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  • 1
    Electronic Resource
    Electronic Resource
    Electron–anode interactions in particle-in-cell simulations of applied-B ion diodes (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 3369-3387 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Particle-in-cell simulations of applied-B ion diodes using the QUICKSILVER code [D. B. Seidel et al., in Proceedings of the Europhysics Conference on Computational Physics, Amsterdam, 1990, edited by A. Tenner (World Scientific, Singapore, 1991), p. 475] have been augmented with Monte Carlo calculations of electron–anode interactions (reflection and energy deposition). Extraction diode simulations demonstrate a link between the instability evolution and increased electron loss and anode heating. Simulations of radial and extraction ion diodes show spatial nonuniformity in the predicted electron loss profile leading to hot spots on the anode that rapidly exceed the 350 °C–450 °C range, known to be sufficient for plasma formation on electron-bombarded surfaces. Thermal desorption calculations indicate complete desorption of contaminants with 15–20 kcal/mole binding energies in high-dose regions of the anode during the power pulse. Comparisons of parasitic ion emission simulations and experiment show agreement in some aspects, but also highlight the need for better ion source, plasma, and neutral gas models. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873576
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  • 2
    Electronic Resource
    Electronic Resource
    Ion divergence in magnetically insulated diodes (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2175-2182 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetically insulated ion diodes are being developed to drive inertial confinement fusion. Ion beam microdivergence must be reduced to achieve the very high beam intensities required to achieve this goal. Three-dimensional particle-in-cell simulations [Phys. Rev. Lett. 67, 3094 (1991)] indicate that instability-induced fluctuations can produce significant ion divergence during acceleration. These simulations exhibit a fast growing mode early in time, which has been identified as the diocotron instability. The divergence generated by this mode is modest, due to the relatively high-frequency ((approximately-greater-than)1 GHz). Later, a low-frequency low-phase-velocity instability develops with a frequency that is approximately the reciprocal of the ion transit time. This instability couples effectively to the ions, and can generate unacceptably large ion divergences ((approximately-greater-than)30 mrad). Linear stability theory reveals that this mode has structure parallel to the applied magnetic field and is related to the modified two-stream instability. Measurements of ion density fluctuations and energy-momentum correlations have confirmed that instabilities develop in ion diodes and contribute to the ion divergence. In addition, spectroscopic measurements indicate that lithium ions have a significant transverse temperature very close to the emission surface. Passive thin-film lithium fluoride (LiF) anodes have larger transverse beam temperatures than laser-irradiated active sources. Calculations of the ion beam source divergence for the LiF film due to surface roughness and the possible loss of adhesion and fragmentation of this film are presented. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871672
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of a proton driven, exploding pusher target on PBFA II (abstract) : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4778-4778 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: During the past year we have conducted a series of PBFA II target experiments. The design of the experiments was threefold: to characterize the response of targets to ion beams, develop our experimental diagnostic capability, and benchmark our theoretical ability to design and predict the response of the experimental diagnostics to ion-beam-heated, ICF targets. We present here an analysis of spherical exploding pusher experiments. The targets were 6-mm-diam, 100-μm-thick, Cl-doped CH spheres, filled with 1.2 atm of deuterium doped with 7 Torr of H2S. The diagnostics included XRDs, x-ray pinhole, framing, and streak cameras, and a spatially resolved, x-ray crystal spectrometer. Our analysis includes comparisons between experimental results and theoretical predictions of diagnostics responses and sulfur line emission from the compressed target using one- and two-dimensional radiation/hydrodynamic code runs. This work supported by the U. S. Department of Energy under Contract No. DE-AC04-76-DP00789.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143559
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  • 4
    Electronic Resource
    Electronic Resource
    Divergence measurement of light ion beams using ultracompact ion pinhole cameras on PBFA II (abstract) : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4782-4782 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Ion beam divergence reduction will increase the power density deliverable to an ICF target and is one step towards demonstrating a credible path to target ignition. Measurement of the divergence is made with an ultracompact ion pinhole camera (UC-IPC). The UC-IPC is mounted in the PBFA II diode near the ion source at a 10° angle to compensate for beam bending in the diode's applied magnetic field. The beam is transported through an entrance pinhole and down an entrance tube to a gold scattering foil. The beam is scattered 90° through a second pinhole to CR39 film where the ion track count is recorded. This paper will describe the results of off-axis ion beam divergence measurements using the UC-IPC. Together with other diagnostics, the UC-IPC provides information about beam species and charge state, about particle energy and about divergence of the beam. This paper will also describe UC-IPC simulation using PICDIAG, a 2D code that models the ion transport and diagnostic response of experiments on Sandia's PBFA II accelerator. This work supported by the U. S. Department of Energy Contract No. DE-AC04-76DP00789.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143561
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  • 5
    Electronic Resource
    Electronic Resource
    Aluminum K-shell line emission as a diagnostic in light ion beam fusion experiments : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 5062-5064 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Kα satellite line emission from targets irradiated by intense light ion beams can be used to diagnose plasma temperatures and densities. The fluorescence lines are created as 2p electrons drop down to fill 1s vacancies that result from ion beam-induced ionizations. We present results from collisional-radiative equilibrium calculations for thin Al diagnostic layers to illustrate the dependence of the Kα emission spectrum on temperature, density, and layer thickness. We also discuss the effects of opacity on the spectrum and the contribution from Kα transitions involving excited states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143492
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  • 6
    Electronic Resource
    Electronic Resource
    ICF target diagnostics on PBFA II (invited) : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4828-4833 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Particle Beam Fusion Accelerator II is a light-ion fusion accelerator that is presently capable of irradiating a 6-mm-diam sphere with ∼50 kJ of 5.5-MeV protons in ∼15 ns. An array of particle and x-ray diagnostics fielded on proton Inertial Confinement Fusion target experiments quantifies the incident particle beam and the subsequent target response. An overview of the ion and target diagnostic setup and capabilities will be given in the context of recent proton beam experiments aimed at studying soft x-ray emission from foam-filled targets and the hydrodynamic response of exploding-pusher targets. Ion beam diagnostics indicate ∼100 kJ of proton beam energy incident within a 1.2-cm radius of the center of the diode with an azimuthal uniformity which varied between 6% and 29%. Foam-filled target temperatures of 35 eV and closure velocities of 4 cm/μs were measured.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143574
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  • 7
    Electronic Resource
    Electronic Resource
    Range and straggling effects on CR-39/range-filter ion energy measurements : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4895-4897 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The CR-39/range-filter technique measures ion energy by determining the maximum filter thickness which ions can penetrate. CR-39 located behind the filter records the ions. This method is used to measure peak voltage in pulsed power accelerators. We investigated range and straggling effects in this diagnostic by exposing it to 8- and 15-MeV protons for both Al and Ta filters. The range agreed with published values to better than ±6%. The range straggling decreased for higher incident ion energy and lower atomic number, as expected, although there were differences up to a factor of 1.7 between the experimental values and predictions. The dependence of the track diameter distribution on ion energy enabled us to establish a signature which is characteristic of ions which penetrate a filter, via straggling. These results can be used to evaluate the errors present when this diagnostic is used to measure accelerator voltage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143543
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  • 8
    Electronic Resource
    Electronic Resource
    Diagnosing plasma conditions in light ion beam fusion experiments using inner-shell x-ray line emission (abstract)a) : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 564-564 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Kα emission spectroscopy is an important diagnostic technique used for plasmas created in intense light ion beam experiments.b),c) Emission lines can be produced as 2p electrons drop down to fill 1s vacancies created by the ion beam. Bailey et al.b) reported the first spectroscopic measurements of Kα x-ray satellites in intense proton beam experiments on PBFA-II at Sandia. Kα emission spectra have also recently been observed in intense Li-beam experiments on PBFA-II.d) Two approaches are used to analyze time-integrated x-ray spectra. In the first, CRE calculations are performed to compute synthetic time-integrated spectra using plasma conditions predicted from radiation-hydrodynamic simulations. In the second approach, plasma conditions are deduced from Kα satellite line intensity ratios measured from the highest ionization stages observed in the experiments. Results will be presented from our analysis of recent PBFA-II x-ray spectra. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146353
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  • 9
    Electronic Resource
    Electronic Resource
    High-accuracy time- and space-resolved Stark shift measurements (invited) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1009-1014 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Stark-shift measurements using emission spectroscopy are a powerful tool for advancing understanding in many plasma physics experiments. We use simultaneous two-dimensional space- and time-resolved spectra to study the electric field evolution in the 20 TW Particle Beam Fusion Accelerator II ion diode acceleration gap. Fiber optic arrays transport light from the gap to remote streaked spectrographs operated in a multiplexed mode that enables recording time-resolved spectra from eight spatial locations on a single instrument. Design optimization and characterization measurements of the multiplexed spectrograph properties include the astigmatism, resolution, dispersion, and sensitivity. A semiautomated line-fitting procedure determines the Stark shift and the related uncertainties. Fields up to 10 MV/cm are measured with an accuracy ±2%–4%. Detailed tests of the procedure confirm that the uncertainty in the wavelength-shift error bars is less than ±20%. Development of an active spectroscopy probe technique that uses laser-induced fluorescence from an injected atomic beam to obtain three-dimensional space- and time-resolved measurements of the electric and magnetic fields is in progress. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147826
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  • 10
    Electronic Resource
    Electronic Resource
    Target diagnostics for intense lithium ion hohlraum experiments on Particle Beam Fusion Accelerator II : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 511-514 
    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 lithium ion-beam hohlraum target experiments on Particle Beam Fusion Accelerator II will be presented. This diagnostic package contains an extensive suite of x-ray spectral and imaging diagnostics that enable measurements of target temperature and x-ray output. The x-ray diagnostics include time-integrated and time-resolved pinhole cameras, energy-resolved one-dimensional streaked imaging diagnostics, time-integrated and time-resolved grazing incidence spectrographs, a transmission grating spectrograph, an elliptical crystal spectrograph, a bolometer array, an 11- element x-ray diode array, and an 11-element PIN diode detector array. The incident Li beam symmetry and an estimate of incident Li beam power density can be measured from ion beam-induced characteristic x-ray line emission and neutron emission. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146334
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