High energy photons and neutrinos from cosmic sources.
High energy photons, cosmic X-rays and hard radiation production mechanisms in interstellar gas, galactic halo and intergallactic medium
PARTICLE PRODUCTION↗
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Results for “X RADIATION”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Series emittance coatings
Series emittance thermal control coatings of polymeric dielectric films overlaying reflectors vacuum exposed to UV, X ray and proton radiation
Griffin, R.↗
Luminescence of Apollo 11 and 12 lunar samples
Luminescence of Apollo 11 and 12 rocks measured with UV, X ray, and proton radiation
Greenman, N. N.↗
Incipient failure detection.
In connection with the preparation for long-range space missions it is highly important to be able to identify potentially failure prone equipment in advance of the launch commitment. Physical phenomena investigated for this purpose include X-ray and gamma radiation, electrical noise, IR and UV radiation, and vibration energy. The technique selected must be capable of detecting the onset and evaluating the progression of conditions that represent basic causes which could lead to failure. As a result of the investigation, techniques based on acoustic energy release were selected as the most promising for incipient failure detection.
Griswold, J. W.↗
Thermoluminescent dosimetry for the Apollo 16 microbial response to space environment experiment (M191)
Lithium fluoride thermoluminescent chips were used to provide an integrated dose from the broad spectrum of ionizing radiation to the Microbial Response to Space Environment Experiment (M191). The chips were positioned in the flight hardware to provide data on ionizing radiation within specific volume segments. A uniform radiation dose of 4.8 x 0.001 plus or minus 2 x 0.0001 joule/kg resulted.
Brown, R. D.↗
Design principles for contamination abatement in scientific satellites.
It is shown that deposition of contamination films on satellite optics can be controlled by the following means: isolating critical optical surfaces from the rest of the spacecraft; avoiding or minimizing the use of nonmetallic material, particularly near or in line of sight of optical surfaces; avoiding materials with high vapor pressures; subjecting materials to vacuum baking prior to use, to drive off the volatile outgassing products; keeping the critical surfaces at temperatures above the ambient; avoiding elevated operational temperatures for nonmetallic materials; paying special attention to optics exposed to intense UV-, X-ray, or particular radiation; avoiding water-vapor sources; and directing RCS plumes away from critical surfaces. Methods of controlling particulate contaminants are also proposed.
Naumann, R. J.↗
Results of the first 150 days of the NTS-1 solar cell experiments
Twelve solar cell experiments were on the Naval Research Laboratory NTS-1 satellite launched on 14 July 1974, into a 13,260 km circular orbit at an inclination of 125 deg. The experiment comprises: 2 ohm-cm n/p, lithium-diffused p/n, violet n/p, p(+) back surface field, and ultra-thin wrap around contact cells. The short-circuit current of the experiments ranged from 2 to 12 percent higher in space than under solar simulators. During the 5 year life of the satellite, the experiments will be exposed to radiation equivalent to 2 x 10 to the 15th power 1-MeV electron cm/2 and to nearly 5500 thermal cycles.
Statler, R. L.↗
Diffractoid x-ray focusing
Presents aspheric concave diffraction surface that is able to focus sharply single wavelength of x-ray or ultraviolet radiation which may originate from either nearby or far-distant source.
Kastner, S. O.↗
Particle energization in the inner, nonazimuthally symmetric magnetospheres of neutron stars
The energization process of magnetic pumping, a combination of time dependent magnetic mirror fields with pitch-angle scattering, is applied to trapped charged particles drifting in corotating, azimuthally nonsymmetric neutron star magnetospheres. When particle energization is balanced by synchrotron radiation loss, it is found that protons, rather than electrons, reach considerable kinetic energies and radiate, in the X-ray regime, at rates up to the 10 to the 6th power MeV/proton/sec.
Borovsky, J. E.↗
Efficient multiphoton dissociation of CF3I/+/ in the metastable X 2 E 1/2 excited state using CW infrared laser radiation
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Thorne, L. R.↗
Positional characteristics of meter-decameter wavelength bursts associated with hard X-ray bursts
Isolated and grouped type III bursts have been observed in temporal association with impulsive hard X-ray bursts in the 26-154 keV range, down to frequencies as low as 30 MHz and out to a distance of 3.1 solar radii from the disk center. The bursts occurred in regions whose electron density may have been as much as 20 times higher than that of the Newkirk-Saito model. The present observations indicate that electron acceleration/injection occurs over a region covering a wide range of magnetic field lines. It is noted that, of the two gradual hard X-ray bursts observed in association with type IV bursts, one was accompanied by a type II event, while the other was not, although both exhibited the same characteristics. It is suggested that the gradual burst associated with a type IV only involved electrons which are trapped in the plasmoid which produces the meter-decameter emission, while another fraction of the population is trapped in the low-lying loops which produce the hard X-ray and centimeter radiation.
Kundu, M. R.↗
SMM observations of K-alpha radiation from fluorescence of photospheric iron by solar flare X-rays
High-resolution Fe K-alpha spectra near 1.94 A observed during solar flares with the Bent Crystal Spectrometer on the Solar Maximum Mission are presented. The evidence for two possible excitation mechanisms, electron impact and fluorescence, is examined. It is found that the fluorescence mechanism satisfactorily describes the results, while the observations do not support electron collisional excitation of the Fe K-alpha transitions in low ionization stages (II-XII) of iron. Using Bai's model of the fluorescent excitation process, the photospheric iron abundance relative to that of hydrogen is estimated to be 5-6 x 10 to the -5th. The mean height of the soft X-ray source producing the K-alpha fluorescence is calculated on the basis of this model for about 40 large flares. The solar K-alpha lines are found to be about 25 percent wider than those measured in the laboratory. Weak line features observed at wavelengths shorter than that of the K-alpha lines are discussed.
Parmar, A. N.↗
Inspecting Hollow Parts With a CAT Scanner
Technique well known in medicine, used on manufactured objects. As it passes through a part, beam of X-rays or other radiation attenuated and scattered. Computer records variations in beam as part rotated and constructs cross section for display on video monitor. Computeraided tomography (CAT) measures wall thickness and detecting flaws in hollow turbine blades or other curved parts.
Kuhr, G. A.↗
Prompt acceleration of ions by oblique turbulent shocks in solar flares
Solar flares often accelerate ions and electrons to relativistic energies. The details of the acceleration process are not well understood, but until recently the main trend was to divide the acceleration process into two phases. During the first phase elctrons and ions are heated and accelerated up to several hundreds of keV simultaneously with the energy release. These mildly relativistic electrons interact with the ambient plasma and magnetic fields and generate hard X-ray and radio radiation. The second phase, usually delayed from the first by several minutes, is responsible for accelerating ions and electrons to relativistic energies. Relativistic electrons and ions interact with the solar atmosphere or escape from the Sun and generate gamma ray continuum, gamma ray line emission, neutron emission or are detected in space by spacecraft. In several flares the second phase is coincident with the start of a type 2 radio burst that is believed to be the signature of a shock wave. Observations from the Solar Maximum Mission spacecraft have shown, for the first time, that several flares accelerate particles to all energies nearly simultaneously. These results posed a new theoretical problem: How fast are shocks and magnetohydrodynamic turbulence formed and how quickly can they accelerate ions to 50 MeV in the lower corona? This problem is discussed.
Decker, R. B.↗
The flare kernel in the impulsive phase
The impulsive phase of a flare is characterized by impulsive bursts of X-ray and microwave radiation, related to impulsive footpoint heating up to 50 or 60 MK, by upward gas velocities (150 to 400 km/sec) and by a gradual increase of the flare's thermal energy content. These phenomena, as well as non-thermal effects, are all related to the impulsive energy injection into the flare. The available observations are also quantitatively consistent with a model in which energy is injected into the flare by beams of energetic electrons, causing ablation of chromospheric gas, followed by convective rise of gas. Thus, a hole is burned into the chromosphere; at the end of impulsive phase of an average flare the lower part of that hole is situated about 1800 km above the photosphere. H alpha and other optical and UV line emission is radiated by a thin layer (approx. 20 km) at the bottom of the flare kernel. The upward rising and outward streaming gas cools down by conduction in about 45 s. The non-thermal effects in the initial phase are due to curtailing of the energy distribution function by escape of energetic electrons. The single flux tube model of a flare does not fit with these observations; instead we propose the spaghetti-bundle model. Microwave and gamma-ray observations suggest the occurrence of dense flare knots of approx. 800 km diameter, and of high temperature. Future observations should concentrate on locating the microwave/gamma-ray sources, and on determining the kernel's fine structure and the related multi-loop structure of the flaring area.
Dejager, C.↗
Comparison of solar hard X-ray and UV line and continuum bursts with high time resolution
The close temporal correlation between the ultraviolet line emission from OV (lambda 1371A) and hard X-rays above 30 keV has been previously established from a comparison of data sets from the Ultraviolet Spectrometer and Polarimeter (UVSP) and Hard X-Ray Burst Spectrometer (HXRBS) instruments on Solar Maximum Mission (SMM). Corresponding features were found to be coincident to within 1 s. Following the SMM repair, similar measurements were made for a flare occurring on May 20, 1984, at 0259 UT, this time with UVSP observing in the continuum near 1600A with much higher time resolution (75ms). The simultaneity of several features in this flare were established to better than 0.1 s, thus reinforcing the close relationship between hard X-ray and UV emission. Following the repair of the UVSP wavelength drive, similar measurements were repeated for a flare occurring at 0148 UT on April 24, 1985. This event was observed simultaneously in the OV line, the UV continuum and in hard X-rays by the same SMM instruments. Temporal comparisons of the three data sets show that, for a few selected features, simultaneity of the hard X-ray and UV emissions does exist. However, cross-correlation analyses of the entire data sets indicate that there is a trend for the fastest OV emission features to be delayed with respect to the hard X-rays by approx. 260 ms. On the other hand the fast OV and UV continuum features are simultaneous to within the instrumental uncertainty. The combined results have established the close relationship of the impulsive phase hard X-ray and UV continuum and OV line emissions. They lend support to the argument that both the hard X-ray and UV radiations originate low in the solar atmosphere.
Orwig, L. E.↗
X-ray background, discrete sources, and diffuse processes
Possible sources are discussed for the cosmic residual X-ray background (XRB) radiation at energies from 3-50 keV. Sources have been identified that can account for at least 50 percent of the XRB. The residual has a spectrum with a flat slope up to 30 keV. Comptonized thermal gas emission is ruled out as the origin of the radiation since the emitting regions would be diffuse and Comptonization would require regions no more than a parsec across. Optically thin bremsstrahlung from discrete sources is a more viable candidate, although the associated spectra would not have been accessible with the Einstein Observatory. Future observations with the AXAF and ROSAT satellites in imaging and spectroscopic modes are discussed for gaining definitive data on the real sources of the XRB.
Giacconi, Riccardo↗
Standard Method For Radiation Tests Of Liquids
Simple procedure provides standard method for radiation tests of liquids. Assures identical handling and dosage so data from different test laboratories compared reliably. Pair of glass vials, joined by frangible neck and equipped with valves, used. Third vial also used. Filled with control specimen and not irradiated. Developed for measuring properties of liquids for use in radiation-resistant liquid-dielectric capacitors, procedure used for any of variety of liquids proposed for use in high-radiation environment - in x-ray and particle-accelerating machines and nuclear reactors, for example.
Bouquet, Frank L.↗