Measurements of xenon filled nuclear irradiated thermionic diodes.
Xe filled thermionic diodes I-V characteristics at increasingly higher nuclear radiation levels, noting space charge neutralization effects
Forman, R.↗
SEARCH · Engineering Papers
Results for “diode effects”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Single-mode lasing of Ho:Tm:YAG at 2.091 microns in a monolithic crystal
This paper demonstrates single-longitudinal-mode lasing of Ho:Tm:YAG at 2.091 microns in a diode-laser-pumped monolithic crystal. Heterodyne detection at 2.1 microns is demonstrated, and energy diffusion effects on spatial hole burning are discussed. Temperature tuning over 4.5 A is demonstrated.
Storm, Mark E.↗
Promoting Robust Design of Diode Lasers for Space: A National Initiative
The Diode-laser Array Working Group (DAWG) is a national-level consumer/provider forum for discussion of engineering and manufacturing issues which influence the reliability and survivability of high-power broad-area laser diode devices in space, with an emphasis on laser diode arrays (LDAs) for optical pumping of solid-state laser media. The goals of the group are to formulate and validate standardized test and qualification protocols, operational control recommendations, and consensus manufacturing and certification standards. The group is using reliability and lifetime data collected by laser diode manufacturers and the user community to develop a set of standardized guidelines for specifying and qualifying laser diodes for long-duration operation in space, the ultimate goal being to promote an informed U.S. Government investment and procurement strategy for assuring the availability and durability of space-qualified LDAs. The group is also working to establish effective implementation of statistical design techniques at the supplier design, development, and manufacturing levels to help reduce product performance variability and improve product reliability for diodes employed in space applications
Tratt, David M.↗
Sub-kHz Linewidth GaSb Semiconductor Diode Lasers Operating Near 2 Micrometers
We report on the phase noise properties of DFB lasers operating near 2.0 microns. Measured noise spectra indicate intrinsic laser linewidths below 1 kHz. An effective linewidth of less than 200 kHz for 5 ms measurement times is estimated.
single-longitudinal-mode DFB lasers↗
Single Longitudinal Mode, High Repetition Rate, Q-switched Ho:YLF Laser for Remote Sensing
Ho:YLF/LuLiF lasers have specific applications for remote sensing such as wind-speed measurement and carbon dioxide (CO2) concentration measurement in the atmosphere because the operating wavelength (around 2 m) is located in the eye-safe range and can be tuned to the characteristic lines of CO2 absorption and there is strong backward scattering signal from aerosol (Mie scattering). Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of with a repetition rate of 5 Hz and pulse energy of 75 mJ [1]. For highly precise CO2 measurements with coherent detection technique, a laser with high repetition rate is required to averaging out the speckle effect [2]. In addition, laser efficiency is critically important for the air/space borne lidar applications, because of the limited power supply. A diode pumped Ho:Tm:YLF laser is difficult to efficiently operate in high repetition rate due to the large heat loading and up-conversion. However, a Tm:fiber laser pumped Ho:YLF laser with low heat loading can be operated at high repetition rates efficiently [3]. No matter whether wind-speed or carbon dioxide (CO2) concentration measurement is the goal, a Ho:YLF/LuLiF laser as the transmitter should operate in a single longitudinal mode. Injection seeding is a valid technique for a Q-switched laser to obtain single longitudinal mode operation. In this paper, we will report the new results for a single longitudinal mode, high repetition rate, Q-switched Ho:YLF laser. In order to avoid spectral hole burning and make injection seeding easier, a four mirror ring cavity is designed for single longitudinal mode, high repetition rate Q-switched Ho:YLF laser. The ramp-fire technique is chosen for injection seeding.
Bai, Yingxin↗
Device for diode tuning in a stripline varactor harmonic multiplier
Stripline varactor harmonic multiplier uses a device for positioning the varactor diode with respect to the stripline circuit to obtain series resonance. The device also reduces detuning effects, due to thermal expansion, over a wide temperature range.
Steele, K. P.↗
A survey of beam-combining technologies for laser space power transmission
The combination of laser beams holds much promise for obtaining powerful beams. Methods are surveyed for beam combination (coherent and incoherent) and two of them are identified as the most effective means for achieving high power transmission in space. The two methods as applied to laser diode arrays are analyzed, and potentially productive work areas for the advancement of technology are delineated.
Kwon, J. H.↗
Damping Relaxation Oscillations in Laser Diodes
Proposed semiconductor laser modulated at frequencies up to near its resonant frequency more efficiently than older devices. New laser uses two different effective carrier lifetimes: one for dc and lowfrequency operation and another for operation near resonant frequency. Laser part of bipolar transistor with capacitor that serves as ac short circuit.
Katz, J.↗
LED Lighting and Plant Growth: Supplemental LED Effects on Development
The growth of plants aboard the International Space Station (ISS) will play a pivotal role in advancing human space exploration to further uncharted destinations. Not only will plants be useful for oxygen production and carbon dioxide reduction, they will also serve as a supplemental food source for the astronaut diet. Research indicates that the most efficient way for these crops to be grown is by using electric lighting – specifically light-emitting diodes (LED) due to their several unique advantages. One of these advantages includes the potential for selecting certain wavelengths. By isolating certain lights, the effects of specific wavelengths on plant growth can be made clearer. This research project examined plant morphology, chlorophyll, biomass production, and nutrient synthesis in ‘Outredgeous’ red romaine lettuce grown under six LED light treatments of white (W), W + blue (B), W + green (G), W + red (R), W + far red (FR), and a Heliospectra lamp (Helio) (-composed of B+G+R+FR LEDs without W LEDS-). It was consistently found that the lettuce grown under the Helio, W + FR, W + R, and W + G treatments all showed improved physiology in terms of shoot length, shoot diameter, fresh mass, and dry mass relative to the W control. The Helio, W + FR, and W + G treatments exhibited significantly larger leaf areas while the Helio and W + FR treatments also produced more leaves on average at 28 days after planting (DAP). The W (control) and W + B treatments showed the highest accumulation of chlorophyll at 28 DAP. In conclusion, lettuce grown under the Helio treatment may be the overall most beneficial for supplementing the astronaut diet in terms of total edible biomass produced in a 28 day crop cycle.
LED↗
On the Long-Term Stability of Microwave Radiometers Using Noise Diodes for Calibration
Results are presented from the long-term monitoring and calibration of the National Aeronautics and Space Administration Jason Microwave Radiometer (JMR) on the Jason-1 ocean altimetry satellite and the ground-based Advanced Water Vapor Radiometers (AWVRs) developed for the Cassini Gravity Wave Experiment. Both radiometers retrieve the wet tropospheric path delay (PD) of the atmosphere and use internal noise diodes (NDs) for gain calibration. The JMR is the first radiometer to be flown in space that uses NDs for calibration. External calibration techniques are used to derive a time series of ND brightness for both instruments that is greater than four years. For the JMR, an optimal estimator is used to find the set of calibration coefficients that minimize the root-mean-square difference between the JMR brightness temperatures and the on-Earth hot and cold references. For the AWVR, continuous tip curves are used to derive the ND brightness. For the JMR and AWVR, both of which contain three redundant NDs per channel, it was observed that some NDs were very stable, whereas others experienced jumps and drifts in their effective brightness. Over the four-year time period, the ND stability ranged from 0.2% to 3% among the diodes for both instruments. The presented recalibration methodology demonstrates that long-term calibration stability can be achieved with frequent recalibration of the diodes using external calibration techniques. The JMR PD drift compared to ground truth over the four years since the launch was reduced from 3.9 to - 0.01 mm/year with the recalibrated ND time series. The JMR brightness temperature calibration stability is estimated to be 0.25 K over ten days.
noise diode (ND)↗
Solar cell array design handbook, volume 1
Twelve chapters discuss the following: historical developments, the environment and its effects, solar cells, solar cell filters and covers, solar cell and other electrical interconnections, blocking and shunt diodes, substrates and deployment mechanisms, material properties, design synthesis and optimization, design analysis, procurement, production and cost aspects, evaluation and test, orbital performance, and illustrative design examples. A comprehensive index permits rapid locating of desired topics. The handbook consists of two volumes: Volume 1 is of an expository nature while Volume 2 contains detailed design data in an appendix-like fashion. Volume 2 includes solar cell performance data, applicable unit conversion factors and physical constants, and mechanical, electrical, thermal optical, magnetic, and outgassing material properties. Extensive references are provided.
Rauschenbach, H. S.↗
PIN photodiodes irradiated with 40- and 85-MeV protons
PIN photodiodes were bombarded with 40- and 85-MeV protons to a fluence of 1.5 x 10 to the 11th p/sq cm, and the resulting change in spectral response in the near infrared was determined. The photocurrent, dark current, and pulse amplitude were measured as a function of proton fluence. Changes in these three measured properties are discussed in terms of changes in the diode's spectral response, minority carrier diffusion length, and depletion width. A simple model of induced radiation effects is presented which is in good agreement with the experimental results. The model assumes that incident protons produce charged defects within the depletion region simulating donor type impurities.
Reft, C. S.↗
Atmospheric transmission coefficients for laser pulses with spectral widths of a few tenths of a nanometer over the wavelength region from 800 to 860 nanometers
Effective atmospheric transmission spectra were calculated from 800 to 860 nanometers for laser sources with spectral widths of a few tenths of a nanometer. In this spectral region, the atmospheric absorption lines (water lines) have linewidths of a few hundredths of a nanometer, so that the transmission coefficient for a relatively wide laser pulse must be computed by taking a weighted average over the pulse spectral width. Laser spectral widths of several tenths of a nanometer are shown to reduce the effective absorption by water lines to as little as 10 to 20 percent, even when the laser is centered on a line or overlaps several lines. Thus, the effect of absorption by atmospheric water lines may be greatly reduced for laser communication systems using laser diode array transmitters, for which the pulse spectral width may be a few tenths of a nanometer.
Safren, H. G.↗
A heat-driven monochromatic light source
The efficiency with which heat may be converted into resonance radiation in a cesium thermionic diode is investigated theoretically. An analytical model of a thermionic converter is used which combines the coupled effects of line radiation transport, excited-state kinetics, and plasma diffusion. Operating regimes are established for various degrees of optical density in the plasma. The results indicate that monochromatic radiation can be produced with efficiencies on the order of 30 percent, provided that there is an adequate voltage drop across the plasma. A drop of 1 V was used since it can be maintained without any electrical power input to the device. It is found that high efficiencies are ude to the higher interelectrode distances which the solutions accommodate, and that radiation can be generated efficiently, even with optically dense gases.
Stefani, Francis↗
Lunar Seismic Detector to Advance the Search for Strange Quark Matter
Detection of small seismic signals on the Moon are needed to study lunar internal structure and to detect possible signals from Strange Quark m&er transit events. The immediate objective is to create a prototype seismic detector using a tunnel diode oscillator with a variable capacitor attached to a proof mass. The device is designed to operate effectively on the Moon, which requires a low power consumption to operate through lunar night, while preserving sensitivity. The goal is capacitance resolution of better than 1 part in 10' and power consumption of less than 1 watt.
Galitzki, Nicholas B.↗
Effect of localized polycrystalline silicon properties on solar cell performance
Several forms of polycrystalline silicon, mostly from cast ingots, (including UCP, SILSO and HEM) were studied. On typical slices, localized properties were studied in two ways. Small area (about 2.5 sq mm) mesa diodes were formed, and localized photovoltaic properties were measured. Also a small area (about .015 sq mm) light spot was scanned across the cells; the light spot response was calibrated to measure local diffusion length directly. Using these methods, the effects of grain boundaries, or of intragrain imperfections were correlated with cell performance. Except for the fine grain portion of SILSO, grain boundaries played only a secondary role in determining cell performance. The major factor was intra-grain material quality and it varied with position in ingots and probably related to solidification procedure.
Leung, D.↗
Shadowgraph Study of Gradient Driven Fluctuations
A fluid or fluid mixture, subjected to a vertical temperature and/or concentration gradient in a gravitational field, exhibits greatly enhanced light scattering at small angles. This effect is caused by coupling between the vertical velocity fluctuations due to thermal energy and the vertically varying refractive index. Physically, small upward or downward moving regions will be displaced into fluid having a refractive index different from that of the moving region, thus giving rise to the enhanced scattering. The scattered intensity is predicted to vary with scattering wave vector q, as q(sup -4), for sufficiently large q, but the divergence is quenched by gravity at small q. In the absence of gravity, the long wavelength fluctuations responsible for the enhanced scattering are predicted to grow until limited by the sample dimensions. It is thus of interest to measure the mean-squared amplitude of such fluctuations in the microgravity environment for comparison with existing theory and ground based measurements. The relevant wave vectors are extremely small, making traditional low-angle light scattering difficult or impossible because of stray elastically scattered light generated by optical surfaces. An alternative technique is offered by the shadowgraph method, which is normally used to visualize fluid flows, but which can also serve as a quantitative tool to measure fluctuations. A somewhat novel shadowgraph apparatus and the necessary data analysis methods will be described. The apparatus uses a spatially coherent, but temporally incoherent, light source consisting of a super-luminescent diode coupled to a single-mode optical fiber in order to achieve extremely high spatial resolution, while avoiding effects caused by interference of light reflected from the various optical surfaces that are present when using laser sources. Results obtained for a critical mixture of aniline and cyclohexane subjected to a vertical temperature gradient will be presented. The sample was confined between two horizontal parallel sapphire plates with a vertical spacing of 1 mm. The temperatures of the sapphire plates were controlled by independent circulating water loops that used Peltier devices to add or remove heat from the room air as required. For a mixture with a temperature gradient, two effects are involved in generating the vertical refractive index gradient, namely thermal expansion and the Soret effect, which generates a concentration gradient in response to the applied temperature gradient. For the aniline/cyclohexane system, the denser component (aniline) migrates toward the colder surface. Consequently, when heating from above, both effects result in the sample density decreasing with altitude and are stabilizing in the sense that no convective motion occurs regardless of the magnitude of the applied temperature gradient. The Soret effect is strong near a binary liquid critical point, and thus the dominant effect is due to the induced concentration gradient. The results clearly show the divergence at low q and the predicted gravitational quenching. Results obtained for different applied temperature gradients at varying temperature differences from the critical temperature, clearly demonstrate the predicted divergence of the thermal diffusion ratio. Thus, the more closely the critical point is approached, the smaller becomes the temperature gradient required to generate the same signal. Two different methods have been used to generate pure concentration gradients. In the first, a sample cell was filled with a single fluid, ethylene glycol, and a denser miscible fluid, water, was added from below thus establishing a sharp interface to begin the experiment. As time went on the two fluids diffused into each other, and large amplitude fluctuations were clearly observed at low q. The effects of gravitational quenching were also evident. In the second method, the aniline/cyclohexane sample was used, and after applying a vertical temperature gradient for several hours, the top and bottom temperatures were set equal and the thermal gradient died on a time scale of seconds, leaving the Soret induced concentration gradient in place. Again, large-scale fluctuations were observed and died away slowly in amplitude as diffusion destroyed the initial concentration gradient.
Cannell, David↗
Effect of reabsorbed recombination radiation on the saturation current of direct gap p-n junctions
The application of the radiative transfer theory for semiconductors to p-n homojunctions subject to low level injection conditions is discussed. By virtue of the interaction of the radiation field with free carriers across the depletion layer, the saturation current density in Shockley's expression for the diode current is reduced at high doping levels. The reduction, due to self-induced photon generation, is noticeable for n-type material owing to the small electron effective mass in direct band-gap III-V compounds. The effect is insignificant in p-type material. At an equilibrium electron concentration of 2 x 10 to the 18th/cu cm in GaAs, a reduction of the saturation current density by 15 percent is predicted. It is concluded that realistic GaAs p-n junctions possess a finite thickness.
Von Roos, O.↗