PPPL, Princeton, New Jersey
HCL, Cambridge, Massachusetts
PU, Princeton, New Jersey
Funding: Research supported by the U.S. Department of Energy.
The evaluation of ion-atom charge-changing cross sections is needed for many accelerator applications. A classical trajectory Monte Carlo (CTMC) simulation has been used to calculate ionization and charge exchange cross sections. For benchmarking purposes, an extensive study has been performed for the simple case of hydrogen and helium targets in collisions with various ions. Despite the fact that the simulations only account for classical mechanics effects, the calculated values are comparable to the experimental results for projectile velocities in the region corresponding to the maximum cross section. Shortcomings of the CTMC method for multi-electron target atoms are also discussed.
PPPL, Princeton, New Jersey
Funding: Research supported by the U. S. Department of Energy.
This paper presents a survey of the present theoretical understanding based on advanced analytical and numerical studies of collective interactions and instabilities for intense one-component ion beams, and for intense ion beams propagating through background plasma. The topics include: discussion of the condition for quiescent beam propagation over long distances; the electrostatic Harris instability and the transverse electromagnetic Weibel instability in highly anisotropic, one-component ion beams; and the dipole-mode, electron-ion two-stream instability (electron cloud instability) driven by an unwanted component of background electrons. For an intense ion beam propagating through a charge-neutralizing background plasma, the topics include: the electrostatic electron-ion two-stream instability; the multispecies electromagnetic Weibel instability; and the effects of a velocity tilt on reducing two-stream instability growth rates. Operating regimes are identified where the possible deleterious effects of collective processes on beam quality are minimized.
PPPL, Princeton, New Jersey
LLNL, Livermore, California
LBNL, Berkeley, California
Voss Scientific, Albuquerque, New Mexico
Funding: Research supported by the US Department of Energy.
Neutralized drift compression offers an effective means for particle beam focusing and current amplification. In neutralized drift compression, a linear radial and longitudinal velocity drift is applied to a beam pulse, so that the beam pulse compresses as it drifts in the focusing section. The beam intensity can increase more than a factor of 100 in both the radial and longitudinal directions, totaling to more than a 10,000 times increase in the beam density during this process. The optimal configuration of focusing elements to mitigate the time-dependent focal plane is discussed in this paper. The self-electric and self-magnetic fields can prevent tight ballistic focusing and have to be neutralized by supplying neutralizing electrons. This paper presents a survey of the present numerical modeling techniques and theoretical understanding of plasma neutralization of intense particle beams. Investigations of intense beam pulse interaction with a background plasma have identified the operating regimes for stable and neutralized propagation of intense charged particle beams.
