Resistive wall wake in the ILC IR work in progress

1
Resistive wall wake in the ILC IR (work in
progress)
Karl Bane ILC BDS Meeting 16 May 06

• a beam moving off-center in a beam pipe will
  experience a head-tail kick due to the resistive
  wall wakefields in the beam pipegt projected
  emittance growth
• concerned about (a) injection tolerances
  jitter/drift, and (b) beam pipe misalignments
• single bunch effect N 2?1010, Gaussian ?z 300
  ?m
• E 250 GeV, ??y 4?10-8 m, L 1600 m
• assume beam pipe round, SS, radius a 0.01 m

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Resistive wall wake

• normal (long-range) rw wake formulas valid for
  ?zgtgt s0 (ca2/2??)1/3
• can also consider ac conductivity of metal,
  anomalous skin effect
• conductivity of SS (50 less than Cu)

Cu s0 20 ?m
SS s0 77 ?m
(Z0c/?a3) 36 MV/(nC-mm-km)
3
lattice
4
1 Drift/jitter sensitivity
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Tracking via Mathematica program

• ignore energy spread, dispersion cut beamline
  into 1.3 m pieces
• slice Gaussian bunch, track slices through
  lattice initial offset y0 ?y0

6
Tolerance y/?y0 that gives ?? 25
driftwrt bunch centroid, jitterwrt axis
y/?y0
y/?y0
9001250 m plated with Cu
inj phase deg
inj phase deg
-- tol_jit 0.75 when assuming no wakes --smooth
focusing approx (tol_drift)_SS 0.75
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2 Beam pipe misalignment tolerance
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Simulations
9001250 m plated with Cu
--100 seeds --smooth focusing approx. gets ??
0.12
an example seed