# Abstracts

## XX International Linac Conference

## MOE11 (Poster)

**Presenter: **Steven Lund (LLNL)

** email: **smlund@lbl.gov

**Status: **Complete

**FullText: **
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**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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