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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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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

The High Resolution Imaging Instrument for HEAO-B

The High Resolution Imaging Instrument for the HEAO-B X-ray Telescope satellite is designed to reproduce images of celestial X-ray sources in the range of 0.2 to 4.0 keV. It provides both imaging and temporal data. The basic detector is a two-stage microchannel plate with a crossed-grid charge detector. Preamplifiers, detector bias supplies, and some processing circuits are colocated with the detector. The remaining electronic circuits are located in a remote central electronic assembly. The processing system is designed for single-photon processing. The imaging data rate is limited to 100 data points per second. Non-imaging total-field count rate is acquired with a maximum dead time of 14 microseconds per event.

Kubierschky, K.↗
NASA NTRS1990

ORFEUS-SPAS - The Berkeley EUV spectrometer

The Berkeley EUV spectrometer of ORFEUS-SPAS, a joint project of NASA and the BMFT, incorporates a set of four novel spherically figured, varied line-space gratings used in a geometry that is similar to that of the classic Rowland mount to span an interval of 390 and 1200 A. Two spectral detector units containing curved microchannel plates and delay-line anodes encode the arriving photons in digital format for telemetry. An additional optic directs the image of the source in the entrance aperture onto a sealed FUV detector which is used to track the source as it drifts during an observation, enabling a postflight reconstruction of the spacecraft pointing vector. This in turn makes it possible to define with precision the wavelength of each recorded photon.

Bowyer, Stuart↗
NASA NTRS1985

Operation of a microchannel plate counting system in a mass spectrometer

A multiplier detector system has been developed as part of a mass spectrometer in an ion counting mode. During its operation ions striking a microchannel plate release pulses of electrons which are accelerated to a phosphor layer. The resulting flash of light is carried by a fiber-optic bundle to a photodiode array. The detector simultaneously counts ions throughout a mass spectrum covering more than 30 amu. It extends the mass spectrometer's operation toward low count rates for trace gas analysis. Each mass peak can be independently measured at count rates between 0.1 and 1000 counts/s. Higher rates on a few peaks do not blind the entire detector. The detector's capabilities have been demonstrated by measuring Kr and Xe isotopes in air at natural abundances. The mass spectrometer, detector, and readout electronics are sufficiently compact to permit use in a balloon-borne experiment.

Murphy, D. M.↗
NASA NTRS1990

An intensified CCD detector using the phosphor TPB

The Research Amplifying Imaging Detector consists of a microchannel plate image intensifier with a thin coating (3500-10,000 A) of the phosphor tetraphenyl-butadiene (TPB) on the entrance window to convert EUV radiation to visible, and coupled via a lens to a CCD detector. This design allows great flexibility in selecting the pixel size and field of view, with a simple mechanical design. The phosphor appears to be quite rugged, with no degradation having appeared during several months of testing both in and out of vacuum. Tests have been made at visible and EUV (304 A) wavelengths of the following performance aspects: EUV spectral sensitivity, spatial resolution (both of components and of the system as a whole), noise, linearity, and dynamic range. An improved detector for the Coronal Diagnostic Spectrometer experiment on the Solar Heliospheric Observatory satellite is being presently designed.

Thompson, William T.↗
NASA NTRS1989

A position sensitive detector for EUV remote sensing

The authors describe a photon-counting extreme ultraviolet (EUV) detector system used in a rocket-borne spectroscopic instrument for remote sensing of upper atmospheric composition and temperature. The detector uses a KBr coated microchannel plate (MCP) Z stack in combination with a wedge-and-strip image readout system. Three separate detector fields of view are used to sense the Earth dayglow spectrum (980 A to 1040 A, and 1300 A to 1360 A) and the solar EUV spectrum (250 A to 1400 A). The authors demonstrate high gain (2 x 107), tight pulse-height distribution (35 percent FWHM), and a spatial resolution of about 35 microns FWHM (full width at half maximum), which is the highest resolution for a wedge-and-strip anode MCP detector flown to date. The background, image linearity, and flat-field performance are discussed. Raw spectra from the rocket flight are also presented.

Siegmund, O. H. W.↗
NASA NTRS1979

A low-energy gamma-ray imaging detector

We describe a hard-X-ray/soft-gamma-ray imaging detector, incorporating a microchannel-plate (MCP) electron multiplier for possible use in future telescopes. In contrast to previous attempts using MCP's this approach promises to achieve high quantum detection efficiencies in addition to high spatial and temporal resolution. Preliminary results indicate not only the capability of simultaneous imaging and single-photon counting, but also coarse energy resolution.

Yin, L. I.↗
NASA NTRS1980

Measurements of mass flow in the transition region and inner corona

A solar rocket experiment launched on June 5, 1979 is described which provides high spectral resolution line profiles across the solar disk. The instrument consists of a small telescope with moderate spatial resolution and a spectrograph with stability and high spectroscopic resolution (about 0.028 A at 600 A). The detector system uses a microchannel plate array to provide 1,024 simultaneous measurements spanning approximately 30 A of the solar spectrum. The spectrograph uses a 3600 l/mm grating, and the spectral range 609-634 A is recorded in second order overlapping 1218-1268 A in first order. The position of the emission lines is determined by a center-of-mass routine and velocity shifts are evident. The qualitative results are in general agreement with the results of Cushman and Rense (1976).

Rottman, G. J.↗
NASA NTRS1987

The AXAF high resolution camera (HRC) and its use for observations of distant clusters of galaxies

The High Resolution Camera being developed for AXAF is briefly described, comparing it with its predecessor, the Einstein HRI, and providing preliminary performance data. The HRC is a 10 cm x 10 cm detector with CsI coated microchannel plates providing a large field of view device with high X-ray quantum efficiency. The overall sensitivity of the HRC on AXAF is about 50 times that of the Einstein HRI. An example of the power of this instrument is discussed in the context of studies of distant clusters of galaxies. The HRC can detect individual galaxies in a cluster of redshift 1, if they are similar to the early-type galaxies in nearby clusters that have been observed by the Einstein instruments. The HRC will be used to measure the luminosity function for clusters of galaxies as a function of their distance up to a redshift of 1. This will allow observation of evolutionary effects in clusters as a whole, while the detection of individual galaxies will permit studies of galaxy evolution in a cluster environment.

Murray, S. S.↗
NASA NTRS1992

Gas ionization solar spectral monitor (GISSMO)

We are currently developing an instrument free from optical components to measure the full-disk solar spectrum in the extreme ultraviolet regime covering wavelengths from 75-500 A. The instrument, which will be launched aboard a NASA Black Brant sounding rocket in September 1992, consists of a windowless noble gas ionization cell followed by a toroidal electrostatic analyzer to spatially disperse photoelectrons as a function of their energies. A microchannel plate based position sensitive detector will be used to detect individual electrons, indirectly returning the solar EUV spectrum.

Vickers, James S.↗
NASA NTRS1993

High-resolution Y-axis readout for delay-line microchannel anodes

We have devised a method to obtain a high-resolution Y-axis event position determination from microchannel plate delay-line detectors. The method is based on the double-delay-line wedge-wedge charge partition principle of Lampton et al. (1990), where the X axis is read out by a pair of side-by-side delay lines and the Y-axis coordinate is determined by comparing the charges on the two parallel delay lines. However, our new method abandons the common field return path of the two delay lines, and splits them into two adjacent but independent transformer coupled timing circuits having no common ground connection except via the charge-measurement amplifiers. Thus we eliminate the large electrostatic capacitance of the delay lines from the input of the charge-measuring system. Over its limited working field, the spatial resolution in the Y coordinate can easily equal the resolution provided in the X coordinate by the delay line. Applications to extreme and FUV photon-counting spectroscopy are envisioned.

Raffanti, R.↗
NASA NTRS1994

AXAF VETA-I mirror ring focus measurements

The AXAF VETA-I mirror ring focus measurements were made with an HRI (microchannel plate) X-ray detector. The ring focus is a sharply focused ring formed by X-rays before they reach the VEAT-I focal plane. It is caused by spherical aberrations due to the finite source distance and the despace in the VETA-I test. The ring focus test reveals some aspects fo the test system distortions and the mirror surface figure which are difficult or impossible to detect at the focal plane. The test results show periodic modulations of the ring radius and width which could be caused by gravity, thermal, and/or epoxy shrinkage distortions. The strongest component of the modulation had a 12-fold symmetry, because these distortions were exerted on the mirror through 12 flexures of the VETA-I mount. Ring focus models were developed to simulate the ring image. The models were compared with the data to understand the test system distortions and the mirror glass imperfection. Further studies will be done to complete this work. The ring focus measurement is a very powerful test. We expect that a similar test for the finally assembled mirror of AXAD-I will be highly valuable.

Tananbaum, H. D.↗
DOE OSTI2020

Timing resolution and rate capability of Photonis miniPlanacon XPM85212/A1-S MCP-PMT

In this paper we report on a set of experiments that focus on measuring the timing performance of the Photonis miniPlanacon XPM85212/A1-S microchannel plate photomultiplier tubes along with the detector response at high event rates. The detector has a single photoelectron timing resolution of 30 ps at low rates ( 10 kHz ). We show that both the gain and the timing start to deteriorate around 1 MHz with 20 photoelectrons per channel at 1 0 4 target gain, giving the current per unit of area limits of 1.38 μ A / cm 2 and 2.38 μ A / cm 2 for the two tested devices. Photo-multiplier tubes with lower micro-channel plate resistivity exhibit a better rate capability due to the faster replenishment of the charge inside the microchannels. As we demonstrate, another method to improve the rate capability is to operate the photon detector tubes at a lower gain by reducing the supply voltage and compensating for the loss of amplitude by an additional amplification stage at the expense of the achieved timing resolution. The tube active area over which the beam is spread also plays a role since the same amount of light yields a better rate capability when spread over a larger area. The tubes exposed to high event rates showed an uncharacteristically slow recovery back to its initial gain with 80 % of the initial gain recovered only after several tens of minutes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1977

The Photicon

The Photicon is a novel imaging optical detector utilizing a conventional semitransparent photocathode, imaging electrostatic optics, microchannel plates, and a crossed-wire-grid position-sensitive charge detector. Its sensitivity to single optical photons over a two-dimensional area, high-resolution imaging, and timing capability render it useful for recording scintillations from X-ray image converters in X-ray astronomy. A digital word indicating the position of a single photon event is produced; the image can be stored in an array or serially. Spatial resolution to 20 microns in a 25 mm diam active area detector is reported, and modifications to achieve a spectral range of 120-730 nm are mentioned.

Kellogg, E.↗
NASA NTRS2011

Radiation Design of Ion Mass Spectrometers

In the harsh radiation environment of Jupiter and with the JUpiter ICy moon Explorer (JUICE) mission including two Europa flybys where local intensities are approx. 150 krad/month behind 100 mils of Al shielding, so background from penetrating radiation can be a serious issue for detectors inside an Ion Mass Spectrometer (IMS). This can especially be important for minor ion detection designs. Detectors of choice for time-of-flight (TOF) designs are microchannel plates (MCP) and some designs may include solid state detectors (SSD). The standard approach is to use shielding designs so background event rates are low enough that the detector max rates and lifetimes are first not exceeded and then the more stringent requirement that the desired measurement can successfully be made (i.e., desired signal is sufficiently greater than background noise after background subtraction is made). GEANT codes are typically used along with various electronic techniques, but such designs need to know how the detectors will respond to the simulated primary and secondary radiations produced within the instrument. We will be presenting some preliminary measurements made on the response of MCPs to energetic electrons (20 ke V to 1400 ke V) using a Miniature TOF (MTOF) device and the High Energy Facility at Goddard Space Flight Center which has a Van de Graaff accelerator.

Sittler, Ed↗
NASA NTRS1992

Calibration of the Verification Engineering Test Article-I (VETA-I) for AXAF using the VETA-I X-ray Detection System

Advanced X-ray Astrophysics Facility (AXAF) X-ray optics testing is conducted by VETA-I, which consists of six nested Wolter type I grazing-incidence mirrors; VETA's X-ray Detection System (VXDS) in turn measures the imaging properties of VETA-I, yielding FWHM and encircled energy of the X-ray image obtained, as well as its effective area. VXDS contains a high resolution microchannel plate imaging X-ray detector and a pinhole scanning system in front of proportional-counter detectors. VETA-I's X-ray optics departs from the AXAF flight configuration in that it uses a temporary holding fixture; its mirror elements are not cut to final length, and are not coated with the metal film used to maximize high-energy reflection.

Kellogg, E.↗
NASA NTRS1997

AXAF Detector Backgrounds Produced By Cosmic Ray Protons

One of the science instruments on the Advanced X-ray Astrophysics Facility (AXAF), planned for launch in 1998 into a highly elliptical (10,000 km x 140,000 km) orbit, is a microchannel plate High Resolution Camera (HRC). This detector is designed to provide imaging and spectroscopic observations of x-rays emitted by stellar sources in the 0.1 to 10 keV energy range. Described here are analyses made to determine the expected time-dependent detector background from prompt and delayed (activation) radiation initiated by galactic cosmic-ray (GCR) proton interactions in the spacecraft and payload. Numerical simulations were made using the coupled set of Monte Carlo radiation transport codes, analysis software, and data bases shown. The major codes are HETC for nucleon-meson transport, EGS for simulating electromagnetic cascades, and MORSE for low-energy (less than 15 MeV) neutron transport. The simulation follows the transport history of photons in the energy range from - 100 GeV down to approx. 0.1 keV due to gamma-ray sources from neutral pion decay, high-energy (spallation) collisions, and low-energy neutron inelastic scattering and capture reactions. Also included is radioisotope production and the tracking of gamma-rays, electrons, and positrons from induced radioactivity.

Armstrong, T. W.↗
NASA NTRS1990

Optical design of Lyman/FUSE

The optical system for the proposed Lyman/Far UV Spectroscopic Explorer (FUSE) orbiting observatory is described and illustrated with drawings and graphs of predicted performance. The system comprises (1) an FUV channel based on a 1.84-m-diameter Rowland circle spectrograph with five high-density modified ellipsiodal near-normal-incidence gratings and an array of four MAMA detectors; (2) an EUV channel with ellipsoidal mirror, planar varied-line-space grating, microchannel-plate array, and wedge-and-strip anode detector; (3) a 70-cm Wolter II glancing-incidence telescope; and (4) a CCD-detector fine-error sensor to provide accurate pointing (within 200 marcsec rms). The resolving powers of the spectrographs are 30,000 in the FUV and 300-600 (wavelength-dependent) in the EUV.

Content, D. A.↗
NASA NTRS1985

An intensified photodiode array detector for space applications

The Hopkins Ultraviolet Telescope (HUT) is a general purpose moderate resolution spectrograph which is now being constructed for launch on the Space Shuttle. The instrument contains a Rowland spectrograph, which is located at the prime focus of a 0.9-m f/2 parabola. A description is given of the progress which has been made in the development of a flight detector for HUT. The detector developed is an intensified photodiode array. The image intensifier part of the detector contains two 25-mm 80:1, 12-micron pore microchannel plates (PCPs). A thin layer of CsI deposited on the front surface of the first microchannel plate has the objective to increase the quantum efficiency of the detector below 1850 A. The detector system utilizes a spectrometer processor (SP) which is based upon a bit-sliced microprocessor. The current status of the HUT detector system is discussed, and aspects of performance are evaluated. It is felt that the developed system will meet or exceed the design requirements.

Long, K. S.↗