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  • 1
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Direct extraction, negative-surface ionization, and sputter-type sources have been designed to efficiently ionize specific members of the group VII A elements (F, Cl, Br, I, and At) for use in the nuclear structure physics and nuclear astrophysics research programs at the Holifield Radioactive Ion Beam Facility (HRIBF). A negative surface ionization source that utilizes a solid, spherical geometry, LaB6 ionizer (φ≅2.7 eV) for negatively ionizing Cl, Br, l, and At. During off-line evaluation, the ionization efficiency for Cl− generation ranged between 15% and 20% and for Br− generation, between 15% and 25%. Chemically active elements, such as fluorine, are often released from refractory host materials in a variety of molecular forms. Consequently, the LaB6 surface ionization source, described above, is ineffective for simultaneously dissociating and negatively ionizing this element. To overcome this problem, a new concept source, referred to as the kinetic ejection negative ion source (KENIS), was developed. The source utilizes the Cs-sputter technique to effectively dissociate molecular carriers and ionize F at efficiencies in excess of 7%. The source has been used on-line to inject 〉3×107 17F−/s into the tandem accelerator and deliver ∼3×106 17F9+/s (fully stripped) to the research station for completion of important nuclear-astrophysics experiments. In this article, emphasis will be placed on the design details, materials of construction, ion optics, operational parameters, thermal transport properties, emittances, and measured ionization efficiencies for these sources. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact, all-permanent-magnet, single-frequency electron cyclotron resonance (ECR) ion source with a large uniformly distributed ECR plasma volume has been designed and is presently under construction at the Oak Ridge National Laboratory. The central region of the field is designed to achieve a flat field (constant mod-B) which extends over the length of the central field region along the axis of symmetry and radially outward to form a uniformly distributed ECR plasma "volume." The magnetic field design strongly contrasts with those used in conventional ECR ion sources where the central field regions are approximately parabolic and the resulting ECR zones are "surfaces." The plasma confinement magnetic field mirror has a mirror ratio Bmax/BECR of slightly greater than 2. The source is designed to operate at a nominal rf frequency of 6 GHz. The central flat magnetic field region can be easily adjusted by mechanical means to tune the source to the resonant conditions within the limits of 5.5–6.8 GHz. The rf injection system is broadband to ensure excitation of transverse electric modes so that the rf power is largely concentrated in the resonant plasma volume which lies along and surrounds the axis of symmetry of the source. Because of the much larger ECR zone, the probability for absorption of microwave power is dramatically increased, thereby increasing the probability for acceleration of electrons, the electron temperature of the plasma, and, consequently, the "hot" electron population within the plasma volume of the source. The creation of an ECR "volume" rather than a "surface" is commensurate with higher charge states and higher beam intensities within a particular charge state. The source has also been designed so that it can be easily converted into a conventional magnetic field geometry source so that comparisons of the performances of the "volume" and "surface" forms of the source can be easily made. The design features of the source and rf injection system will be described in detail in this article. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 1630-1633 
    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
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  • 4
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Holifield Radioactive Ion Beam Facility now under construction at the Oak Ridge National Laboratory will use the 25 MV tandem accelerator for the acceleration of radioactive ion beams to energies appropriate for research in nuclear physics; negative ion beams are, therefore, required for injection into the tandem accelerator. Because charge exchange is an efficient means for converting initially positive ion beams to negative ion beams, both positive and negative ion sources are viable options for use at the facility. The choice of the type of ion source will depend on the overall efficiency for generating the radioactive species of interest. Although direct-extraction negative ion sources are clearly desirable, the ion formation efficiencies are often too low for practical consideration; for this situation, positive ion sources, in combination with charge exchange, are the logical choice. The high-temperature version of the CERN-ISOLDE positive ion source has been selected and a modified version of the source designed and fabricated for initial use at the facility because of its low emittance, relatively high ionization efficiencies, and species versatility, and because it has been engineered for remote installation, removal, and servicing as required for safe handling in a high-radiation-level ISOL facility. The source will be primarily used to generate ion beams from elements with intermediate to low electron affinities. Prototype plasma-sputter negative ion sources and negative surface-ionization sources are under design consideration for generating radioactive ion beams from high-electron-affinity elements. The design features of these sources and expected efficiencies and beam qualities (emittances) will be described in this report.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1520-6025
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    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
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2006-2011 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A versatile, high-intensity, negative ion source has been designed and is now under construction which can be operated in either the cesium-sputter or plasma-sputter mode. The cesium-sputter mode can be effected by installation of a newly designed conical-geometry cesium-surface ionizer; for operation in the plasma-sputter mode, the surface ionizer is removed and either a hot filament or rf antenna plasma-discharge igniter is installed. A multicusp magnetic field is specifically provided confining the plasma in the radial direction when the plasma-sputter mode is selected. This arrangement allows comparison of the two modes of operation. Brief descriptions of the design features, ion optics, and anticipated performances of the two source geometries will be presented in this report.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact, all-permanent-magnet, single-frequency electron cyclotron resonance (ECR) ion source with a large uniformly distributed ECR plasma volume has been designed and is presently under construction at the Oak Ridge National Laboratory. The central region of the field is designed to achieve a flat field (constant mod-B) which extends over the length of the central field region along the axis of symmetry and radially outward to form a uniformly distributed ECR plasma "volume." The magnetic field design strongly contrasts with those used in conventional ECR ion sources where the central field regions are approximately parabolic and the resulting ECR zones are "surfaces." The plasma confinement magnetic field mirror has a mirror ratio Bmax/BECR of slightly greater than 2. The source is designed to operate at a nominal rf frequency of 6 GHz. The central flat magnetic field region can be easily adjusted by mechanical means to tune the source to the resonant conditions within the limits of 5.5–6.8 GHz. The rf injection system is broadband to ensure excitation of transverse electric modes so that the rf power is largely concentrated in the resonant plasma volume which lies along and surrounds the axis of symmetry of the source. Because of the much larger ECR zone, the probability for absorption of microwave power is dramatically increased, thereby increasing the probability for acceleration of electrons, the electron temperature of the plasma, and, consequently, the "hot" electron population within the plasma volume of the source. The creation of an ECR "volume" rather than a "surface" is commensurate with higher charge states and higher beam intensities within a particular charge state. The source has also been designed so that it can be easily converted into a conventional magnetic field geometry source so that comparisons of the performances of the "volume" and "surface" forms of the source can be easily made. The design features of the source and rf injection system will be described in detail in this article. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A versatile, high-intensity, negative ion source has been designed and is now under construction which can be operated in either the cesium-sputter or plasma-sputter mode. The cesium-sputter mode can be effected by installation of a newly designed conical-geometry cesium-surface ionizer; for operation in the plasma-sputter mode, the surface ionizer is removed and either a hot-filament or rf antenna plasma-discharge igniter is installed. A multicusp magnetic field is specifically provided for confining the plasma in the radial direction when the plasma-sputter mode is selected. This arrangement allows comparison of the two modes of operation. Brief descriptions of the design features, ion optics, and anticipated performances of the two source geometries will be presented in this report.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Holifield Radioactive Ion Beam Facility now under construction at the Oak Ridge National Laboratory will use the 25-MV tandem accelerator for the acceleration of radioactive ion beams to energies appropriate for research in nuclear physics; negative ion beams are, therefore, required for injection into the tandem accelerator. Because charge exchange is an efficient means for converting initially positive ion beams to negative ion beams, both positive and negative ion sources are viable options for use at the facility. The choice of the type of ion source will depend on the overall efficiency for generating the radioactive species of interest. Although direct-extraction negative ion sources are clearly desirable, the ion formation efficiencies are often too low for practical consideration; for this situation, positive ion sources, in combination with charge exchange, are the logical choice. The high-temperature version of the CERN-ISOLDE positive ion source has been selected and a modified version of the source designed and fabricated for initial use at the facility because of its low emittance, relatively high ionization efficiencies and species versatility, and because it has been engineered for remote installation, removal and servicing as required for safe handling in a high-radiation-level ISOL facility. The source will be primarily used to generate ion beams from elements with intermediate to low ionization potentials. Prototype plasma-sputter negative ion sources and negative surface-ionization sources are under design consideration for generating radioactive ion beams from high-electron-affinity elements. The design features of these sources and expected efficiencies and beam qualities (emittances) will be described in this report.
    Type of Medium: Electronic Resource
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