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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

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

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

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

Knock-on electrons in the target chamber

Description: It is virtually certain that heavy ion beams will produce massive quantities of knock-on electrons for target chamber pressures above 1 torr. It was shown that the magnitude of the resulting current is more than sufficient to pinch the knock-on beam in most cases, assuming that a substantial fraction of this beam actually gets out ahead of the ion beam pulse. Although at least some of the ion beam experiences this defocusing, the overall effect on beam propagation is minimal if field reversal induced by the ion beam occurs near the beam head.
Date: January 1, 1979
Creator: Hubbard, R.F.; Goldstein, S.A. & Tidman, D.A.
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

Molecular mechanism by which cyclic amp regulates myocardial contractility

Description: From these experiments, it appears that the phosphorylated 22,000 dalton protein does not regulate the transport properties of the ATPase. Instead phosphorylation of the 22,000 dalton protein causes it to become buried in the membrane, transporting Ca/sup 2 +/ into the sarcoplasmic reticulum and thereby, elevating the Ca/sup 2 +/ concentration in the sarcoplasmic reticulum available for release to the myofibrils.
Date: January 1, 1979
Creator: Bidlack, J.M.
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

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

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

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

Characteristics of a RF-Driven Ion Source for a Neutron Generator Used For Associated Particle Imaging

Description: We present recent work on a prototype compact neutron generator for associated particle imaging (API). API uses alpha particles that are produced simultaneously with neutrons in the deuterium-tritium (2D(3T,n)4 alpha) fusion reaction to determine the direction of the neutrons upon exiting the reaction. This method determines the spatial position of each neutron interaction and requires the neutrons to be generated from a small spot in order to achieve high spatial resolution. The ion source for API is designed to produce a focused ion beam with a beam spot diameter of 1-mm or less on the target. We use an axial type neutron generator with a predicted neutron yield of 108 n/s for a 50 muA D/T ion beam current accelerated to 80 kV. The generator utilizes a RF planar spiral antenna at 13.56 MHz to create a highly efficient inductively-coupled plasma at the ion source. Experimental results show that beams with an atomic ion fraction of over 80percent can be obtained while utilizing only 100 watts of RF power in the ion source. A single acceleration gap with a secondary electron suppression electrode is used in the tube. Experimental results, such as the current density, atomic ion fraction, electron temperature, and electron density, from ion source testing will be discussed.
Date: August 8, 2008
Creator: Wu, Ying; Hurley, John P.; Ji, Qing; Kwan, Joe & Leung, Ka-Ngo
Partner: UNT Libraries Government Documents Department

Heavy particle clinical radiotherapy trial at Lawrence Berkeley Laboratory. Progress report, July 1975-July 1979

Description: The primary objectives of the clinical radiotherapy program are: to evaluate the potential of improved dose localization particularly as exemplified by helium ion irradiation; and to evaluate the combined potential of improved dose localization and increased biologic effect available with heavier ions such as carbon, neon, and argon. It was possible to make modifications rapidly to provide for large field, fractionated, Bragg peak irradiation at the 184-inch cyclotron with the helium ion beam. This allowed the opportunity to gain experience with charged particle irradiation treatment techniques, patient immobilization techniques, treatment planning and dosimetry studies including the utilization of CT scanning for tumor localization and charged particle dose distributions as well as beginning studies in compensating for tissue inhomogeneities in the beam path. These treatment techniques have been directly transferable to the Bevalac facility where a similar patient positioner has been installed for human irradiation with heavier particles. For the studies both with helium and now with heavier particles, patients with multiple skin and subcutaneous metastatic nodules for evaluation of skin RBE data and patients with locally advanced and/or unresectable tumors unlikely to be effectively treated by any conventional modality were sought. In order to facilitate intercomparison with megavoltage irradiation techniques, a conventional dose fractionation scheme has been adopted. A few exceptions to this dose specification scheme have been patients in which pulmonary, subcutaneous or skin nodules have been irradiated with larger fraction sizes ranging up to 400 rads per fraction in order to obtain clinical RBE studies in 8 to 10 fractions of heavy particles.
Date: January 1, 1979
Creator: Castro, J.R.
Partner: UNT Libraries Government Documents Department

Heavy Ion Fusion Program. Year-end report, October 1978-September 1979

Description: The more significant activities and results reported for this year are: (1) Commissioning, in January 1979, of a large-area Cs/sup +1/ ion source of 1.2 amperes at 500 kV. (2) Commissioning, in July 1979, of the first drift-tube of the three drift-tube accelerator. (3) Acceleration, in January 1979, of a high-brightness, 40 milliampere Xe/sup +1/ beam through a Cockcroft-Walton column to 500 kV and confirmation of satisfactory emittance and charge distribution. (4) Development of a conceptual design for a 500 J induction linac test-bed facility to test many of the features needed for the success of an igniter (LBL PUB 5031). (5) Improvements to the systems studies of a Heavy Ion Induction Linac Driver over a wide parameter range with emphasis on cost and efficiency trade-off. (6) Start-up of a (Cs/sup +1/, Cs/sup +1/) ion-ion cross section measurement program. Initial results of the scattering of Cs/sup +1/ ions on Xe gas (electronically similar to Cs/sup +1/) have shown some surprising results. (7) Expansion of theoretical studies on the behavior of space-charge dominated ion beams.
Date: January 1, 1979
Partner: UNT Libraries Government Documents Department