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Quick and accurate profile monitor for irradiated fuel. [Gas chambers]

Description: A new instrument has been developed for the rapid measurement of the activity profile of irradiated fuel pins and assemblies. Through prototype examinations it has been shown that the profile shapes agree with the shapes as measured by an intrinsic germanium detector and a Be(..gamma..,n) detector. This new technique can reduce the profile measurement time by more than an order of magnitude over existing measurement times.
Date: January 1, 1979
Creator: Lee, D.M.; Phillips, J.R.; Hsue, S.T.; Kaieda, K.; Halbig, J.K.; Medina, E.G. et al.
Partner: UNT Libraries Government Documents Department

Experience using a spent-fuel measurement system

Description: A portable nondestructive measurement system has been developed and used to measure neutron and gross gamma-ray emission from irradiated BWR and PWR fuel assemblies. The system has two principal components: a water-tight polyethylene detector head containing two sets of ion chambers and fission chambers for measuring opposite sides of the fuel assembly simultaneously, and a battery-powered electronics unit with a microprocessor for performing internal diagnostics and for assisting the operator in collection and analysis of the data. An average of 5-7 min is required to: (1) position the fuel-handling bridge, (2) vertically raise the fuel assembly partially out of the storage rack, (3) perform the measurements, and (4) replace the fuel assembly in the storage rack. The neutron results with proper calibration are used to determine the exposures of individual fuel assemblies with an average accuracy of about 5%. Consistency of operator-declared values for cooling time and exposure can be verified using the gross gamma-ray measurements with an average accuracy of about 10%. Fuel assemblies with unusual irradiation histories or reconstituted fuel pins are easily identified.
Date: January 1, 1983
Creator: Phillips, J.R.; Bosler, G.E.; Halbig, J.K.; Klosterbuer, S.F.; Menlove, H.O. & Rinard, P.M.
Partner: UNT Libraries Government Documents Department

Program and abstracts. [Buffalo, New York, October 17--20, 1978]

Description: This volume contains the program and abstracts of the conference. The following topics are included: metal vapor molecular lasers, magnetohydrodynamics, rare gas halide and nuclear pumped lasers, transfer mechanisms in arcs, kinetic processes in rare gas halide lasers, arcs and flows, XeF kinetics and lasers, fundamental processes in excimer lasers, electrode effects and vacuum arcs, electron and ion transport, ion interactions and mobilities, glow discharges, diagnostics and afterglows, dissociative recombination, electron ionization and excitation, rare gas excimers and group VI lasers, breakdown, novel laser pumping techniques, electrode-related discharge phenomena, photon interactions, attachment, plasma chemistry and infrared lasers, electron scattering, and reactions of excited species. (RWR)
Date: January 1, 1978
Partner: UNT Libraries Government Documents Department

Ames Laboratory quarterly report, October 1, 1987--December 31, 1987

Description: This report contains papers on the following topics: laser induced luminescence and multiphoton ionization in gaseous and low temperature matrices; fundamental studies of chemical carcinogenesis by fluorescence line narrowing spectroscopy; analytical applications of supersonic jet spectroscopy; measurement of toxic compounds and metabolites present in environmental and biological samples; and quantitation in electrophoresis based on lasers.
Date: February 1, 1988
Partner: UNT Libraries Government Documents Department

Collisions of fast multicharged ions in gas targets: charge transfer and ionization

Description: Measurements of cross sections for charge transfer and ionization of H/sub 2/ and rare-gas targets have been made with fast, highly stripped projectiles in charge states as high as 59+. We have found an empirical scaling rule for electron-capture cross section in H/sub 2/ valid at energies above 275 keV/amu. Similar scaling might exist for other target gases. Cross sections are generally in good agreement with theory. We have found a scaling rule for electron loss from H in collisions with a fast highly stripped projectile, based on Olson's classical-trajectory Monte-Carlo calculations, and confirmed by measurements in an H/sub 2/ target. We have found a similar scaling rule for net ionization of rare-gas targets, based on Olson's CTMC calculations and the independent-electron model. Measurements are essentially consistent with the scaled cross sections. Calculations and measurements of recoil-ion charge-state spectra show large cross sections for the production of highly charged slow recoil ions.
Date: May 1, 1981
Creator: Schlachter, A.S.
Partner: UNT Libraries Government Documents Department

Inner-shell photoemission from atoms and molecules using synchrotron radiation

Description: Photoelectron spectroscopy, in conjunction with synchrotron radiation, has been used to study inner-shell photoemission from atoms and molecules. The time structure of the synchrotron radiation permits the measurements of time-of-flight (TOF) spectra of Auger and photoelectrons, thereby increasing the electron collection efficiency. The double-angle TOF method yielded angle-resolved photoelectron intensities, which were used to determine photoionization cross sections and photoelectron angular distributions in several cases. Comparison to theoretical calculations has been made where possible to help explain observed phenomena in terms of the electronic structure and photoionization dynamics of the systems studied. 154 references, 23 figures, 7 tables.
Date: December 1, 1983
Creator: Lindle, D.W.
Partner: UNT Libraries Government Documents Department

Auger decay mechanism in photon-stimulated desorption of ions from surfaces

Description: Photon-stimulated desorption (PSD) of positive ions was studied with synchrotron radiation using an angle-integrating time-of-flight mass spectrometer. Ion yields as functions of photon energy near core levels were measured from condensed gases, alkali fluorides, and other alkali and alkaline earth halides. These results are compared to bulk photoabsorption measurements with emphasis on understanding fundamental desorption mechanisms. The applicability of the Auger decay mechanism, in which ion desorption is strictly proportional to surface absorption, is discussed in detail. The Auger decay model is developed in detail to describe Na/sup +/ and F/sup +/ desorption from NaF following Na(1s) excitation. The major decay pathways of the Na(1s) hole leading to desorption are described and equations for the energetics of ion desorption are developed. Ion desorption spectra of H/sup +/, Li/sup +/, and F/sup +/ are compared to bulk photoabsorption near the F(2s) and Li(1s) edges of LiF. A strong photon beam exposure dependence of ion yields from alkali fluorides is revealed, which may indicate the predominance of metal ion desorption from defect sites. The large role of indirect mechanisms in ion desorption condensed N/sub 2/-O/sub 2/ multilayers is demonstrated and discussed. Ion desorption spectra from several alkali halides and alkaline earth halides are compared to bulk photoabsorption spectra. Relative ion yields from BaF/sub 2/ and a series of alkali halides are discussed in terms of desorption mechanisms.
Date: November 1, 1983
Creator: Parks, C.C.
Partner: UNT Libraries Government Documents Department

Atomic photoelectron-spectroscopy studies using synchrotron radiation

Description: Photoelectron spectroscopy combined with tunable synchrotron radiation has been used to study the photoionization process in several atomic systems. The time structure of the synchrotron radiation source at the Stanford Synchrotron Radiation Laboratory (SSRL) was used to record time-of-flight (TOF) photoelectron spectra of gaseous Cd, Hg, Ne, Ar, Ba, and Mn. The use of two TOF analyzers made possible the measurement of photoelectron angular distributions as well as branching ratios and partial cross sections.
Date: February 1, 1983
Creator: Kobrin, P.H.
Partner: UNT Libraries Government Documents Department

Plasma injection and atomic physics models for use in particle simulation codes

Description: Models of plasma injection (creation) and charged/neutral atomic physics which are suitable for incorporation into particle simulation codes are described. Both planar and distributed source injection models are considered. Results obtained from planar injection into a collisionless plasma-sheath region are presented. The atomic physics package simulates the charge exchange and impact ionization interactions which occur between charged particles and neutral atoms in a partially-ionized plasma. These models are applicable to a wide range of problems, from plasma processing of materials to transport in the edge region of a tokamak plasma. 18 refs., 6 figs.
Date: June 12, 1991
Creator: Procassini, R.J. (Lawrence Livermore National Lab., CA (USA) California Univ., Berkeley, CA (USA). Electronics Research Lab.)
Partner: UNT Libraries Government Documents Department

Two-electron excitation in slow ion-atom collisions: Excitation mechanisms and interferences among autoionizing states

Description: The two-electron capture or excitation process resulting from collisions of H{sup +} and O{sup 6+} ions with He atoms in the energy range from 0.5 keV/amu to 5 keV/amu is studied within a molecular representation. The collision dynamics for formation of doubly excited O{sup 4+} ions and He** atoms and their (n{ell}, n{prime}{ell}{prime}) populations are analyzed in conjunction with electron correlations. Autoionizing states thus formed decay through the Auger process. An experimental study of an ejected electron energy spectrum shows ample structures in addition to two characteristic peaks that are identified by atomic and molecular autoionizations. These structures are attributable to various interferences among electronic states and trajectories. We examine the dominant sources of the interferences. 12 refs., 5 figs.
Date: January 1, 1990
Creator: Kimura, M. (Argonne National Lab., IL (USA) Rice Univ., Houston, TX (USA). Dept. of Physics)
Partner: UNT Libraries Government Documents Department

Calibration and characterization of Bayard-Alpert gauges operating in high magnetic fields. Revision 1

Description: Information is presented on the calibration and characterization of Bayard-Alpert gages in operation within high magnetic fields. Standard Bayard-Alpert commercial gages were used, and were unshielded from the local TMX-U magnetic field and were housed in stainless-steel cyclinders. (JDB)
Date: January 1, 1986
Creator: Pickles, W.L. & Hunt, A.L.
Partner: UNT Libraries Government Documents Department

Studies of photoionization processes from ground-state and excited-state atoms and molecules

Description: Recent triply-differential photoelectron spectroscopy experiments designed for the study of correlation effects in atoms and molecules are described. Final-state symmetry of the n=2 state of helium has been determined. The non-Franck-Condon behavior of vibrational branching ratios and large variations of the angular asymmetry parameter has been observed for shape resonances and autoionizing resonances in CO and other molecules. Recent observations of the photoionization of excited sodium atoms are also described.
Date: January 1, 1982
Creator: Ederer, D.L.; Parr, A.C. & West, J.B.
Partner: UNT Libraries Government Documents Department

Autoionization spectra of He excited by fast (MeV) H/sup +/, He/sup +/, and Li/sup n+/ (n = 1,2,3) ions

Description: Autoionization spectra of He following excitation by 1 to 3 MeV H/sup +/, He/sup +/, and Li/sup n+/ (n = 1,2,3) have been measured as a function of observation angle. The (2p/sup 2/)/sup 1/D and (2s2p)/sup 1/P resonances have been examined and a strong dependence on projectile velocities, charge state and observation angle was found.
Date: January 1, 1983
Creator: Schneider, D.; Arcuni, P.; Bruch, P. & Stoeffler, W.
Partner: UNT Libraries Government Documents Department

Environmental Research Division: fundamental molecular physics and chemistry. Annual report, January-December 1983. Part I

Description: Research progress is reported in the following areas: (1) photoionization of radicals or excited states; (2) molecular spectroscopy by resonant multiphoton ionization; (3) studies conducted with the synchrotron radiation facility at the National Bureau of Standards; (4) theoretical studies on molecular photoabsorption; (5) analysis of photoabsorption spectra of open-shell atoms; (6) the electron energy-loss spectra of molecules; and (7) cross sections and stopping powers. Items have been individually abstracted for the data base. (ACR)
Date: March 1, 1985
Partner: UNT Libraries Government Documents Department

Mayer-Fermi theory and the long sequences in the periodic table

Description: Changes in the radial wave functions for d electrons which occur preceding the onset of the transition series of elements and for f electrons preceding the onset of the lanthanide and actinide series are examined. The sensitivity of the radial wave functions to variations in the effective potential is discussed, and the large variation in the radial wave functions between the LS terms of certain types of excited configurations in these regions of the periodic system is analyzed. Several examples of electron-impact ionization are explained by analyzing the effective potentials for the excited electrons in the intermediate autoionizing states. 46 refs., 18 figs. (WRF)
Date: January 1, 1986
Creator: Griffin, D.C.; Cowan, R.D. & Pindzola, M.S.
Partner: UNT Libraries Government Documents Department

Real-time measurement of plutonium in air by direct-inlet surface ionization mass spectrometry. Status report

Description: A new technique is being developed for monitoring low-level airborne plutonium on a real-time basis. The technique is based on surface ionization mass spectrometry of airborne particles. It will be capable of measuring plutonium concentrations below the maximum permissible concentration (MPC) level. A complete mass spectrometer was designed and constructed for this purpose. Major components which were developed and made operational for the instrument include an efficient inlet for directly sampling particles in air, a wide dynamic range ion detector and a minicomputer-based ion-burst measurement system. Calibration of the direct-inlet mass spectrometer (DIMS) was initiated to establish the instrument's response to plutonium dioxide as a function of concentration and particle size. This work revealed an important problem - bouncing of particles upon impact with the ionizing filament. Particle bounce results in a significant loss of measurement sensitivity. The feasibility of using an oven ionizer to overcome the particle bounce problem has been demonstrated. A rhenium oven ionizer was designed and constructed for the purpose of trapping particles which enter via the direct inlet. High-speed particles were trapped in the oven yielding a measurement sensitivity comparable to that for particles which are preloaded. Development of the Pu DIMS can now be completed by optimizing the oven design and calibrating the instrument's performance with UO/sub 2/ and CeO/sub 2/ particles as analogs to PuO/sub 2/ particles.
Date: April 1, 1980
Creator: Stoffels, J.J.
Partner: UNT Libraries Government Documents Department

Sampling and analysis of suspended particles and vapors by continuum source particle beams

Description: Two continuum source particle beam methods are proposed for the on-line measurement of suspended particles or material which is suspendable in a gas. The first method can be used to size separate the various molecular and particulate species present in the beam. The second method is used to obtain a molecular composition analysis of individual beam particles or a composition distribution for a sample containing a large number of particles. The two methods are complementary and can be used together to obtain molecular composition analyses of size-separated beam particles.
Date: January 1, 1979
Creator: Dahneke, B.
Partner: UNT Libraries Government Documents Department

Mechanism of the optogalvanic effect in a hollow-cathode discharge

Description: There are two significantly different mechanisms proposed for the origin of the optogalvanic effect in a hollow-cathode discharge: (1) laser excitation of atoms to higher electronic states leads to an increased cross section for electron impact ionization, with the result that the excited atom becomes ionized and the conductivity of the discharge increases; and (2) laser excitation of atoms to higher electronic states perturbs the equilibrium established between the electron temperature and the atomic excitation temperature. Superelastic collisions between the electrons and the laser-excited atoms restore the equilibrium, with the excess energy ending up in an increased electron temperature and therefore an increased conductivity of the discharge. Both mechanisms undoubtedly proceed simultaneously and what needs to be determined is their relative importance at different discharge conditions and different excitation conditions. This is important because laser isotope enrichment schemes have been proposed using selective excitation in a hollow-cathode discharge. In order for these schemes to work, (1) must be the predominant mechanism. We have measured the optogalvanic signal, concentration of uranium atoms, impedance of the discharge, and electron temperature as a function of the discharge current in a neon-filled uranium hollow-cathode discharge. The hollow cathode operating characteristics are used as input parameters in a simple discharge model. Predictions of electron density, changes in electron temperature, and discharge impedance compare well with experimental observations. Our model and experimental observations yield a qualitative understanding of the optogalvanic effect in a hollow-cathode discharge and estimate the relative importance of the two optogalvanic mechanisms.
Date: June 17, 1983
Creator: Keller, R.A.; Warner, B.E.; Zalewski, E.F.; Dyer, P.; Engleman, R. Jr. & Palmer, B.A.
Partner: UNT Libraries Government Documents Department

Workshop report on new directions in soft x-ray photoabsorption

Description: The Workshop Report integrates what was said at the Workshop on New Directions in Soft X-Ray Photoabsorption, which focused on the region from 100 eV to 10 keV. The report clarifies the current state of theory and experiment and identifies the opportunities which new theoretical methods and experimental facilities could be expected to provide. The understanding of photoabsorption (which requires experimental photoabsorption cross section data) is a key to understanding the properties and behavior of atoms, molecules and solids. The Workshop participants were forty-three physicists and quantum chemists, from twenty-four institutions in four countries, all interested in photoabsorption from different perspectives.
Date: September 17, 1984
Creator: Bartlett, R.; Del Grande, N.K.; Lindau, I.; Manson, S.; Merts, A.L. & Pratt, R.
Partner: UNT Libraries Government Documents Department

Comparison of the response of a NaI scintillation crystal with a pressurized ionization chamber as a function of altitude, radiation level and Ra-226 concentration

Description: The Grand Junction Uranium Mill Tailings Remedial Action-Radiological Survey Activities Group (UMTRA-RASA) program employs a screening method in which external exposure rates are used to determine if a property contaminated with uranium mill tailings is eligible for remedial action. Portable NaI detectors are used by survey technicians to locate contaminated areas and determine exposure rates. The exposure rate is calculated using a regression equation derived from paired measurements made with a pressurized ionization chamber (PIC) and a NaI detector. During July of 1985 extensive measurements were taken using a PIC and a NaI scintillator with both analogue and digital readout for a wide range of exposure rates and at a variety of elevations. The surface soil was sampled at most of these locations and analyzed for /sup 226/Ra. The response of the NaI detectors was shown to be highly correlated to radiation level but not to /sup 226/Ra concentration or elevation.
Date: January 1, 1986
Creator: Provencher, R.; Smith, G.; Borak, T.B. & Kearney, P.
Partner: UNT Libraries Government Documents Department

Experiments in atomic and applied physics using synchrotron radiation

Description: A diverse program in atomic and applied physics using x rays produced at the X-26 beam line at the Brookhaven National Synchrotron Light Source is in progress. The atomic physics program studies the properties of multiply-ionized atoms using the x rays for photo-excitation and ionization of neutral atoms and ion beams. The applied physics program builds on the techniques and results of the atomic physics work to develop new analytical techniques for elemental and chemical characterization of materials. The results are then used for a general experimental program in biomedical sciences, geo- and cosmochemistry, and materials sciences. The present status of the program is illustrated by describing selected experiments. Prospects for development of new experimental capabilities are discussed in terms of a heavy ion storage ring for atomic physics experiments and the feasibility of photoelectron microscopy for high spatial resolution analytical work. 21 refs., 11 figs., 2 tabs.
Date: January 1, 1987
Creator: Jones, K.W.
Partner: UNT Libraries Government Documents Department

Experiments with a synchrotron x-ray source and conventional, ECR, and storage-ring ion sources

Description: The present intensities of photon beams produced by synchrotron-radiation x-ray sources and of ion beams from conventional ion sources, electron-cyclotron resonance ion sources (ECRIS), and cooled heavy-ion storage rings (CHISR) make possible investigations of photoionization and photoexcitation processes that have not previously been feasible. An evaluation of the signal and background rates for experiments that employ the different types of ion sources is given here. 11 refs., 3 figs., 6 tabs.
Date: January 1, 1988
Creator: Jones, K.W.; Johnson, B.M. & Meron, M.
Partner: UNT Libraries Government Documents Department

Laser photodetachment spectra of C/sub 6/F/sub 6//sup -/ in nonpolar liquids

Description: Aromatic anions absorb in the visible region of the spectrum and energetic considerations suggest that in solution photodetachment may be an important process at these wavelengths. This study reports electron photodetachment cross sections for C/sub 6/F/sub 6//sup -/ for wavelengths between 415 and 700 nm. The anion is generated by electron attachment to solute C/sub 6/F/sub 6/ during an x-ray pulse. Detachment is observed as a change in conductivity induced by a subsequent light pulse from a tunable dye laser. The threshold values are reported for tetramethylsilane, n-butane, cyclopentane, n-pentane, 2,2,4-trimethylpentane, 2,2 dimethylbutane, and neopentane. The thresholds are consistent with an electron affinity of 1.09 +- 0.04 eV for the C/sub 6/F/sub 6/ molecule. Comparison of the data to the absorption spectrum of C/sub 6/F/sub 6//sup -/ shows that for photon energies above threshold the major process is photodetachment. The relationship of photodetachment data to other properties of the excess electrons in these solvents are discussed.
Date: January 1, 1979
Creator: Sowada, U. & Holroyd, R.A.
Partner: UNT Libraries Government Documents Department

A neutral-beam diagnostic for fast confined alpha particles in a burning plasma: Application on CIT (Compact Ignition Tokamak)

Description: Diagnostic methods for fast confined alpha particles are essential for a burning-plasma experiment. We review one- and two-electron-capture methods using energetic neutral beams, and provide quantitative estimates of signal level for a two-electron-capture method applicable to CIT. The best probe is a ground-state helium-atom beam because of its relatively good penetration into a CIT plasma and the large cross section for two-electron capture; it can be produced in useful quantities from HeH/sup +/. We calculate a signal level of the order of 10/sup 7/ counts/s for 100 mA of accelerated HeH/sup +/, which is sufficient to allow time-resolved measurements of the alpha-particle velocity distribution. Limited position information could be obtained for appropriate access port geometry. This diagnostic is feasible, and we recommend further research and development leading to implementation on CIT. 39 refs., 16 figs., 5 tabs.
Date: October 1, 1987
Creator: Schlachter, A.S.; Stearns, J.W. & Cooper, W.S.
Partner: UNT Libraries Government Documents Department