[SLAC Pubs and Reports]
The RF Design of an HOM Polarized RF Gun for the ILC
The ILC requires a polarized electron beam. While a
highly polarized beam can be produced by a GaAs-type
cathode in a DC gun of the type currently in use at SLAC,
JLAB and elsewhere, the ILC injector system can be
simplified and made more efficient if a GaAs-type
cathode can be combined with a low emittance RF gun.
Since this type of cathode is known to be extremely
sensitive to vacuum contamination including back
bombardment by electrons and ions, any successful
polarized RF gun must have a significantly improved
operating vacuum compared to existing RF guns. We
present a new RF design for an L-Band normal
conducting (NC) RF gun for the ILC polarized electron
source. This design incorporates a higher order mode
(HOM) structure, whose chief virtue in this application is
an improved conductance for vacuum pumping on the
cathode. Computer simulation models have been used to
optimize the RF parameters with two principal goals:
first to minimize the required RF power; second to reduce
the peak surface field relative to the field at the cathode in
order to suppress field emitted electron bombardment.
The beam properties have been simulated initially using
PARMELA. Vacuum and other practical issues for
implementing this design are discussed.
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