Determination of electron motion in ERL wigglers 
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Cornell University has a 780m long circular accelerator, CESR, that
collides electrons with positrons.  The energy of these collisions
creates elementary particles that are registered in the detector
CLEO. Furthermore CESR produces highly focused and intense x-ray beams
for the CHESS laboratory.  These x-rays are used in an extremely wide
range of applications, e.g. surface analysis and the determination of
protein structure.

To resolve finer structures with x-ray microscopes and to
resolve how chemical processes evolve with time, one needs to have an
electron beam that is narrower as well as shorter than what CESR could
ever deliver.  Therefore an upgrade, extension, and fundamental
rebuilding of the CESR accelerator is currently being studied which
would incorporate an energy recovery linac (ERL) and should be able
to produce significantly improved electron beam parameters.

The accelerated electron beam would be sent through an arrangement of
many short permanent magnets with alternating polarity.  The fields
cause the electron beam to wiggle through these magnets and such an
arrangement is therefore referred to as wiggler or undulate.  The
curved motion of the electrons creates the intense x-ray
radiation that the CHESS laboratory will use for its experiments.

However, the strong magnetic fields in these wigglers change the
particle distribution in the electron bunches and can cause an
undesired increase of the beam size.

The task for the REU student would be:
(a) Given realistic parameters for the high energy electron beam,
    determine parameters of the wigglers that lead to the desired x-ray 
beams.
    A computer code exists that performs the required calculation.
(b) Compute the magnetic fields in these wigglers.  For this
    one can initially use analytical formulas that assume a simplified
    geometry.
(c) Compute how the bunch shape changes due to the fields of these 
wigglers and
    find ways to compensate the destructive effects.  A computer program 
exists
    that can simulate the particle motion in these fields.  Furthermore
    the compensation of similar destructive effects coming from sextupole
    magnets has already been performed and the code which was used for this
    purpose can be adjusted to deal with the wiggler fields.

Georg Hoffstaetter would supervise the work.  Dave Sagan and Ivan
Bazarov who have written a program that uses analytical formulas to
determine particle motion in simplified wiggler geometries, know the
required x-ray parameters and have performed optimization of particle
motion will help the student to achieve these goals.  But to have work
on the desired x-ray parameters, an interface to CHESS is needed which
has not jet been discussed.