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  • 1
    Electronic Resource
    Electronic Resource
    Metal-nitroxyl interactions. 4. Electron-electron exchange in spin-labeled metalloporphyrins (1977)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 99 (1977), S. 4854-4855 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00456a068
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  • 2
    Electronic Resource
    Electronic Resource
    Electron production in low pressure gas ionized by an intense proton beam (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 582-590 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron density measurements from previous ion-beam-induced gas ionization experiments [F. C. Young et al., Phys. Plasmas 1, 1700 (1994)] are re-analyzed and compared with a recent theoretical model [B. V. Oliver et al., Phys. Plasmas 3, 3267 (1996)]. Ionization is produced by a 1 MeV, 3.5 kA, 55 ns pulse-duration, proton beam, injected into He, Ne, or Ar gas in the 1 Torr pressure regime. Theoretical and numerical analysis indicates that, after an initial electron population is produced by ion beam impact, ionization is dominated by the background plasma electrons and is proportional to the beam stopping power. The predicted electron density agrees with the measured electron densities within the factor of 2 uncertainty in the measurement. However, in the case of Ar, the theoretically predicted electron densities are systematically greater than the measured values. The assumptions of a Maxwellian distribution for the background electrons and neglect of beam energy loss to discrete excitation and inner shell ionization in the model equations are considered as explanations for the discrepancy. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873203
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  • 3
    Electronic Resource
    Electronic Resource
    Ballistic transport and solenoidal focusing of intense ion beams for inertial confinement fusion (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 395-404 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Light-ion inertial confinement fusion requires beam transport over distances of a few meters for isolation of the diode hardware from the target explosion and for power compression by time-of-flight bunching. This paper evaluates ballistic transport of light-ion beams focused by a solenoidal lens. The ion beam is produced by an annular magnetically insulated diode and is extracted parallel to the axis by appropriate shaping of the anode surface. The beam propagates from the diode to the solenoidal lens in a field-free drift region. The lens alters the ion trajectories such that the beam ballistically focuses onto a target while propagating in a second field-free region between the lens and the target. Ion orbits are studied to determine the transport efficiency ηt (i.e., the fraction of the beam emitted from the diode which hits the target) under various conditions relevant to light-ion inertial confinement fusion. Analytic results are given for a sharp boundary, finite thickness solenoidal lens configuration, and numerical results are presented for a more realistic lens configuration. From the analytic results, it is found that ηt can be in the range of 75%–100% for parameter values that appear to be achievable. Numerical results show that using a more realistic magnetic-field profile for the lens yields similar values of ηt for small radius diodes but significantly reduced values of ηt for large radius diodes. This reduction results from the radial gradient in the focusing field at larger radius.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351867
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  • 4
    Electronic Resource
    Electronic Resource
    Z-discharge transport of intense ion beams for inertial confinement fusion (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5292-5305 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion inertial confinement fusion requires beam transport over distances of a few meters for isolation of the diode hardware from the target explosion and for power compression by time-of-flight bunching. This paper evaluates light ion beam transport in a wall-stabilized z-discharge channel, where the discharge azimuthal magnetic field radially confines the ion beam. The ion beam is focused onto the entrance aperture of the transport channel by shaping the diode to achieve beam convergence in a field-free drift region separating the diode from the transport section. Ion orbits are studied to determine the injection efficiency (i.e., the fraction of the beam emitted from the diode which is transported) under various conditions. Ions that are focused onto the channel entrance at too large of an angle for confinement hit the wall and are lost. For a multimodular scheme (10–30 beams), individual transport channels are packed around the target with the exit apertures at some standoff distance from it. The fraction of the beam that is lost in this field-free standoff region is also evaluated under various conditions. The standoff efficiency is then combined with the injection efficiency to give the dependence of the total transport efficiency ηt on diode, focusing, transport and standoff parameters. It is found that ηt can be in the range of 75%–100% for parameter values that appear to be achievable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350239
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  • 5
    Electronic Resource
    Electronic Resource
    Wire-guided transport of intense ion beams (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 639-655 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Light ion inertial confinement fusion requires beam transport over distances of a few meters for isolation of the diode hardware from the target explosion and for power compression by time-of-flight bunching. This paper evaluates a wire-guided transport system that uses the azimuthal magnetic field, produced by a current driven through a thin wire, to radially confine the ion beam. Ion orbits are studied to determine the injection efficiency (i.e., the fraction of the beam which is transported) under various conditions. Some ions hit the wire because of too small angular momentum at injection; others hit the wire or are lost to large radius during transport because of chaotic orbit behavior induced by a small number of return-current wires close to the beam envelope. For a multimodular scheme (10–30 beams), individual transport system are packed around the target at some standoff distance. The fraction of the beam which is lost in this field-free standoff region is also evaluated under various conditions. The standoff efficiency is then combined with the injection efficiency to give the dependence of the total transport efficiency, ηt, on diode, focusing, transport, and standoff parameters. It is found that ηt can be as large as about 60% for parameter values which appear to be achievable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347344
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  • 6
    Electronic Resource
    Electronic Resource
    Interaction of intense MeV light-ion beams with low-pressure gasesf| (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1700-1707 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interaction of intense proton beams with low-pressure (0.25 to 4 Torr) background gases is studied to evaluate beam-current neutralization during transport. Electrons to neutralize the beam are provided by beam-induced ionization of the gas. In experiments with 1 MeV, 1 kA/cm2 protons, net currents outside the beam envelope and electron densities within the beam envelope are measured for helium, neon, argon, and air. Net-current fractions are 2% to 8% and ionization fractions are 0.6% to 5% for 5 to 7 kA beams. Simulations of the experiments for helium and argon suggest that fast electrons play an important role in generating a significant fraction of the return current in a halo outside the beam. As a result, net currents inside the beam may be larger than inferred from magnetic-field measurements outside the beam. Ions at the head of the beam are observed to lose more energy than expected from collisional energy losses in the background gas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870673
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  • 7
    Electronic Resource
    Electronic Resource
    Self-pinched transport of an intense proton beam (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 346-358 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion beam self-pinched transport (SPT) experiments have been carried out using a 1.1-MeV, 100-kA proton beam. A Rutherford scattering diagnostic and a LiF nuclear activation diagnostic measured the number of protons within a 5 cm radius at 50 cm into the transport region that was filled with low-pressure helium. Time-integrated signals from both diagnostics indicate self-pinching of the ion beam in a helium pressure window between 35 and 80 mTorr. Signals from these two diagnostics are consistent with ballistic transport at pressures above and below this SPT pressure window. Interferometric measurements of electron densities during beam injection into vacuum are consistent with ballistic transport with co-moving electrons. Interferometric measurements for beam injection into helium show that the electron density increases quadratically with pressure through the SPT window and roughly linearly with pressure above the SPT window. The ionization fraction of the helium plateaus at about 1.5% for pressures above 80 mTorr. In the SPT window, the electron density is 3 to 20 times the beam density. Numerical simulations of these beam transport experiments produce results that are in qualitative agreement with the experimental measurements. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873803
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  • 8
    Electronic Resource
    Electronic Resource
    Intense ion-beam-transport experiments using a z-discharge plasma channel (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 176-189 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A z-discharge plasma channel is used to confine and transport an intense proton beam. A pinch-reflex ion diode on the NRL Gamble II accelerator focuses a proton beam onto the entrance aperture of a 2.5 cm diam, 1.2 m long z-discharge transport system. The beam ions are charge and current neutralized in the discharge plasma, and execute betatronlike orbits in the magnetic field of the discharge. Ion beam diagnostics include shadowbox imaging and prompt-γ radiation measurements from LiF targets. Under appropriate conditions, 95% particle transport and 90% energy transport are observed, with the only energy loss attributed to classical stopping in the channel gas. The transverse phase-space distribution of the beam measured by the shadowbox is consistent with full charge and current neutralization of the transported beam.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860851
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  • 9
    Electronic Resource
    Electronic Resource
    Numerical simulation of a low-density plasma erosion opening switch (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 2724-2735 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Current conduction through a low density (∼1012 cm−3) collisionless plasma injected between two coaxial conducting cylinders is simulated using a 2 (1)/(2) -D, electromagnetic particle-in-cell code. Plasma is injected through the anode towards the cathode with flow velocity, VF, and is assumed to be azimuthally symmetric. Current is driven through the plasma so that the 100 kA level is reached in (approximately-equal-to)5 nsec. The opening process, when current is diverted to a load, is also treated. Electrons are found to carry current in a narrow current channel across the plasma by E×B drift. A large electric field is established by charge separation in the plasma in order to provide the drift. The motion of the anode end of the current channel controls the time of opening and is found to be independent of VF and to depend strongly on density and length.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865513
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  • 10
    Electronic Resource
    Electronic Resource
    Radiachromic film as a detector for intense MeV proton beams : Proceedings of the 12th topical conference on high temperature plasma diagnostics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1201-1204 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple technique has been developed to image intense pulsed proton beams with radiachromic film and to measure their spatial distribution. The optical density (OD) of 50 μm thick film, sufficient to stop 1.5 MeV protons, is measured to infer the incident beam fluence. The OD increases nearly linearly with fluence up to 0.25 cal/cm2. This film is used to measure the uniformity of large-area beams as well as the detector in a multiple-pinhole camera to determine the source uniformity and divergence of applied-magnetic field and pinched-beam ion diodes. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149298
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