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At least 91 records · Page 5

Design and development of solid state detector for SCADS

Solid state detector technology was applied to the fabrication and testing of cadmium sulfide and silicon narrow slit detector/preamplifier subassemblies. Fabrication of the silicon detector and the cadmium sulfide detectors was accomplished by utilizing cadmium sulfide cells and silicon cells. Fabrication of the preamplifiers for both silicon and cadmium sulfide slit type detectors was also carried out. The design of these preamplifiers was adjusted to ascertain that the limiting noise source of the detector/preamplifier subassembly is the detector and the input cable.

Source record↗

Performance of the Zero Degree Detector

The Zero Degree Detector (ZDD) is a large area pixelated silicon detector that measures secondary particle angular distributions from heavy ion interactions. The ZDD is part of the instrumentation being used in an ongoing measurement program to measure fragmentation cross-sections of heavy nuclei and evaluate the relative effectives of novel materials for spacecraft shielding. The initial performance of the ZDD has been assessed using the primary heavy ions measured. We report here on the ZDD's design, capabilities and signal calibration using heavy ions.

Christl, Mark J.↗

Fabrication of Pop-up Detector Arrays on Si Wafers

High sensitivity is a basic requirement for a new generation of thermal detectors. To meet the requirement, close-packed, two-dimensional silicon detector arrays have been developed in NASA Goddard Space Flight Center. The goal of the task is to fabricate detector arrays configured with thermal detectors such as infrared bolometers and x-ray calorimeters to use in space fliGht missions. This paper focuses on the fabrication and the mechanical testing of detector arrays in a 0.2 mm pixel size, the smallest pop-up detectors being developed so far. These array structures, nicknamed "PUDS" for "Pop-Up Detectors", are fabricated on I pm thick, single-crystal, silicon membranes. Their designs have been refined so we can utilize the flexibility of thin silicon films by actually folding the silicon membranes to 90 degrees in order to obtain close-packed two-dimensional arrays. The PUD elements consist of a detector platform and two legs for mechanical support while also serving as electrical and thermal paths. Torsion bars and cantilevers connecting the detector platform to the legs provide additional flexures for strain relief. Using micro-electromechanical structure (MEMS) fabrication techniques, including photolithography, anisotropic chemical etching, reactive-ion etching, and laser dicing, we have fabricated PLTD detector arrays of fourteen designs with a variation of four parameters including cantilever length, torsion bar length and width, and leg length. Folding tests were conducted to test mechanical stress distribution for the array structures. We obtained folding yields and selected optimum design parameters to reach minimal stress levels. Computer simulation was also employed to verify mechanical behaviors of PUDs in the folding process. In addition, scanning electron microscopy was utilized to examine the flatness of detectors and the alignment of detector pixels in arrays. The fabrication of thermistors and heaters on the pop-up detectors is under way, preparing us for the next step of the experiment, the thermal test.

Li, Mary J.↗

Power monitoring in space nuclear reactors using silicon carbide radiation detectors

Space reactor power monitors based on silicon carbide (SiC) semiconductor neutron detectors are proposed. Detection of fast leakage neutrons using SiC detectors in ex-core locations could be used to determine reactor power: Neutron fluxes, gamma-ray dose rates and ambient temperatures have been calculated as a function of distance from the reactor core, and the feasibility of power monitoring with SiC detectors has been evaluated at several ex-core locations. Arrays of SiC diodes can be configured to provide the required count rates to monitor reactor power from startup to full power Due to their resistance to temperature and the effects of neutron and gamma-ray exposure, SiC detectors can be expected to provide power monitoring information for the fill mission of a space reactor.

silicon carbide detectors↗

Low-background direct readout array performance

The development and evaluation of an integrated array of antimony-doped silicon detectors is described. The spectral range of extrinsic silicon-integrated arrays useful for low-background IR astronomical applications is extended to about 31 microns with this development. The 58 x 62-element array is accessed by a direct readout multiplexer. The device is evaluated with a flexible microcomputer-based drive and readout electronics system in a low-background test dewar. Acceptance testing indicates single-pixel NEPs in the mid-10 to the -18th W/sq rt Hz range, and good global uniformity statistics.

Goebel, J. H.↗

Application of the Langley plot for calibration of sun sensors for the Halogen Occultation Experiment (HALOE)

The calibration of the Halogen Occultation Experiment (HALOE) sun sensor is described. This system consists of two energy-balancing silicon detectors which provide coarse azimuth and elevation control signals and a silicon photodiode array which provides top and bottom solar edge data for fine elevation control. All three detectors were calibrated on a mountaintop near Tucson, Ariz., using the Langley plot technique. The conventional Langley plot technique was modified to allow calibration of the two coarse detectors, which operate wideband. A brief description of the test setup is given. The HALOE instrument is a gas correlation radiometer that is now being developed for the Upper Atmospheric Research Satellite.

Moore, Alvah S., Jr.↗

Design of the particles experiment subsystem of the Apollo lunar subsatellite.

In August 1971 an eighty pound subsatellite was ejected from Apollo 15 into lunar orbit. The subsatellite is expected to remain in lunar orbit for at least one year. The Particles Experiment Subsystem of the subsatellite was designed to implement the Particle Shadows/Boundary Layer Experiment. The objective of the experiment is to obtain data for the study of the formation and the dynamics of the earth's magnetosphere, the interaction of plasmas with the moon, and the physics of solar flares. The design of the particle detector telescopes is considered together with details of collimator design, silicon detectors, the absorber foil, and the power subsystems. The instrument performance in lunar orbit is discussed.

Baum, J. J.↗

Biology and Medicine, Spring 1965 Semiannual report

Reports on radiobiology studies, pion studies with silicon detectors, immunology, ultracentrifuge rotor temperature and speed measurement by radio telemetry, and radiosensitivity investigations

RADIOBIOLOGY↗

Biology and Medicine, Fall 1965 Semiannual report

Reports on radiation medicine, radiobiology, EPR STUDIES of OH radicals in ice, radiation doses on manned space missions, silicon detectors, and recovery of yeast after irradiation

X-RAY IRRADIATION↗

1985 Nuclear Science Symposium, 32nd, and 1985 Symposium on Nuclear Power Systems, 17th, San Francisco, CA, October 23-25, 1985, Proceedings

The present conference ranges over topics in high energy physics instrumentation, detectors, nuclear medical applications, health physics and environmental monitoring, reactor instrumentation, nuclear spacecraft instrumentation, the 'Fastbus' data acquisition system, circuits and systems for nuclear research facilities, and the development status of nuclear power systems. Specific attention is given to CCD high precision detectors, a drift chamber preamplifier, a Cerenkov ring imaging detector, novel scintillation glasses and scintillating fibers, a modular multidrift vertex detector, radial wire drift chambers, liquid argon polarimeters, a multianode photomultiplier, the reliability of planar silicon detectors, the design and manufacture of wedge and strip anodes, ultrafast triode photodetectors, photomultiplier tubes, a barium fluoride plastic scintillator, a fine grained neutron hodoscope, the stability of low leakage silicon photodiodes for crystal calorimeters, and X-ray proportional counters. Also considered are positron emission tomography, single photon emission computed tomography, nuclear magnetic resonance imaging, Geiger-Muller detectors, nuclear plant safeguards, a 32-bit Fastbus computer, an advanced light water reactor, and nuclear plant maintenance.

Source record↗

High-spatial resolution and high-spectral resolution detector for use in the measurement of solar flare hard X-rays

In the areas of high spatial resolution, the evaluation of a hard X-ray detector with 65 micron spatial resolution for operation in the energy range from 30 to 400 keV is proposed. The basic detector is a thick large-area scintillator faceplate, composed of a matrix of high-density scintillating glass fibers, attached to a proximity type image intensifier tube with a resistive-anode digital readout system. Such a detector, combined with a coded-aperture mask, would be ideal for use as a modest-sized hard X-ray imaging instrument up to X-ray energies as high as several hundred keV. As an integral part of this study it was also proposed that several techniques be critically evaluated for X-ray image coding which could be used with this detector. In the area of high spectral resolution, it is proposed to evaluate two different types of detectors for use as X-ray spectrometers for solar flares: planar silicon detectors and high-purity germanium detectors (HPGe). Instruments utilizing these high-spatial-resolution detectors for hard X-ray imaging measurements from 30 to 400 keV and high-spectral-resolution detectors for measurements over a similar energy range would be ideally suited for making crucial solar flare observations during the upcoming maximum in the solar cycle.

Desai, U. D.↗

Si(Li) position sensitive detector

A position sensitive detector was made using the lithium diffused layer of a lithium-drifted-silicon detector as the uniform resistive layer. An expression is derived for estimating the resistance from the thickness of the lithium layer. Expressions for the noise and ballistic deficit for single differentiation-double integration pulse shaping are presented. Room temperature data for a 1 Mev proton beam on a 45 mm long detector shows that the linearity is better than .05% and that the position resolution is 1.06 + or - .05 mm.

Gigante, J. R.↗

LWIR detector behavior at very low frequencies

Measurements have been made of the signal and noise characteristics of extrinsic photoconductive silicon detectors. The measurements were made at several background levels, bias voltages and detector operating temperatures. Data are shown at modulation frequencies as low as 0.01 Hz, operating temperatures as low as 2.5K and background photon flux densities down to 8 x 10 to the 7th photons/sec-sq cm. Data on the temporal characteristics of the detector signal are presented. In addition, some interesting data on 'spontaneous noise spikes' are also shown.

Arrington, D. C.↗