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EPDL97: the evaluated photo data library `97 version

Description: The Evaluated Photon Data Library, 1997 version (EPLD97), is designed for use in photon transport calculations at Lawrence Livermore National Laboratory. This library includes photon interaction data for all elements with atomic number between Z = 1 (hydrogne) and 100 (fermium), including: photoionization, photoexcitation, coherent and incoherent scattering, and pair and triplet porduction cross sections. For use in applications data is provided for all elements over the energy range 1 eV to 100 GeV. This report documents the sources and treatment of the data included inthis library. EPDL97 completely supersedes the earlier 1989 version of EPDL and it is highly recommended that useres only use the most recent version of this library.
Date: September 19, 1997
Creator: Cullen, D.E.; Hubbell, J.H. & Kissel, L.
Partner: UNT Libraries Government Documents Department

Development of an ultra cold neutron source at MLNSC

Description: Ultra Cold Neutrons (UCN) can be produced at spallation sources using a variety of techniques. To date the technique used has been to Bragg scatter and Doppler shift cold neutrons into UCN from a moving crystal. This is particularly applicable to short-pulse spallation sources. We are presently constructing a UCN source at LANSCE using this method. In addition, large gains in UCN density should be possible using cryogenic UCN sources. Research is under way at Gatchina to demonstrate technical feasibility of a frozen deuterium source. If successful, a source of this type could be implemented at future spallation sources, such as the long pulse source being planned at Los Alamos, with a UCN density that may be two orders of magnitude higher than that presently available at reactors.
Date: September 1, 1996
Creator: Seestrom, S.J.; Bowles, T.J.; Hill, R.; Greene, G.L. & Morris, C.L.
Partner: UNT Libraries Government Documents Department

Summary of recent color coherence results

Description: Recent experimental results on color coherence phenomena from e{sup +}e{sup -}, ep, and p{anti p} collisions are presented. The data are compared to analytic perturbative QCD calculations based on the modified leading logarithm approximation and the local parton hadron duality hypothesis.
Date: August 1, 1998
Creator: Varelas, N., University of Chicago
Partner: UNT Libraries Government Documents Department

Improved performance (transmission) gratings

Description: Results of the study produced the following conclusions: higher line density gratings could be produced immediately by superimposing existing gratings (after reducing wire widths); unwanted higher orders could be reduced by chemical treatment of existing ''deep groove'' gratings; symmetric phase gratings could be produced immediately by plating with a low absorption material instead of with gold; symmetric phase plates (gratings) can be etched with existing equipment (a combination of two would focus beam on a spot, with up to 16% efficiency); to improve performance, eventually one should manufacture asymmetric phase gratings, and ''tailor'' the contours of absorption gratings; in the longrun, probably ''shingle gratings'' will offer the best performance; and the conjectured ''Impossibility Theorem'' may limit the performance of gratings, no mater how they are constructed.
Date: January 1, 1978
Creator: Csonka, P.L.
Partner: UNT Libraries Government Documents Department

Misalignment sensitivity of an inclined crystal monochromator

Description: The sensitivity of a novel inclined crystal monochromator design to misalignments has been calculated, and compared to data. Rocking curve line narrowing as well as broadening can occur because the asymmetry factor of dynamical diffraction given by b=s{sub O}{center dot}n/s{sub H}{center dot}n can have an absolute value larger or smaller than unity. Here s{sub O}{center dot}n and s{sub H}{center dot}n are the direction cosines of the incident and diffracted beams, respectively, and n is the inward surface normal. An inclined double crystal monochromator which is perfectly aligned would have b = {minus}1 for both crystals, and only then would the diffraction by symmetric. We have computed b and rocking curve widths for inclination angles of 70.53{degree} and 85.00{degree}, and we compare the 70.53{degree} case to data for silicon {l brace}111{r brace} reflections using 8 KeV (CuK{alpha}{sub 1}) radiation. The 70.53{degree} case applies to (11{bar 1}) reflection from a (111) oriented crystal. We report that rotations around the reciprocal lattice vector have the expected effect on b.
Date: October 1, 1991
Creator: Macrander, A.T. & Lee, W.K.
Partner: UNT Libraries Government Documents Department

Coherent rho 0 photoproduction in bulk matter at high energies

Description: The momentum transfer {Delta}k required for a photon to scatter from a target and emerge as a {rho}{sup 0} decreases as the photon energy k rises. For k > 3 x 10{sup 14} eV, {Delta}k is small enough that the interaction cannot be localized to a single nucleus. At still higher energies, photons may coherently scatter elastically from bulk matter and emerge as a {rho}{sup 0}, in a manner akin to kaon regeneration. Constructive interference from the different nuclei coherently raises the cross section and the interaction probability rises linearly with energy. At energies above 10{sup 23} eV, coherent conversion is the dominant process; photons interact predominantly as {rho}{sup 0}. We compute the coherent scattering probabilities in slabs of lead, water and rock, and discuss the implications of the increased hadronic interaction probabilities for photons on ultra-high energy shower development.
Date: January 9, 2009
Creator: Couderc, Elsa & Klein, Spencer
Partner: UNT Libraries Government Documents Department

Solution structures of {beta}-amyloid{sub 10-35} and {beta}-amyloid{sub 10-35} PEG3000 aggregates.

Description: Small angle neutron and x-ray scattering (SANS/SAXS) studies were conducted on the structure of the aggregates formed from both the truncated model peptide {beta}-Amyloid(10-35) (A{beta}{sub 10-35}) and a block copolymer {beta}-Amyloid (10-35)-PEG3000 (A{beta}{sub 10-35}-PEG) in D{sub 2}O at pHs from 3.0 to 7.0. These studies indicate that A{beta}{sub 10-35} aggregates into rod-like particles (fibril) and their radii are strongly dependent on the Pm of the solution. The fibril-fibril association in A{beta}{sub 10-35} solutions is less of pH < 5.6, but becomes larger at higher pH. A{beta}{sub 10-35}-PEG also assembles into rod-like particles whose radius is larger by about 30 {angstrom} than that for A{beta}{sub 10-35} fibril at pH 4.2, while it is about 23 {angstrom} larger at higher pH. Contrast matching SAXS/SANS experiments that eliminate the coherent scattering from PEG reveal that PEG moiety is located at the periphery of the fibril. Also, the mass per unit length of the peptide portion is similar for both A{beta}{sub 10-35} and A{beta}{sub 10-35}-PEG fibrils at pH 5.6. The mass per unit length of the rods from SANS provides key information on the packing of A{beta}{sub 10-35} peptides in the fibril.
Date: July 2, 1999
Creator: Benzinger, T. L. S.; Burkoth, T. S.; Gordon, D.; Lynn, D. G.; Meredith, S. C.; Morgan, D. M. et al.
Partner: UNT Libraries Government Documents Department

Near neighbor separations of surface atoms. Progress report

Description: The construction phase of the work to develop a technique to measure near-neighbor distances of low-Z atoms that are adsorbed at solid surfaces is nearly complete. The instrument will measure EXAFS-like variations that are associated with core-level loss features in the secondary yield of high-energy electrons. The goal is to then combine the knowledge of these spacings with analysis of electron diffraction data to determine the structure of surfaces. The apparatus that was constructed is described. It became apparent in the course of this work that the instrument would also be well suited for reflection high-energy electron diffraction (RHEED), and therefore the applicability of RHEED to studies of surface structure was investigated. Exploratory measurements were made on an existing RHEED system that was available. The conclusion is that RHEED is ideally suited to study the distribution of steps on surfaces.
Date: January 1, 1981
Partner: UNT Libraries Government Documents Department

The effectiveness of metal coated diffraction gratings at grazing and near normal incidence as harmonic scrubbers

Description: High power free electron lasers (FEL) can produce significant amounts of harmonic radiation. These harmonic components represent a substantial damage threat to the optical elements comprising the laser resonator. In this paper we discuss the merits of using blind gratings in both the paraboloid and grazing incidence hyperboloid mirrors of a 1.06 micron FEL under construction by the Boeing Aerospace Company. Grating designs developed for use at grazing incidence are not very efficient for dispersing harmonics. However, blind gratings positioned in the paraboloid exhibit better filtering capability. 6 refs., 8 figs., 3 tabs.
Date: January 1, 1988
Creator: Wantuck, P.J.; Appert, Q.D.; Tong, K. & Pistoresi, D.J.
Partner: UNT Libraries Government Documents Department

Small molecule single crystal diffractometry

Description: Emphasis is on the use of ''standard'' diffractometers under the control of ''standard computer programs.'' The factors which affect the various decisions required of an operator are discussed in general terms but few how-to procedures are advocated.
Date: January 1, 1978
Creator: Williams, G.J.B.
Partner: UNT Libraries Government Documents Department

Localized Measurement of Turbulent Fluctuations in Tokamaks with Coherent Scattering of Electromagnetic Waves

Description: Localized measurements of short-scale turbulent fluctuations in tokamaks are still an outstanding problem. In this paper, the method of coherent scattering of electromagnetic waves for the detection of density fluctuations is revisited. Results indicate that the proper choice of frequency, size and launching of the probing wave can transform this method into an excellent technique for high-resolution measurements of those fluctuations that plasma theory indicates as the potential cause of anomalous transport in tokamaks. The best spatial resolution can be achieved when the range of scattering angles corresponding to the spectrum of fluctuations under investigation is small. This favors the use of high frequency probing waves, such as those of far infrared lasers. The application to existing large tokamaks is discussed.
Date: August 19, 2002
Creator: Mazzucato, E.
Partner: UNT Libraries Government Documents Department

Research in nuclear spectroscopy and x rays. Annual report

Description: The scope of this research program is to study the structure of nuclei and the properties of the nuclear force, in particular its symmetries, using the tools of nuclear spectroscopy. To this end a unique set of instruments is at disposal, including curve crystal diffraction monochromators, high resolution beta spectrometers and Moessbauer spectrometers.
Date: April 20, 1970
Creator: Boehm, F.
Partner: UNT Libraries Government Documents Department

Effective vibration isolation system for perfect-crystal neutron interferometry

Description: Perfect-crystal neutron interferometers are subject to degradation of their performance caused by vibrational accelerations. It is shown that the most seriously offending accelerations are rotational, and an effective and simple vibration isolation system that has been developed at the MIT Neutron Diffraction Laboratory is described.
Date: 1985~
Creator: Arthur, J.
Partner: UNT Libraries Government Documents Department

Laser/plasma theory for microwave modeling experiments. Final report

Description: During the last year, we have carried out theoretical investigations of microwave-plasma interactions in support of both the UCLA program, and the TRW program. The UCLA program concentrated on experimental studies of Stimulated Brillouin Scattering (SBS). We derived a theory which successfully explained the basic features of their experiment. The TRW program was originally conceived of as an investigation of electron heating and thermal transport; however, the subject was later changed to the interaction of SBS and self focusing. The experimental program has not yet started; however, we have developed a theoretical description of the expected interaction.
Date: January 1, 1980
Creator: Thomson, J J & Divergilio, W F
Partner: UNT Libraries Government Documents Department

Influence of the interface on the crystallization of amorphous Ge in Pb/Ge multilayers

Description: The amorphous to crystalline phase transition of Ge in contact with Pb has been extensively investigated in Pb/Ge multilayers. We find that the Ge crystallizes at reduced temperatures in the range of 100-200/degree/C depending on the thickness of the Ge and the Pb. Simultaneously the texture of the Pb improves and the layered structure completely disappears. The basis for the reduction of the crystallization temperature is the enhanced diffusion kinetics at the interface, caused by the adjacent Pb layer. 20 refs., 4 figs.
Date: January 1, 1988
Creator: Sevenhans, W.; Locquet, J.P.; Bruynseraede, Y.; Homma, H. & Schuller, I.K.
Partner: UNT Libraries Government Documents Department

Symmetry, stability, and diffraction properties of icosahedral crystals

Description: In a remarkable experiment on an Mn-Al alloy, Shechtman et al. observed a diffraction spectrum with icosahedral symmetry. This is inconsistent with discrete translational invariance since the symmetry includes a five-fold axis. In this paper, it is shown that the crystallography and diffraction pattern can be described by a six-dimensional space group. The crystal structure in 3d is obtained as a cut along a 3d hyperplane in a regular 6d crystal. Displacements of the 6d crystal along 6 orthogonal directions define 6 continuous symmetries for the icosahedral crystal, three of which are phase symmetries describing internal rearrangements of the atoms.
Date: January 1, 1985
Creator: Bak, P.
Partner: UNT Libraries Government Documents Department

Broadband diffractive lens

Description: Significant progress has been made toward solving the century-old problem of chromatic aberrations in diffractive optics. Our approach exploits modern materials and microfabrication technology and is very different from the purely diffractive strategy,'' which is commonly employed and which results in multiple diffractive elements separated by a finite distance. We have developed a Fresnel zone plate lens comprised of a serial stack of patterned minus-filters which allows broadband radiation to be focused (or imaged) without longitudinal or transverse chromatic aberrations. 7 refs., 4 figs.
Date: May 28, 1991
Creator: Ceglio, N.M.; Hawryluk, A.M.; London, R.A.; Seppala, L.G. (Lawrence Livermore National Lab., CA (USA)) & Gaines, D.P. (Brigham Young Univ., Provo, UT (USA))
Partner: UNT Libraries Government Documents Department

Study of short-range motion of atomic hydrogen in amorphous silicon by neutron reflectometry

Description: Preliminary results of neutron reflectometry (NR) measurements on rf sputter-deposited a-Si:H/a-Si:D bilayers indicate that this technique may be used to monitor H and D motions over distances of {approx} 10 to 200 {Angstrom} with a nominal resolution of 5--10 {Angstrom}. In studying rf sputter-deposited thin films containing a high density of microvoids annealed at 270 C, we found that the hydrogen diffused a distance of only {approx} 100 {Angstrom}. Further annealing at 270 and 280 C produced no additional motion. This result is consistent with a model of this system in which the hydrogen is trapped in microvoids after moving a relatively short distance.
Date: May 1, 1992
Creator: Dozier, W.D. (Argonne National Lab., IL (United States)); Herwig, K.W. (Missouri Univ., Columbia, MO (United States). Research Reactor Facility); Shinar, R. (Iowa State Univ. of Science and Technology, Ames, IA (United States). Microelectronics Research Center); Jia, H. & Shinar, J. (Ames Lab., IA (United States))
Partner: UNT Libraries Government Documents Department

Physical characterization of magmatic liquids

Description: Long-range goals of this research project are: (1) Characterization of seismic velocity and attenuation (V{sub p}, V{sub S}, Q{sub p}{sup {minus}1}, Q{sup S}{sup {minus}1}) and electrical properties of selected Hawaiian and related rocks under appropriate controlled environments of pressure, temperature and volatile/fluid content; and, (2) Characterization of the elastic, viscoelastic and thermodynamic properties (V{sub p}, V{sub S}, Q{sub P}{sup {minus}1}, Q{sub S}{sup {minus}1}, viscosity and compressibility) of molten basalts, picrites and komatites, and related silicate melts to {approximately} 1600{degrees}C using the ultrasonic interferometry method. In addition, the pressure dependences of V{sub p},V{sub S} and bulk modulus will be determined using the Brillouin scattering and diamond- anvil cell techniques.
Date: January 1, 1991
Creator: Manghnani, M.H.
Partner: UNT Libraries Government Documents Department

Structural study of multilayered vanadium/nickel superlattices

Description: We have studied the microstructure of V/Ni metallic superlattice, using x-ray and neutron diffraction. We find a sharp and broad rocking curves around the first-order Bragg peak, and attribute them to a columnar structure which gives rise to two modulation structures; one the ordinary layered structure within the columns and the other the averaged modulation structure which produces the sharp rocking peak.
Date: July 1, 1985
Creator: Homma, H.; Lepetre, Y.; Murduck, J.M.; Schuller, I.K. & Majkrzak, C.F.
Partner: UNT Libraries Government Documents Department

Fresnel diffraction in an optical system with focusing

Description: The migration of the axial intensity maximum from the geometrical focus toward the diffracting aperture, known as the focal shift, is explained in terms of the asymmetry of the Fresnel diffraction about focus. Conditions for the reversal or elimination of the focal shift are predicted. 8 refs.
Date: January 1, 1985
Creator: Wenzel, R.G.
Partner: UNT Libraries Government Documents Department

Structure solution methods for superstructures

Description: The analysis techniques described are applicable mainly to superstructures and modulated structures without significant disorder. Other methods not discussed here are needed for handling disorder and diffuse intensity problems. Mechanistic perturbation techniques and conventional crystallographic techniques, suitably modified, are both applicable in crystal structure analysis of superstructures and modulated structures. It is strongly recommended that conventional crystallographic techniques be used whenever possible because of the greater opportunity to recognize unexpected physical results not built into the trial model.
Date: January 1, 1979
Creator: Johnson, C.K.
Partner: UNT Libraries Government Documents Department