We are developing a new sounding rocket payload, the Advanced Technology Solar Spectroscopic Imager (ATSSI), that will use an 8 X 8 array of transition edge sensors (TES) to obtain true spectroheliograms in a spectral bandpass spanning approximately 50 eV to approximately 3 keV. The TES array will be flown at the focus of a Wolter I telescope, where it will image as 3 arc-min by 3 arc-min field of view with a pixel resolution of approximately 6 arc-sec. In this way, it will obtain approximately 1000 individual spectra with an expected average energy resolution of approximately 3 eV FWHM. In addition to the TES array, the ATSSI will employ six multilayer telescopes with bandpasses centered on atomic lines at 17.1 angstrom (Fe XVII), 195.1 angstrom (Fe XII), 171.1 angstrom (Fe IX), 57.9 angstrom (Mg X), 98.3 angstrom (Ne VIII), and 150.1 angstrom (O VI). Two additional telescopes with bandpasses centered at 1550 angstrom (C IV) and 1216 angstrom (H I) will also be used. The eight narrowband telescopes will provide high spatial resolution (<EQ 1 arc- sec), full-disk solar images and will be complemented by two grating slit spectroheliographs. One grating will obtain high resolution spectroheliograms between 2750 angstrom and 2850 angstrom (for Mg II h- and k-line studies), and the other will be multilayer-based and will probe the Fe IX/X - O V/VI complex around 171 Angstrom (73 eV). With this set of instruments, we expect to explore more fully the nature of the energy flow between small-scale coronal, chromospheric and transition region structures, as well as to address the issue of what mechanisms are responsible for heating the quiescent solar atmosphere.
Imaging x-ray microscopes currently under development at the Marshall Space Flight Center utilize multilayer x-ray/EUV optical systems and structural components similar to those developed for normal incidence imaging solar x-ray telescopes. The Water Window Imaging X-Ray Microscope is specifically designed to operate at x-ray wavelengths within the `water window' regime, wherein water is relatively transmissive and carbon is highly absorptive. This important natural property of the interaction of x-rays with matter should permit this microscope to sharply delineate carbon based structures within living cells. The ability to image living cells in aqueous physiological environments, with high spatial resolution and high contrast, may afford advantages not available with conventional microscopes and make possible non-invasive strategies for examining living tumor cells without the need of stains or exogeneous chemicals that can produce limiting artifacts. The Water Window Imaging X-Ray Microscope represents a `spinoff' of multilayer x-ray telescope technology. This paper reviews the multilayer x-ray telescope developments which led to this x-ray microscope research. It considers the design, fabrication, optical assembly, alignment, and testing of the prototype microscopes and provides the results of recent studies of ultrahigh resolution photographic films and the design of high reflectivity multilayer coatings for applications in the water window.
An analysis is presented of the stray light expected in a Coronagraph/Polarimeter operating at the H I Lyman (alpha) (Ly-(alpha) ) line ((lambda) 121.6 nm) and utilizing multilayer interference film optics and ultrasmooth substrates (i.e., rms-smoothness
The Wide Field H-Lyman (alpha) Coronagraph/Polarimeter is currently being developed for solar research. This instrument has been designed to produce high resolution full-disk images of the Sun in a narrow bandpass centered at the neutral hydrogen Lyman (alpha) (Ly-(alpha) ) line ((lambda) 1215.7 angstroms). It has higher sensitivity and a wider field-of-view than the coronagraph which produced solar Ly-(alpha) images on May 13, 1991 during the MSSTA flight. The all-reflecting polarizers use advanced induced transmission and absorption thin film multilayer coatings to optimize the reflectivity and polarization properties at 1215.7 angstroms. We describe the instrument and discuss the current status of the fabrication of the Wide Field H-Lyman (alpha) Coronagraph/Polarimeter.
The S-056 Wolter I soft x-ray mirror used originally on Skylab for x-ray observations of the Sun is still in use today. The mirror has been flow polished to a surface finish of 5 angstroms for spatial frequencies from 1 - 1000 mm-1 and has been tested in the AXAF x- ray calibration facility located at Marshall Space Flight Center, Alabama. The mirror performance was enhanced by a new polishing technique and was found to have an experimental point spread function full width half maximum of less than 1 arc second at 8.3 angstroms. No change in the figure was observed.
The surface finishing of X-ray grazing incidence optics is the most demanding area of optical processing. both in terms of metrology and application of optical finishing techniques.This paper discusses the application of specialized metrology and finishing techniques in producing a low x-ray scatter grazing incidence telescope.
The HiRES sounding rocket payload has been described in detail in previous SPIE Proceedings. Here, optical design of the toroidal grating spectrograph is presented and discussed. Ray tracing results are presented which outline the extreme ultraviolet (EUV) performance theoretically attainable with the HiRES instrument. Effects of optical system misalignment on the spectrograph image quality are investigated. Laboratory test results of two f/15 toroidal diffraction gratings using a 1 meter vacuum spectrograph and a multi-anode microchannel array detector are presented and discussed. The test toroidal gratings are fabricated using the elastic substrate replication technique from a ruled master grating with either a 3600 lines/mm or 1800 lines/mm density. EUV images of 10 25 micrometers pinholes with 250 micrometers center-to-center spacing taken with a hollow cathode discharge lamp are presented. Interferometric studies of toroidal figure accuracy as well as optical and electron microscopy investigations into surface quality are presented and discussed. It is found that the current toroidal gratings exhibit good imaging characteristics across a wide wavelength range but suffer from excessive EUV scatter and spectral ghosting.
We have designed, analyzed, and are now fabricating an All-Reflecting H-Lyman-alpha Coronagraph/Polarimeter for solar research. This new instrument operates in a narrow bandpass centered at 215.7 A - the neutral hydrogen Ly-alpha line. It is shorter and faster than the telescope which produced solar Ly-alpha images as a part of the MSSTA payload that was launched on May 13, 1991. The Ly-alpha line is produced and linearly polarized in the solar corona by resonance scattering, and the presence of a magnetic field modifies this polarization according to the Hanle effect. The Lyman-alpha Coronagraph/Polarimeter instrument has been designed to measure coronal magnetic fields by interpreting, via the Hanle effect, the measured linear polarization of the coronal Ly-alpha line. Ultrasmooth mirrors, polarizers, and filters are being flow-polished for this instrument from CVD silicon carbide substrates. These optical components will be coated using advanced induced transmission and absorption thin film multilayer coatings to optimize the reflectivity and polarization properties at 1215.7 A. We describe some of the solar imaging results obtained with the MSSTA Lyman-alpha coronagraph. We also discuss the optical design parameters and fabrication plans for the All-Reflecting H-Lyman-alpha Coronagraph/Polarimeter.
The measurement of the shape and optical performance of toroidal mirrors has always presented a challenge to the manufacturer and user of these types of optical elements. This report presents a technique for evaluating the complex shape and optical performance of long radius toroidal mirrors that are to be used in the EUV. The measurement techniques will be discussed and examples given. Interferometric analysis will be presented. Performance spot diagrams and MTF analysis will be discussed. Manufacturing techniques will be evaluated with respect to the application of more definitive measurement technology.
We discuss and analyze the possible sources of observational and instrumental uncertainty that can be encountered in measuring magnetic fields of the solar corona through polarimetric observations of the Hanle effect of the coronal Ly-alpha line. The Hanle effect is the modification of the linear polarization of a resonantly scattered line, due to the presence of a magnetic field. Simulated observations are used to examine how polarimetric measurements of this effect are affected by the line-of-sight integration, the electron collisions, and the Ly-alpha geocorona. We plan to implement the coronal magnetic field diagnostics via the Ly-alpha Hanle effect using an all-reflecting Ly-alpha coronagraph/polarimeter (Ly-alphaCoPo) which employs reflecting multilayer mirrors, polarizers, and filters. We discuss here the requirements for such an instrument, and analyze the sources of instrumental uncertainty for polarimetric observations of the coronal Ly-alpha Hanle effect. We conclude that the anticipated polarization signal from the corona and the expected performance of the Ly-alphaCoPo instrument are such that the Ly-alpha Hanle effect method for coronal field diagnostics is feasible.
We have designed, analyzed, fabricated, and tested Schwarzschild multilayer X-ray microscopes. These instruments use flow-polished Zerodur mirror substrates which have been coated with multilayers optimized for maximum reflectivity at normal incidence at 135 A. They are being developed as prototypes for the Water Window Imaging X-Ray Microscope. Ultrasmooth mirror sets of hemlite grade sapphire have been fabricated and they are now being coated with multilayers to reflect soft X-rays at 38 A, within the biologically important 'water window'. In this paper, we discuss the fabrication of the microscope optics and structural components as well as the mounting of the optics and assembly of the microscopes. We also describe the optical alignment, interferometric and visible light testing of the microscopes, present interferometrically measured performance data, and provide the first results of optical imaging tests.
High quality multilayers with 2d spacings as short as about 44 A have been used successfully for astronomical observations. Observation of both the sun and cosmic X-ray sources (for which radiation longward of the carbon edge at about 44 A is strongly attenuated by interstellar matter) are possible at wavelengths shorter than 40 A with current multilayer technology, if mirrors are used at nonnormal angles of incidence. We discuss several configurations which are suitable for high resolution solar imaging observations in the wavelength interval between 0.5 and 50 A. We also describe the design and anticipated performance of a multilayer optical system we are currently developing for a rocketborne solar observatory.
This paper will discuss the optical testing of extreme grazing incidence mirror systems and normal incidence high-precision mirror systems during fabrication processing of the optical substrates. The optical metrology is closely coupled with an advanced material removal process which will be discussed in terms of the optical metrology. Interferometric data will be presented of the optical surfaces. Surface roughness data will be shown and discussed.
We have developed seven compact soft X-ray/EUV (XUV) multilayer coated and two compact FUV interference film coated Cassegrain and Ritchey-Chretien telescopes for a rocket borne observatory, the Multi-Spectral Solar Telescope Array. We report here on extensive measurements of the efficiency and spectral bandpass of the XUV telescopes carried out at the Stanford Synchrotron Radiation Laboratory.
The Water Window Imaging X-Ray Microscope is a doubly reflecting, multilayer optical system configured to operate within the biologically important narrow spectral range known as the `water window.'' Within this x-ray waveband, which lies between the K absorption edges of oxygen (23.3 angstroms) and carbon (43.62 angstroms), water is relatively highly transmissive and carbon is highly absorptive. Consequently, this high resolution microscope can obtain high contrast images of carbon-based structures within living cells in aqueous physiological environments. This new multilayer x-ray microscope should afford ultrasensitive detection and analysis advantages not available with conventional microscopes. The Stanford/MSFC/LLNL Rocket X-Ray Spectroheliograph flight of 1987 achieved the first solar images with a doubly reflecting multilayer telescope and conclusively established the power of multilayer optics. During the MSFC X-Ray Microscope program, we theoretically established that high resolution multilayer x-ray imaging microscopes could be achieved with spherical optics in the Schwarzschild configuration and with aspherical optics. Advanced flow polishing techniques were used to fabricate ultrasmooth concave and convex spherical mirror substrates of zerodur and hemlite-grade sapphire. Atomic force microscopy and Zygo profilometer tests revealed these mirror substrates to have surface smoothness ranging from 0.5 angstrom rms (sapphire) to 2.0 angstroms rms (zerodur). In this paper, we discuss the fabrication and testing of the optical and mechanical components of the x-ray microscope.
The development of multilayer reflective coatings now permits soft X-ray, EUV and FUV radiation to be efficiently imaged by conventional normal incidence optical configurations. Telescopes with quite modest apertures can, in principle, achieve images with resolutions which would require apertures of 1.25 meters or more at visible wavelengths. The progress is reviewed which has been made in developing compact telescopes for ultra-high resolution imaging of the sun at soft X-ray, EUV and FUV wavelengths, including laboratory test results and astronomical images obtained with rocket-borne multilayer telescopes. The factors are discussed which limit the resolution which has been achieved so far, and the problems which must be addressed to attain, and surpass the 0.1 arc-second level. The application of these technologies to the development of solar telescopes for future space missions is also described.
We describe the development of the water window imaging x-ray microscope based on normal-incidence multilayer x-ray mirrors. The narrow bandpass response inherent in multilayer x-ray optics is accurately tuned to wavelengths within the "water window." Similar doubly-reflecting multilayer optical systems have been fabricated for our astronomical rocket-borne x-ray/EUV telescopes. Previous theoretical studies performed during the MSFC X-Ray Microscope Development Program established that high-resolution multilayer x-ray imaging microscopes are possible by using either spherical (Schwarzschild configuration) optics or aspherical configu rations. These microscopes require ultrasmooth mirror substrates, which have been fabricated using advanced flow polishing methods. Hemlite-grade sapphire microscope optic substrates have been accurately figured and polished to a smoothness of 0.5-Å rms, as measured by the Zygo profilometer. We describe the current status of fabrication and testing of the optical and mechanical subsystems for the water window imaging x-ray microscope. This new instrument should yield images of carbon-based microstructures within living cells of unprecedented spatial resolution and contrast, without need for fixatives, dyes, and chemical additives.
Previous attempts to analyze the corneal surface have been limited to geometric
interpretation of ring displacement (Placido disc technology). Use of holographic interferometry
allows real time optical measurement of the corneal surface. Clinical examples of holographic
interferometry will be presented.
We have developed seven compact soft x-ray/EUV (XUV) multilayer- coated and two compact FUV interference-film-coated Cassegrain and Ritchey-Chrétien telescopes for a rocket-borne observatory, the Multi-Spectral Solar Telescope Array. We report here on extensive measurements of the efficiency and spectral band pass of the XUV telescopes carried out at the Stanford Synchrotron Radiation Laboratory.
Silicon nitride (Si3N4) has been demonstrated to be an effective high- temperature anti-oxidant, especially when deposited in its (alpha) -crystalline form. UTRC has developed a pilot scale chemical vapor deposition (CVD) reactor capable of depositing (alpha) -Si3N4 from ammonia (NH3) and silicon tetrafluoride (SiF4) at 1450 C. Coherent anti-Stokes Raman spectroscopy (CARS) has been applied to this reactor which has been fitted with line-of- sight optical access ports. Temperature and concentration measurements have been performed on gas phase species during the deposition of Si3N4. Based on the CARS detection of H2, the importance of high temperature surface (Si3N4) catalyzed decomposition of NH3: 2NH3(Delta )yields3H2 + N2, is established as a competing reaction to: 4NH3 + 3SiF4(Delta) )yieldsSi3N4 + 12HF, in the CVD reactor under deposition conditions. Mass spectroscopic measurements, performed on the reactor exhaust, confirm that the primary gas phase species are N2, H2 and HF. H2 is observed spectroscopically both in the presence and absence of SiF4, and in a variety of precursor composition ratios.
The authors have theoretically designed and analyzed the optical components and mechanical structures for an imaging x-ray microscope which will be configured to operate in the water window. This instrument affords new and noninvasive strategies for examining living tumor cells without the use of dyes, stains or other exogenous chemicals, which can produce limiting artifacts. The Water Window Imaging X-Ray Microscope is based on doubly reflecting, normal incidence multilayer optical technology, such as has been previously employed in telescopes for high resolution x-ray imaging of the sun. Multilayer coatings have now been fabricated with near theoretical reflectivities and perfect bandpass matching for the new rocket-borne solar observatory, the Multi-Spectral Solar Telescope Array (MSSTA). These telescopes employ multilayer mirror substrates with sub-angstrom (rms) smoothness which are made possible by Advanced Flow Polishing. Recent developments in multilayer coating technology and Advanced Flow Polishing methods used with Zerodur and Hemlite grade sapphire have paved the way for the development of the Water Window Imaging X-Ray Microscope. In this narrow water window wavelength regime of the x-ray spectrum, which lies between the K absorption edges of oxygen (23.3 $ANS) and of carbon (43.62 $ANS), water is relatively highly transmissive and carbon is highly absorptive. This principle allows the Water Window Imaging X-Ray Microscope to delineate, with high resolution and high contrast, carbon-based structures in the aqueous physiological environments found within living cells. The theoretical design and analysis of the microscope optical and mechanical components are described and the fabrication effort underway for the development of this new optical instrument, which should improve diagnosis and greatly benefit experimental studies of tumor cell biology, is discussed.
Previous attempts to analyze the corneal surface have been limited to geometric interpretation of ring displacement (Placido disc technology). Use of holographic interferometry allows real time optical measurement of the corneal surface. Clinical examples of holographic interferometry are presented.
The Multi-Spectral Solar Telescope Array (MSSTA) is a sounding rocket borne observatory for investigations
of the Sun in the soft x-ray/EUV and FUV regimes of the electromagnetic spectrum. At soft x-ray
wavelengths (),\ < 100 A), the MSSTA utilizes single reflection multilayer coated Herschelian telescopes.
For selected wavelengths in the EUV (100 - 1000 A) the MSSTA employs five doubly reflecting, multilayer
coated Ritchey-Chretien and two Cassegrain telescopes. In the FUV ()\ > 1000 A) the MSSTA utilizes
two Ritchey-Chretien telescopes, with optics coated with thin film interference coatings. In this paper,
we describe the interferometric alignment, testing, focusing, visible light testing, and optical performance
characteristics of the Ritchey-Chretien and Cassegrain telescopes.
We have developed compact soft x-ray/EUV (XUV) and farultraviolet (FUV) multilayer coated telescopes for the study of the solar chromosphere corona, and corona/solar wind interface. Because they operate
at short wavelengths (-40 < X < 1550 A), the modest apertures of 40 to 127 mm allow observations at very high angular resolution (0.1 to 0.7 arcsec). In addition to permitting traditional normal incidence optical configurations such as Cassegrain, Ritchey-Chrétien, and Herschelian to be used at XUV wavelengths, multilayer coatings also allow a narrow
wavelength band (X/zX - 30 to 100) to be selected for imaging. The resuIting telescopes provide a very powerful and flexible diagnostic instrument for the study of both the fine scale structure of the chromosphere/ corona interface and the large scale structure of the corona and corona/solar wind interface. In previous papers we described a new solar
rocket payload, the Multi-Spectral Solar Telescope Array (MSSTA), composed of 17 of these compact telescopes. In this paper we report on the
performance of the seven MSSTA Ritchey-Chrétien telescopes.
We have developed compact soft x-rayfEUV (XUV), and far-ultraviolet (FtJV) multilayer coated telescopes
for the study of the solar chromosphere, corona, and corona/solar wind interface. Because they operate at short
wavelengths (4O A < ). < 1550 A), the modest apertures of 40 mm - 127 mm allow observations at very high
angular resolution (0.1 - 0.7arc second). In addition to permitting traditional normal incidence optical configurations
such as Cassegrain, Ritchey-Chrétien and Herschelian to be used at soft x-ray/EUV wavelengths, multilayer coatings
also allow a narrow wavelength band (A/AX -45 - 100) to be selected for imaging. The resulting telescopes provide a
very powerful and flexible diagnostic instrument for the study of both the fine scale structure of the
chromosphere/corona interface, and the large scale structure of the corona and corona/solar wind interface. In previous
papers we have described a new solar rocket payload, the Multi-Spectral Solar Telescope Array (MSSTA) composed
of 17 of these compact telescopes. In the present paper, we report on the performance of the 7 MSSTA Ritchey-
Chrétien telescopes.
Subject terms: Multilayers, XUV, far ultraviolet, solar corona
An interferometric, holographic instrument has been developed by the authors which can precisely characterize the entire
corneal surface with submicron accuracy. An air-cooled argon ion laser was run at all wavelengths to construct the hologram
and an interference filter picked out a single wavelength for reconstruction and viewing. The holograms were recorded by a
holographic camera on a thermoplastic recording medium. The laser and optics were layed out in a modified Twyman-Green
interferometer setup. A CCD camera imaged the resulting hologram on a video screen and fringe analysis software
subsequently digitized and analyzed the data. Head and eye movement were minimized by the use of a rigid head and chin
rest, a fixation light, and a short exposure time. This technique was completely noninvasive in that no physical alien
surface made contact with the corneal surface. The amount of optical radiation which entered the eye was orders of
magnitude lower than the exposure limit standards set by ANSI Z-136.1 guidelines.
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