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Neutron spectroscopy of high-density amorphous ice.

Description: Vibrational spectra of high-density amorphous ice (hda-ice) for H{sub 2}O and D{sub 2}O samples were measured by inelastic neutron scattering. The measured spectra of hda-ice are closer to those for high-pressure phase ice-VI, but not for low-density ice-Ih. This result suggests that similar to ice-VI the structure of hda-ice should consist of two interpenetrating hydrogen-bonded networks having no hydrogen bonds between themselves.
Date: July 17, 1998
Creator: Kolesnikov, A. I.
Partner: UNT Libraries Government Documents Department

In situ neutron spectroscopy on the martian surface: modeling the hydra instrument for different mission scenarios

Description: Neutron spectroscopy has proven to be highly successful in remotely detecting and measuring the abundance of water on planetary surfaces such as Mars and the Moon. Because of the central role played by water on Mars and the need to make in situ measurements of water abundances for landed missions, neutron spectroscopy is being investigated as a technique for quickly determining the near-surface water abundance for fhture Mars missions, such as the Mars Smart Larider (MSL).
Date: January 1, 2003
Creator: Lawrence, David J. (David Jeffery),; Elphic, R. C. (Richard C.); Feldman, W. C. (William C.); Moore, K. R. (Kurt R.); Prettyman, T. H. (Thomas H.) & Weins, R. C. (Roger C.)
Partner: UNT Libraries Government Documents Department

Effects of an RTG power source on neutron spectroscopy measurements on the martian surface.

Description: A continuing goal of Mars science is to identify the exact locations of near-surface water and/or hydrated minerals using in situ measurements. Recent data from the Mars Odyssey mission has used both neutron and gamma-ray spectroscopy to measure large amounts of water ice near both polar regions . Furthermore, these data have also determined that in the mid-latitude regions, there likely exist relatively large amounts of hydrogen (-4-7 equivalent H2O wt.%), although it is not certain in which form this hydrogen exists . While these are exciting results, one drawback of these measurements is that they are averaged over a large (-400 km) footp ri nt and do not reflect any small (<1 km) inhomogenieties in hydrogen abundance that likely exist on the Martian surface. For any future in situ mission (e g, Mars Smart Lander (MSL)) that seeks to measure and characterize nearsurface H 2O, especially in the mid-latitude regions, is will be necessary to know th e locati ons of the H20.
Date: January 1, 2003
Creator: Lawrence, David J. (David Jeffery),; Elphic, R. C. (Richard C.) & Wiens, R. C. (Roger C.)
Partner: UNT Libraries Government Documents Department

Quasi-elastic neutron scattering studies of protein dynamics. Final report, November 1, 1991--March 31, 1995

Description: Proteins are formed from long polymer chains of amino acids that have been cross linked into a complex three dimensional structure. The structure is not unique, since there are many conformation substates of nearly equal energy, separated by small energy barriers, that are obtained by slight shifts in positions of various segments of the molecule. Transitions among these conformations substates are of a diffusive nature, and they can lead to substantial changes in the shape of the molecule. These changes in shape are important for the biological reactions in the cell. Such diffusive motion is inaccessible to the diffraction methods or to the computer simulations, since it occurs on a long time scale. It is accessible to incoherent quasi-elastic neutron scattering (QNS) studies, which permit a direct determination of the properties of the diffusive motion of the protons in the molecules. The authors have used the IQNS method to study the motions of the side chains in trypsin, a protein of beta-sheet structures and myoglobin, a protein of {alpha}-helical structures, at various D{sub 2}O hydration levels.
Date: April 10, 1995
Creator: Huang, H.W.
Partner: UNT Libraries Government Documents Department

Novel gene complex structure determination

Description: This is the final report of a one-year, Laboratory-Directed Research and Development (LORD) project at the Los Alamos National Laboratory. `Operative` chromatin containing exclusively the minor hasten variants was successfully isolated. Linker hasten H1 is quantitatively missing from operative chromatin. One of the aims of this proposal was to determine the proteins responsible for stabilizing operative chromatin. This chromatin is stabilized by microtubule proteins tar and tubulin. Another goal of this project was the structural characterization of operate chromatin nucleosomes. Using solution scattering, nucleosomes containing the minor variants were shown to be structurally distinct from major variant containing nucleosomes. The unusual structure and stabilization of operative chromatin by microtubule proteins provides a possible mechanism for direct interaction of transcription machinery with specific chromatin domains.
Date: August 1, 1997
Creator: Gatewood, J.M.
Partner: UNT Libraries Government Documents Department

Predicted Performance of Neutron Spectrometers Using Scintillating Fibers

Description: One class of neutron spectrometers is devices that provide a measure of the neutron spectrum by using moderating and absorbing materials together with thermal-neutron detectors. Pacific Northwest National Laboratory has developed scintillating fibers that are sensitive to thermal neutrons. Because these fibers are thin, they present an enabling technology for several applications, including highly efficient neutron spectroscopy. The underlying concept is to arrange the fibers in an array of layers separated by materials whose characteristics have been chosen to optimize the instrument function for the application. Monte Carlo experiments have been performed to characterize the conceptual design and to determine the value of the concept as a tool for research and other applications.
Date: February 14, 2000
Creator: Craig, Richard A & Bliss, Mary
Partner: UNT Libraries Government Documents Department

Accelerator requirements for fast-neutron interrogation of luggage and cargo

Description: Several different fast-neutron based techniques are being studied for the detection of contraband substances in luggage and cargo containers. The present work discusses the accelerator requirements for fast-neutron transmission spectroscopy (FNTS), pulsed fast-neutron analysis (PFNA), and 14-MeV neutron interrogation. These requirements are based on the results of Monte-Carlo simulations of neutron or gamma detection rates. Accelerator requirements are driven by count-rate considerations, spatial resolution and acceptable uncertainties in elemental compositions. The authors have limited their analyses to luggage inspection with FNTS and to cargo inspection with PFNA or 14-MeV neutron interrogation.
Date: May 1, 1995
Creator: Micklich, B.J.; Fink, C.L. & Yule, T.J.
Partner: UNT Libraries Government Documents Department

Motion and structure of water adsorbed in type-A zeolites.

Description: The motion of water adsorbed in Type-Azeotites has been measured using quasielastic and inelastic neutron spectroscopy. Changes in the charge-compensating cation has a dramatic effect on the low frequency vibrational spectrum, which has a well defined low frequency feature for sodium and lithium but no such peak is present for the case of potassium and calcium. At 297K the low frequency feature is still visible, while there is also quasielastic broadening of the elastic line due to diffusion of the water protons. These measurements are interpreted in the light of the results from computer simulations of these materials.
Date: March 5, 1998
Creator: Trouw, F. R.
Partner: UNT Libraries Government Documents Department

Can Handheld Plastic Detectors Do Both Gamma and Neutron Isotopic Identification with Directional Source Location?

Description: This paper demonstrates, through MCNPX simulations, that a compact hexagonal array of detectors can be utilized to do both gamma isotopic identification (ID) along with neutron identification while simultaneously finding the direction of the source relative to the detector array. The detector array itself is composed of seven borated polyvinyl toluene (PVT) hexagonal light pipes approximately 4 inches long and with a 1.25 inch face-to-face thickness assembled in a tight configuration. The gamma ID capability is realized through judicious windowing algorithms as is the neutron spectral unfolding. By having multiple detectors in different relative positions, directional determination of the source can be realized. By further adding multiplicity counters to the neutron counts, fission events can be measured.
Date: April 18, 2008
Creator: Hayes, Robert
Partner: UNT Libraries Government Documents Department

High Intensity, Pulsed, D-D Neutron Generator

Description: Single ion-beam RF-plasma neutron generators are presented as a laboratory source of intense neutrons. The continuous and pulsed operations of such a neutron generator using the deuterium-deuterium fusion reaction are reported. The neutron beam can be pulsed by switching the RF plasma and/or a gate electrode. These generators are actively vacuum pumped so that a continuous supply of deuterium gas is present for the production of ions and neutrons. This contributes to the generator's long life. These single-beam generators are capable of producing up to 1E10 n/s. Previously, Adelphi and LBNL have demonstrated these generators' applications in fast neutron radiography, Prompt Gamma Neutron Activation Analysis (PGNAA) and Neutron Activation Analysis (NAA). Together with an inexpensive compact moderator, these high-output neutron generators extend useful applications to home laboratory operations.
Date: August 1, 2008
Creator: Williams, D. L.; Vainionpaa, J. H.; Jones, G.; Piestrup, M. A.; Gary, C. K.; Harris, J. L. et al.
Partner: UNT Libraries Government Documents Department

PINS Measurements and Simulations for Stand-Off Detection of High Explosives

Description: There has been some interest in the ability of Idaho National Laboratory's (INL) Portable Isotopic Neutron Spectroscopy System's (PINS) ability to detect high explosives at a distance. In order to assess the system's ability to perform this task, laboratory experiments on simulated or mock explosives and Monte Carlo simulations using MCNP on both mock and real explosives have been performed. The simulations and experiments on mock explosives have essentially identical configurations, allowing the models to be confirmed with experiment. This provides greater confidence in the simulations on real explosives without the need for experiment on live explosives.
Date: July 1, 2011
Creator: Seabury, E.H.
Partner: UNT Libraries Government Documents Department

CdZnTe gamma ray spectrometer for orbital gamma ray spectroscopy.

Description: We present the design and analysis of a new gamma ray spectrometer for planetary science that uses an array of CdZnTe detectors to achieve the detection efficiency needed for orbital measurements. The use of CdZnTe will provide significantly improved pulse height resolution relative to scintillation-based detectors, with commensurate improvement in the accuracy of elemental abundances determined by gamma ray and neutron spectroscopy. The spectrometer can be flown either on the instrument deck of the spacecraft or on a boom. For deck-mounted systems, a BGO anticoincidence shield is included in the design to suppress the response of the CdZnTe detector to gamma rays that originate in the spacecraft. The BGO shield also serves as a backup spectrometer, providing heritage from earlier planetary science missions and reducing the risk associated with the implementation of new technology.
Date: January 1, 2001
Creator: Prettyman, T. H. (Thomas H.); Feldman, W. C. (William C.); Fuller, K. R. (Kenneth R.); Storms, S. A. (Steven A.); Soldner, S. A.; Lawrence, David J. (David Jeffery), et al.
Partner: UNT Libraries Government Documents Department

PINS Measurements of Explosive Simulants for Cargo Screening

Description: As part of its efforts to prevent the introduction of explosive threats on commercial flights, the Transportation Security Administration (TSL) is evaluating new explosives detection systems (EDSs) for use in air cargo inspection. The TSL has contracted Battelle to develop a new type of explosives simulant to assist in this development. These are designed to mimic the elemental profile (C, H, N, O, etc.) of explosives as well as their densities. Several “neutron in—gamma out” (n,?) techniques have been considered to quantify the elemental profile in these new simulants and the respective explosives. The method chosen by Battelle is Portable Isotopic Neutron Spectroscopy (PINS), developed by Idaho National Laboratory (INL). Battelle wishes to validate that the simulants behave like the explosive threats with this technology. The results of the validation measurements are presented in this report.
Date: June 1, 2008
Creator: Seabury, E. H.
Partner: UNT Libraries Government Documents Department

Neutron Spectroscopy by Double Scatter and Associated Particle Techniques.

Description: Multiple detectors can provide [1,2] both directional and spectroscopic information. Neutron spectra may be obtained by neutron double scatter (DSNS), or the spontaneous fission associated particle (AP) technique. Spontaneous fission results in the creation of fission fragments and the release of gamma rays and neutrons. As these occur at the same instant, they are correlated in time. Thus gamma ray detection can start a timing sequence relative to a neutron detector where the time difference is dominated by neutron time-of-flight. In this paper we describe these techniques and compare experimental results with Monte Carlo calculations.
Date: October 28, 2007
Creator: Dioszegi, I.
Partner: UNT Libraries Government Documents Department

NEUTRON IMAGING, RADIOGRAPHY AND TOMOGRAPHY.

Description: Neutrons are an invaluable probe in a wide range of scientific, medical and commercial endeavors. Many of these applications require the recording of an image of the neutron signal, either in one-dimension or in two-dimensions. We summarize the reactions of neutrons with the most important elements that are used for their detection. A description is then given of the major techniques used in neutron imaging, with emphasis on the detection media and position readout principle. Important characteristics such as position resolution, linearity, counting rate capability and sensitivity to gamma-background are discussed. Finally, the application of a subset of these instruments in radiology and tomography is described.
Date: March 2002
Creator: Smith, G. C.
Partner: UNT Libraries Government Documents Department

Neutron Spectrometry for Identification of filler material in UXO - Final Report

Description: Unexploded ordnance (UXO)-contaminated sites often include ordnance filled with inert substances that were used in dummy rounds. During UXO surveys, it is difficult to determine whether ordnance is filled with explosives or inert material (e.g., concrete, plaster-of-paris, wax, etc.) or is empty. Without verification of the filler material, handling procedures often necessitate that the object be blown in place, which has potential impacts to the environment, personnel, communities and survey costs. The Department of Defense (DoD) needs a reliable, timely, non-intrusive and cost-effective way to identify filler material before a removal action. A new technology that serves this purpose would minimize environmental impacts, personnel safety risks and removal costs; and, thus, would be especially beneficial to remediation activities.
Date: September 12, 2007
Creator: Bliss, Mary
Partner: UNT Libraries Government Documents Department

Neutron velocity spectroscopy using the Nevis synchrocyclotron. Progress report, July 30, 1972--June 30, 1973

Description: The period August 1, 1972, to June 30, 1973, was marked by the continuing of the analysis of the vast amounts of data obtained during 1968 and 1970 pulsed-neutron time-of-flight spectroscopy runs using the Nevis Synchrocyclotron. Many major research papers from that period have now appeared in print. The numerous evolving results for even A nuclei having atomic mass 150 < A < 190 have given first conclusive (and growing) confirmation of Dyson's theories concerning level spacing systematics. Monte Carlo studies leading to a better understanding of the implications of these theories have also been published. The important paper on /sup 238U and /sup 232/Th is now published, as is that for the Yb isotopes. Papers on the W isotopes, on Na, and on K have been submitted for publication. Results for the Gd and Sm isotopes, for the Cd isotopes, for Ta, for argon, for calcium, for sodium, for potassium, for copper (63/Cu and /sup 65/Cu), and for chlorine are contained in the full report COO- 2174-15. (auth)
Date: June 1, 1973
Creator: Rainwater, J.
Partner: UNT Libraries Government Documents Department

Multi-purpose neutron radiography system

Description: A conceptual design is given for a low cost, multipurpose radiography system suited for the needs of the Los Alamos National Laboratory (LANL). The proposed neutron source is californium-252. One purpose is to provide an in-house capability for occasional, reactor quality, neutron radiography thus replacing the recently closed Omega-West Reactor. A second purpose is to provide a highly reliable standby transportable neutron radiography system. A third purpose is to provide for transportable neutron probe gamma spectroscopy techniques. The cost is minimized by shared use of an existing x-ray facility, and by use of an existing transport cask. The achievable neutron radiography and radioscopy performance characteristics have been verified. The demonstrated image qualities range from high resolution gadolinium - SR film, with L:D = 100:1, to radioscopy using a LIXI image with L:D = 30:1 and neutron fluence 3.4 x 10{sup 5} n/cm{sup 2}.
Date: July 1, 1996
Creator: Barton, J.P.; Bryant, L.E. & Berry, P.
Partner: UNT Libraries Government Documents Department

Neutron resonances in the compound nucleus: Parity nonconservation to dynamic temperature measurements

Description: Experiments using epithermal neutrons that interact to form compound-nuclear resonances serve a wide range of scientific applications. Changes in transmission which are correlated to polarization reversal in incident neutrons have been used to study parity nonconservation in the compound nucleus for a wide range of targets. The ensemble of measured parity asymmetries provides statistical information for the extraction of the rms parity-violating mean-square matrix element as a function of mass. Parity nonconservation in neutron resonances can also be used to determine the polarization of neutron beams. Finally the motion of target atoms results in an observed temperature-dependent Doppler broadening of resonance line widths. This broadening can be used to determine temperatures on a fast time scale of one microsecond or less.
Date: August 1, 1997
Creator: Yuan, V.W.
Partner: UNT Libraries Government Documents Department

Dynamic temperature and velocity measurements using neutron resonance spectroscopy

Description: The use of Doppler broadening in neutron resonances as a quantitative way to measure temperatures has been proposed and investigated for cases of static or quasi-static temperature measurements. Neutrons are temperature probes that can penetrate a sample to view its interior. At the same time products that may shield a sample optically are not opaque to neutrons so that temperature measurements can be made in their presence. When neutrons are attenuated by a sample material, the time-of-flight (TOF) spectrum of the transmitted neutrons exhibits a series of characteristic dips or resonances. These resonances appear when neutrons are captured from the beam in the formation of excited states in the A + 1 nucleus (n + A {ge} (A + 1){sup *}). Subsequent de-excitation of these states, by gamma emission or particle emission into 4{pi} steradians, effectively eliminates the captured neutrons from the transmitted beam. The resonance locations and lineshapes which appear in the TOF spectrum are unique to each isotopic element, and temperature determinations can be localized through the positioning of resonant tags.
Date: August 1, 1997
Creator: Yuan, V.W.; Asay, B.W. & Boat, R.
Partner: UNT Libraries Government Documents Department

Dynamic measurement of temperature in detonating PBX 9502 using neutron resonance spectroscopy

Description: Accurate temperature measurements in dynamic systems have been pursued for decades and have usually relied on optical techniques. These approaches are generally hampered by insufficient information regarding the emissivity of the system under study, particularly when looking at detonating energetic materials. This results from the complex chemical change that the detonating system is undergoing, from neat organic crystals with discrete set of electronic states and molecular vibrations embedded in a binder, to gas phase products, with a different set of discrete states. Typically, when making an optical measurement, one makes the grey body approximation and measures the photon flux at a few discrete bands to extract a temperature from the light emission. We are developing NRS techniques to measure temperature in dynamic systems and overcome the limitations of optical systems. Many elements have neutron resonances with narrow enough intrinsic Breit-Wigner (Lorentzian) widths such that the resonance is substantially broadened by atomic motion even at room temperature. Thus, accurate measurement of the Doppler contribution allows one to infer the material temperature, and for the conditions achieved using standard high explosives, the probe itself is not perturbed by the high temperature and pressure. Moreover, since the opacity of energetic materials to neutrons is much less than it is to infrared, visible, or ultraviolet light, we probe the internal temperature, in contrast to measuring the surface temperature through a laser or an emission technique. Also, NRS is much less affected by the opacity of soot or other particulate than are optical methods.
Date: September 1, 1997
Creator: Funk, D.J.; Rabie, R. & Mace, J.
Partner: UNT Libraries Government Documents Department