Engineering topics

Walker, Arthur B. C., Jr.

Publications and source records attributed to Walker, Arthur B. C., Jr..

49 records · Page 3

NASA NTRS1990

The Ultra High Resolution XUV Spectroheliograph

The Ultra High Resolution XUV Spectroheliograph (UHRXS), a solar observatory planned for the Space Station Freedom, is described. The UHRXR instruments include nine XUV Ritchey-Chretien telescopes covering a spectral range of 70-350 A, which will provide images of solar atmosphere structures ranging in temperature from 50,000 to 20,000,000 K. The images will be obtained with spatial resolution that is an order of magnitude better than any other currently planned solar satellite experiment.

Walker, Arthur B. C., Jr.↗

NASA NTRS1990

Design and analysis of a Schwarzschild imaging multilayer X-ray microscope

Several Schwarzschild X-ray microscope optics were designed. Diffraction analysis indicates that better than 600 A spatial resolution in the object plane up to a 0.7 mm field of view can be achieved with 100 A radiation. Currently, a 20 x normal incidence multilayer X-ray microscope of 1.35 m overall length is being fabricated. Other microscope systems for use in conjunction with X-ray telescopes were also analyzed and designed. This paper reports on the results of these studies and the X-ray microscope fabrication effort.

Shealy, David L.↗

NASA NTRS1990

Astronomical observations with normal incidence multilayer optics - Recent results and future prospects

High-resolution X-ray and EUV images of the solar corona have been obtained with two rocket-borne normal incidence Cassegrain multilayer telescopes. The Cassegrain images correspond to material at about 10 to the 6th K and about 80,000 K. Other images, at somewhat lower resolution, were obtained with Herschelian multilayer telescopes and Wolter-Schwarzschild hybrid grazing incidence/multilayer optical systems. The Cassegrain and Herschelian images are discussed emphasizing the analysis of polar plumes observed at the limb of the sun. The application of specific multilayer techniques to astronomical observations is discussed, emphasizing observations of the sun. Current efforts to develop a comprehensive Multi-Spectral Solar Telescope Array rocket instrument for the study of a wide variety of problems related to the solar atmosphere are reported.

Walker, Arthur B. C., Jr.↗

NASA NTRS1990

Multi-Spectral Solar Telescope Array

This paper descibes the design and the characteristics of the Multispectral Solar Telescope Array (MSSTA), a new rocket spectroheliograph to be launched in August 1990. The MSSTA includes five multilayer Ritchey-Chretien telescopes covering the spectral range 150-300 A and eight multilayer Herschelian telescopes covering the spectral range 40-1550 A, making it possible to obtain spectrohelipgrams over the soft X-ray/extreme UV/FUV spectral range. The MSSTA is expected to obtain information regarding the structure and dynamics of the solar atmosphere in the temperature range 10 to the 4th-10 to the 7th K.

Walker, Arthur B. C., Jr.↗

NASA NTRS1990

Astronomical EUV/X-ray observatories on the moon

A proposed Lunar EUV/X-ray/Far-Ultraviolet Observatory (LEXO) is described, which consists of a monolithic array of multilayer, grazing incidence, and far-UV telescopes, coronagraphs, and spectroscopic instruments for ultrahigh spectral and spatial resolution investigations of the sun from the lunar base. The LEXO can provide a very powerful observational tool for the study of numerous critical issues in galactic and extragalactic astronomy. The advantages of performing both solar and nonsolar observations with a single LEXO are discussed.

Walker, Arthur B. C., Jr.↗

NASA NTRS1989

Design of a normal incidence multilayer imaging X-ray microscope

Normal incidence multilayer Cassegrain X-ray telescopes were flown on the Stanford/MSFC Rocket X-ray Spectroheliograph. These instruments produced high spatial resolution images of the sun and conclusively demonstrated that doubly reflecting multilayer X-ray optical systems are feasible. The images indicated that aplanatic imaging soft X-ray/EUV microscopes should be achievable using multilayer optics technology. A doubly reflecting normal incidence multilayer imaging X-ray microscope based on the Schwarzschild configuration has been designed. The design of the microscope and the results of the optical system ray trace analysis are discussed. High resolution aplanatic imaging X-ray microscopes using normal incidence multilayer X-ray mirrors should have many important applications in advanced X-ray astronomical instrumentation, X-ray lithography, biological, biomedical, metallurgical, and laser fusion research.

Shealy, David L.↗

NASA NTRS1989

Development of a normal incidence multilayer, imaging X-ray microscope

This paper describes the design, analysis, and fabrication of a normal-incidence multilayer 20x Schwarzschild imaging X-ray microscope. The microscope is being fabricated using much of the technology implemented in the Multispectral Solar Telescope Array. Results of diffraction analysis show that better than 400 A spatial resolution in the object plane up to a 1-mm field of view can be achieved with 125 A radiation. Other microscope systems for use in conjunction with X-ray telescopes are analyzed and designed.

Shealy, David L.↗

NASA NTRS1989

Design and analysis of optical systems for the Stanford/MSFC Multi-Spectral Solar Telescope Array

This paper reports on the design and the theoretical ray trace analysis of the optical systems which will comprise the primary imaging components for the Stanford/MSFC Multi-Spectral Solar Telescope Array (MSSTA). This instrument is being developed for ultra-high resolution investigations of the sun from a sounding rocket. Doubly reflecting systems of sphere-sphere, ellipsoid-sphere (Dall-Kirkham), paraboloid-hyperboloid (Cassegrain), and hyperboloid-hyperboloid (Ritchey-Chretien) configurations were analyzed. For these mirror systems, ray trace analysis was performed and through-focus spot diagrams, point spread function plots, and geometrical and diffraction MTFs were generated. The results of these studies are presented along with the parameters of the Ritchey-Chretien optical system selected for the MSSTA flight. The payload, which incorporates seven of these Ritchey-Chretien systems, is now being prepared for launch in late September 1989.

Hadaway, James B.↗

NASA NTRS1988

Soft X-ray images of the solar corona with a normal-incidence Cassegrain multilayer telescope

High-resolution images of the sun in the soft X-ray to EUV regime have been obtained with normal-incidence Cassegrain multilayer telescopes operated from a sounding rocket in space. The inherent energy-selective property of multilayer-coated optics allowed distinct groups of emission lines to be isolated in the solar corona and the transition region. The Cassegrain telescopes provided images in bands centered at 173 and 256 A. The bandpass centered at 173 A is dominated by emission from the ions Fe IX and Fe X. This emission is from coronal plasma in the temperature range (8-14) x 10 to the 6th K. The images have angular resolution of about 1.0-1.5 arcsec and show no degradation because of X-ray scattering. Many features of coronal structure, including magnetically confined loops of hot plasma, coronal plumes, polar coronal holes, faint structures on the size scale of supergranulation and smaller, and features due to everlying cool prominences are visible in the images. The density structure of polar plumes, which are thought to contribute to the solar wind, has been derived from the observations out to 1.7 solar radii.

Walker, Arthur B. C., Jr.↗

NASA NTRS1988

Multispectral observations complementary to the study of high-energy solar phenomena

Multispectral observations of phenomena associated with nonthermal events on the sun and characterized by the transient acceleration of electrons and ions to energies ranging from several keV to tens of GeV are discussed. It is shown that observations of the thermal and quasi-thermal phenomena preceeding, coinciding with, and following the impulsive acceleration and heating event itself can be used to study the evolution of magnetic structures in the solar convection zone and atmosphere. Observational techniques are discussed in detail.

Walker, Arthur B. C., Jr.↗

NASA NTRS1988

High-energy facility development plan

Approaches to the deployment of instruments for the study of high-energy solar emissions alone or in conjunction with other solar instruments are considered. The Space Station has been identified as the preferred mode for the deployment of the Advanced Solar Observatory, and it is suggested that a proposed High-Energy Facility could be on a coorbiting platform. The implementation plan for the High-Energy Facility involves the definition of the interface structures required to mount the facility instruments to the Space Station and the development of hard X-ray and gamma-ray imaging, spectroscopic, and polarimetric instruments.

Walker, Arthur B. C., Jr.↗

NASA NTRS1988

Soft X-ray/extreme ultraviolet images of the solar atmosphere with normal incidence multilayer optics

High-resolution images of the sun in the soft-X-ray/XUV range have been obtained with normal-incidence multilayer coated optics (MCOs) during a sounding-rocket flight on October 23, 1987 from White Sands. MCOs were used in two Cassegrain telescopes, as off-axis primary mirrors, and as tertiary mirrors operating with a Wolter-Schwarzschild (WS) grazing-incidence mirror. The inherent energy-selective property of MCOs allowed distinct groups of emission lines to be isolated in the solar corona and the transition region. Images were recorded at 173 and 256 A with the Cassegrain telescopes, at 256 A with a Herschelian telescope, and at 44, 173, and 256 A with the WS hybrid telescope. In addition, soft-X-ray images in the 8-18-A bandpass were obtained at the prime focus of the WS optics. The images show many features of the solar corona and transition region, including magnetically confined loops of hot solar plasma, coronal plumes, polar coronal holes, supergranulation, and features associated with overlying cool prominences.

Lindblom, Joakim F.↗

NASA NTRS1988

Design of an imaging microscope for soft X-ray applications

An imaging soft X-ray microscope with a spatial resolution of 0.1 micron and normal incidence multilayer optics is discussed. The microscope has a Schwarzschild configuration, which consists of two concentric spherical mirrors with radii of curvature which minimize third-order spherical aberration, coma, and astigmatism. The performance of the Stanford/MSFC Cassegrain X-ray telescope and its relevance to the present microscope are addressed. A ray tracing analysis of the optical system indicates that diffraction-limited performance can be expected for an object height of 0.2 mm.

Hoover, Richard B.↗