shuttle flight software for simulation of the computational effects of operation of space shuttle avionics. This software can be run on inexpensive computer workstations. Heretofore, it was necessary to use real flight computers to perform such tests and simulations. The package includes a program that emulates the space shuttle orbiter general- purpose computer [consisting of a central processing unit (CPU), input/output processor (IOP), master sequence controller, and buscontrol elements]; an emulator of the orbiter display electronics unit and models of the associated cathode-ray tubes, keyboards, and switch controls; computational models of the data-bus network; computational models of the multiplexer-demultiplexer components; an emulation of the pulse-code modulation master unit; an emulation of the payload data interleaver; a model of the master timing unit; a model of the mass memory unit; and a software component that ensures compatibility of telemetry and command services between the simulated space shuttle avionics and a mission control center. The software package is portable to several host platforms.
Color television system using single gun color cathode ray tube
Two-primary color and single gun system provides quality differential color and variation in brightness for specific colors by varying current and controlling duty cycle of electron beam. Number of video amplifiers, deflection circuits, and guns required to display color TV picture is reduced and less complex tube is required.
Bio-medical flow sensor
A bio-medical flow sensor including a packageable unit of a bottle, tubing and hypodermic needle which can be pre-sterilized and is disposable. The tubing has spaced apart tubular metal segments. The temperature of the metal segments and fluid flow therein is sensed by thermistors and at a downstream location heat is input by a resistor to the metal segment by a control electronics. The fluids flow and the electrical power required for the resisto to maintain a constant temperature differential between the tubular metal segments is a measurable function of fluid flow through the tubing. The differential temperature measurement is made in a control electronics and also can be used to control a flow control valve or pump on the tubing to maintain a constant flow in the tubing and to shut off the tubing when air is present in the tubing.