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Kaganovich, I.

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WEZC02 Extreme Compression of Heavy Ion Beam Pulses: Experiments and Modeling 2030
  • A. B. Sefkow, R. C. Davidson, P. Efthimion, E. P. Gilson, I. Kaganovich
    PPPL, Princeton, New Jersey
  • J. J. Barnard
    LLNL, Livermore, California
  • J. E. Coleman, P. K. Roy, P. A. Seidl
    LBNL, Berkeley, California
  • D. R. Welch
    Voss Scientific, Albuquerque, New Mexico
  Funding: Research supported by the U. S. Department of Energy.

Intense heavy ion beam pulses need to be compressed in both the transverse and longitudinal directions for warm dense matter and heavy ion fusion applications. Previous experiments and simulations utilized a drift region filled with high-density plasma in order to neutralize the space-charge and current of a 300 keV K+ beam, and achieved transverse and longitudinal focusing separately to a radius < 2 mm and pulse width < 5 ns, respectively. To achieve simultaneous beam compression, a strong solenoid is employed near the end of the drift region in order to transversely focus the beam to the longitudinal focal plane. Simulations of near-term experiments predict that the ion beam can be focused to a sub-mm spot size coincident with the longitudinal focal plane, reaching a peak beam density in the range 1012 - 1013 cm-3, provided that the plasma density is large enough for adequate neutralization. Optimizing the compression under the appropriate experimental constraints offers the potential of delivering higher intensity per unit length of accelerator to the target, thereby allowing more compact and cost-effective accelerators and transport lines to be used as ion beam drivers.

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THPAS083 Charge and Current Neutralization of an Ion Beam Pulse by Background Plasma in Presence of Applied Magnetic Field and Gas Ionization 3675
  • J. S. Pennington
    USC, Los Angeles, California
  • R. C. Davidson, I. Kaganovich, A. B. Sefkow, E. Startsev
    PPPL, Princeton, New Jersey
  Funding: *Research supported by the U. S. Department of Energy under the auspices of the Heavy Ion Fusion Science Virtual National Laboratory.

Background plasma can be used as a convenient tool for manipulating intense charge particle beams, for example, for ballistic focusing and steering, because the plasma can effectively reduce the space-charge potential and self-magnetic field of the beam pulse. We previously developed a reduced analytical model of beam charge and current neutralization for an ion beam pulse propagating in a cold background plasma. The reduced-fluid description provides an important benchmark for numerical codes and yields useful scaling relations for different beam and plasma parameters. This model has been extended to include the additional effects of a solenoidal magnetic field and gas ionization. Analytical studies show that a sufficiently large solenoidal magnetic field can increase the degree of current neutralization of the ion beam pulse. The linear system of equations has been solved analytically in Fourier space. For a strong enough applied magnetic field, poles emerge in Fourier space. These poles are an indication that whistler waves and lower hybrid waves are excited by the beam pulse.

THPAS084 Calculation of the Charge-changing Cross Sections of Ions or Atoms colliding with Fast Ions using the Classical Trajectory Method 3678
  • A. Shnidman
    PU, Princeton, New Jersey
  • R. C. Davidson, I. Kaganovich
    PPPL, Princeton, New Jersey
  Funding: Research supported by the U. S. Department of Energy under the auspices of the Heavy Ion Fusion Science Virtual National Laboratory.

Evaluation of ion-atom charge-changing cross sections is needed for many accelerator applications. The validity of the classical trajectory approximation has been studied by comparing the results of simulations with available experimental data and full quantum-mechanical calculations [1]. Additionally, a theoretical criterion has been developed for the validity of the classical trajectory approximation [2]. For benchmarking purposes, a Classical Trajectory Monte Carlo simulation (CTMC) is used to calculate ionization and charge exchange cross sections for most simple, hydrogen and helium targets in collisions with various ions. The calculated cross sections compare favorably with the experimental results for projectile velocities near the projectile velocity corresponding to the maximum of cross section as a function of projectile velocity. At higher or lower velocities, quantum-mechanical effects become more significant and the CTMC results agree less well with the experimental values of the cross sections.

[1] I. D. Kaganovich, et al., , New Journal of Physics 8, 278 (2006).
[2] Igor D. Kaganovich, et al., Nucl. Instr. and Methods A 544, 91(2005).