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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

High-resolution spectroscopy with the multi-anode microchannel array detector systems

The results of a series of high-resolution spectroscopic observations undertaken with a linear (1 x 1024)-pixel visible-light Multi-Anode Microchannel Array (MAMA) detector on the Coudespectrograph of the 2.2-meter telescope at the Mauna Kea Observatory and on the vacuum spectrograph of the McMath Solar telescope at the Kitt Peak National Observatory are described. In addition, the two-dimensional MAMA detector systems with (16 x 1024)-pixel, (24 x 1024)-pixel, and (256 x 1024)-pixel formats which are now being readied for use in a series of ground-based, balloon, and sounding-rocket observing programs are briefly described.

Timothy, J. G.↗
NASA NTRS1982

Speckle spectroscopy; an application for the multi-anode microchannel array detector system

Plans to combine the High Angular Resolution Imager/Spectrometer on the 4-meter Mayall telescope at the Kitt Peak National Observatory and the (256 x 1024)-pixel Multi-Anode Microchannel Array detector system to produce a unique instrument for speckle spectroscopy are described. The pulse-counting detector system will provide distortion-free imaging and will time tag each spatially-resolved photon event with an accuracy of 100 ns. The Imager/Spectrometer will provide a spatial resolution of 0.07 arcsec orthogonal to the plane of dispersion and 0.18 arcsec in the plane of dispersion.

Butcher, H. R.↗
NASA NTRS1984

Comparative lifetesting results for microchannel plates in windowless EUV photon detectors

Microchannel plates (MCPs) from seven manufacturers were subjected to a series of tests to determine their suitability for the Extreme Ultraviolet Explorer satellite. Comparative data are presented for sixteen MCP tandem pairs with channel length to diameter ratios (l/d) ranging from 40:1 to 60:1 and for two saturable (curved channel) MCPs with l/d's of 80:1. Results for MCPs with funnelled channel throats are also discussed. Properties of the MCPs which were monitored include: background count rate, output charge pulse height distribution (PHD), modal gain, PHD full width half maximum (FWHM), and extreme ultraviolet (EUV) photon quantum efficiency. Five detectors were chosen for further lifetime testing consisting of a mild bake to 100 C, and charge extraction to 0.01 coulombs, repeated high voltage cycling and reexposure to one atmosphere conditions. The results of these tests and their implications for the flight detectors are discussed. Erratic events in the detector background were recorded, probably due to field emission from high voltage surfaces or the absorption of water vapor into the electrode following exposure to air. The steps taken to control the detector background are discussed.

Malina, R. F.↗
NASA NTRS1984

Microchannel plate EUV detectors for the Extreme Ultraviolet Explorer

The design and operating characteristics of the prototype imaging microchannel plate (MCP) detector for the Extreme Ultraviolet Explorer (EUVE) Satellite are discussed. It is shown that this detector has achieved high position resolution performance (greater than 512 x 512 pixels) and has low (less than one percent) image distortion. In addition, the channel plate scheme used has tight pulse height distributions (less than 40 percent FWHM) for UV radiation and displays low (less than 0.2 cnt/sq cm-s) dark background counting rates. Work that has been done on EUV filters in relation to the envisaged filter and photocathode complement is also described.

Siegmund, O. H. W.↗
NASA NTRS1984

Photometry with Multi-anode Microchannel Arrays (mamas) and Charge Injection Devices (cids)

The characteristics of two kinds of detectors are summarized with emphasis on those aspects that would affect their use in high accuracy astronomical photometry. The first type, the multianode microchannel arrays (MAMA), are a family of pulse counting array detectors. Components and operation principles are reviewed and quantum efficiency, noise characteristics, and dynamic range characteristics are described. The second type, charge injection devices (CID), are discussed in reference to their applicability to photometric detection at optical wavelengths.

Timothy, J. G.↗
NASA NTRS1984

Absolute and angular efficiencies of a microchannel-plate position-sensitive detector

This paper presents a characterization of a commercially available position-sensitive detector of energetic ions and neutrals. The detector consists of two microchannel plates followed by a resistive position-encoding anode. The work includes measurement of absolute efficiencies of H(+), He(+), and O(+) ions in the energy range between 250 and 5000 eV, measurement of relative detection efficiencies as a function of particle impact angle, and a simple method for accurate measurement of the time at which a particle strikes the detector.

Gao, R. S.↗
NASA NTRS1985

Investigation of large format microchannel plate Z configurations

The performance of triplet (Z) stacks of microchannel plates (MCPs) has been studied as a part of the instrument development for the Extreme Ultraviolet Explorer (EUVE) satellite mission. Relatively large MCPs with a 60-mm diameter and having a large 80:1 channel length to diameter (L:D) ratio were used in several configurations. The MCPs were used in the EUVE prototype imaging detector to provide more than 512 x 512 pixels with low image distortion (less than 1 percent). The gain and pulse height characteristics of the MCPs were examined, showing that both high gains (more than 2 x 10 to the 7th) and tight output pulse height distributions (less than 30 percent FWHM) may be achieved. Simple distribution techniques have also allowed low intrinsic background event rates (less than 0.15 events per sq cm/s) to be obtained. Variation of the quantum efficiency of the MCPs over the wavelength range 160-1216 A has been investigated for a range of angles of incidence. The effect of temperature variations on MCP operating characteristics has also been evaluated.

Siegmund, O. H. W.↗
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 NTRS1985

Persistence of phosphor glow in microchannel plate image intensifiers

Image intensifier tubes using microchannel plate amplification stages and phosphor output stages are being increasingly used in various detection applications. In this paper, measurements of the decay times of what are attributed to be the P20 phosphors in various image intensifiers are reported. It is found that the long tail on the decay curve of the phosphor following illumination can be a limitation for certain observations. In addition, the background level of phosphor glow (which is seen by the subsequent detection system as a light signal) continues to build with continuing illumination.

Torr, M. R.↗
NASA NTRS1986

The development and test of multi-anode microchannel array detector systems. Part 2: Soft X-ray detectors

Detector systems based on the high gain microchannel plate (MCP) electron multiplier were used extensively for imaging at soft X-ray wavelengths both on the ground and in space. The latest pulse counting electronic readout systems provide zero readout noise, spatial resolutions (FWHM) of 25 microns or better and can determine the arrival times of detected photons to an accuracy of the order of 100 ns. These systems can be developed to produce detectors with active areas of 100 nm in diameter or greater. The use of CsI photocathodes produces very high detective quantum efficiencies at wavelengths between about 100 and 1A (approximately 0.1 to 10 keV) with moderate energy resolution. The operating characteristics of the different types of soft X-ray MCP detector systems are described and the prospects for future developments are discussed.

Timothy, J. G.↗
NASA NTRS1984

Performance characteristics of multi-anode microchannel array detector systems

The multi-anode microchannel arrays (MAMAs) are state-of-the-art, pulse-counting, photoelectric array detectors designed specifically for use in space astrophysics instruments. The present paper provides a description of recent progress related to the development of ultraviolet and visible-light versions of the MAMA detectors, taking into account a comparison of the operating characteristics of these devices with those of photoconductive array detectors, such as the CCDs. Attention is given to MAMA detector system design parameters, the operating characteristics of MAMAs and CCDs, MAMA performance characteristics, and future developments.

Timothy, J. G.↗
NASA NTRS1986

The development and test of multi-anode microchannel array detector systems. Part 2: Soft X-ray detectors

Multi-Anode Microchannel Array (MAMA) detector systems with formats of 256 x 1024 pixels and active areas of 6 x 26 square mm are now under evaluation at visible, ultraviolet and soft x-ray wavelengths. Very-large-format versions of the MAMA detectors with formats of 2048 x 2048 pixels and active areas of 52 x 52 square mm are under development for use in the NASA Goddard Space Flight Center's Space Telescope Imaging Spectrograph (STIS). Open-structure versions of these detectors with CsI photocathodes can provide a high-resolution imaging capability at extreme ultraviolet (EUV) and soft x-ray wavelengths and can deliver a maximum count rate from each array in excess of 1 million counts s-1. In addition, these detector systems have the unique capability to determine the arrival time of a detected photon to an accuracy of 100 ns or better. The construction, mode-of-operation and performance characteristics of the MAMA detectors are described and the program for the development of the very-large-format detectors is outlined.

Timothy, J. G.↗
NASA NTRS1986

A new approach to large area microchannel plate manufacture

Methods of manufacture of twisted single elements as the base for producing microchannel plates (MCP) are discussed. Initial evaluations validated the off-axis channel concept and no technological roadblocks were identified which would prevent fabrication of high gain, high spatial resolution, large format MCP's using this technique. The first MP's have operated at stable gains of 3 million with pulse height resolution superior to results obtained by standard chevron MCP's.

Source record↗
NASA NTRS1986

Microchannel plates and image detection at soft X-ray wavelengths

Detector systems based on the high-gain microchannel plate (MCP) electron multiplier have been used extensively for imaging at soft X-ray wavelengths both on the ground and in space. The latest pulse-counting electronic readout systems provide zero readout-noise, spatial resolutions (FWM) of 25 microns or better and can determine the arrival times of detected photons to an accuracy of the order of 100 ns. These systems can br developed to produce detectors with active areas of 100 mm in diameter or greater. The use of CsI photocathodes produces very high detective quantum efficiencies to wavelengths between about 100 and 1A (0.1 to 10 keV) with moderate energy resolution. The operating characteristics of the different types of soft X-ray MCP detector systems are described, and the prospects for future developments are discussed.

Timothy, J. G.↗
NASA NTRS1987

Ultraviolet quantum detection efficiency of potassium bromide as an opaque photocathode applied to microchannel plates

The quantum detection efficiency (QDE) of potassium bromide as a photocathode applied directly to the surface of a microchannel plate over the 250-1600 A wavelength range has been measured. The contributions of the photocathode material in the channels and on the interchannel web to the QDE have been determined. Two broad peaks in the QDE centered at about 450 and about 1050 A are apparent, the former with about 50 percent peak QDE and the latter with about 40 percent peak QDE. The photoelectric threshold is observed at about 1600 A, and there is a narrow QDE minimum at about 750 A which correlates with 2X the band gap energy for KBr. The angular variation of the QDE from 0 to 40 deg to the channnel axis has also been examined. The stability of Kbr with time is shown to be good with no significant degradation of QDE at wavelengths below 1216 A over a 15-day period in air.

Siegmund, Oswald H. W.↗
NASA NTRS1986

Calibration of photon counting imaging microchannel plate detectors for EUV astronomy

The calibration of photon counting imaging detectors for satellite based EUV astronomy is a complex process designed to ensure the validity of the data received 'in orbit'. The methods developed to accomplish calibration of microchannel plate detectors for the Extreme Ultraviolet Explorer are described and illustrated. The characterization of these detectors can be subdivided into three categories: stabilization, performance tests, and environmental tests.

Siegmund, O. H. W.↗
NASA NTRS1986

Imaging at soft X-ray wavelengths with high-gain microchannel plate detector systems

Multianode microchannel array (MAMA) detector systems with formats of 256 x 1024 pixels and active areas of 6 x 26 mm are now under evaluation at visible, UV and soft X-ray wavelengths. Very-large-format versions of the MAMA detectors with formats of 2048 x 2048 pixels and active areas of 52 x 52 mm are under development for use in the NASA Goddard Space Telescope Imaging Spectrograph (STIS). Open-structure versions of these detectors with Cs I photocathodes can provide a high-resolution imaging capability at EUV and soft X-ray wavelengths and can deliver a maximum count rate from each array in excess of 10 to the 6th counts/s. In addition, these detector systems have the unique capability to determine the arrival time of a detected photon to an accuracy of 100 ns or better. The construction, mode of operation, and performance characteristics of the MAMA detectors are described, and the program for the development of the very-large-format detectors is outlined.

Timothy, J. Gethyn↗
NASA NTRS1987

Delay line anodes for microchannel-plate spectrometers

A photon-counting readout system for microchannel-plate spectrometers is described that uses a delay line and timing circuit for the wavelength coordinate and a wedge-wedge charge division system for the orthogonal spatial coordinate. A novel zigzag layout allows these two anode patterns to coexist on a common planar substrate and share the charge from each photoevent, thereby simultaneously localizing the photon in each of its two dimensions. Unlike wedge-and-strip or resistive anode encoders, the delay line offers a spatial resolution that is relatively independent of the format length. Unlike discrete anode systems, the delay line readout system's complexity is also independent of the field of view size. These facts make the delay line readout system advantageous in large format detectors. A testbed detector having a delay line propagation speed of 2.2 mm/ns and a time resolution of 33 ps FWHM has been assembled. Ultraviolet testing shows a Gaussian event distribution having a 70-micron FWHM width; the readout system blur contribution is less than 50-micron FWHM.

Lampton, M.↗