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An analysis of reflecting diffraction gratings by the application of holographic techniques is presented. The subjects discussed are: (1) holographic grating properties, (2) calculation of aberrant optical path, (3) analytical expression of stigmatic points, (4) spherical aberration and limitation of grating width, and (5) determination of construction parameters.
Device can operate in close-open-close mode. Beam splitter placed behind static-slit assembly allows use of more than one camera. Each frame in particular series may be conveniently varied in exposure time and spacing. This can be done independent of other frames in the series. In ''open'' position, shutter transmits light over wide wavelength range.
Instrument provides information on spatial distribution of electron density of gas flow in high-performance shock tube. System permits measurement of profiles of hydrogen-alpha and -beta lines with enough spectral range to record spectral features from the near ultraviolet to the long-wavelength cutoff of photographic film.
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The design and fabrication of holographic gratings requires an understanding of Fermat's principle. This principle states that the path of a light ray from one point to another is that which requires the least time. The aberrant, optical path of an object point to an image was studied using Fermat principles.
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Certain techniques and procedures are developed and evaluated for the ascertainment of the relative spectral-photometric characteristics of standard and special spectroscopic films and plates in the visible and UV regions. These films are used in ground based and rocket launched instruments. Two photographic spectral sensitometers were developed. One instrument is a vacuum sensitometer covering a range of 1,000 to 3,000 Angstroms and the other sensitometer is the device this investigator used to study its spectral responses in the visible region of the spectrum through the utilization of a computer microdensitometric and photometric plot and contour routines.
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The spectrum of comet West (1975 n) was recorded on March 7 and 11, 1976, in the wavelength interval from 5700 to 8200 A at an intermediate resolution. One hundred twenty-two emission lines are reported, with 78 lines having identifications with spectral features of NH2, H2O(+), C2, O I forbidden emission, and Na I.
Thin, unbacked, aluminum film filters were used on two extreme ultraviolet (XUV) instruments flown on the Apollo Telescope Mount of Skylab by the Naval Research Laboratory to transmit the XUV radiation while blocking the longer wavelength radiation that would saturate the detector. The requirements placed on these filters - large size, resistance to degradation by high acoustic and vibration fields, and low pinhole transmittances - were far more severe than those placed on any filters previously flown. Special techniques were developed for vacuum evaporation of the aluminum, removal of the films from the substrates, supporting the films and mounting them to obtain finished filters, and storing them so that no degradation took place. A description of these techniques will be given.
An experimental gas turbine engine was destroyed as a result of the combustion of its titanium components. Several engine oil samples (before and after the failure) were analyzed with a Ferrograph as well as plasma, atomic absorption, and emission spectrometers. The analyses indicated that a lubrication system failure was not a causative factor in the engine failure. Neither an abnormal wear mechanism, nor a high level of wear debris was detected in the oil sample from the engine just prior to the test in which the failure occurred. However, low concentrations of titanium were evident in this sample and samples taken earlier. After the failure, higher titanium concentrations were detected in oil samples taken from different engine locations. Ferrographic analysis indicated that most of the titanium was contained in spherical metallic debris after the failure.
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The generation and collection of charge carriers created during the passage of energetic protons through a silicon photodiode array are modeled. Pulse height distributions of noise charge collected during exposure of a digicon type diode array to 21 and 75 MeV protons were obtained. The magnitude of charge collected by a diode from each proton event is determined not only by diffusion, but by statistical considerations involving the ionization process itself. Utilizing analytical solutions to the diffusion equation for transport of minority carriers, together with the Vavilov theory of energy loss fluctuations in thin absorbers, simulations of the pulse height spectra which follow the experimental distributions fairly well are presented and an estimate for the minority carrier diffusion length L sub d is provided.
An instrument for advanced studies of the solar corona is described. Its optical system provides nearly stigmatic imaging of selected portions of the sun over the spectral range from 22.5 to 44.0 nm. Both spectroheliograms and emission line profiles of coronal features will be obtained over a wide range of coronal temperatures.
The NASA plans for FUSE, a satellite which obtains spectra with resolutions between 100,000 and 100 in the spectral regions from 912 to 1216A and 100 to 912A, are outlined. Scientific problems which can be tackled by FUSE, but not by IUE or the Space Telescope, are discussed. A grazing incidence echelle and a hybrid echelle design are presented. They have high throughput, large simultaneous spectral range, and low background photon counting statistics. The satellite operational organization is similar to that of IUE.
An instrument concept which offers high throughput nondispersive spectroscopy in the 35-150 keV band for measuring line intensities and widths of faint supernovae is described. The design is based on existing xenon filled, two-dimensional, position sensitive, multiwired proportional counters. Effective detector areas of 1000 sq cm are readily achievable, and expansion to 10,000 sq cm per unit is feasible. Either single-unit or array operation to provide all-sky coverage with one arcmin resolution is possible. The instrument could be used to record gamma ray bursts and would have the capability of distinguishing particle events. Observations could also be made of X ray cyclotron lines and the Ti-44 lines expected to issue from a supernova explosion.
High spatial resolution spectroheliograms of the 1600 A region obtained during the HRTS rocket flight of 1978 February 13 are presented. The morphology, fine structure, and temporal behavior of emission bright points (BPs) in active and quiet regions are illustrated. In quiet regions, network elements persist as morphological units, although individual BPs may vary in intensity while usually lasting the flight duration. In cell centers, the BPs are highly variable on a 1 minute time scale. BPs in plages remain more constant in brightness over the observing sequence. BPs cover less than 4 percent of the quiet surface. The lifetime and degree of packing of BPs vary with the local strength of the magnetic field.
The design of aspheric concave gratings for high-resolution spectroscopes is examined theoretically, using the requirements of the proposed Far-UV Spectroscopic Explorer (effective area 100 sq cm and lambda/delta lambda = 30,000 in the 90-120-nm range) as a concrete example and taking the limitations of current fabrication technology (straight grooves only and maximum density 6000 lines/mm) into account. The total-path function derived by Namioka (1961) for an ellipsoidal grating is subjected to aberration analysis to obtain the optical surface best suited to the design requirements; expressions for corrections to the conventional stigmatic Rowland-circle mount are obtained and shown to produce significant performance improvements; and the design advantages of coma-corrected non-Rowland geometries are explored. Ray tracings and deviation contours are provided.