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  • Electronic Resource  (30)
  • 1995-1999  (17)
  • 1990-1994  (13)
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  • Electronic Resource  (30)
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  • 1
    Electronic Resource
    Electronic Resource
    A multiple-sample, cesium-sputter, negative ion source : Proceedings of the fourth International Conference on Ion Sources (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2450-2452 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A multiple-sample, cesium-sputter, negative-ion source which permits sample changes without disruption of on-line tandem electrostatic accelerator operations is described. The source is equipped with provisions for remotely selecting and moving into the beam position any one of 60 samples by means of stepping motors equipped with absolute shaft encoders. A spherical-sector cesium ionizer is used to produce the cesium beam for sputtering the sample material. The source is equipped with a three-element electrode system which has been designed to increase the perveance for cesium ion beam generation and to improve negative ion beam extraction from the source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142907
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  • 2
    Electronic Resource
    Electronic Resource
    A simple, high efficiency, negative surface ionization source : Proceedings of the fourth International Conference on Ion Sources (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2453-2454 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A spherical-geometry, self-extraction negative ion source has been designed and fabricated. The source utilizes direct surface ionization to form negative ion beams resulting from interactions between high electron affinity gaseous elemental or molecular materials and a negatively biased, spherical-sector LaB6 surface ionizer maintained at ∼1300 K. The design features of this source and principles upon which the source is based are discussed in this report.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142908
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  • 3
    Electronic Resource
    Electronic Resource
    A pulsed-mode, high intensity, heavy negative ion source : Proceedings of the fourth International Conference on Ion Sources (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2455-2457 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A high intensity, plasma-sputter, negative ion source, which utilizes multicusp, magnetic-field, plasma confinement techniques is described. The source is an axial-geometry version of a radial-geometry source which has demonstrated a pulsed-mode peak intensity level of several mA for a wide spectrum of heavy negative ion species. The mechanical design features include provisions for fast interchange of sputter samples, ease of maintenance, direct cooling of the discharge chamber, and the use of easily replaced coaxial LaB6 cathodes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142909
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  • 4
    Electronic Resource
    Electronic Resource
    A combined thermal dissociation and electron impact ionization source for radioactive ion beam generation (abstract)a) : Proceedings of the 6th international conference on ion sources (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 1189-1189 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The probability for simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecular feed materials with conventional, hot-cathode, electron-impact ion sources is low and consequently, the ion beams from these sources often appear as mixtures of several molecular sideband beams. This fragmentation process leads to dilution of the intensity of the species of interest for radioactive ion beam (RIB) applications where beam intensity is at a premium. We have conceived an ion source that combines the excellent molecular dissociation properties of a thermal dissociator and the high ionization efficiency characteristics of an electron impact ionization source that will, in principle, overcome this handicap. The source concept will be evaluated as a potential candidate for use for RIB generation at the Holifield Radioactive Ion Beam Facility, now under construction at the Oak Ridge National Laboratory. The design features and principles of operation of the source are described in this article. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147233
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  • 5
    Electronic Resource
    Electronic Resource
    Selection of targets and ion sources for radioactive ion beam generation at the Holifield Radioactive Ion Beam Facilitya) (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3831-3842 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article, we describe the performance characteristics for a selected number of target ion sources that will be employed for initial use at the Holifield Radioactive Ion Beam Facility as well as prototype ion sources that show promise for future use for radioactive ion beam applications. A brief review of present efforts to select target materials and to design composite target matrix/heat-sink systems that simultaneously incorporate the short diffusion lengths, high permeabilities, and controllable temperatures required to effect fast and efficient diffusion release of the short-lived species is also given. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147284
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  • 6
    Electronic Resource
    Electronic Resource
    The electron-beam-plasma ion source as source of negative fluorine : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 773-773 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Radioactive ion beams (RIBs) of short-lived isotopes of fluorine are in demand for investigating astrophysical phenomena related to the hot CNO cycle and rp processes responsible for stellar nucleosynthesis. Since negative ion beams are required for injection into tandem electrostatic accelerators, such as the 25 MV tandem accelerator used for post acceleration of RIBs for the Holifield radioactive ion beam facility research program at the Oak Ridge National Laboratory, efficient, direct-formation F− ion sources are highly desirable. We have conceived and evaluated a direct extraction F− source for potential RIB applications which is predicated on the reverse polarity operation of a positive electron-beam-plasma target/ion source (EBPTIS) while simultaneously feeding fluorine-rich compounds and Cs vapor into the source. The source is found to operate in two separately distinct temperature regimes for the generation of F−: (1) a high cathode temperature regime or plasma mode and (2) a lower cathode temperature regime or surface ionization mode. For the latter mode of operation, net efficiencies of η=0.2% were attained for the EBPTIS; delay times, τ, attributable to the transport of F and fluoride compounds from the target to the ionization chamber of the source, typically, were found to be τ∼60 s. Brief descriptions of the EBPTIS and experimental techniques used in the studies, as well as net efficiency and effusive flow data for the negative EBPTIS, are presented in this article. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148734
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  • 7
    Electronic Resource
    Electronic Resource
    Prototype negative ion sources for radioactive ion beam generation (abstract) : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 775-775 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Radioactive ion beams (RIBs) of 17F and 18F are of interest for investigation of astrophysical phenomena such as the "hot" CNO cycle and the rp stellar nuclear synthesis processes. In order to generate useful beam intensities of atomic F−, the species must be efficiently and expediently released from the target material, thermally dissociated from fluoride release products during transport to the ionization chamber of the ion source, and efficiently ionized in the source upon arrival. We have conceived and evaluated two prototype negative ion sources for potential use for RIB generation: a direct extraction source and a kinetic ejection source. Both sources utilize Cs vapor to enhance F− formation. The mechanical design features, operational parameters, ionization efficiencies for forming atomic F− and delay times for transport of F and fluoride compounds for the respective sources are presented. The efficiency η for formation and extraction of F− for the direct extraction negative ion source is found to be η∼1.0%, while the characteristic delay time τ for transport of F and fluorides through the source is typically, η∼120 s; the analogous efficiencies and delay times for the kinetic ejection negative ion source are, respectively: η=∼3.2% and τ=∼70 s. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148736
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  • 8
    Electronic Resource
    Electronic Resource
    A combined thermal dissociation and electron impact ionization source for radioactive ion beam generationa) (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 1626-1629 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The probability for simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecular feed materials with conventional, hot-cathode, electron-impact ion sources is low and consequently, the ion beams from these sources often appear as mixtures of several molecular sideband beams. This fragmentation process leads to dilution of the intensity of the species of interest for radioactive ion beam (RIB) applications where beam intensity is at a premium. We have conceived an ion source that combines the excellent molecular dissociation properties of a thermal dissociator and the high ionization efficiency characteristics of an electron impact ionization source that will, in principle, overcome this handicap. The source concept will be evaluated as a potential candidate for use for RIB generation at the Holifield Radioactive Ion Beam Facility, now under construction at the Oak Ridge National Laboratory. The design features and principles of operation of the source are described in this article. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146903
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  • 9
    Electronic Resource
    Electronic Resource
    Effusive flow delay times for gaseous species in a compact rf ion source (abstract) : Proceedings of the 6th international conference on ion sources (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 1353-1353 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A rf ion source is presently being developed and evaluated as a potential candidate for use in generating radioactive ion beams (RIBs) for the experimental research program at the Holifield Radioactive Ion Beam Facility (HRIBF) now under construction at the Oak Ridge National Laboratory. For this application, any time delays that are excessively long with respect to the half-life of the radioactive species of interest can result in significant losses of the RIB intensity; therefore the times for effusive flow through the ion source are of fundamental importance since they set limits on the minimum half-life of radioactive species that can be processed in the source. Complementary experimental and computational techniques have been developed which can be used to determine the characteristic delay times for gaseous species in low-pressure ion source assemblies. These techniques are used to characterize the effusive delay times for the stable counterparts of various atomic and molecular radioactive species in the ORNL-rf source: He, Ne, Ar, Kr, Xe, H2, CO, CO2, N2, N2O, and O2. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147245
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  • 10
    Electronic Resource
    Electronic Resource
    A high-efficiency positive (negative) surface ionization source for radioactive ion beam (abstract)a) : Proceedings of the 6th international conference on ion sources (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 1189-1189 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A versatile, new concept, spherical-geometry, positive (negative) surface-ionization source has been designed and fabricated which will have the capability of generating both positive- and negative-ion beams without mechanical changes to the source. The source utilizes a highly permeable, high-work-function Ir ionizer (φ≡5.29 eV) for ionizing highly electropositive atoms/molecules; while for negative-surface ionization, the work function is lowered to φ≡1.43 eV by continually feeding cesium vapor through the ionizer matrix. The use of this technique for negative ion beam generation has the potential of overcoming the chronic poisoning effects experienced with LaB6 while enhancing considerably the efficiency for negative surface ionization of atoms and molecules with intermediate electron affinities. The flexibility of operation in either mode makes it especially attractive for radioactive ion beam applications and, therefore, the source will be used as a complementary replacement for the high-temperature electron impact ionization sources presently in use at the Holifield radioactive beam facility. The design features and operational principles of the source will be described in this report. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147236
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