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  • 1
    Electronic Resource
    Electronic Resource
    Generation of GW VHF power pulses with a magnetically swept e beam and inverse e beam diodes (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 4653-4661 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The concept of converting a multi-kA relativistic e beam into an ultrahigh-power rf pulse with a magnetically swept e-beam switch is studied. Two short VHF pulses are created by rapidly switching a 60-ns, 900-keV, 15-kA e beam between a pair of inverse e-beam diodes. The switching is done by a transverse 500-G, sinusoidal B field, oscillating at 50 MHz. The e-beam pulses are transported 1.6–4.6 cm in vacuum and ballistically or magnetically focused onto the collectors of the inverse diodes. The inverse diodes extract electrical energy from the deflected e-beam pulses and transport the energy to resistive loads that varied between 30 and 130 Ω. Numerical simulations of the e-beam transport with self-electric and magnetic fields are performed that show the sources of electrical inefficiency. These occur because the e beam is near the space-charge limit during transport. Peak unipolar powers of 2.0 and 0.5 GW are coupled to the resistive loads for the ballistically and magnetically transported e-beam geometries, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339014
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  • 2
    Electronic Resource
    Electronic Resource
    Operation of a 120-MW ion beam source using an Applied-Bθ ion diode (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 745-753 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The operation of an Applied-Bθ ion diode has been studied at voltages up to 1.8 MV and diode currents of 250 kA. Peak ion currents up to 80 kA were observed at diode current efficiencies of up to 33% during the 60 ns power pulse. Ion and electron flow patterns have been carefully measured which indicate electron loss at locations far removed from the anode-cathode gap and ion current density enhancement at the inner anode radius due to motion of the cathode electron sheath. Numerical simulations performed with particle-in-cell codes agree well with the experimentally determined diode parameters including electron dynamics and ion and electron fluxes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339727
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  • 3
    Electronic Resource
    Electronic Resource
    Two-cavity autoacceleration of an intense relativistic electron beam (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 4760-4770 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Three series of experiments have been performed using two 40-Ω coaxial autoacceleration cavities to accelerate an intense relativistic electron beam. First, conventional magnetic transport was used to propagate a 1.8-MeV, 11-kA beam through two 1-m-long cavities. An increase of 700±130 keV in kinetic energy was achieved which represents 80% of the maximum theoretical acceleration for an 11-kA beam passing through two 40-Ω cavities. Multiple accelerated pulses were generated and no adverse interaction between the cavities was observed. In the second experiment, ion focused transport (IFT) was used to successfully propagate a 9-kA beam through the accelerator again achieving multipulse operation with both cavities. An energy increase of 560±30 keV was attained which is 78% of the theoretical maximum. Finally, IFT was used to propagate a (approximately-equal-to)25-kA beam through a 1-m-long cavity, then a 0.5-m-long cavity, demonstrating two stages of temporal energy compression. Gap leakage and current transport losses limited the acceleration to 1.25±0.16 MeV which corresponded to an 84% increase in kinetic energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338814
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  • 4
    Electronic Resource
    Electronic Resource
    Beam deflection phenomena in a Pulselac post-acceleration gap (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 20-35 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The post-acceleration of a 400-keV, 10-kA proton beam by a 200-kV magnetically insulated gap is investigated. The defections from self- and applied E and B fields are measured and compared to calculated values. Several important principles of post-acceleration gap operation are observed for the first time that are important for multigap operation. First, the beam is inadequately space-charge neutralized without gas puffs or preformed plasma in regions of transverse applied-B field to allow efficient transport. The beam is also noncurrent neutralized in these regions. Second, the applied-B field defines equipotential surfaces in the gap allowing the voltage on the gap to steer and focus the beam, and it has an axial field component that acts like a pair of solenoidal lenses to focus the beam. It is also pointed out how azimuthal asymmetries in the beam current density and cathode plasma cause beam self-field asymmetries that lead to growth of beam emittance. Finally, we discuss a model which can be used to extrapolate the experimental results to multigap operation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338858
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  • 5
    Electronic Resource
    Electronic Resource
    Lithium fluoride ion source experiments on PBFA II : International conference on ion sources (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 556-558 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Lithium fluoride, field-enhanced ion source experiments are being performed on PBFA II. The source consists of a thin coating of LiF on a microscopically rough substrate. Diagnostics to measure ion beam energy, purity, and transport include electrical monitors, Faraday cups, nuclear activation, ion pinhole camera, Rutherford magnetic spectrograph, and shadowbox aperture array. With PBFA II operating at three-quarters energy, the source has produced 16 TW of ion power and 550 kJ of ion energy with 70% diode efficiency. Over 26 kJ of lithium beam energy has been focused to the diode center axis with a peak energy density of about 1.3 kJ/cm2 . PICDIAG simulations of the lithium focus indicate the intrinsic source divergence is about 45 mrad with a 20-μm-grade porous stainless-steel substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141250
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  • 6
    Electronic Resource
    Electronic Resource
    Intense ion beam diagnostics for particle beam fusion experiments on PBFA II (invited) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1860-1865 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A review of the diagnostics used at Sandia National Laboratories to measure the parameters of intense proton and lithium beams generated on the PBFA-II accelerator will be presented. These diagnostics consist of several types, namely: Kα x-ray pinhole cameras, a multiframe dE/dx ion pinhole camera, a p-i-n array ion pinhole camera, Thomson parabola spectrographs, a Rutherford magnetic spectrograph, plasma visible spectroscopy, and several nuclear activation diagnostics. These components, when taken together, enable a rather thorough description of the 5-MV, 10-TW ion beams presently being produced. A unique feature of these diagnostics is that they are capable of operating in hard (several MeV) x-ray bremsstrahlung backgrounds of some 109–1010 rad/s. Details of each diagnostic, its integration, data reduction procedures, and recent PBFA-II data will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140089
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  • 7
    Electronic Resource
    Electronic Resource
    Rutherford magnetic spectrograph for intense ion beam measurements on PBFA-II (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1700-1702 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A time-resolved magnetic spectrograph employing a gold Rutherford-scattering foil has been constructed to measure the parameters of the intense ion beams generated by Sandia National Laboratories' PBFA-II accelerator. The spectrograph operates by allowing the direct intense beam of PBFA-II to scatter from a thin gold foil to reduce its intensity for magnetic analysis. Details of the spectrograph's construction, detector package, and recent PBFA-II proton data are included in the paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140138
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  • 8
    Electronic Resource
    Electronic Resource
    Intense ion beam Kα measurements on PBFA-II (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1706-1708 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Inertial confinement fusion research efforts at Sandia National Laboratories center on generating and focusing high-intensity light ion beams on the Particle Beam Fusion Accelerator PBFA-II. A time-integrating three-frame ion beam spatial monitor was developed for these experiments to determine proton and lithium ion beam uniformity and orbit characteristics by imaging the ion-induced Kα line radiation. The three views of the ion beam are made off axis in three diode quadrants at a 3.8-cm radius. This spatial monitor, in conjunction with other beam diagnostics, allows experimenters to determine the high-voltage focusing characteristics of the ion diode.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140140
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  • 9
    Electronic Resource
    Electronic Resource
    Multiframe ion pinhole camera for intense ion beam transport and focusing experiments (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1703-1705 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed a new ion pinhole camera to obtain energy density profiles of a focused multiterawatt ion beam as a function of ion energy. Beam ions that are elastically scattered from a thin gold foil are imaged through six baffled pinholes onto six separate areas of a sheet of CR-39 nuclear track detector. Each of the areas is covered by an aluminum range filter and records an image with a different lower bound on the ion energy. Subtracting images with adjacent cutoff energies results in images with upper and lower bounds on the ion energy. Ion images are read from the CR-39 with VERA, a fully automatic, image-processor-based nuclear track counting system. Images of the Particle Beam Fusion Accelerator-II (PBFA-II) proton beam have been obtained and show that the beam has been focused to achieve a horizontal FWHM of 5.7 mm and has delivered 9 kJ/cm2 to a target.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140139
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  • 10
    Electronic Resource
    Electronic Resource
    Simulation and interpretation of ion beam diagnostics on PBFA-II (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1709-1711 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Ion diode and beam focusing experiments are in progress on PBFA-II working toward an ultimate goal of significant burn of an ICF pellet. Beam diagnostics on these experiments include a Thomson parabola, Kα x-ray pinhole cameras, filtered ion pinhole cameras, and a magnetic spectrometer. We are developing two new computer programs to simulate and interpret the data obtained from these diagnostics. vida is a VAX-based program that manipulates and unfolds data from digitized particle and x-ray diagnostic images. vida operations include: image display, background subtraction, relative-to-absolute coordinate transformations, and image projection into the beam reference frame. picdiag allows us to study the effects of time-dependent ion focusing on the performance of ion beam diagnostics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140141
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