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Spectral gamma-ray logging for the 100-N Area, Hanford, Washington

Description: The objective of this effort was to delineate the vertical distribution and concentration of anthropogenic radionuclides in the subsurface surrounding nine boreholes in the 100-N Area available for geophysical logging with the Radionuclide Logging System (RLS). Cesium was defined in eight boreholes, and the ninth hole was found to not contain any such radionuclides.
Date: October 2, 1996
Creator: Szwartz, G.J.
Partner: UNT Libraries Government Documents Department

Overview of reaction mechanisms for calculating the high energy component of fast-nucleon induced gamma spectra

Description: This presentation reviews the current status of quantum mechanical models for understanding the high-energy component of gamma spectra resulting from radiative capture of fast nucleons; i.e., the part of the spectrum that is not amenable to standard statistical model (Hauser-Feshbach) treatments. These models are based on the direct-semidirect (DSD) model and its variants. Included are recent results on the extension of the DSD model to unbound final states, a discussion of problems and improvements in understanding the form factors in this model, and a brief discussion of a model closely related to the DSD, the pure-resonance model.
Date: February 21, 1995
Creator: Dietrich, F.S.
Partner: UNT Libraries Government Documents Department

Simultaneous neutron and gamma spectrum adjustment

Description: The spectrum adjustment procedure was extended to simultaneous neutron and gamma spectrum adjustment, and the feasibility of this technique is demonstrated in the analysis of HFIR dosimetry experiments. Conditions in which gamma rays may contribute considerably to radiation damage in steels are discussed. Beryllium helium accumulation fluence monitors (HAFMs) were found to be good monitors in gamma fields of intensities high enough to contribute to steel embrittlement. Use of {sup 237}Np, {sup 238}U, and {sup 9}Be HAFM as gamma dosimeters is proposed for high-dose irradiations in high-energy, high-intensity gamma fields.
Date: October 1, 1996
Creator: Remec, I.
Partner: UNT Libraries Government Documents Department

First measurement of the degree of fragmentation of the decay out cascade from the superdeformed yrast band in {sup 192}Hg

Description: The decay spectrum of the yrast superdeformed band in {sup 192}Hg comprises a quasicontinuum with discrete lines ranging from 1 to 3.2 MeV. The intensity fluctuations of this quasicontinuum give information on the degree of fragmentation of the decay cascades and on the effect of pairing correlations on the level density {rho}(U) in the normal deformed well (0 < U < U{sub SD}).
Date: December 1, 1996
Creator: Lopez-Martens, A.; Hannachi, F. & Schueck, C.
Partner: UNT Libraries Government Documents Department

The quasi-continuum of gamma rays following the decay of superdeformed bands in the Hg region

Description: The quasi-continuum of the spectrum associated with the decay-out of the yrast superdeformed band in {sup 194}Hg has been extracted. It has for the first time been possible to compare the spin and excitation energy determined from the analysis of the quasi-continuum {gamma} rays to the exact result obtained from the on-step linking transitions.
Date: December 31, 1996
Creator: Lauritsen, T.; Khoo, T.L. & Janssens, R.V.F. and others
Partner: UNT Libraries Government Documents Department

Chemical identity of atoms using core electron annihilations

Description: Positron annihilation spectroscopy is a sensitive probe for studying the electronic structure of defects in solids. The high momentum part of the Doppler-broadened annihilation spectra can be used to distinguish different elements. This is achieved by using a new two-detector coincidence system and by imposing appropriate kinematic cuts to exclude background events. The new setup improves the peak to background ratio in the annihilation spectrum to {approximately}10{sup 5}. As a result, the line shape variations arising from different core electrons can be studied. The new approach adds elemental specificity to the Doppler broadening technique, and is useful in studying elemental variations around a defect site. Results from several case studies are reviewed.
Date: June 27, 1997
Creator: Asoka-Kumar, P.
Partner: UNT Libraries Government Documents Department

Thermal-neutron capture in light nuclei

Description: We have made considerable progress toward the goal of carrying out thermal-neutron capture {gamma}-ray measurements on all stable isotopes below A=60. Information processed till now has significantly augmented the existing knowledge on the detailed nuclear level structure of many light nuclides. Most of this knowledge comes from our {gamma}-ray energies, level placements, and branching ratios of secondary transitions between low-lying states. Spectroscopic information is also contained in the cross sections of the primary transitions originating from the capturing state. This is deduced from the success of ``direct`` theories of neutron capture for many nuclides, especially those of light and near closed-shell character. 23 refs, 1 tab, 3 figs.
Date: October 1, 1996
Creator: Raman, S.; Jurney, E.T. & Lynn, J.E.
Partner: UNT Libraries Government Documents Department

High sensitivity gamma spectrometry of air samples near SRS during 1985-1995

Description: High sensitivity gamma analysis of off-site air samples near the Savannah River Site (SRS) is achieved by collecting large volume air samples for analysis by ultra-low-level gamma spectrometry. A review of the 1985-1995 measurements has highlighted local and distant releases of man-made radionuclides, along with cosmogenic radionuclides which correlate with both solar and seasonal phenomena. Measurements typically involve 2-day air collection of a 70,000 m{sup 3} sample on a 51 cm x 51 cm cellulose filter using a high-capacity pump. Short-lived radon background activity is allowed to decay a few days, and then the filter is configured into a smaller calibrated volume and counted 1-3 days on a 30 percent-efficient HPGe in the Ultra-Low-Level Counting Facility. Representative detection limits for this method are shown in Table 1, and even lower limits are achievable by counting on the low-background 160 percent-efficient HPGe of the Underground Counting Facility.
Date: July 1, 1997
Creator: Winn, W.G. & Cadieux, J.R.
Partner: UNT Libraries Government Documents Department

Extended direct semidirect mechanism and the role of multistep processes in fast nucleon radiative capture

Description: We have recently developed an extension of the direct-semidirect (DSD) radiative capture model to unstable final states and have confirmed its utility in explaining the spectrum of rays from capture of polarized 19.6-MeV protons on {sup 89}Y. It was found that the extended DSD model, supplemented by a Hauser-Feshbach contribution, successfully explains the observed spectra, angular distributions, and analyzing powers, without requiring additional mechanisms, such as precompound or multistep emission, or nucleon-nucleon bremsstrahlung. In this contribution we show that the model also successfully explains data at higher energies (34 MeV incident protons), and that there is no need for additional contributions other than Hauser-Feshbach at this energy as well. The extended DSD model treats capture to unbound final states and also to bound single-particle states that damp into a compound system. An optical (complex) potential is used to describe the propagation of the captured particle. Application of this model to the {gamma} spectrum in the {sup 89}Y(p,{gamma} ) reaction at 19.6 MeV is shown. We have performed new calculations at higher energy (34 MeV protons), and have compared them with the spectra and angular distributions measured in [2] on targets of natural Cu, Ag, and Au. An example of the results, for the spectrum from Cu, is shown in the right-hand part of the figure. In both cases the DSD calculation is shown by a solid line, and a Hauser-Feshbach calculation by a dashed line. The 34-MeV calculations were very similar to those at 19.6 MeV as described in [1]. In both cases, the sum of DSD and Hauser-Feshbach calculations adequately describes the measured spectra. Although not shown, the angular distributions are also well described. There are no significant deficiencies in the comparison with experiment that indicate a need for multistep processes or other additional reaction mechanisms. Such processes are ...
Date: May 1, 1997
Creator: Dietrich, F.S.; Chadwick, M.B. & Kerman, A.K.
Partner: UNT Libraries Government Documents Department

PC/FRAM, Version 3.2 User Manual

Description: This manual describes the use of version 3.2 of the PC/FRAM plutonium isotopic analysis software developed in the Safeguards Science and Technology Group, NE-5, Nonproliferation and International Security Division Los Alamos National Laboratory. The software analyzes the gamma ray spectrum from plutonium-bearing items and determines the isotopic distribution of the plutonium 241Am content and concentration of other isotopes in the item. The software can also determine the isotopic distribution of uranium isotopes in items containing only uranium. The body of this manual descnies the generic version of the code. Special facility-specific enhancements, if they apply, will be described in the appendices. The information in this manual applies equally well to version 3.3, which has been licensed to ORTEC. The software can analyze data that is stored in a file on disk. It understands several storage formats including Canberra's S1OO format, ORTEC'S `chn' and `SPC' formats, and several ASCII text formats. The software can also control data acquisition using an MCA and then store the results in a file on disk for later analysis or analyze the spectrum directly after the acquisition. The software currently only supports the control of ORTEC MCB'S. Support for Canbema's Genie-2000 Spectroscopy Systems will be added in the future. Support for reading and writing CAM files will also be forthcoming. A versatile parameter fde database structure governs all facets of the data analysis. User editing of the parameter sets allows great flexibility in handling data with different isotopic distributions, interfering isotopes, and different acquisition parameters such as energy calibration, and detector type. This manual is intended for the system supervisor or the local user who is to be the resident expert. Excerpts from this manual may also be appropriate for the system operator who will routinely use the instrument.
Date: February 23, 1999
Creator: Kelley, T.A. & Sampson, T.E.
Partner: UNT Libraries Government Documents Department

Approximate Public Key Authentication with Information Hiding

Description: This paper describes a solution for the problem of authenticating the shapes of statistically variant gamma spectra while simultaneously concealing the shapes and magnitudes of the sensitive spectra. The shape of a spectrum is given by the relative magnitudes and positions of the individual spectral elements. Class-specific linear orthonormal transformations of the measured spectra are used to produce output that meet both the authentication and concealment requirements. For purposes of concealment, the n-dimensional gamma spectra are transformed into n-dimensional output spectra that are effectively indistinguishable from Gaussian white noise (independent of the class). In addition, the proposed transformations are such that statistical authentication metrics computed on the transformed spectra are identical to those computed on the original spectra.
Date: October 1, 2000
Creator: Thomas, Edward V. & Draelos, Timothy J.
Partner: UNT Libraries Government Documents Department

Gamma-ray burst spectra and time histories from 2 to 400 keV

Description: The Gamma-Ray burst detector on Ginga consisted of a proportional counter to observe the x-rays and a scintillation counter to observe the gamma-rays. Both instrument recorded the time histories in phase with each other and with 0.03125 s temporal resolution. The author compares the average of 21 gamma-ray bursts to determine the delay, in any, between the peak of the x-rays and the peak of the gamma-rays. The delay is less than or about equal to 30 msec. Thus, models must content with two average features of the temporal behavior. First, as a function of energy, the time structure scales as {approximately}E{sup {minus}0.45}. Second, the x-rays are not appreciable delayed relative to the gamma-rays. Some cooling models might have difficulties explaining these features.
Date: July 1, 1998
Creator: Fenimore, E.E.
Partner: UNT Libraries Government Documents Department

Spectral measurements of few-electron uranium ions produced and trapped in a high-energy electron beam ion trap

Description: Measurements of 2s{sub l/2}-2p{sub 3/2} electric dipole and 2p{sub 1/2}-2p{sub 3/2} magnetic dipole and electric quadrupole transitions in U{sup 82+} through U{sup 89+} have been made with a high-resolution crystal spectrometer that recorded the line radiation from stationary ions produced and trapped in a high-energy electron beam ion trap. From the measurements we infer {minus}39.21 {plus_minus} 0.23 eV for the QED contribution to the 2s{sub 1/2}-2p{sub 3/2} transition energy of lithiumlike U{sup 89+}. A comparison between our measurements and various computations illustrates the need for continued improvements in theoretical approaches for calculating the atomic structure of ions with two or more electrons in the L shell.
Date: November 4, 1994
Creator: Beiersdorfer, P.
Partner: UNT Libraries Government Documents Department

Analysis of gamma-ray spectra from foils activated in a range-thick lead target by 800-MeV protons. Final technical report

Description: Approximately 400 gamma-ray spectra have been analyzed to obtain the types and quantities of radioisotopes produced when 800-MeV protons interact with a range-thick lead target. These spectra were obtained from the radioactive decay of product isotopes in lead disks placed at various depths and radial positions within the target. These spectra were analyzed with the computer code HYPERMET and the photopeak areas were reduced to nuclei produced per incident proton per cubic centimeter of material. Product nuclei ranged from atomic mass 160 to mass 206 and over a range of half lives from a few minutes to several weeks. The results of this analysis have been outlined in this report and transmitted on computer disk to Los Alamos National Laboratory. The consistency of these analyses have been confirmed by a comparison of photopeak areas obtained at LANL with the computer code GAMANAL with those from HYPERMET for two gamma-ray spectra. Also, the nuclear production per proton per cm{sub 3} obtained from these two spectra analyzed both at LANL and at EKU have been found to agree to within the statistical accuracy of the peak-fitting programs. This analysis of these 400 gamma-ray spectra has determined the nuclear production per incident proton per cm{sub 3} at five regularly-spaced radial positions and depths up to 40 cm into a range-thick lead target.
Date: June 12, 1995
Creator: Laird, C.E. & Mullins, D.H.
Partner: UNT Libraries Government Documents Department

A method to improve spectral resolution in planar semiconductor gamma-ray detectors

Description: This paper describes an empirically derived algorithm to compensate for charge trapping in CdTe, CdZnTe, and other planar semiconductor detectors. The method is demonstrated to be an improvement over available systems and application to experimental data is shown.
Date: May 1, 1995
Creator: Keele, B.D.; Addleman, R.S. & Troyer, G.L.
Partner: UNT Libraries Government Documents Department

The {alpha}-induced thick-target {gamma}-ray yield from light elements

Description: The {alpha}-induced thick-target {gamma}-ray yield from light elements has been measured in the energy range 5.6 MeV {le} E{sub {alpha}} {le} 10 MeV. The {gamma}-ray yield for > 2.1 MeV from thick targets of beryllium, boron nitride, sodium fluoride, magnesium, aluminum and silicon were measured using the {alpha}-particle beam from the Lawrence Berkeley Laboratories 88 in. cyclotron. The elemental yields from this experiment were used to construct the {alpha}-induced direct production {gamma}-ray spectrum from materials in the SNO detector, a large volume ultra-low background neutrino detector located in the Creighton mine near Sudbury, Canada. This background source was an order of magnitude lower than predicted by previous calculations. These measurements are in good agreement with theoretical calculations of this spectrum based on a statistical nuclear model of the reaction, with the gross high energy spectrum structure being reproduced to within a factor of two. Detailed comparison of experimental and theoretical excitation population distribution of several residual nuclei indicate the same level of agreement within experimental uncertainties.
Date: October 1994
Creator: Heaton, R. K.
Partner: UNT Libraries Government Documents Department


Description: Sonar and speech techniques have been investigated to improve functionality and enable handheld and other man-portable, mobile, and portal systems to positively detect and identify illicit nuclear materials, with minimal data and with minimal false positives and false negatives. RadSonar isotope detection and identification is an algorithm development project funded by NA-22 and employing the resources of Savannah River National Laboratory and three University Laboratories (JHU-APL, UT-ARL, and UW-APL). Algorithms have been developed that improve the probability of detection and decrease the number of false positives and negatives. Two algorithms have been developed and tested. The first algorithm uses support vector machine (SVM) classifiers to determine the most prevalent nuclide(s) in a spectrum. It then uses a constrained weighted least squares fit to estimate and remove the contribution of these nuclide(s) to the spectrum, iterating classification and fitting until there is nothing of significance left. If any Special Nuclear Materials (SNMs) were detected in this process, a second tier of more stringent classifiers are used to make the final SNM alert decision. The second algorithm is looking at identifying existing feature sets that would be relevant in the radioisotope identification context. The underlying philosophy here is to identify parallels between the physics and/or the structures present in the data for the two applications (speech analysis and gamma spectroscopy). The expectation is that similar approaches may work in both cases. The mel-frequency cepstral representation of spectra is widely used in speech, particularly for two reasons: approximation of the response of the human ear, and simplicity of channel effect separation (in this context, a 'channel' is a method of signal transport that affects the signal, examples being vocal tract shape, room echoes, and microphone response). Measured and simulated gamma-ray spectra from a hand-held Radioisotope Identification Device were used to evaluate the algorithms. ...
Date: June 17, 2010
Creator: Salaymeh, S. & Jeffcoat, R.
Partner: UNT Libraries Government Documents Department

Gamma Spectra Resulting From the Annihilation of Positrons with Electrons in Single, Selected Core Levels of Cu, Ag and Au

Description: The {gamma}-ray energy spectra due to positron annihilation with the 3p core-level of Cu, the 4p core-level of Ag, and 5p core level of Au were obtained separately from the total annihilation spectrum by measuring the energies of {gamma}-rays time coincident with Auger electrons emitted as a result of filling the core-hole left by annihilation. The results of these measurements are compared to the total annihilation spectra and with LDA based theoretical calculations. A comparison of area normalized momentum distributions with the individual cores extracted from the Doppler measurements shows good qualitative agreement, however, in all three spectra, the calculated values of the momentum density appears to fall below the measured values as the momentum increases. The discrepancies between theory and experiment are well outside the statistical uncertainties of the experiment and become more pronounced with increasing Z going down the column from Cu to Ag to Au. The comparison with the experimental results clearly indicates that the calculations are not predicting the correct ratio of high momentum to low momentum spectral weight and suggest the need to improve the treatment of many body electron-positron correlation effects in annihilation as they pertain to core levels.
Date: July 25, 2005
Creator: Kim, S; Eshed, A; Goktepeli, S; Sterne, P A; Koymen, A R; Chen, W C et al.
Partner: UNT Libraries Government Documents Department