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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Development of high resolution imaging detectors for x ray astronomy

This final report summarizes our past activities and discusses the work performed over the period of 1 April 1990 through 1 April 1991 on x-ray optics, soft x-ray (0.1 - 10 KeV) imaging detectors, and hard x-ray (10 - 300 KeV) imaging detectors. If microchannel plates (MCPs) can be used to focus x-rays with a high efficiency and good angular resolution, they will revolutionize the field of x-ray optics. An x-ray image of a point source through an array of square MCP pores compared favorably with our ray tracing model for the MCP. Initial analysis of this image demonstrates the feasibility of MCPs for soft x-rays. Our work continues with optimizing the performance of our soft x-ray MCP imaging detectors. This work involves readout technology that should provide improved MCP readout devices (thin film crossed grid, curved, and resistive sheets), defect removal in MCPs, and photocathode optimization. In the area of hard x-ray detector development we have developed two different techniques for producing a CsI photocathode thickness of 10 to 100 microns, such that it is thick enough to absorb the high energy x-rays and still allow the photoelectrons to escape to the top MCP of a modified soft x-ray imaging detector. The methods involve vacuum depositing a thick film of CsI on a strong back, and producing a converter device that takes the place of the photocathode.

Murray, S. S.↗
NASA NTRS1992

A new-speckle interferometry system for the MAMA detector

We have developed a new system for making speckle observations with the multianode microchannel array (MAMA) detector. This system is a true photon-counting imaging device which records the arrival time of every detected photon and allows for reconstruction of image features near the diffraction limit of the telescope. We present a description of the system and summary of observational results obtained at the Lick Observatory 1-m reflector in 1991 September. The diffraction limit of the 1-m telescope at 5029 A is about 0.125 arcsec and we have successfully resolved the catalogued interferometric binary HD 202582 with a separation of 0.157 +/- 0.031 arcsec. A pair of stars in the open cluster Chi Persei separated by 2.65 +/- 0.22 arcsec with approximate V magnitudes 8.6 and 11.5 has also been successfully analyzed with the speckle technique.

Horch, E.↗
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 NTRS1991

Geoscience Laser Ranging System design and performance predictions

The Geoscience Laser System (GLRS) will be a high-precision distance-measuring instrument planned for deployment on the EOS-B platform. Its primary objectives are to perform ranging measurements to ground targets to monitor crustal deformation and tectonic plate motions, and nadir-looking altimetry to determine ice sheet thicknesses, surface topography, and vertical profiles of clouds and aerosols. The system uses a mode-locked, 3-color Nd:YAG laser source, a Microchannel Plate-PMT for absolute time-of-flight (TOF) measurement (at 532 nm), a streak camera for TOF 2-color dispersion measurement (532 nm and 355 nm), and a Si avalanche photodiode for altimeter waveform detection (1064 nm). The performance goals are to make ranging measurements to ground targets with about 1 cm accuracy, and altimetry height measurements over ice with 10 cm accuracy. This paper presents an overview of the design concept developed during a phase B study. System engineering issues and trade studies are discussed, with particular attention to error budgets and performance predictions.

Anderson, Kent L.↗
NASA NTRS1992

Optical design of the Ultraviolet Imaging Spectrograph for the Cassini mission to Saturn

When the Cassini spacecraft arrives at Saturn early in the next century it will carry an Ultraviolet Imaging Spectrograph (UVIS). Observations made with the UVIS will support a broad set of scientific investigations including spectroscopy, imaging, and occultations. The UVIS consists of three spectroscopic channels covering the wavelength ranges 55-115 nm, 115-190 nm, and 160-320 nm. Each channel has an off-axis parabolic telescope followed by a toroidal grating spectrograph and an imaging microchannel plate-CODACON detector. The UVIS configuration was selected as a balanced solution to a large number of engineering and scientific constraints. We describe these constraints, the optical design, and the anticipated performance of the instrument.

Mcclintock, William E.↗
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 NTRS1992

The WIDe-angle GEocoronal Telescope (WIDGET)

We describe the WIDe-angle GEocoronal Telescope, or WIDGET. The telescope is designed to image the cold plasma constituent of the magnetosphere, the plasmasphere, by imaging the He II 304 A emission. It utilizes a spherical normal incidence f/2 mirror with a microchannel plate imaging detector positioned near the focal point of the mirror. The instrument has a 30-deg field of view with a .5-1-deg angular resolution. The mirror has a multilayer coating which, combined with an Al/C filter and the detector response, provides a peak sensitivity of approximately 0.5 ct/sec/Rayleigh/bin at 304 A with a bandpass of about 60 A. The instrument will be flown on a sounding rocket in the Fall of 1992 as a test of its capabilities. It can easily be adapted to different wavelengths (584, 834, and 1216 A) using suitable mirror coatings and filters. In this way, a series of WIDGETs could image different aspects of the inner magnetosphere simultaneously, thus providing a more unified picture of this complex region.

Cotton, Daniel↗
NASA NTRS1992

Coded aperture devices for viewing extended objects from space

Coded aperture sensors for photons or energetic neutral atoms (ENAs), which incorporate FOV limiters and subdivide the object field into a number of elements which is smaller than the number of detector pixels, are described. A least squares fit to the data is made in reconstructing the object field. To evaluate the optics and reconstruction algorithms, two 'breadboard' sensors have been constructed, one based on a film camera and the other upon a UV-light sensitive microchannel plate detector system. Results obtained thus far show that the concept is viable, and no special difficulties should be encountered in adapting the detector geometries to neutral particle imaging systems. Charged particle deflection plates could be incorporated into the region between the FOV limiter and the aperture, or installed ahead of the limiter.

Curtis, C. C.↗
NASA NTRS1991

Monolithic integrated circuit charge amplifier and comparator for MAMA readout

Prototype ICs for the Solar Heliospheric Observatory's Multi-Anode Microchannel Array (MAMA) have been developed; these ICs' charge-amplifier and comparator components were then tested with a view to pulse response and noise performance. All model performance predictions have been exceeded. Electrostatic discharge protection has been included on all IC connections; device operation over temperature has been consistent with model predictions.

Cole, Edward H.↗
NASA NTRS1991

High-dynamic-range MCP structures

We report on the development of a new high-dynamic-range two-stage Multi-Anode Microchannel Array (MAMA) imaging tube designed for improved high count rate performance at FUV and EUV wavelengths. The new two-stage MAMA tube employs two 25-mm-diameter format MCPs placed in tandem with a small gap between the plates. The front (input) MCP is designed to be a low-gain converter plate that supports an opaque photocathode and converts the detected photons to electrons, while the second (output) MCP is of higher conductivity and thus maintains the overall gain of the multiplier at high count rates. The second MCP is mounted in proximity focus with a (224 x 960)-pixel fine-fine coincidence MAMA array for high-spatial-resolution imaging studies. The applied voltage across each MCP can be controlled independently. We report on the gain and dynamic range performance characteristics of the two-stage MAMA tube in two different configurations: first, with the output MCP having moderate conductivity (about 100 MOhm); and second, with the output MCP having very high conductivity (about 2 MOhm). These results are compared and contrasted with those of the more conventional MAMA tube configuration which employs a single high-gain curved-channel MCP.

Slater, David C.↗
NASA NTRS1991

Performance characteristics of the imaging MAMA detector systems for SOHO, STIS, and FUSE/Lyman

Imaging Extreme Ultraviolet (EUV) Multi-Anode Microchannel Array (MAMA) detector systems with formats of 360 x 1024 pixels and pixel dimensions of 25 x 25 sq microns are being fabricated and tested for flight in two instruments on the ESA/NASA Solar and Heliospheric Observatory (SOHO). In addition, very-large-format (1024 x 1024)- and (2048 x 2048)-pixel Far Ultraviolet (FUV) and EUV MAMA detectors with pixel dimensions of 25 x 25 sq microns are being fabricated and tested for use in the NASA Goddard Space Flight Center's Hubble Space Telescope Imaging Spectrograph (STIS), a second-generation instrument scheduled for in-orbit installation in 1997. Finally, FUV MAMA detectors with formats of 224 x 960 pixels and pixel dimensions of 14 x 14 sq microns are being evaluated as prototypes of the detector for the prime FUV spectrograph of the Far Ultraviolet Spectroscopic Explorer (FUSE/Lyman) mission. The configurations and performance characteristics of the different detector systems are described, and the plans for further development of the Advanced Technology MAMA detector system discussed.

Timothy, J. G.↗
NASA NTRS1991

High throughput narrowband 83.4 nm self-filtering camera

Photometric imaging of ionospheric/magnetospheric O II emission at 83.4 nm is a primary objective for mapping the distribution of O(+) ions. However, instrumental sensitivity has been a major barrier to realizing this goal. We report an instrumental design employing a low focal ratio three-mirror camera where the reflecting surfaces act as both narrowband reflection filters at 83.4 nm and as a high quality imaging system. The design includes coatings with reflectances that are relatively insensitive to the angle of incidence of light. The peak reflectance per mirror is more than 60 percent at 83.4 nm with the average reflectance for out-of-band wavelengths of less than 5 percent. The net reflective transmission for the three mirrors is greater than 20 percent with 6.8 nm bandwidth and 0.01 percent maximum transmittance for out-of-band wavelengths. The transmittance at 30.4 nm is 0.03 percent at 58.4 nm 0.05 percent, and at 121.6 nm 0.004 percent. When used with an open microchannel plate detector, contamination by H Ly-alpha is essentially eliminated. With this spectral purity and effective elimination of major contributors to background contamination noise, a signal-to-noise ratio (excluding detector noise) of 10 is achievable for a 0.01 R signal in 8.8 seconds for the full 6 deg field-of-view.

Zukic, Muamer↗
NASA NTRS1991

Uniformity and transmission of proportional counter window materials for use with AXAF

The X-ray detection system used to calibrate the Advanced X-ray Astrophysics Facility (AXAF) mirrors will include gas flow and sealed proportional counters. To meet the ultimate 1 percent goal of the calibration project, the transmission and uniformity of the windows must be well known for the soft X-ray wavelengths involved. Various window materials for use with proportional counters are examined for transmission at X-ray wavelengths in the range of 0.1 to 5.9 keV. These include the usual window materials (polypropylene and beryllium), as well as materials only recently employed for detector applications (polyimide and diamond). The transmission uniformity of beryllium at 1.49 keV is examined with a microchannel plate detector, producing a 'shadowgraph' of the window material illuminated with soft X-rays. This technique allows us to investigate nonuniformities on a spatial scale of about .2 mm.

Flanagan, K.↗
NASA NTRS1993

Preliminary results from the MAMA detectors for the SOHO mission

Multi-Anode Microchannel Array (MAMA) detector systems are being fabricated and tested for use in the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) and the Ultraviolet Coronagraph Spectrometer (UVCS) instruments on the ESA/NASA Solar and Heliospheric Observatory (SOHO) mission. The SOHO MAMA detector systems have formats of 360 x 1024 pixels and pixel dimensions of 25 x 25 sq microns and are optimized for operation at Extreme Ultraviolet (EUV) wavelengths between 40 and 160 nm. In this paper we report on the initial results of measurements of the performance characteristics of the first flight-configuration detector system employing the new custom Application Specific Integrated Circuits (ASICs) which are designed to improve both the dynamic range and the uniformity of response. The performance characteristics of this detector system are compared with those of earlier breadboard systems employing discrete-component electronics circuits.

Slater, David C.↗
NASA NTRS1993

HiRES - High Resolution Extreme Ultraviolet Spectroheliometer toroidal diffraction grating performance evaluation

The ray-tracing results presented characterize the theoretically achievable EUV performance of the HiRES instrument. The effects of optical system misalignment on spectrograph images, and the laboratory results for two f/15 toroidal diffraction gratings that employ a multianode microchannel array, are also presented. Interferometric studies of toroidal figure accuracy, as well as optical and electron microscopy investigations of surface quality, are discussed. While the current toroidal gratings are noted to furnish good imaging across a wide wavelength range, they exhibit excessive EUV scatter, as well as spectral ghosting.

Berger, Thomas E.↗
NASA NTRS1992

Multilayer and grazing incidence X-ray/EUV optics; Proceedings of the Meeting, San Diego, CA, July 22-24, 1991

The present conference discusses the Advanced X-ray Astrophysics Facility (AXAF) calibration by means of synchrotron radiation and its X-ray reflectivity, X-ray scattering measurements from thin-foil X-ray mirrors, lobster-eye X-ray optics using microchannel plates, space-based interferometry at EUV and soft X-ray wavelengths, a water-window imaging X-ray telescope, a graded d-spacing multilayer telescope for high energy X-ray astronomy, photographic films for the multispectral solar telescope array, a soft X-ray ion chamber, and the development of hard X-ray optics. Also discussed are X-ray spectroscopy with multilayered optics, a slit aperture for monitoring X-ray experiments, an objective double-crystal spectrometer, a Ly-alpha coronagraph/polarimeter, tungsten/boron nitride multilayers for XUV optical applications, the evaluation of reflectors for soft X-ray optics, the manufacture of elastically bent crystals and multilayer mirrors, and selective photodevices for the VUV.

Hoover, Richard B.↗
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 NTRS1992

The Solar/Stellar Coronal Explorer and the Solar/Stellar Coronal Observatory

The Solar/Stellar Coronal Explorer (SSCE) carries six identical Ritchey-Chretien Telescopes of 127 mm aperture each; their images will be recorded by multianode microchannel-array detectors. The mirrors of five of the telescopes are coated with multilayer reflecting structures that select narrow XUV wavelength bands corresponding to strong emission lines emitted by solar or stellar coronal plasmas. Also noted here is a larger explorer mission concept, that of the Solar/Stellar Coronal Observatory, which will undertake more extensive spectroscopic observations.

Walker, Arthur B. C., Jr.↗