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Formation of inner-shell autoionizing CO+ states below the CO++ threshold

Description: We report a kinematically complete experiment on the production of CO{sup +} autoionizing states following photoionization of carbon monoxide below its vertical double ionization threshold. Momentum imaging spectroscopy is used to measure the energies and body-frame angular distributions of both photo- and autoionization electrons, as well as the kinetic energy release (KER) of the atomic ions. This data, in combination with ab initio theoretical calculations, provides insight into the nature of the cation states produced and their subsequent dissociation into autoionizing atomic (O*) fragments.
Date: December 27, 2009
Creator: Osipov, Timur; Weber, Thorsten; Rescigno, Thomas N; Lee, Sun; Orel, Ann; Schoffler, Markus et al.
Partner: UNT Libraries Government Documents Department

Production of negative hydrogen and deuterium ions in microwave-driven ion sources.

Description: The authors report progress they have made in the production of negative hydrogen and deuterium atomic ions in magnetically-confined microwave-driven (2.45 GHz) ion sources. The influence of source surface material, microwave power, source gas pressure and magnetic field configuration on the resulting ion current is discussed. Results strongly suggest that, at least in the source, vibrationally excited molecular hydrogen, the precursor to atomic negative ion production, is produced via a surface mechanism suggested by Hall et al. rather than via a gas phase reaction as is generally believed to be the case in most ion sources.
Date: September 11, 1998
Creator: Spence, D.
Partner: UNT Libraries Government Documents Department

Determination of Optimum Conditions for Distinguishing the Pulse Height Distributions of Atomic and Polyatomic Ions

Description: This work explored the use of pulse height distributions (PHD) from multiplier-type detectors as a means of detecting and eliminating the effects of polyatomic interferences in secondary ion mass spectrometry (SIMS). We explored the behavior of PHD for {sup 235}U{sup +}, {sup 208}Pb{sup 27}Al{sup +} and {sup 207}Pb{sup 28}Si{sup +}, all with a nominal mass-to-charge ratio of 235. In every case, the distribution for the atomic ion ({sup 235}U{sup +}) was clearly shifted relative to the distributions for {sup 208}Pb{sup 27}Al{sup +} and {sup 207}Pb{sup 28}Si{sup +}. When the first surface of the detector is metallic in character, the polyatomic ions are shifted to larger pulse heights relative to the atomic ion. When the first surface of the detector is oxide in character, the atomic ion is shifted to larger pulse heights relative to the polyatomic ions. The relative positioning appear to be stable for a given detector over time at the same secondary ion impact energy. Consequently, it appears to be feasible to use PHD data to detect interfering polyatomic ions and eliminate their deleterious effects using peak deconvolution techniques. Consequently, the updated Ultrafast RAE detector will be designed to make the pulse height information available to the data acquisition system.
Date: December 12, 2006
Creator: Kristo, M J
Partner: UNT Libraries Government Documents Department

Investigating ion-surface collisions with a niobium superconducting tunnel junction detector in a time-of-flight mass spectrometer

Description: The performance of an energy sensitive, niobium superconducting tunnel junction detector is investigated by measuring the pulse height produced by impacting molecular and atomic ions at different kinetic energies. Ions are produced by laser resorption and matrix-assisted laser desorption in a time-of-flight mass spectrometer. Results show that the STJ detector pulse height decreases for increasing molecular ion mass, passes through a minimum at around 2000 Da, and the increases with increasing mass of molecular ions above 2000Da. The detector does not show a decline in sensitivity for high mass ions as is observed with microchannel plate ion detectors. These detector plus height measurements are discussed in terms of several physical mechanisms involved in an ion-surface collision.
Date: December 1, 1999
Creator: Westmacott, G.; Zhong, F.; Frank, M.; Friedrich, S.; Labov, S. & Benner, W.H.
Partner: UNT Libraries Government Documents Department

A low-energy linear oxygen plasma source

Description: A new version of a Constricted Plasma Source is described,characterized by all metal-ceramic construction, a linear slit exit of180 mm length, and cw-operation (typically 50 kHz) at an average power of1.5 kW. The plasma source is here operated with oxygen gas, producingstreaming plasma that contains mainly positive molecular and atomic ions,and to a much lesser degree, negative ions. The maximum total ion currentobtained was about 0.5 A. The fraction of atomic ions reached more than10 percent of all ions when the flow rate was less then 10 sccm O2,corresponding to a chamber pressure of about 0.5 Pa for the selectedpumping speed. The energy distribution functions of the different ionspecies were measured with a combinedmass spectrometer and energyanalyzer. The time-averaged distribution functions were broad and rangedfrom about 30eV to 90 eV at 200 kHz and higher frequencies, while theywere only several eV broad at 50 kHz and lower frequencies, with themaximum located at about 40 eV for the grounded anode case. This maximumwas shifted down to about 7 eV when the anode was floating, indicatingthe important role of the plasma potential for the ion energy for a givensubstrate potential. The source could be scaled to greater length and maybe useful for functionalization of surfaces and plasma-assisteddeposition of compound films.
Date: January 8, 2007
Creator: Anders, Andre & Yushkov, Georgy Yu.
Partner: UNT Libraries Government Documents Department

Compact neutron generator developement and applications

Description: The Plasma and Ion Source Technology Group at the Lawrence Berkeley National Laboratory has been engaging in the development of high yield compact neutron generators for the last ten years. Because neutrons in these generators are formed by using either D-D, T-T or D-T fusion reaction, one can produce either mono-energetic (2.4 MeV or 14 MeV) or white neutrons. All the neutron generators being developed by our group utilize 13.5 MHz RF induction discharge to produce a pure deuterium or a mixture of deuterium-tritium plasma. As a result, ion beams with high current density and almost pure atomic ions can be extracted from the plasma source. The ion beams are accelerated to {approx}100 keV and neutrons are produced when the beams impinge on a titanium target. Neutron generators with different configurations and sizes have been designed and tested at LBNL. Their applications include neutron activation analysis, oil-well logging, boron neutron capture therapy, brachytherapy, cargo and luggage screening. A novel small point neutron source has recently been developed for radiography application. The source size can be 2 mm or less, making it possible to examine objects with sharper images. The performance of these neutron generators will be described in this paper.
Date: January 18, 2004
Creator: Leung, Ka-Ngo; Reijonen, Jani; Gicquel, Frederic; Hahto, Sami & Lou, Tak-Pui
Partner: UNT Libraries Government Documents Department

Investigations into the origins of polyatomic ions in inductively coupled plasma-mass spectrometry

Description: An inductively coupled plasma-mass spectrometer (ICP-MS) is an elemental analytical instrument capable of determining nearly all elements in the periodic table at limits of detection in the parts per quadrillion and with a linear analytical range over 8-10 orders of magnitude. Three concentric quartz tubes make up the plasma torch. Argon gas is spiraled through the outer tube and generates the plasma powered by a looped load coil operating at 27.1 or 40.6 MHz. The argon flow of the middle channel is used to keep the plasma above the innermost tube through which solid or aqueous sample is carried in a third argon stream. A sample is progressively desolvated, atomized and ionized. The torch is operated at atmospheric pressure. To reach the reduced pressures of mass spectrometers, ions are extracted through a series of two, approximately one millimeter wide, circular apertures set in water cooled metal cones. The space between the cones is evacuated to approximately one torr. The space behind the second cone is pumped down to, or near to, the pressure needed for the mass spectrometer (MS). The first cone, called the sampler, is placed directly in the plasma plume and its position is adjusted to the point where atomic ions are most abundant. The hot plasma gas expands through the sampler orifice and in this expansion is placed the second cone, called the skimmer. After the skimmer traditional MS designs are employed, i.e. quadrupoles, magnetic sectors, time-of-flight. ICP-MS is the leading trace element analysis technique. One of its weaknesses are polyatomic ions. This dissertation has added to the fundamental understanding of some of these polyatomic ions, their origins and behavior. Although mainly continuing the work of others, certain novel approaches have been introduced here. Chapter 2 includes the first reported efforts to include high temperature corrections to ...
Date: January 1, 2010
Creator: McIntyre, Sally M.
Partner: UNT Libraries Government Documents Department

First PGAA and NAA experimental results from a compact high intensity D-D neutron generator

Description: Various types of neutron generator systems have been designed and tested at the Plasma and Ion Source Technology Group at Lawrence Berkeley National Laboratory. These generators are based on a D-D fusion reaction. These high power D-D neutron generators can provide neutron fluxes in excess of the current state of the art D-T neutron generators, without the use of pre-loaded targets or radioactive tritium gas. Safe and reliable long-life operations are the typical features of these D-D generators. All of the neutron generators developed in the Plasma and Ion Source Technology Group are utilizing powerful RF-induction discharge to generate the deuterium plasma. One of the advantages of using the RF-induction discharge is it's ability to generate high fraction of atomic ions from molecular gases, and the ability to generate high plasma densities for high extractable ion current from relatively small discharge volume.
Date: May 13, 2003
Creator: Reijonen, J.; Leung, K.-N.; Firestone, R.B.; English, J.A.; Perry, D.L.; Smith, A. et al.
Partner: UNT Libraries Government Documents Department

Systems/cost summary

Description: The purpose of the meeting was to discuss and develop cost-estimating methods for heavy-ion fusion accelerator systems. The group did not consider that its purpose was to make technical judgements on proposed systems, but to develop methods for making reasonable cost estimates of these systems. Such estimates will, it is hoped, provide material for systems studies, will help in guiding research and development efforts by identifying ''high-leverage'' subsystems (areas that account for a significant part of total system cost and that might be reduced in cost by further technical development) and to begin to provide data to aid in an eventual decision on the optimum type of accelerator for heavy-ion fusion.
Date: January 1, 1977
Creator: Grand, P.; Danby, G.; Keane, J.; Spiro, J.; Sutter, D.; Cole, F. et al.
Partner: UNT Libraries Government Documents Department

Heavy ion fusion half-year report, October 1, 1979-March 31, 1980

Description: Major elements of the program in the first half of Fiscal Year 1980 included: (1) characterization of the 1 amp, 1 MV, 2 ..mu..s beam after acceleration through one pulsed drift tube; (2) observation of current and energy spikes at the onset of the beam pulse occasioned by the unusually long transit-time (approx. 1 ..mu..sec) of the mass 133 ions across the diode gap; (3) completion of the full system, comprising of source and three drift-tubes, in February 1980; (4) development of new beam diagnostic probes for high-intensity ion beams; and (5) a major re-direction of the design effort on the Induction Linac Test Bed to bring costs, based on R/D funds that include overhead, down from the 40 million system (described in LBL PUB-5031) to the canonical 25 million.
Date: March 1, 1980
Partner: UNT Libraries Government Documents Department

Transmission electron microscope studies of laser and thermally annealed ion implanted silicon

Description: Transmission electron microscopy has been used to study the effects of high power laser pulses on boron, phosphorous and arsenic implanted (100) silicon crystals. No defects (dislocations, dislocation loops and/or stacking faults) were observed in either as-grown or implanted silicon after one pulse of ruby laser irradiation (lambda = 0.694 ..mu..m, pulse energy density 1.5 to 1.8 J cm/sup -2/, 50 x 10/sup -9/ pulse duration time). The concentration of boron in solution, as inferred from electrical measurements, could exceed the equilibrium solubility. In thermally annealed specimens, on the other hand, significant damage remained even after annealing at 1100/sup 0/C for 30 minutes. On thermally annealing the implanted, laser-treated specimens, precipitation of the implanted boron ions occurred whenever the implanted doses were in excess of the equilibrium solubility limits. The relationship of these observations to the results of electrical measurements made on these samples will be discussed.
Date: January 1, 1978
Creator: Narayan, J; Young, R T & White, C W
Partner: UNT Libraries Government Documents Department

Scattering of suprathermal ions by partially ionized impurities

Description: The pitch-angle scattering of suprathermal ions by partially ionized impurities in laboratory fusion-oriented plasmas is treated using the Thomas--Fermi statistical model for the charge density of the electron cloud and the impulse approximation for the angular deviation resulting from a collision. An analytic approximation to the exact Thomas--Fermi potential for an ion of arbitrary ionization is found and used to calculate the addition required to the classical ln..lambda.. for 10 to 90% ionized impurities and incident energies in the range (10/sup -2/ to 10/sup 3/) keV x Z/sub n//sup 4/3/ where Z/sub n/ is the nuclear charge of the impurity. The correction can be comparable in magnitude to the classical result, e.g., for 40 keV protons incident on 30 times ionized tungsten ions the addition to ln..lambda.. is approximately 6.
Date: January 1, 1979
Creator: Andrews, P.L. & Goldston, R.J.
Partner: UNT Libraries Government Documents Department

Emission coefficient for a singly ionized uranium plasma: experimental and theoretical treatment

Description: Absolute emission coefficient measurements on arc-generated singly ionized uranium (UII) in local thermodynamic equilibrium are described for a wavelength bandwidth of 1050 to 6000 A. Plasma temperature and uranium partial pressure at the arc centerline were approximately 8000/sup 0/K and 0.01 atm, respectively. The arc emission data compare favorably with experimental results obtained from UF/sub 6/ discharges, once allowance is made for the effects of cold-layer UF/sub 6/ photoabsorption on uranium plasma emission. Observed variation in the emission coefficient is well correlated with a composite of calculated oscillator-strength distribution for selected UII and UIII transition arrays. The theoretical treatment is based on a modified Hartree--Fock method for calculating the appropriate radial wave functions. Slater--Condon theory provides a detailed calculation of energy-level structures for both the upper and lower configuration of each transition array computed. However, the number of terms were truncated, when necessary, to accommodate size limitations of the matrices involved. With this theoretical approach, predictions are also offered as to the location of strong emission features for a hypothetical plasma dominated by doubly and triply ionized uranium. It is suggested that the capability now exists to predict successfully the location of major emission features of uranium and other complex systems for a substantial range of ionization stages.
Date: January 1, 1978
Creator: Mack, J.M. & Radziemski, L.J.
Partner: UNT Libraries Government Documents Department

Simulation of multispecies impurity transport in tokamaks

Description: To simulate multispecies impurity transport in tokamaks, a set of coupled continuity equations including source and sink terms from atomic processes (rate terms) were solved numerically. The diffusion and rate terms are integrated separately in time using a fractional step-splitting technique which is accurate to second order in the time step. Calculations were performed treating individually all the ionization stages of oxygen and iron impurities in a hydrogen plasma. Calculated O VI and O VII relative density profiles agree qualitatively with profiles measured in the Adiabatic Toroidal Compressor (ATC) tokamak when purely neoclassical diffusion coefficients are used.
Date: June 1, 1978
Creator: Amano, T. & Crume, E.C.
Partner: UNT Libraries Government Documents Department

Observed magnetic dipole transitions in the ground terms of Ti XIV, Ti XV, and Ti XVII

Description: Four observed spectrum lines in titanium-containing tokamak discharges have been identified as follows: TiXIV 2s/sup 2/2p/sup 5/ /sup 2/P/sub 1/2/ ..-->.. /sup 2/P/sub 3/2/ at 2115.3 A, TiXV 2s/sup 2/2p/sup 4/ 3P/sub 1/ ..-->.. /sup 3/P/sub 2/ at 2544.8 A, TiXVII 2s/sup 2/2p/sup 2/ /sup 3/P/sub 2/ ..-->.. /sup 3/P/sub 1/ at 3834.4 A and /sup 3/P/sub 1/ ..-->.. /sup 3/P/sub 0/ at 3371.5 A. The identifications are based on observed time behavior and correlation with intensities of resonance lines of other titanium ions, and on general agreement with predicted wavelengths and intensities.
Date: September 1, 1979
Creator: Suckewer, S.; Fonck, R. & Hinnov, E.
Partner: UNT Libraries Government Documents Department

Dielectronic satellite spectrum of helium-like iron (Fe XXV)

Description: Dielectronic satellite spectra of Fe XXV near 1.8500 A have been observed from PLT (Princeton Large Torus) tokamak plasma discharges for electron temperatures in the range from 1.5 to 3 keV and an electron density of 2 x 10/sup 13/ cm/sup -3/. The electron temperature was independently determined from the electron cyclotron radiation emitted by the plasma. The quality of the spectra allows a detailed comparison with theoretical prediction, which is of importance in view of diagnostic applications.
Date: April 1, 1979
Creator: Bitter, M.; Hill, K.W.; Sauthoff, N.R.; Efthimion, P.C.; Meservey, E.; Roney, W. et al.
Partner: UNT Libraries Government Documents Department

Lattice location of implanted As and Sb in silicon after pulsed laser annealing

Description: The substitutional fractions for As and Sb implanted into silicon and subjected to pulsed laser annealing have been determined using ion channeling techniques. Substitutional fractions of 98 to 99% are achieved by laser annealing for both of these dopants at doses up to approximately 1.4 x 10/sup 16//cm/sup 2/. Channeling results are also presented showing the effect of different laser energy densities on the removal of lattice damage and the incorporation of As into substitutional lattice sites.
Date: August 1, 1978
Creator: White, C.W.; Pronko, P.P.; Appleton, B.R. & Wilson, S.R.
Partner: UNT Libraries Government Documents Department

Stability diagrams for fourfold coordination of polyvalent metal ions in molten mixtures of halide salts

Description: The stability of local fourfold coordination for divalent and trivalent metal ions in liquid mixtures of polyvalent metal halides and alkali halides is classified by means of structural coordinates obtained from properties of the elements. In parallel with earlier classifications of compound crystal structures and molecular shapes, the elemental properties are taken from first-principles calculations of valence electron orbitals in atoms, in the form of (i) the nodal radii of Andreoni, Baldereschi and Guizzetti or (ii) the pseudopotential radii or Zunger and Cohen. As a third alternative a classification based on Pettifor's phenomenological chemical scale of the elements is also considered. The alternative structural classification schemes that are developed from these elemental properties are generally successfully in distinguishing molten mixtures in which the available experimental evidence indicates long-lived fourfold coordination of polyvalent metal ions. In addition, Pettifor's chemical scale scheme is useful in sorting out finer details of local coordination in the liquid state. 3 figs., 71 refs.
Date: November 1, 1988
Creator: Akdeniz, Z. (International Centre for Theoretical Physics, Trieste (Italy) Istanbul Univ. (Turkey). Dept. of Physics) & Tosi, M.P. (Trieste Univ. (Italy). Dipt. di Fisica Teorica Argonne National Lab., IL (USA))
Partner: UNT Libraries Government Documents Department

2s 2p /sup 3/P/sub 1//sup 0/. -->. 2s/sup 2/ /sup 1/S/sub 0/ intercombination line in beryllium-like krypton, molybdenum and tungsten

Description: Transition probabilities are evaluated for the 2s 2p /sup 3/P/sub 1//sup 0/ ..-->.. 2s/sup 2/ /sup 1/S/sub 0/ transition in beryllium-like ions for krypton, molybdenum and tungsten, using configuration-interaction wavefunctions. The importance of the 2s 3p /sup 1/P/sub 1//sup 0/ configuration is considered.
Date: January 1, 1979
Creator: Glass, R
Partner: UNT Libraries Government Documents Department

Oscillator strengths and transition probabilities for the intercombination transitions in Fe XXII

Description: Oscillator strengths and transition probabilities are evaluated for the intercombination transitions between the 2s/sup 2/ 2p, 2s 2p/sup 2/ and 2p/sup 3/ states of Fe XXII using configuration interaction wavefunctions. The fine-structure splittings have also been calculated. Some significant differences with previous calculations are obtained.
Date: January 1, 1979
Creator: Glass, R
Partner: UNT Libraries Government Documents Department

500 kV mercury accelerator

Description: The objective of building a low-cost pre-accelerator for low energy heavy ion particle accelerator was realized by using standard, readily available material and hardware. Some savings were obtained in the construction of the dome by avoiding welding, expensive metal spinnings and unnecessary corona rings. Larger monetary economies were realized by unique approach to building the high voltage column utilizing a glass tube.
Date: January 1, 1979
Creator: Brodowski, J.; Maschke, A.W.; Mobley, R.M.; Keane, J.T. & Meier, E.
Partner: UNT Libraries Government Documents Department

Lawrence Berkeley Laboratory year-end-report on heavy-ion fusion program

Description: An intensive theoretical program was launched to try to understand the conditions for safe propagation of intense beam currents in focussing systems, such as continuous and interrupted solenoid lens systems, and quadrupole strong-focussing systems. Analytic methods have led to significant advances in understanding of the new problems; with computational techniques a large amount of new information has been generated on space-charge-dominated transport phenomena; also, at this time a new LBL particle numerical simulation code is almost ready to give new results. Because the Bevalac is an operating heavy ion linac and synchrotron facility with an ongoing R and D effort and in expectation of imminent upgrading to bring it up to a uranium-ion capability, it was a natural choice to make an addition to these activities to examine low-..beta.. rf accelerating structures and ion sources suitable for HIF. An experimental program on intense beam propagation was briefly discussed. (MOW)
Date: September 30, 1977
Creator: Keefe, D.
Partner: UNT Libraries Government Documents Department

Reactions and diffusion in the silver--arsenic chalcogenide glass system

Description: The diffusion of Ag in amorphous As/sub 2/S/sub 3/ and As/sub 2/Se/sub 3/ at 175/sup 0/C is accompanied with the reduction of As from a valence of +3 to +2 and +2 to +1 to maintain charge neutrality in the glass. The reactions for the sulfide and selenide glasses are identical. Ag/sup +/ alone diffuses at this temperature, all other ions are essentially immobile. An amorphous reaction product phase is formed in the diffusion zone with a composition range of 28.6 to 44.4 atomic percent Ag. The lower limit corresponds to all As cations of +2 valence (amorphous Ag/sub 2/As/sub 2/S/sub 3/). The upper limit, the maximum solubility of Ag in these glasses, corresponds to all As cations of +1 valence (amorphous Ag/sub 4/As/sub 2/S/sub 3/). The diffusivity of Ag in these glasses at 175/sup 0/C in the concentration range of 10 to 35 atomic percent Ag is: Sulfide--4 x 10/sup -14/ exp(+0.23 +- .01) (atomic % Ag), Selenide--2 x 10/sup -12/ exp(+0.14 +- .01) (atomic % Ag).
Date: September 1, 1977
Creator: Holmquist, G.A.
Partner: UNT Libraries Government Documents Department

Interactions of fast atomic and molecular ions with matter

Description: Argonne's 5-MV Dynamitron accelerator is used to study the interactions of fast (MeV) atomic and molecular ions with matter. A unique feature of the apparatus is the exceptionally high resolution, in angle and time-of-flight, obtained in detecting particles emerging from the target. New imaging detector systems have been developed which allow detection of multiparticle events consisting of up to 12 particles. The work has as its main objective a general study of the interactions of fast charged particles with matter, but with the emphasis on those aspects that take advantage of the unique features inherent in employing molecular-ion beams (e.g., the feature that each molecular ion incident upon a solid target forms a tight cluster of atomic ions that remain correlated in space and time as they penetrate the target). In particular, these techniques have allowed the direct determination of the geometrical structures of the molecular ions entering the target, providing the first direct measure of the fully correlated nuclear densities within small molecules.
Date: January 1, 1989
Creator: Belkacem, A.; Kanter, E.P. & Vager, Z.
Partner: UNT Libraries Government Documents Department