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abstract:
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It has recently been shown that by illuminating a photocathode
with an ultra-short laser pulse of appropriate transverse
profile, a uniform density, ellipsoidally shaped bunch
is dynamically formed, which then has linear space-charge
fields in all dimensions inside of the bunch. We study here
this process, and its marriage to the standard emittance
compensation scenario that is implemented in most modern
photoinjectors. It is seen that the two processes are compatible,
with simulations indicating that a very high brightness
beam can be obtained. The scheme has produced stimulus
for a series of experiments at the SPARC injector at Frascati
in 2006-2007. An initial time-resolved experiment has
been performed involving Cerenkov radiation produced at
an aerogel. We discuss the results of this preliminary experiment,
as well as plans for future experiments to resolve
the ellipsoidal bunch shape at low energy. Future measurements
at high energy based on fs resolution RF sweepers
are discussed.
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