Single Side Coupler for input coupler of L01

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Single Side Coupler for input coupler of
L0-1 Jan27-04 Agenda C.Limborg Tolerances
based on maximum emittance growth Review of Blue
book analytical computation Zenghai
Li Computations with S3P of angular kicks from
single side input coupler Discussion of
geometry define dual coupler geometry to be run
by Zenghai Discussion on other studies gun dual
feed, gun geometry, wakefields at first iris
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Reminder The 80 emittance is around 0.9 mm.mrad
Tolerance No more than 1-2 growth from
Head-Tail Wakefield effects
Linear Head-Tail kick at entrance of L0-1
No Solenoid, No Wakefield
With Solenoid, No Wakefield
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First Linac Section Alignment Wakefield effects
Effects of Wakefields (ignoring ) Position
?150 ?m maximum Angular ? 120 ?rad maximum
At end beamline
At end beamline
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PHASE TERM In phase with force Fz Centroid
deflection if field on crest
AMPLITUDE TERM In quadrature with force
Fz Strong Head-to-tail effect if field on crest
Without cavity offset
With cavity offset
determined from microwave perturbation
measurements , but conditions are not described
in blue book
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Without Cavity Offset Amplitude term dominant
(around crest)
With Cavity Offset Amplitude term corrected but
not phase term (which becomes dominant beyond /-
20 degrees off crest)
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Conclusions Tolerance is 120 ?rad for a 10 ps
bunch (due to wakefields along the structure)
Without cavity offset , amplitude term is
dominant with a 1.2 mrad head-to-tail
differential kick when cavity operated around
crest With the cavity offset, only amplitude
term is corrected. The amplitude of the
head-to-tail is now small enough around crest for
a 10 ps bunch, however we want to be able to
operate at least /- 40 degrees off-crest run
20ps bunch l This result is based on the 0.1
factor measured many years ago (in conditions
that we ignore in particular for the field
gradient) For all those reasons a numerical
computation was needed