Wakefields%20in%20XFEL%20undulator%20intersections

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Wakefields in XFEL undulator intersections
Igor Zagorodnov Beam Dynamics Group
Meeting 26.02.07
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(No Transcript)
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Aluminium
Elliptical chamber length 5122 mm
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Absorber length 3mm Tapers 29.5 mm width
9mm heigh 8mm
Copper
Absorber length 22 mm
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Cavity BPM design, Dirk Lipka
Copper
absorber
round pipe
Round pipe length 690mm
elliptical pipe
Cavity BPM 2 Pillbox cavities with gap 10mm
and distance 45 mm between them
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Elements
Elliptical chamber 5122 mm
Absorber 22 mm
Round pipe 690 mm
51222269050 5884 mm
Cavity BPM 2 Pillbox cavities with gap 10mm
and distance 45 mm between them
Pumping slots 22550 mm
Not considered (see TESLA FEL 2005-10)
216 mm
(50001100)-5884266
Flange gaps? Belows? ???
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Absorber
5 mm
4 mm
9.5 mm
3 mm
5 mm
4 mm
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Absorber. Effect of Tapering
Loss, V/pC Spread, V/pC
step 89 35
taper 48 39
taper step 52 26
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Absorber. Effect of Tapering
This taper has no effect.
The taper angle should be about 3 grad.
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Absorber. Long Elliptical Step Collimator
Loss86 V/pC
G.Stupakov, K.L.F.Bane, I.Zagorodnov Optical
approximation in the theory of geometric
impedance, in preparation The semi-analytical
approach developed in the paper allows to
calculate high-frequency impedance of any short
transition.
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AbsorberRound Pipe
Elliptical 15mm8.8mm
Absorber 9mm8mm
Round R?
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EllipticalRound Pipe
Elliptical 15mm8.8mm
Round R?
Elliptical 15mm8.8mm
ER
RE
Loss V/pC
Let us forget about absorber and suggest that we
want to have a round pipe. Why do not take a
round absorber with R5mm?
Total
ER
RE
R cm
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AbsorberRound PipeElliptical Pipe
Elliptical 15mm8.8mm
Absorber 9mm8mm
Round R?
Elliptical 15mm8.8mm
EA
AR
RE
Loss V/pC
Total
AR
RE
R cm
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Geometric Wakes
Type I
Old
Loss V/pC
R cm
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Geometric Wakes
Type I
Type II
Loss V/pC
Old
40
R cm
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GeometricResistive Wakes
Loss kV/nC
Spread kV/nC
geom.
resistive
R cm
R cm
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GeometricResistive Wakes
L690mm
R4.5mm
resistive
Loss, V/pC Spread, V/pC
res. 22 27
geom. 87 34
total 109 55
geom.
total
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(T.Wohlenberg)
Main Pipe (resistiveoxid layerroughness)
Aluminium
resistive total
Loss 225 241
Spread 238 310
resistive
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BPM
10 mm
10 mm
45 mm
38.58 mm
4.5 mm
26.29 mm
only first pillbox total
Loss 25 48
Spread 10 19
BPM
2pillbox
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Pumping Slots
2 items?
Old geometry!
Loss 9218
Spread 428
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Impedance Budget
Undulator pipe Pump (2 items) BPM (2 pillboxes) Round pipe in intersection with absorber Round pipe in intersection with absorber
15mm 8.8mm (5122 mm) Old geometry 210mm pipe R4.5 absorber 8mm9mm (69022712mm) pipe R5mm absorber R5mm (712mm)
Loss, kV/nC 241 18 48 109 74
Spread, kV/nC 310 8 25 55 41
Old budget from TESLA-FEL 2005-10 (elliptical
pipe 157.6 mm)
Energy Spread
V/pC
Loss, V/pC Spread, V/pC
Total geom. pro section 70 25
resistive (Al) 6.1m 303 325
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Conclusion

• In new budget the energy spread is larger by 14
  .
• Intersection causes about 25 of the energy
  spread.
• Round pipe with R4.5 mm does not increase
  longitudinal wake.
• To suppress the geometric wake the tapers should
  be less than 3 grad.
• Why do not take a round absorber with R5mm?
• A description of 216 mm? (bellows, flange gaps,
  etc)

Energy Spread
V/pC