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XX International Linac Conference

MOE11 (Poster)

Presenter: Steven Lund (LLNL)
Status: Complete
FullText: ps.gz or pdf
Eprint: physics/0009095

Emittance Growth from the Thermalization of Space Charge Nonuniformities

Steven M. Lund, John J. Barnard (Lawrence Livermore National Laboratory Lawrence Berkeley National Laboratory)

Real beams are expected to have some degree of space-charge nonuniformity and rms envelope mismatch in any accelerator system. For intense beams, such perturbations will evolve and can become thermalized as the distribution relaxes to a more thermal-like distribution characterized by uniform density and temperature. Past studies [1] have employed a continuous focusing model and energy conservation to estimate emittance increases from the thermalization of initial rms mismatches in the beam envelope and initial space-charge nonuniformities. Here we extend these studies to analyze the emittance growth of an initial beam composed of a space-charge dominated beam equilibrium with an azimuthally symmetric normal mode perturbation. These normal modes were derived in an earlier study using a fluid theory [2] and are expected to be characteristic of beams with flat density profiles -- a general feature of smooth equilbrium distributions in a space-charge dominated regime. The initially perturbed beam is taken to have the nonuniform space-charge profile and self-consistent envelope mismatch characteristic of a single normal mode perturbation. Since an arbitrarily perturbed beam will evolve as a superposition of normal modes, this formulation helps characterize possible emittance increases associated with classes of nonuniformities in a self-consistent manner.
[1] Martin Reiser, Theory and Design of Charged Particle Beams (Wiley, New York, 1994).
[2] Steven M. Lund and Ronald C. Davidson, Physics of Plasmas 5, 3028, (1998).
*This work was performed under the auspices of the U.S. Department of Energy by University of California at Lawrence Livermore National Laboratory and Lawrence Berkeley National Laboratory under contract Nos. W-7405-Eng-48 and DE-AC03-76SF00098.

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