1. XFEL Beam Dynamics Activity at CANDLE
V. Tsakanov for CANDLE (Armenia)
XFEL Beam Project Meeting , 19 Dec 2005

2. Parameter list BC Booster Linac Energy (GeV) 0.5-2.0 2.0-20
Main linac
2. GeV
20 GeV
0.5 GeV
Booster Linac
Energy (GeV)
Accel. Grad (MV/m)
FODO cells
Emittance (mm-mrad)
Bunch charge (nC)
Bunch rms length (μm)
Initial cor. energy spread % %
Inital uncor. Energy spread keV keV
(includes laser heater)
Misal. Quads, Cav. (mm)
BPM – 0.1mm, res – 0.02mm

3. T. Weiland, I. Zagorodnov, TESLA Rep. 2003-19, 2003.
Wake Potentials
Wake functions
T. Weiland, I. Zagorodnov, TESLA Rep , 2003.

4. Energy Spread σcor=0.4% σcor=0.012% (2.4 MeV) M. Dohlus
Linac Entrance-2 GeV
Linac End – 20 GeV
σcor=0.4%
σcor=0.012% (2.4 MeV)

5. Without initial energy spread
20.8 MV/m
With initial energy spread

6. Coherent Oscillations
Wakefield Effects ( Zero initial energy spread)
Transverse wake
Longitudinal Wake (chromatic)
XFEL Lattice : chromatic dominated emittance dilution

7. Coherent Oscillations
Chromatic effects ( initial energy spread)
Uncorrelated
Correlated x x’ Eo
Eo+ΔE
Eo-ΔE

8. Cavity Misalignments F D
σcavity=0.5mm

9. Modules Misalignments
Standard cell
2,4 and 6 modules per FODO cell

10. Correlated MisalignmentsF D
σcor=0.5mm
Δμ- phase advance per cor. length
Betatron phase contrib.
Δμ=130o (~4 modules)
R.Brinkmann, V.Tsakanov, Snowmass, 2001

11. Cavity tilts F D
σtilt=0.25mrad

12. Quadrupoles misalignments. One-to- One Correction

13. One-to One Correction
Uncorrelated effects

14. Quad misalignments. One-to-One Correction
Correlated effects

15. Summary of Emittance Dilution (Standard Cell)
Booster Linac
Coherent oscillations
uncorrelated · ·10-4
correlated · ·10-3
Cavity Misalignments · ·10-7
Modules Misalignments · ·10-6
Correlated Misal. (130o) ·10-6
Cavity tilts
uncorrelated · %
correlated % %
One-to-One correction
uncorrelated · %
correlated % %
Total Emittance dilution <5% with 2 Modules/Cell

16. Possible modification
Modules per cell Mod 4 Mod Mod
Emittance preservation <5% < 2% ~ 1%
Beta max m ~ 70 m ~100m
Number of FODO cells
Number of quads
Quad Strength K (m-2) ~ ~0.12
Total length m ~1050m ~1000m