Challenges for the European XFEL Project at DESY

Challenges for the European XFEL Project at DESY Wakefield Calculations and Impedance Database 2% 4% 23% 32% 22% Igor Zagorodnov 11% 1% 4% COL CAV TDS BPMA KICK PIP 20 PUMCL FLANG ICFA mini-Workshop on “Electromagnetic wake fields and impedances in particle accelerators“ Erice, Sicily 23 -28. April 2014

Overview ØThe European XFEL Project Ø Wakefield Calculations for the XFEL Ø Cavity and Coupler Wakes Ø Collimators Ø High-Frequency Impedances Ø Resistive, Roughness, Oxide Layer Wakes Ø Wakefields in Undulator Section Ø Impedance Database Ø Start-to-End Simulations with Wakes Ø Impact of Wakes on FEL Performance Ø Challenges Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 2

The European XFEL Project Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 3

The European XFEL Project Linac Coherent Spring-8 Angstrom European XFEL Light Source Compact Laser (LCLS) (SACLA) Location USA Japan Start of 2009 2011 commissioning Accelerator normal conducting technology Number of light flashes per 120 60 second Minimum 0. 15 nm 0. 1 nm wavelength Length of the facility 3000 m 750 m Deutschland 2016 superconducting 27 000 0. 05 nm 3400 m Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 4

The European XFEL Project Layout 3 rd harmonic RF Gun dogleg BC 0 laser heater σs = 2 mm Ipeak= 50 A Q = 1 n. C 12 accelerator modules 4 accelerator modules BC 1 main linac collimator BC 2 SASE 1 bunch compressors σs = 1 mm Ipeak= 100 A E = 130 Me. V σs = 0. 1 mm Ipeak= 1 k. A E = 600 Me. V σs = 0. 01 -0. 02 mm Ipeak= 5 -10 k. A E = 2400 Me. V Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 5

Cavity and Coupler Wakes Wakefunctions of TESLA Cryomodule 2 Cryomodule 1 1 8 8 cavities + 9 belows =12 m 1 8 12 m Cryomodule 3 1 8 12 m Ø Wakes for short bunches up to 50 um have been studied Ø To reach the steady state solution 3 cryomodules are considered Ø For longitudinal case the wakes were studied earlier by A. Novokhatski et al*. The transverse results are calculated with ECHO**. *Novokhatski A, Timm M, Weiland T. Single Bunch Energy Spread in the TESLA Cryomodule, DESY, TESLA-1999 -16, 1999 **Weiland T. , Zagorodnov I, The Short-Range Transverse Wake Function for TESLA Accelerating Structure, DESY, TESLA-2003 -19, 2003 Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 6

Cavity and Coupler Wakes Wakefunctions of TESLA Cryomodule One-cell structure Periodic structure a – iris rtadius, g – cavity gap - fit parameters K. L. F. Bane, SLAC-PUB-9663, LCC-0116, 2003 Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 7

Cavity and Coupler Wakes Wakefunctions of TESLA Cryomodule Comparison of numerical (points) and analytical (lines) integral parameters for the third cryomodule Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 8

Cavity and Coupler Wakes Transverse wake of TESLA Cryomodule Comparison of numerical (grays) and analytical (dashes) transverse wakes Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 9

Cavity and Coupler Wakes Coupler Kick Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 10

Cavity and Coupler Wakes Coupler Kick Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 11

Cavity and Coupler Wakes Coupler Kick Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 12

Cavity and Coupler Wakes Transverse Deflecting Structure TESLA Report 2004 -01, DESY, 2004 Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 13

Cavity and Coupler Wakes Transverse Deflecting Structure Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 14

Cavity and Coupler Wakes Transverse Deflecting Structure Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 15

Cavity and Coupler Wakes Transverse Deflecting Structure Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 16

Cavity and Coupler Wakes Transverse Deflecting Structure Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 17

Cavity and Coupler Wakes Third-Harmonic Section Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 18

Cavity and Coupler Wakes Third-Harmonic Section Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 19

Collimator Wakes Tapered Collimators The bunch moves very close to the aperture wall! Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 20

Collimator Wakes I. Zagorodnov et al, DESY, TESLA-2003 -19, 2003 M. Dohlus et al. , DESY, FEL Report 2010 -04, 2010 Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 21

Collimator Wakes Short/Long 3 D Step Collimators Kick factor vs. collimator length. A round collimator (left), a square or rectangular collimator (s = 0. 3 mm, right). Zagorodnov I. , Bane K. , Wakefield Calculations for 3 D Collimators, in Proceedings of EPAC 2006 Conference, Edinburgh, Scotland, 2006 (SLAC-PUB-11938) Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 22

Collimator Wakes Short/Long 3 D Step Collimators long short Zagorodnov I. , Bane K. , Wakefield Calculations for 3 D Collimators, in Proceedings of EPAC 2006 Conference, Edinburgh, Scotland, 2006 (SLAC-PUB-11938) Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 23

Collimator Wakes Short/Long Round Collimators long short Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 24

High-Frequency Impedances Optical Approximation , Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 25

High-Frequency Impedances Transverse Impedance of Laser Mirror of RF Gun Analytical Numerical ky(0, 0), ky(d), ky(q), V/p. C/ m 13. 1 V/p. C/ m 12. 1 11. 6 V/p. C/ m 13 24 V/p. C/ m 12 7. 5 0. 124 0. 120 Analytical Numerical 0. 12 0. 08 Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 26

High-Frequency Impedances Transverse Impedance of OTR Screens Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 27

High-Frequency Impedances Longitudinal Impedance of Round-to-Rectangular Transitions in Bunch Compressors Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 28

High-Frequency Impedances of Round Misaligned Pipe M. Dohlus et al, High Frequency Impedances in European XFEL, DESY 10 -063, 2010 Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 29

High-Frequency Impedances Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 30

Resistive, Roughness, Oxide Layer Wakes Round Resistive Pipe with Roughness and Oxide Layer The effect of the oxide layer and the roughness can be taken into account through the inductive surface impedance M. Dohlus. TESLA 2001 -26, 2001 A. Tsakanian et al, TESLA-FEL 2009 -05 Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 31

Resistive, Roughness, Oxide Layer Wakes Round vs. Elliptical pipe Loss, V/p. C Spread, V/p. C round 237 285 elliptical 239 274 Mathcad script for arbitrary shape with roughness and oxide layer (author M. Dohlus) http: //www. desy. de/fel-beam/s 2 e/codes. html Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 32

Wakefields in Undulator Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 33

Wakefields in Undulator N Element from to Effective Length mm mm mm Material Conduct. Relax. Time Oxid layer Rough ness 1/Omm/m sec nm nm 1 Eliptical pipe 0 5288 5161 Aluminium 3, 66 E+07 7, 10 E-15 5 300 2 Pump 5161 5266 105 Aluminium 3, 66 E+08 7, 10 E-15 5 300 3 Absorber/Round transition 5266 5288 22 Copper 5, 80 E+07 2, 46 E-14 5 300 4 Round pipe 5288 6100 652 Copper 5, 80 E+07 2, 46 E-14 5 300 5 Below 5288 5318 30 Be. Cu 174 2, 78 E+07 2, 46 E-14 5 300 1, 40 E+06 2, 40 E-15 5 300 2, 78 E+07 2, 46 E-14 5 300 6 BPM 5373 5473 100 Stainless Steel 304 7 Below 5513 5543 30 Be. Cu 174 8 Round/Eliptical transition 6100 0 1 2 3 5 6 7 4 Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 34 8

Wakefields in Undulator Absorber in 3 D (2005) taper 10 mm Loss (Spread), V/p. C step 110 (43) taper 10 mm 74 (48) taper 20 mm 50 (43) Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 35

Wakefields in Undulator Impedance of Eliptical-to-Round Transition with Absorber Dependence of the loss factor from the radius of the round pipe. The left graph presents the results without the absorber, the right graph presents the results with the absorber included. The black dots show the numerical results from CST Particle Studio. Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 36

Wakefields in Undulator Pump Loss, V/p. C Spread, V/p. C Peak, V/p. C pump 15 10 -24 pillbox 40 16 -57 Pillbox 2 D/3 D Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 37

Wakefields in Undulator Energy Spread for Gaussian Bunch (25 μm) Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 38

Wakefields in Undulator Transitive Resistive and Geometrical Wakes in Undulator A. Tsakanian, Ph. D Thesis, 2010 Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 39

Impedance Database Ø There are hundreds of wakefield sources in XFEL beam line. Ø The bunch shape changes along the beam line. Ø Hence, a database with wake functions for all element is required. Ø The wake functions are not functions but distributions (generalized functions). Ø How to keep information about such functions? Ø We need a model. Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 40

Impedance Database Wake function model regular part capacitive singular part (cannot be tabulated directly) resistive inductive it describes singularities s-a, a<1 Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 41

Impedance Database Pillbox Cavity Step-out transition Tapered collimator Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 42

Impedance Database Wake potential for arbitrary bunch shape derivative of the bunch shape Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 43

Impedance Database Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 44

Impedance Database Undulator wake for Q=1 n. C bunch resistive wake Total wake Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 45

Impedance Database Accelerator wakes. Q=1 n. C “warm” pipe 2% 4% collimators 19% 14% 10% 1% 1% 1% 2% 4% cavities COL BPMA TORAO PUMCL CAV OTRA KICK FLANG TDS BPMR PIP 20 Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 46

Impedance Database Longitudinal+Transverse Wakes 3 D Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 47

Start-to-End Simulations with Wakes Beam dynamics simulation (2010) Full 3 D simulation method (200 CPU, ~10 hours) W 1 TM W 3 4 W 1 TM 12 W 1 TM 64 W 1 ASTRA ( tracking with 3 D space charge, DESY, K. Flötmann) CSRtrack (tracking through dipoles, DESY, M. Dohlus, T. Limberg) W 1 -TESLA cryomodule wake (TESLA Report 2003 -19, DESY, 2003) W 3 - ACC 39 wake (TESLA Report 2004 -01, DESY, 2004) TM - transverse matching to the design optics Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 48

Start-to-End Simulations with Wakes 2013 CSRtrack+ASTRA (Guangyao Feng) Elegant (Hyunchang Jin) G. Feng et al. FEL Report 2010 -04, 2013 Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 49

New Results and Comparison with Elegant, Q = 1 n. C Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 50

New Results and Comparison with Elegant, Q = 250 p. C Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 51

SASE for Nominal Bunch Parameters Mismatch and wake Q=1 n. C bunch resistive wake total wake Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 52

SASE for Nominal Bunch Parameters Radiation Q=1 n. C +Wake+Taper +Wake Averaged through 8000 slices Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 53

SASE for Nominal Bunch Parameters Mismatch and wake Q=250 p. C bunch resistive wake Total wake Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 54

SASE for Nominal Bunch Parameters Radiation Q=250 p. C +Wake+Taper +Wake Averaged through 2400 slices Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 55

Impact of Accelerator Wakes on SASE Accelerator wakes. Q=1 n. C “warm” pipe 2% collimators 4% 19% 14% 10% 1% 1% 1% 2% 4% cavities COL BPMA TORAO PUMCL CAV OTRA KICK FLANG TDS BPMR PIP 20 Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 56

Impact of Accelerator Wakes on SASE Accelerator wakes. Q=1 n. C current Full wake Cavities wake Full wake Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 57

Impact of Accelerator Wakes on SASE Beam matched in the peak current. Q=1 n. C at z=85 m full wake (full wake) x 4 (full wake) x 8 current Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 58

Impact of Accelerator Wakes on SASE Beam matched in the peak current. Q=1 n. C Normalized spectrum at z=85 m (full wake) x 8 (full wake) x 4 full wake FWHM=0. 14% FWHM=0. 23% FWHM=0. 6% Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 59

Impact of Accelerator Wakes on SASE Accelerator wakes. Q=250 p. C. “warm” pipe 2% 4% collimators 23% 32% 22% 11% 1% 4% cavities COL CAV TDS BPMA KICK PIP 20 PUMCL FLANG Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 60

Impact of Accelerator Wakes on SASE Accelerator wakes. Q=250 p. C. Cavities wake Full wake Cavities wake Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 61

Impact of Accelerator Wakes on SASE Beam matched in the peak current. Q=250 p. C Normalized spectrum at z=85 m (full wake) x 8 (full wake) x 4 full wake FWHM=0. 29% FWHM=0. 30% FWHM=0. 38% Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 62

Impact of Accelerator Wakes on SASE Summary Energy in the radiation pulse at z=175 m, m. J Spectrum width at z=85 m, % Bunch charge, n. C Accelerator wake 1 0. 25 0. 02 x 1 9 2. 3 0. 46 x 4 8 2. 3 0. 44 x 8 6 2. 3 0. 43 x 1 0. 14 0. 29 0. 55 x 4 0. 23 0. 30 0. 58 x 8 0. 6 0. 38 1. 0 We have considered only the longitudinal wake in a quite coarse model (adding the missed part of the accelerator wake at the undulator entrance). The transverse wakes are neglected. Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 63

Challenges Ø Chamber Wakefields in Bunch Compressors Ø Impact of All (Longitudinal+Transverse) Wakes on the Results of Start-to-End Simulations Ø Transverse Impedance Database Ø Impact of Transverse Wakes on FEL Performance Igor Zagorodnov| Collaboration Meeting at PAL| 2 -6. August 2013 | Seite 64