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  • 1
    Electronic Resource
    Electronic Resource
    Design and operation of a 30-kV accelerator for negative ion beams (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2402-2408 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A 30-kV triode accelerator has been constructed to test the design and operating characteristics of accelerators for negative hydrogen ion beams. Incorporating both a quadrupole electron trap and an octupole electron suppressor, the accelerator has been used to extract, accelerate, and focus H− ion beams of up to current densities of 20 mA cm−2. The results suggest that this accelerator design is capable of focusing across a wide range of ion current densities (0–20 mA cm−2) and acceleration voltages (15–30 kV) using the variation of a single-gap potential to achieve the required focusing. Applying a bias voltage of up to 2 V between the beam forming electrode and the anode of the source suppresses electrons and has allowed accelerator power efficiencies of over 73% to be obtained for all ion current densities up to 20 mA cm−2 so far extracted. Initial evidence that the extracted and accelerated negative ion beam may be undergoing self-focusing is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139085
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  • 2
    Electronic Resource
    Electronic Resource
    Extraction of H− and D− ions from a large magnetic multipole source (1987)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 223-234 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Results are presented on the production of H− ions in a large (55×31×20 cm3) magnetic multipole discharge, which is sufficiently large to act as the plasma generator for a neutral beam injector. H− ion current densities up to 57 mA/cm2 have been extracted in pulses up to 3 s in length at low energies. When the discharge is operated in deuterium, a maximum D− current density of 27 mA/cm2 is obtained. The scaling laws of the H− production are consistent with production by dissociative attachment to rovibrationally excited molecules and loss by mutual recombination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139312
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  • 3
    Electronic Resource
    Electronic Resource
    Transport of negative ions produced at a barium surface located within a multicusp ion source (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 539-546 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An experimental study on the production of negative ions at a pure barium surface mounted in a multicusp bucket source is presented. The conversion efficiency, i.e., the ratio of the extracted negative-ion current and the positive-ion current incident on the surface, for deuterium and for hydrogen, have been measured as a function of source pressure, converter bias, and distance between conversion surface and extraction aperture. The conversion efficiency for deuterium is somewhat larger when compared to hydrogen. The conversion efficiencies obtained agree with a model, taking into account the concentration of hydrogen in the barium surface layers. The cross sections which were measured for the stripping of negative ions by neutral gas agreed well with values from literature. The experimentally determined divergence of the surface-produced beam was 4.5° for hydrogen and 3.6° for deuterium at an energy of 100 eV. At a source pressure of 5 mTorr, the volume-produced negative-ion current could be enhanced by 10%; for 1 mTorr this enhancement was of the order of 25%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140360
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  • 4
    Electronic Resource
    Electronic Resource
    H− beam extraction experiments on the Culham small multipole source (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 895-901 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Beam extraction experiments have been carried out on a multicusp volume H− ion source operated in a dc mode. With an extraction aperture of 16-mm diameter, negative ion beams of up to 15 mA cm−2 have been extracted. Some experiments have been performed to investigate the physics of beam extraction from the plasma that indicate a fixed plasma boundary. The beam emittance has been measured as a function of various arc and accelerator parameters. The negative ion temperatures inferred from the emittance measurements cannot at present be explained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139799
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  • 5
    Electronic Resource
    Electronic Resource
    Development of a high proton yield plasma source with multipole confinement and a magnetic filter (1987)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 1369-1381 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Proton yields in magnetic multipole sources can be increased by the creation of a magnetic "filter'' within the discharge volume, although this may introduce nonuniformity in the plasma. We have investigated the properties of a filter which can satisfy the requirements of plasma uniformity and discharge electrical efficiency and creates a proton yield of 87% when a 60-A beam is extracted at 80 keV. A model describing the behavior of the filter is also described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139417
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  • 6
    Electronic Resource
    Electronic Resource
    H− and electron production in a magnetic multipole source (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1697-1702 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An investigation has been made of the yield of H− ions and electrons extracted from a magnetic multipole, or bucket, ion source as a function of the parameters of the source. Under optimum conditions the H− current density attains a value equal to half of the positive ion current density (H+3) measured at the extraction plane. The experimental results indicate that, while the H− current rises linearly with arc current, the extracted electron current shows a quadratic dependence. There is also a strong dependence of the electron current on the magnetic field applied across the extraction aperture, and source filling pressure. Probe measurements within the plasma volume show considerable axial variation of the fluxes of electrons, H− ions and H+3 ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138126
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  • 7
    Electronic Resource
    Electronic Resource
    Intense negative ion sources at Culham Laboratory (invited) : Proceedings of the 5th international conference on ion sources (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1153-1158 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Over the past 20 years, Culham Laboratory has been involved in the development of ion sources. Initially these were positive ion systems using magnetic multipole sources for neutral beam heating in the fusion program. However, the development of high proton yield sources with a magnetic filter at Culham has led to a major program in negative ion sources based on the so-called volume-type source which has a similar design. This work has been the basis of a range of negative ion sources for industrial, defence, and fusion applications, all of which are described. A significant part of this work lies in the basic physics of these sources, both for modeling and ion beam acceleration. Numerical models of these are presented. Recently the effects of catalysts such as cesium on the discharge has been shown to cause considerable enhancement in H− and D− yield. The cesium itself also acts as a discharge component and a large source and accelerator for a pure cesium diagnostic beam has been developed. This technique is applicable to other vapors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145043
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  • 8
    Electronic Resource
    Electronic Resource
    Recent results on negative ion production and extraction from the Culham Ion Source Test Stand : International conference on ion sources (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 412-414 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The plasma characteristics of a volume negative ion source are described. An indirect measurement of the negative ion current density in the source has been made. Beam extraction measurements are used to attempt to verify the measurement in the source. The two are found to be in proportion. The difference between the two is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141256
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  • 9
    Electronic Resource
    Electronic Resource
    Development of large area rf ion sources for fusion applications : Proceedings of the fourth International Conference on Ion Sources (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2735-2737 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A rf ion source with a large extraction area suitable for fusion applications is considered. The source is a metallic magnetic multipole bucket with an internal antenna to couple the rf (at a frequency of 2 MHz) to the plasma. The source is diagnosed by an array of Langmuir probes to measure uniformity, density, and temperature and a small probe accelerator to extract a negative ion beam. A two-turn antenna is found to couple more power into the plasma than a half-turn antenna. When operated as a negative ion source at low powers, the source efficiency is found to be high and not to have a strong dependence on gas pressure. An extracted negative ion current density of about 4 mA/cm2 at 7 mTorr was obtained when 3 kW of power was coupled into the plasma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142839
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  • 10
    Electronic Resource
    Electronic Resource
    Investigation of the electron fluid equations in a hydrodynamic model of the 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. 2720-2722 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The "hydrodynamic model'' developed by Haas, Holmes, and Lea has been extended to include all elastic collision processes between the species. The properties of the electron momentum equations are investigated in detail; the solution of these equations revealing a critical point along the source axis at which the electron drift velocity reverses direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142834
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