Search NASA⌕ Search

SEARCH · Search NASA

Results for “charge collection”

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.

At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Modeling of single-event upset in bipolar integrated circuits

The results of work done on the quantitative characterization of single-event upset (SEU) in bipolar random-access memories (RAMs) have been obtained through computer simulation of SEU in RAM cells that contain circuit models for bipolar transistors. The models include current generators that emulate the charge collected from ion tracks. The computer simulation results are compared with test data obtained from a RAM in a bipolar microprocessor chip. This methodology is applicable to other bipolar integrated circuit constructions in addition to RAM cells.

Zoutendyk, J. A.↗
NASA NTRS1986

Improved Electronic Control for Electrostatic Precipitators

Electrostatic precipitators remove particulate matter from smoke created by burning refuse. Smoke exposed to electrostatic field, and particles become electrically charged and migrate to electrically charged collecting surfaces. New microprocessor-based electronic control maintains precipitator power at maximum particulate-collection level. Control automatically senses changes in smoke composition due to variations in fuel or combustion and adjusts precipitator voltage and current accordingly. Also, sensitive yet stable fault detection provided.

Johnston, D. F.↗
NASA NTRS1986

Simulating Single-Event Upsets in Bipolar RAM's

Simulation technique saves testing. Uses interactive version of SPICE (Simulation Program with Integrated Circuit Emphasis). Device and subcircuit models available in software used to construct macromodel for an integrated bipolar transistor. Time-dependent current generators placed inside transistor macromodel to simulate charge collection from ion track. Significant finding of experiments is standard design practice of reducing power in unaddressed bipolar RAM cell increases sensitivity of cell to single-event upsets.

Zoutendyk, J. A.↗
NASA NTRS1986

Dust particles detected near Giacobini-Zinner by the ICE plasma wave instrument

During the ICE flyby of Giacobini-Zinner the plasma wave instrument detected numerous impulsive signals caused by dust impacts on the spacecraft. Most of the impacts occurred within 30,000 km of the comet. The impact rate averaged over the inbound and outbound legs varies approximately as 1/r-squared, as would be expected for an isotropic constant velocity radial outflow. Small differences between the inbound and outbound legs exist which may be indicative of azimuthal variations in the dust production rate. A simple model of the impact ionization and charge collection by the antenna indicates that the particles have a mass on the order of 10 to the -12 to 10 to the -10th gm, corresponding to particles with radii of a few microns.

Gurnett, D. A.↗
NASA NTRS1986

Formation of a pn junction on an anisotropically etched GaAs surface using metalorganic chemical vapor deposition

A continuous p-type GaAs epilayer has been deposited on an n-type sawtooth GaAs surface using MOCVD. A wet chemical etching process was used to expose the intersecting (111)Ga and (-1 -1 1)Ga planes with 6-micron periodicity. Charge-collection microscopy was used to verify the presence of the pn junction thus formed and to measure its depth. The ultimate goal of this work is to fabricate a V-groove GaAs cell with improved absorptivity, high short-circuit current, and tolerance to particle radiation.

Leon, R. P.↗
NASA NTRS1989

Metal Film Increases CCD Quantum Efficiency

Thin layer of platinum or other high-work-function metal applied to back side of rear-illuminated charge-coupled device (CCD) achieves quantum efficiency (QE)-pinned state, an ideal condition allowing sensor to achieve 100-percent internal charge-collection efficiency within its photosensitive volume. Metal layer, called flash gate, easily applied by tungsten vacuum deposition during last step of sensor fabrication.

Janesick, James R.↗
NASA NTRS1989

Metal Coat Increases Output Sensitivity

Charge-coupled photodetector optimized for maximum quantum efficiency (QE), high charge-collection efficiency, and ultralow read noise. Called "flash-coupled" photodetector, sensor delivers high quantum-efficiency sensitivity in spectral range extending from soft x ray to near infrared.

Janesick, James R.↗
NASA NTRS1988

Investigation of single-event upset (SEU) in an advanced bipolar process

An extensive analytical and experimental study SEU in an advanced silicon bipolar process was made. The modeling used process and device parameters to model the SEU charge, collection, and circuit response derived from a special version of PISCES in cylindrical coordinates and SPICE, respectively. Data are reported for test cells of various sizes.

Zoutendyk, John A.↗
NASA NTRS1990

Multi-Pinned-Phase Charge-Coupled Device

Multi-pinned-phase (MPP) technology allows charge-coupled device (CCD) to operate totally inverted during both integration and readout while maintaining other performance characteristics. MPP-CCD made with positive doping implants defining barrier phases. When all phases biased together into inversion, dark current reduced, and potential of charge-collecting wells is difference between potentials of barrier and collection phases. Advantages include complete elimination of residual image effects during integration and readout, low pixel nonuniformity, and increase in quantum efficiency in near infrared because higher operating temperatures used. More tolerant to ionizing radiation environments.

Janesick, James R.↗
NASA NTRS1989

The soft x ray telescope for Solar-A

The Solar-A satellite being prepared by the Institute for Sapce and Astronautical Sciences (ISAS) in Japan is dedicated to high energy observations of solar flares. The Soft X Ray Telescope (SXT) is being prepared to provide filtered images in the 2 to 60 A interval. The flight model is now undergoing tests in the 1000 foot tunnel at MSFC. Launch will be in September 1991. Earlier resolution and efficiency tests on the grazing incidence mirror have established its performance in soft x rays. The one-piece, two mirror grazing incidence telescope is supported in a strain free mount separated from the focal plane assembly by a carbon-epoxy metering tube whose windings and filler are chosen to minimize thermal and hygroscopic effects. The CCD detector images both the x ray and the concentric visible light aspect telescope. Optical filters provide images at 4308 and 4700 A. The SXT will be capable of producing over 8000 of the smallest partial frame images per day, or fewer but larger images, up to 1024 x 1024 pixel images. Image sequence with two or more of the five x ray analysis filters, with automatic exposure compensation to optimize the charge collection by the CCD detector, will be used to provide plasma diagnostics. Calculations using a differential emission measure code were used to optimize filter selection over the range of emission measure variations and to avoid redundancy, but the filters were chosen primarily to give ratios that are monotonic in plasma temperature.

Brown, W. A.↗
NASA NTRS1990

A parallel particle-in-cell model for the massively parallel processor

The availability of the nearest-neighbor communication-incorporating Massively Parallel Processor has prompted the development of a two-dimensional, particle-in-cell algorithm which loads particles in a cell randomly onto a row of processors, filling only half of them with particles. Due to the simplification of communications among processors achieved in a row by the vacant processors and the random-particle sequence, the algorithm efficiently sorts particles and performs gather/scatter procedures for collecting charge density according to their cells. The algorithm calculates electric fields at the cells by FFT.

Lin, C. S.↗
NASA NTRS1989

Open pinned-phase CCD technology

A novel CCD technology, open pinned-phase (OPP) technology, is presented. Particular attention is given to the design and process features of an OPP-CCD that unite multi- and virtual-phase technologies. It is found that the OPP/CCD will produce a modest short-wavelength QE and excellent charge collection efficiency characteristics which are similar to those of the virtual-phase CCD. However, expensive processes related to thinning, backside accumulation, and packaging are not required in the present case.

Janesick, James↗
NASA NTRS1989

Infrared focal plane performance in the South Atlantic anomaly

Proton-induced pulse height distributions (PHD's) in Si:XX detectors were studied analytically and experimentally. In addition, a preliminary design for a flight experiment to characterize the response of Si:XX detectors to the trapped proton environment and verify PHD models was developed. PHD's were computed for two orbit altitudes for a variety of shielding configurations. Most of the proton-induced pulses have amplitudes less that about 3.5 x 10(exp 5) e-h pairs. Shielding has a small effect on the shape of the PHD's. The primary effect of shielding is to reduce the total number of pulses produced. Proton-induced PHD's in a Si:Sb focal plane array bombarded by a unidirectional 67-MeV beam were measured. The maximum pulse height recorded was 6 x 10(exp 5) pairs. The distribution had two peaks: the larger peak corresponded to 3.8 x 10(exp 5) pairs and the smaller peak to 1.2 x 10(exp 5) pairs. The maximum pulse height and the larger peak are within a factor of two of predicted values. The low-energy peak was not expected, but is believed to be an artifact of inefficient charge collection in the detector. The planned flight experiment will be conducted on a Space Shuttle flight. Lockheed's helium extended life dewar (HELD) will be used to provide the required cryogenic environment for the detector. Two bulk Si:Sb arrays and two Si:As impurity band conduction arrays will be tested. The tests will be conducted while the Space Shuttle passes through the South Atlantic Anomaly. PHD's will be recorded and responsivity changes tracked. This experiment will provide a new database on proton-induced PHD's, compare two infrared detector technologies in a space environment, and provide the data necessary to validate PHD modeling.

Junga, Frank A.↗
NASA NTRS1992

Preventing Blooming In CCD Images

Clocking scheme for charge-coupled-device (CCD) imaging photodetector prevents smearing of bright spots and eliminates residual images. Also imposes charge-collecting electric field of optimum-full-well configuration, minimizes nonuniformities among picture elements, and keeps dark current low. Works under almost any lighting conditions.

Janesick, James↗
NASA NTRS1993

Upper-Bound SEU Rates In Anisotropic Fluxes

Upper bounds on rates of single-event upsets (SEU's) in digital integrated circuits and other electronic devices exposed to anisotropic fluxes of energetic ionizing particles computed by use of improved method. Derived from simplified, worst-case mathematical models of charge-collecting volumes and physical phenomena in electronic devices.

Edmonds, Larry D.↗
NASA NTRS1993

Transparent conductive coatings in the far ultraviolet

In certain cases a space-borne optical instrument with a dielectric window requires a transparent conductive coating deposited on the window to remove the electrostatic charge collected due to the bombardment of ionized particles. Semiconductor and metal films are studied for use as transparent conductive coatings for the front window of far ultraviolet camera. Cr is found to be the best coating material. The theoretical search for the semiconductor and metal coating materials and experimental results for ITO and Cr films are reported.

Kim, Jongmin↗
NASA NTRS1994

Variable Temperature Performance of a Si(Li) Detector Stack

New experimental data is presented which displays 137Cs resolution of both single Si(Li) devices and a detector stack 2 cm in height as a function of temperature (85 K greater than or equal to T greater than or equal to 245 K). We also discuss variations in photopeak shape which indicate that detector charge collection may be temperature dependent over the range of interest.

Hubbard, G. Scott↗