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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

Method and Apparatus for Accurately Calibrating a Spectrometer

A calibration assembly for a spectrometer is provided. The assembly includes a spectrometer having n detector elements, where each detector element is assigned a predetermined wavelength value. A first source emitting first radiation is used to calibrate the spectrometer. A device is placed in the path of the first radiation to split the first radiation into a first beam and a second beam. The assembly is configured so that one of the first and second beams travels a path-difference distance longer than the other of the first and second beams. An output signal is generated by the spectrometer when the first and second beams enter the spectrometer. The assembly includes a controller operable for processing the output signal and adapted to calculate correction factors for the respective predetermined wavelength values assigned to each detector element.

Youngquist, Robert C.↗
NASA NTRS1975

The generation of transition radiation by relativistic particles in plastic foam radiators

The design of large area transition radiation detectors for highly relativistic particles can be greatly simplified if plastic foam radiators are employed. Using electron beams with energies 1-9 GeV at the Cornell synchrotron, we have studied the properties of a large variety of transition radiators consisting of commercially available foam materials. In most cases, a measurable transition radiation signal has been observed, but only a few materials have been found to be suitable for practical purposes. The observed radiation yield is in these cases very similar to that of equivalent multifoil radiators. A detailed discussion is given of the particle detection efficiency that can be obtained with high yield foam radiators.

Prince, T. A.↗
NASA NTRS1977

Charge-equilibrium and radiation of low-energy cosmic rays passing through interstellar medium

The charge equilibrium and radiation of an oxygen and an iron beam in the MeV per nucleon energy range, representing a typical beam of low-energy cosmic rays passing through the interstellar medium, is considered. Electron loss of the beam has been taken into account by means of the First Born approximation allowing for the target atom to remain unexcited, or to be excited to all possible states. Electron capture cross sections have been calculated by means of the scaled Oppenheimer-Brinkman-Kramers approximation, taking into account all atomic shells of the target atoms. Radiation of the beam due to electron capture into the excited states of the ion, collisional excitation and collisional inner-shell ionization of the ions has been considered. Effective X-ray production cross sections and multiplicities for the most energetic X-ray lines emitted by the Fe and O beams have been calculated.

Rule, D. W.↗
NASA NTRS2006

Update On the Status of the FLUKA Monte Carlo Transport Code*

The FLUKA Monte Carlo transport code is a well-known simulation tool in High Energy Physics. FLUKA is a dynamic tool in the sense that it is being continually updated and improved by the authors. We review the progress achieved since the last CHEP Conference on the physics models, some technical improvements to the code and some recent applications. From the point of view of the physics, improvements have been made with the extension of PEANUT to higher energies for p, n, pi, pbar/nbar and for nbars down to the lowest energies, the addition of the online capability to evolve radioactive products and get subsequent dose rates, upgrading of the treatment of EM interactions with the elimination of the need to separately prepare preprocessed files. A new coherent photon scattering model, an updated treatment of the photo-electric effect, an improved pair production model, new photon cross sections from the LLNL Cullen database have been implemented. In the field of nucleus-- nucleus interactions the electromagnetic dissociation of heavy ions has been added along with the extension of the interaction models for some nuclide pairs to energies below 100 MeV/A using the BME approach, as well as the development of an improved QMD model for intermediate energies. Both DPMJET 2.53 and 3 remain available along with rQMD 2.4 for heavy ion interactions above 100 MeV/A. Technical improvements include the ability to use parentheses in setting up the combinatorial geometry, the introduction of pre-processor directives in the input stream. a new random number generator with full 64 bit randomness, new routines for mathematical special functions (adapted from SLATEC). Finally, work is progressing on the deployment of a user-friendly GUI input interface as well as a CAD-like geometry creation and visualization tool. On the application front, FLUKA has been used to extensively evaluate the potential space radiation effects on astronauts for future deep space missions, the activation dose for beam target areas, dose calculations for radiation therapy as well as being adapted for use in the simulation of events in the ALICE detector at the LHC.

Ferrari, A.↗
NASA NTRS1975

Production of hard X rays in a plasma focus

A model of a plasma focus is examined wherein large axial electric fields are produced by an imploding current sheet during the final nanoseconds of the collapse phase and where the fields provide a mechanism for creating a beam of electrons of highly suprathermal energies. The expected bremsstrahlung radiation above 100 keV is calculated for such a beam, which has a power-law spectrum, both from electron-deuteron collisions in the focused plasma and when the beam reaches the wall of the device. It is concluded that, since the experimental results indicate little or no radiation above 100 keV originating in the walls, that the electrons in the beam must be decelerated after leaving the plasma and before reaching the wall. Comparisons with the results and the total energy of the device yield qualitative agreement with the expected angular distribution of hard X-rays and reasonable agreement with the total energy in accelerated electrons required to produce the observed total energy in hard X-rays by this mechanism.

Newman, C. E.↗
NASA NTRS1995

Kilometric type 3 radio bursts observed from high southern ecliptic latitudes by Ulysses

The Ulysses URAP experiment has provided the first measurements of remote and in-situ wave phenomena from high southern latitudes. Remote sensing of type 3 solar radio bursts constitute an important component of the Ulysses observations. Type 3 radio emissions, which have never before been viewed from outside the ecplitic plane, have been observed by Ulysses to its maximum southern latitude (approximately 80 deg S), although their frequency of occurrence has generally diminished due to the declining phase of the solar cycle. In addition, the Ulysses radio receiver measures both the direction of arrival and the complete polarization state of incident radiation. These physical parameters provide information on the origin and nature of the radio emission. Preliminary analyses have indicated that kilometric type 3 radiation is often approximately 10-20% circularly polarized at the highest URAP frequencies. New directional information provides crucial information on the effects of beaming and scattering of the radiation in the interplanetary medium.

Reiner, M. J.↗
NASA NTRS1973

Type 2 and type 3 burst theory

The present state of the theory of type 3 bursts is reviewed by dividing the problem into the exciting agency, radiation source, and propagation of radiation between the source and the observer. In-situ measurements indicate that the excitors are electron streams of energy about 40 keV which are continuously relaxing. An investigation of neutralization of an electron stream indicates that n sub s is much less than 100,000 n sub e, where n sub s is the stream density and n sub e the coronal electron density. In situ observations are consistent with this result. An analysis of propagation of electrons in the current sheets of coronal streamers shows that such propagation at heights greater than 1 solar radius is impossible. The mechanisms for radiation are reviewed; it is shown that fundamental radiation at high frequencies (approximately 100 MHz) is highly beamed in the radial direction and that near the earth second harmonic radiation must be dominant. Because of beaming of the fundamental at high frequencies, it can often be quite weak near the limb so that the second harmonic is dominant. In considering propagation to the observer, the results of scattering of radiation are discussed. The present state of the theory of type 2 bursts is reviewed in the same manner as type 3 bursts.

Smith, D. F.↗
NASA NTRS1982

30/20 GHz communications satellite multibeam antenna

A 20 GHz downlink satellite antenna design is described. The aperture simultaneously radiates 18 fixed, 0.3 deg width pencil beams directed at 18 cities distributed over CONUS for Trunking Service. All beams use the same trunk frequency allocation for 18 reuses of the band. The same aperture also radiates six additional 0.3 deg spot beams for Customer Premises Service (CPS) for TDMA beam hopping operation to small terminals anywhere in CONUS. Each CPS beam scans one sector of CONUS and all six beams are frequency reused in a CPS band. Offset dual reflector optics are used with a feed array and multiport beam forming network (BFN). For so many frequency reuses, sidelobes per beam must be 30 to 40 dB down over CONUS. Novel dual reflector optics were devised with shaped surfaces providing low aberrations for all beam positions over CONUS (+ or - 12 BW by + or - 5 BW). Scan loss under 1 dB is calculated with nearly constant sidelobes. For each beam position, a 7-element cluster of feeds is activated in the feed array with coefficients adjusted by the BFN to maintain low sidelobes and thus high beam isolation for frequency reuse.

Scott, W. G.↗
NASA NTRS1981

Processing of silicon solar cells by ion implantation and laser annealing

Methods to improve the radiation tolerance of silicon cells for spacecraft use are described. The major emphasis of the program was to reduce the process-induced carbon and oxygen impurities in the junction and base regions of the solar cell, and to measure the effect of reduced impurity levels on the radiation tolerance of cells. Substrates of 0.1, 1.0 and 10.0 ohm-cm float-zone material were used as starting material in the process sequence. High-dose, low-energy ion implantation was used to form the junction in n+p structures. Implant annealing was performed by conventional furnace techniques and by pulsed laser and pulsed electron beam annealing. Cells were tested for radiation tolerance at Spire and NASA-LeRC. After irradiation by 1 MeV electrons to a fluence of 10 to the 16th power per sq cm, the cells tested at Spire showed no significant process induced variations in radiation tolerance. However, for cells tested at Lewis to a fluence of 10 to the 15th power per sq cm, ion-implanted cells annealed in vacuum by pulsed electron beam consistently showed the best radiation tolerance for all cell resistivities.

Minnucci, J. A.↗
NASA NTRS2007

Sun Glint and Sea Surface Salinity Remote Sensing

The Aquarius/SAC-D mission will employ three L-band (1.41 GHz) radiometers dedicated to remote sensing of Sea Surface Salinity. The mission will be in a dawn/dusk sun-synchronous orbit with the beam oriented toward the night time side of the orbit in order to limit interference from the Sun. The effect of surface roughness on solar radiation reflected from the surface will be examined. It will be shown that including the small scale roughness (waves) can have a major impact. Also, it will be shown that when the small scale waves are included it is possible to have significant radiation reflected into the main beam during seasonal extremes when a portion of the main beam is on the illuminated side of day-night terminator.

Dinnat, Emmanuel P.↗
NASA NTRS2018

Acoustic Radiation Pressure

The theoretical foundation of acoustic radiation pressure in plane wave beams is reexamined. It is shown from finite deformation theory and the Boltzmann-Ehrenfest Adiabatic Principle that the Brillouin stress tensor (BST) is the radiation stress in Lagrangian coordinates (not Eulerian coordinates) and that the terms in the BST are not the momentum flux density and mean excess Eulerian stress but are simply contributions to the variation in the wave oscillation period resulting from changes in path length and true wave velocity, respectively, from virtual variations in the strain. It is shown that the radiation stress in Eulerian coordinates is the mean Cauchy stress (not the momentum flux density, as commonly assumed) and that Langevin's second relation does not yield an assessment of the mean Eulerian pressure, since the enthalpy used in the traditional derivations is a function of the thermodynamic tensions - not the Eulerian pressure. It is shown that the transformation between Lagrangian and Eulerian quantities cannot be obtained from the commonly-used expansion of one of the quantities in terms of the particle displacement, since the expansion provides only the difference between the value of the quantity at two different points in Cartesian space separated by the displacement. The proper transformation is obtained only by employing the transformation coefficients of finite deformation theory, which are defined in terms of the displacement gradients. Finite deformation theory leads to the result that for laterally unconfined, plane waves the Lagrangian and Eulerian radiation pressures are equal with the value (1/4)(2K) along the direction of wave propagation, where (K) is the mean kinetic energy density, and zero in directions normal to the propagation direction. This is contrary to the Langevin result that the Lagrangian radiation pressure in the propagation direction is equal to (2K) and the BST result that the Eulerian radiation pressure in that direction is the momentum flux density.

Finite deformation theory↗
NASA NTRS1979

Charge equilibrium and radiation of low-energy cosmic rays passing through interstellar medium

The charge equilibrium and radiation of an oxygen and an iron beam in the MeV per nucleon energy range, representing a typical beam of low-energy cosmic rays passing through the interstellar medium, are considered. Electron loss of the beam has been taken into account by means of the first Born approximation, allowing for the target atom to remain unexcited or to be excited to all possible states. Electron-capture cross sections have been calculated by means of the scaled Oppenheimer-Brinkman-Kramers approximation, taking into account all atomic shells of the target atoms and capture into all excited states of the projectile. The capture and loss cross sections are found to be within 20%-30% of the existing experimental values for most of the cases considered. Radiation of the beam due to electron capture into the excited states of the ion, collisional excitation, and collisional inner-shell ionization, taking into account the fluorescence yield of the ions, has been considered. Effective X-ray production cross sections and multiplicities for the most energetic X-ray lines emitted by the Fe and O beams have been calculated, and error estimates made for the results.

Rule, D. W.↗
NASA NTRS1977

Ultraviolet absorption: Experiment MA-059

A technique devised to permit the measurement of atmospheric species concentrations is described. This technique involves the application of atomic absorption spectroscopy and the quantitative observation of resonance fluorescence in which atomic or molecular species scatter resonance radiation from a light source into a detector. A beam of atomic oxygen and atomic nitrogen resonance radiation, strong unabsorbable oxygen and nitrogen radiation, and visual radiation was sent from Apollo to Soyuz. The density of atomic oxygen and atomic nitrogen between the two spacecraft was measured by observing the amount of resonance radiation absorbed when the line joining Apollo and Soyuz was perpendicular to their velocity with respect to the ambient atmosphere. Results of postflight analysis of the resonance fluorescence data are discussed.

Donahue, T. M.↗
NASA NTRS1986

Calculations on the production and use of superfine holographic X-ray gratings for astrophysical observations

Superfine holograhic X-ray gratings may be produced by transferring onto metal an interference pattern generated by two branches of a sufficiently coherent X-ray beam, emitted in the form of synchrotron radiation from high energy electron storage rings. Generation of the coherent beam requires restrictions on the beam size. A calculation is presented which allows an exact evaluation of this restriction. The effect of defocusing optics on the expected resolution is also studied.

Csonka, P. L.↗
NASA NTRS1995

Raman Spectroscopy as a Method for Mineral Identification on Lunar Robotic Exploration Missions

The sharp, nonoverlapping Raman bands for plagioclase, pyroxene, and olivine would be advantageous for on-surface, active mineralogical analysis of lunar materials. A robust, light-weight, low-power, rover-based Raman spectrometer with a laser exciting source, entirely transmission-mode holographic optics, and a charge-coupled device (CCD) detector could fit within a less than 20 cm cube. A sensor head on the end of an optical fiber bundle that carried the laser beam and returned the scattered radiation could be placed against surfaces at any desired angle by a deployment mechanism; otherwise, the instrument would need no moving parts. A modem micro-Raman spectrometer with its beam broadened (to expand the spot to 50-micrometer diameter) and set for low resolution (7/cm in the 100-1400/cm region relative to 514.5-nm excitation), was used to simulate the spectra anticipated from a rover instrument. We present spectra for lunar mineral grains, less than 1 mm soil fines, breccia fragments, and glasses. From frequencies of olivine peaks, we derived sufficiently precise forsterite contents to correlate the analyzed grains to known rock types and we obtained appropriate forsterite contents from weak signals above background in soil fines and breccias. Peak positions of pyroxenes were sufficiently well determined to distinguish among orthorhombic, monoclinic, and triclinic (pyroxenoid) structures; additional information can be obtained from pyroxene spectra, but requires further laboratory calibration. Plagioclase provided sharp peaks in soil fines and most breccias even when the glass content was high.

Wang, Alian↗
NASA NTRS2004

Broadband, Low-Loss Phase Shifters Based on Thin Ferroelectric Films

Several different types of microwave transmission line phase shifters based on thin ferroelectic films have been developed at the NASA Glenn Research Center. These include a series of coupled microstrip lines, slotline incorporating Marchand balms, odd-mode coplanar strips, and hybrid devices incorporating a switch to toggle the output termination between an open and virtual short circuit. A review of the theory of operation of each of these devices will be presented along with measured performance. Also, devices of the first variety have been subjected to total dose (proton) radiation exposure using a 200 MeV beam energy with a total dose up to nearly 1 kRad (Si). Results of these radiation tests will be discussed.

Romanofsky, Robert↗