DISPERSION BASED BEAM TILT CORRECTION

Transkript

1 DISPERSION BASED BEAM TILT CORRECTION Marc Guetg Paul Scherrer Institut December 17, 2013

2 PSI HIPA

3 PSI HIPA SINQ

4 PSI HIPA SLS SINQ

5 PSI HIPA SLS SINQ SwissFEL

6 SwissFEL

7 SwissFEL

8 Operation mode Gun S/X-Band injector BC1 C-Band Linac BC2 C-BandAlinac 450AMeV 2.1AGeV 2.9AGeV Athos <A3.4AGeV C-BandAlinac Collimator Aramis <A5.8AGeV Undulator period 15 mm Saturation pulse energy 60 µj Saturarion power 2 GW ø brightness #photons/mm mrad 2 s 0.1% bandwidth

9 Operation parameters Energy BC1 BC2 colimator Normal mode Large bandwidth mode Short pulse Long pulse Large bandwidth Charge [pc] σ z [fs] Compression ε slice [nm] Peak current [A]

10 SwissFEL injector test facility Gun S-Band X-Band BC Transverse deflector 7 MeV 180 MeV Test procedures Test components

11 Motivation Undulator x z x x s z Slice centroid oscillation reduces overlap between electron and radiation Reduces FEL performance Increases spot size ε projected Discrepancy between ε projected and ε slice increases

12 Correction of centroid misalignment Source Kick: x c(z)

13 Correction of centroid misalignment Source Propagate Kick: x c(z) Propagate: x c(z) & x c (z)

14 Correction of centroid misalignment Source Propagate Kick: x c(z) Propagate: x c(z) & x c (z) Energy chirp p z Chirp

15 Correction of centroid misalignment Source Propagate Kick: x c(z) Propagate: x c(z) & x c (z) Energy chirp p z Dispersion x z Dispersion Chirp

16 Correction of centroid misalignment Source Propagate Kick: x c(z) Propagate: x c(z) & x c (z) Energy chirp p z Dispersion x z Multipole x c(z) Multipole Dispersion Chirp

17 Correction of centroid misalignment Source Propagate Kick: x c(z) Propagate: x c(z) & x c (z) Energy chirp p z Dispersion x z Multipole x c(z) Second knob x c(z) & x c (z) Multipole Dispersion Chirp

18 Energy induced orbit jitter Gun RF Laser RF power RF power

19 Energy induced orbit jitter Gun RF Laser RF power RF power Phase jitter Amplification trough BC

20 Energy induced orbit jitter Gun RF Laser RF power RF power Phase jitter Amplification trough BC Analogue for amplitude jitter

21 Energy induced orbit jitter Gun RF Laser RF power RF power Phase jitter Amplification trough BC Analogue for amplitude jitter Charge jitter leads to energy jitter

22 Energy induced orbit jitter Gun RF Laser RF power RF power Phase jitter Amplification trough BC Analogue for amplitude jitter Charge jitter leads to energy jitter Leaking dispersion from correction η R 56 = ρ ds BC

23 Parametrization of beam tilt (χ) x c(z) σ x + x c(z) σ x i = Taylor expansion of slice offset x c (z) and angle x c(z) Combine both series into complex values ( ) z n χ n σ z n=0

24 Parametrization of beam tilt (χ) x c(z) σ x + x c(z) σ x i = ( ) z n χ n σ z n=0 Taylor expansion of slice offset x c (z) and angle x c(z) Combine both series into complex values Zero order Orbit x z

25 Parametrization of beam tilt (χ) x c(z) σ x + x c(z) σ x i = ( ) z n χ n σ z n=0 Taylor expansion of slice offset x c (z) and angle x c(z) Combine both series into complex values Zero order Orbit First order Linear tilt x z

26 Parametrization of beam tilt (χ) x c(z) σ x + x c(z) σ x i = ( ) z n χ n σ z n=0 Taylor expansion of slice offset x c (z) and angle x c(z) Combine both series into complex values Zero order Orbit First order Linear tilt Second order Quadratic tilt x z

27 Optics perturbation through χ 1 3 ~ ε χ ε = ε α = 0 ε = ε Influences optics 1 + χ 1 2 (1 + α 2 ) + 2α 1 + α 2 Re(χ 1 ) Im(χ 1 ) 1 + χ 1 2

28 Source: Transverse wakefields off = 0 V x = 0 s V x (s) = W x (s s ) off x (s ) λ(s )ds

29 Source: Transverse wakefields off = 0 V x = 0 off 0 V x 0 s V x (s) = W x (s s ) off x (s ) λ(s )ds

30 Source: Transverse wakefields off = 0 V x = 0 off 0 V x 0 Defocussing s V x (s) = W x (s s ) off x (s ) λ(s )ds

31 Source: Coherent Synchrotron Radiation BC Incoherent Synchrotron Radiation Independent on current profile

32 Source: Coherent Synchrotron Radiation BC Incoherent Synchrotron Radiation Independent on current profile Coherent Synchrotron Radiation Longitudinal dependent energy loss Dispersion varies effectively along bunch Transverse kick of recaptured synchrotron light Dipole

33 Beamsize along at the SITF σx(μm) 80 BC Optics R 16 T 166 Total 20 Dominated by 1 η in the BC 2 η contribution is negligible 0 s Matched Normal (10x) compression Linear longitudinal phase space

34 Ideal, zero length magnets Magnets in dispersive section Dipole 1 η x / 1 η x 0 x 1 η y / 1 η y 0 2 η x / 2 η x 0 s

35 x Ideal, zero length magnets Dipole s Quadrupole magnet Magnets in dispersive section Quad ( 1 η x δ) + x β = η x δ + x β f η χ 1 = f ε x γ < δ > 1 η x / 1 η x 0 1 η y / 1 η y 0 2 η x / 2 η x 0

36 x Ideal, zero length magnets Dipole s Quadrupole magnet Magnets in dispersive section Sextupole ( 1 η x δ) + x β = η x δ + x β f η χ 1 = f ε x γ < δ > Sextupole magnet 1 η x / 1 η x 0 1 η y / 1 η y 0 2 η x / 2 η x 0 ( 2 η x δ 2 ) + ξ x + O(x 2 β + y 2 β) = y 2 β (1 η x δ + x β ) 2 m

37 x Ideal, zero length magnets Dipole s Quadrupole magnet Magnets in dispersive section Skew quad ( 1 η x δ) + x β = η x δ + x β f η χ 1 = f ε x γ < δ > Sextupole magnet 1 η x / 1 η x 0 1 η y / 1 η y 0 2 η x / 2 η x 0 ( 2 η x δ 2 ) + ξ x + O(x 2 β + y 2 β) = y 2 β (1 η x δ + x β ) 2 Skew quadrupole magnet Analogue m

38 Ideal, zero length magnets Magnets in dispersive section y Dipole s Quadrupole magnet ( 1 η x δ) + x β = η x δ + x β f η χ 1 = f ε x γ < δ > Sextupole magnet Skew quad 1 η x / 1 η x 0 1 η y / 1 η y 0 2 η x / 2 η x 0 ( 2 η x δ 2 ) + ξ x + O(x 2 β + y 2 β) = y 2 β (1 η x δ + x β ) 2 Skew quadrupole magnet Analogue m

39 Streak y y p x x t p z z y Operator can only observe x y

40 Streak y y p x x t p z z y Operator can only observe x y x z is not measurable

41 Streak y y p x x t p z z y Operator can only observe x y x z is not measurable Accelerate in y with RF

42 Streak y y p x x t p z z y Operator can only observe x y x z is not measurable Accelerate in y with RF Use longitudinal energy dependence combined with dispersion

43 Method to measure χ z visible tilt - Im(χ) x betatronic phase advance Streak Scan phase advance Normalize Correlate Reconstruct at one point x c(z) + x c(z) i = σ x σ x ( ) z n χ n σ z n=0

44 Beam Algorithm Prepare Streak Measure Optics Momentum < δ > Streak Minimize mismatch

45 Beam Algorithm Prepare Measure PM Streak Knobs in the bunch compressor Quadrupole Sextupole Skew quadrupole Penalty for several phase advances 1. & 2. order x z correlation Chromaticity Correct mismatch

46 Beam Algorithm Prepare Measure PM Correct Streak Use pseudo inverse Apply changes

47 Beam Algorithm Prepare Measure PM Correct Cleanup Streak Remove streak Rematch Check compression

48 Beam Algorithm Prepare Measure PM Correct Cleanup Streak Iterate process

49 Beam Algorithm Prepare Measure PM Correct Cleanup Streak Iterate process Reuse perturbation matrix

50 Beam Algorithm Prepare Measure PM Correct Cleanup Streak Iterate process Reuse perturbation matrix Very robust Optics mismatch Machine drifts

51 GUI

52 Setup for sensitivity study Gun S-Band Laserkk heater S-Band X-Band BC Trans. deflector C-Band BC C-Band C-Band Energy colimator Undulator Spectr. Laser Dipole Skewkquad Sextupole Quad Monte Carlo simulations for combined jitter sources Charge (σ Q /Q = 0.1) RF phase (σ φ = 0.05 ) RF amplitude (σ A /A = )

53 RF and laser stability x y shot-shot orbit [μm] RF tolerances Jitter shot-shot orbit [μm] RF tolerances Jitter 1 σ 2 σ 3 σ Simulations for SwissFEL Orbit jitter low Bunch length jitter negligible Current profile jitter negligible

54 Setup of SwissFEL Gun S-Band Laserkk heater S-Band X-Band BC Trans. deflector C-Band BC C-Band C-Band Energy colimator Undulator Spectr. Laser Dipole Skewkquad Sextupole Quad Tilt sources CSR (3 Stages) Wakefields (X- & C-Band) Knobs in BC1 & BC2 2x2 Quadrupole 2x2 Skew quadrupole 2x2 Sextupole

55 Simulation results x z Large bandwith mode growth [%] pc 200 pc LBW χ 1,x χ 2,x [1e 3] χ 1,y χ 2,y [1e 3] ε x ε y z Simulations using elegant Clear reduction for all cases Higher order modes still uncorrected

56 Setup of SwissFEL Injector Test Facility Gun S-Band X-Band BC Trans. deflector Spectr. Dipole Skew quad Quad Key features Moveable bunch compressor Moveable X-Band cavity

57 Setup of SwissFEL Injector Test Facility Gun S-Band X-Band BC Trans. deflector Spectr. Dipole Skew quad Quad Key features Moveable bunch compressor Moveable X-Band cavity Streaking Transverse deflection cavity

58 Setup of SwissFEL Injector Test Facility Gun S-Band X-Band BC Trans. deflector Spectr. Dipole Skew quad Quad Key features Moveable bunch compressor Moveable X-Band cavity Streaking Transverse deflection cavity Skew quadrupole within BC

59 Setup of SwissFEL Injector Test Facility Gun S-Band X-Band BC Trans. deflector Spectr. Dipole Skew quad Quad Key features Moveable bunch compressor Moveable X-Band cavity Streaking Transverse deflection cavity Skew quadrupole within BC Quadrupole within BC

60 Setup of SwissFEL Injector Test Facility Gun S-Band X-Band BC Trans. deflector Spectr. Dipole Skew quad Quad Key features Moveable bunch compressor Moveable X-Band cavity Streaking Transverse deflection cavity Skew quadrupole within BC Quadrupole within BC

61 Original Measurement results Corrected Measurement Simulation χ offset (mm) arg(χ) offset (mm) [412 nm] ε ε 0 ε offset (mm) Reduction for all phase advances Significant reduction of ε Significant reduction of χ z x

62 Summary Introduction of χ Very robust tilt correction procedure Relevant reduction of χ and ε Works simultaneously in both transversal planes

63 Thank you for your attention My special thanks to Sven Reiche Bolko Beutner Eduard Prat Masamitsu Aiba Simona Bettoni Hans Braun Marco Pedrozzi Thomas Schietinger All technical groups involved at the SITF

64 Optics with χ For χ = χ 0 + χ 1 Beam size σ x = σ x 1 + Im(χ1 ) 2 σ x = σ x 1 + Re(χ1 ) 2 ε = ε 1 + χ 1 2 (1 + α 2 ) + 2α 1 + α 2 Re(χ 1 ) Im(χ 1 ) Optics α = ε ε ( α ) 1 + α 2 Re(χ 1 ) Im(χ 1 ) 1 + α β = β 1 + α 1 + Im(χ 1) Re(χ 1 ) α γ = γ 1 + α 1 + Re(χ 1) Im(χ 1 ) 2 Transfer for frozen longitudinal phase space ( ) Im(χ1 ) = ( 1 ) β β Re(χ 1 ) 0 γ0 1 γ R ( Im(χ1,0 ) Re(χ 1,0 ) )

65 K. Bane, Short-range Dipole Wakefields in Accelerating Structures for the NLC, SLAC-PUB-9663, 2003 M. Borland, elegant: A Flexible SDDS-Compliant Code for Accelerator Simulation, Advanced Photon Source LS-287, D. Edwards, An Introduction to the Physics of High Energy Accelerators, Wiley-vch, 2004.