Ultra-Short Low Charge Operation at FLASH and the European XFEL

Transcription

1 Ultra-Short Low Charge Operation at FLASH and the uropean XFL Igor Zagorodnov DSY, Hamburg, Germany 5.8. The 3nd FL Conference, Malmö

2 Outline FLASH layout and desired beam parameters Technical constraints and choosing of machine parameters Simulation methods FLASH beam dynamic simulations for different charges Radiation properties for different charges at FLASH First experimental results for low charges at FLASH Beam dynamics simulations for uropean XFL

3 FLASH layout and desired beam parameters short radiation wavelength ~ high electron energy In accelerator modules ACC, ACC,..., ACC7 the energy of the electrons is increased from 5 MeV (gun) upto MeV (undulator). ACC39 ACC4/5/6/7 In compressors the peak current I is increased from.5-5 A (gun) to 5 A (undulator). short gain length L g 5/ 6 ~ O( ) I (for the optimal beta function) high peak current

4 FLASH layout and desired beam parameters small emittance short gain length L g 5/ 6 ~ O( ) I (for the optimal beta function) small energy spread high peak current lectron beam properties for good lasing High peak current ~ 5 A. Small slice emittance (.3- mm). Small slice energy spread (< 3 kev). ACC39 ACC4/5/6/7 High harmonic module installed in

5 FLASH layout and desired beam parameters rollover compression vs. linearized compression Q=.5 nc ~.5 ka slice emittance > mm Q= nc ACC39 ACC4/5/6/7 ~.5 ka slice emittance ~.3 - mm

6 Technical constraints and choosing of machine parameters r r m m r mm ACC39 V 5 MV V 39 6 MV V 36 MV ACC4/5/6/7 How to provide () a well conditioned electron beam and () what are the properties of the radiation? () Self consistent beam dynamics simulations. () FL simulations.

7 x [ m] 5 Technical constraints and choosing of machine parameters Optics correction y [ m] new V z [m] z [m] a small transverse bunch size before the last dipole M.Dohlus, T. Limberg, Impact of optics on CSR-related emittance growth in bunch compressor chicanes, PAC 5, 5

8 Technical constraints and choosing of machine parameters Working points (8 macroparameters) inverse compression factors s Z () s s () s Z Z Z? ACC39 ACC4/5/6/7 r r What is the optimal choice? 3MeV, 45MeV, r.93m, r 6m, Z 48, Z?, Z?, Z? s - particle position before BC s - particle position between BC and BC3 s - particle position after BC3 s=s =s = for the reference particle

9 v V,, Technical constraints and choosing of machine parameters RF tolerance in ACC for % change of the compression exact approx.( t ) 56( i) Optimum from the approximate solution C r r 56() 56() v Z, k A B 56() 56() v v A r r ky t 56() kx Z ky r 56() r 56() k B t 56() ky r 56() r 56() k v ( X, Y ) T,,, X V v.z,, V,, V, v Z,, cos,,,,, Y Y sin Z r r Z 56() 56() kr r ( ) 56() 56() C Z 3 - optimal compression in BC

10 Technical constraints and choosing of machine parameters Z () s..5 inverse compression function Z very strong compression at the bunch head Z C s[mm] bunch head To avoid very strong compression at the bunch head Z

11 Technical constraints and choosing of machine parameters Z m v V,,, Tolerances ( % change of compression) V V RF tolerances at ACC,, Voltage requirements V, 5MV V,3 6MV V 5 5 Z [m ] Z [m - ] - V v V Z [m ] RF tolerances at the third harmonic module,3,3,3,3,3

12 I [ka] Technical constraints and choosing of machine parameters Z Z Z MeV 45MeV r.93m C Z =48 C Z.84 r Z 6m m Z - m - a free parameter to move the peak

13 Charge Q, nc Technical constraints and choosing of machine parameters Working points (8 macroparameters) nergy in BC, [MeV] nergy in BC3, [MeV] Deflecting radius in BC r, [m] Deflecting radius in BC3 r, [m] Compression Total First Second in BC compression derivative derivative C C Z ', Z '', [m - ] [m - ] e e e e e3 C : scaling for different charges '' I x kxx x C ( Q) I ( ) 3 3 A x x y (trajectory equation in FODO cell) Q We have used a more aggressive scaling.

14 Technical constraints and choosing of machine parameters 8 macroparameters define 6 equations s (), () () Z, s 3 s s () s Z, () Z, () Z 3. s s s *I.Zagorodnov and M.Dohlus, Multistage bunch compression, WPB3 Analytical solution without self-fields* A( x) f x A ( f ) nonlinear operator (defined analytically) x V V V,,,3,3 f Z Z Z Z ACC39 V,,,,3,,3 V V, ACC4/5/6/7

15 Technical constraints and choosing of machine parameters Analytical solution without self-fields x A ( f ) Solution with self-fields A( x) f nonlinear operator (tracking with self-fields) ( ) ( ) x A A x f A x numerical tracking n n n ( ) ( ) x A A x f A x f A( x ) n n f f f n n g g f n n n xn A ( gn) residual in macroscopic parameters analytical correction of RF parameters

16 FLASH beam dynamic simulations for different charges 3d simulation method (self-consistent) ACC39 ACC4/5/6/7 W TM W 3 W TM 3W TM ASTRA ( tracking with space charge, DSY, K. Flötmann) CSRtrack (tracking through dipoles, DSY, M. Dohlus, T. Limberg) ALIC (3D FL code, DSY, I. Zagorodnov, M. Dohlus ) W -TSLA cryomodule wake (TSLA Report 3-9, DSY, 3) W3 - ACC39 wake (TSLA Report 4-, DSY, 4) TM - transverse matching to the design optics

17 FLASH beam dynamic simulations for different charges simulation methods (looking for working points) d analytical solution without collective effects (8 macroparameters -> 6 RF settings) d tracking with space charge and wakes ~ seconds ( cpu) accelerator s s V ks compressor quasi 3d tracking with all collective effects ~ 3 min ( cpu) cos s s s s s 3 s s r t u accelerator s s V ks cos s s matrix transport for x & y CSRtrack x A ( f ) A ( x ) f x x A( x) f initial guess ~ 5 iterations ~ 5 iterations 3d tracking with all collective effects ~ h (46 cpu-s) Astra CSRtrack A( x) f f f final result

18 FLASH beam dynamic simulations for different charges 8 macroparameters define 6 equations A( x) f Analytical solution without self-fields + iterative procedure with them RF settings in accelerating modules Charge, nc V,, [MV],, [deg] V,3, [MV],3, [deg] V, [MV], [deg] ACC39 ACC4/5/6/7

19 FLASH beam dynamic simulations for different charges Q= nc [MeV] Phase space Current, emittance, energy spread I [ka] x [μm] 34fs y [μm].5 [MeV] bunch head x y 3[μm].4 [μm]

20 FLASH beam dynamic simulations for different charges Q=.5 nc [MeV] Phase space 4.5 Current, emittance, energy spread fs I [ka] x [μm] y [μm] [MeV] bunch head x.5[μm] y.84 [μm]

21 FLASH beam dynamic simulations for different charges [MeV] Phase space Q=.5 nc.5.5 Current, emittance, energy spread I [ka] 5fs Space charge impact bunch head.5 y [μm] x [μm] [MeV] x y.4 [μm].74 [μm]

22 FLASH beam dynamic simulations for different charges Q=. nc [MeV] Phase space 4 Current, emittance, energy spread I [ka].5.5 5fs x [μm] y [μm] bunch head [MeV] x y [μm].6 [μm]

23 [MeV] FLASH beam dynamic simulations for different charges Q=. nc Phase space Current, emittance, energy spread I [ka] fs.5 [MeV] x [μm] y [μm] bunch head x y.48[μm].5[μm]

24 FLASH beam dynamic simulations for different charges Q=. nc.6a 3.8 5A 3.4=6A ACC39 ACC4/5/6/7 [MeV] xy,.7 [μm] x y. [μm].7 [μm] [MeV] x y.7 [μm].7 [μm] [MeV] CSR impact.3.5. [kev].5. x [μm].5 I [ka].5..5 I [A] x [μm].5 y [μm] I [ka] [MeV]

25 FLASH beam dynamic simulations for different charges Q=. nc r 56 = [m], t 566 =.6 [m] ACC39 ACC4/5/6/7 x y.9 [μm].3[μm] [MeV] [MeV] x y.5[μm].4 [μm] x y [MeV].5[μm].5[μm] Space charge impact.5 I [ka].5 I [ka].5 I [ka]

26 FLASH beam dynamic simulations for different charges Tolerances (analytically) without self fields ( % change of compression) Q, nc ACC V /V , degree ACC39 V /V , degree ACC/3 V /V , degree Tolerances (from tracking) with self fields agree with this table

27 Radiation properties for different charges How to provide () a well conditioned electron beam and () what are the properties of the radiation? () Self consistent beam dynamics simulations. We are able to provide the well conditioned electron beam for different charges. But RF tolerances for low charges are tough. () FL simulations (next slides).

28 Radiation properties for different charges Slice parameters are extracted from S simulations for SAS simulations x y x' y' I x y x y x y [ mm] x.5 slice emittance Q nc Q.5 nc I [ka].5.5 current Q nc Q.5 nc Q.5 nc.5 Q. nc Q. nc s s s -5 5 Charge Q, nc.5. Longitudinal electron beam size s, mm Transverse electron beam size r, mm

29 Q μj nc 3. nc Radiation properties for different charges Radiation energy statistics (-5 runs) Mean energy nc. 5 nc z [m] z fs Radiation pulse width (RMS) nc.5 nc. nc zm [ ] Charge, nc Mean radiation energy, mj Pulse radiation width (FWHM), fs

30 .5.5 p ( ) Q= nc Radiation properties for different charges 4% M48 z=m p ( ) Q=. nc Gamma distr. 5% M p ( ) 3 p ( ) 8 3% z=m.5 %

31 .6 Radiation properties for different charges Q= nc Q=. nc P i GW z=m I [a.u] P GW I [a.u] t[fs] P GW P i GW t[fs] 8 P i GW 8 P i GW 6 4 I [a.u] z=m 6 4 I [a.u] P GW P GW t[fs] - - t[fs]

32 Radiation properties for different charges at FLASH with harmonic module without* Bunch charge, nc Wavelength, nm Beam energy, MeV Peak current, ka Slice emmitance,mm-mrad Slice energy spread, MeV Saturation length, m 3-3 nergy in the rad. pulse, mj Radiation pulse duration FWHM, fs Averaged peak power, GW Spectrum width, % Coherence time, fs *).L.Saldin at al, xpected properties of the radiation from VUV-FL at DSY, TSLA FL 4-6, 4.

33 First experimental results for low charges at FLASH acknowledgments to Ch. Behrens Q=.4 nc C.Behrens, C.Gerth, Measurement of Sliced-Bunch Parameters at FLASH, MOPC8. strong compression at the bunch head Z we need, Z I=.6 ka increase third harmonic voltage or reduce BC energy

34 acknowledgments to Ch. Behrens Q=. nc First experimental results for low charges at FLASH strong compression at the bunch head Z we need, Z I=8 A increase third harmonic voltage or reduce BC energy

35 Beam dynamics simulations for the uropean XFL 3 stage bunch compression system: BC BC BC3 x[m] z[m]

36 Beam dynamics simulations for the uropean XFL Working points ( macroparameters) s Z () s s () s Z s3 Z3 () s Z 3 Z 3 Gun M M 4 M, M,3 M 3 3 MeV r? 7 MeV r? 4 MeV 3 3 r? What is the optimal choice? r?, r?, r?, C?, C? 3

37 Beam dynamics simulations for the uropean XFL r?, r?, r?, C?, C? 3 Wake compensation Restriction on maximal energy chirp at BCs r L 3 56(3) CC C W3 r56(3) r56(3) r56(3) max(,min ) r L 56() C C 56() 56() 56() r max( r,min r ) L r56() C r max( r,min r ) 56() 56() 56() C r 56(3) C r56() C r56() 8 C C C

38 C RF tolerance % i Beam dynamics simulations for the uropean XFL v V,.5% i, 5 max i( s) min i( s) s s RF constrains Q=. nc C Current, emittance, energy spread [MeV] I 5 ka x [μm] y [μm] x y [μm]. [μm] Longitudinal phase space

39 C i Beam dynamics simulations for the uropean XFL RF tolerance 4%..8 v V.8..4,, 5.6.5% RF constrains max i( s) min i( s) s s i Q=. nc C x [μm] Current, emittance, energy spread I 5 ka y [μm] fs -5 5 [MeV] - - x y 5-5.5[μm].[μm] Longitudinal phase space

40 Beam dynamics simulations for the uropean XFL Beam properties for different charges Bunch charge, nc Peak current, ka ~ 5 Slice emmitance,mm-mrad Slice energy spread, MeV (without laser heater) Bunch length FWHM, fs Schneidmiller, M.V.Yurkov, xpected Properties of the Radiation from the uropean XFL Operating at the nergy of 4 GeV, MOPC5.

41 Summary () Self consistent beam dynamics simulations for FLASH and uropean XFL We are able to provide the well conditioned electron beam for different charges. But RF tolerances for low charges are tough. () FL simulations for FLASH The charge tuning (- pc) in SAS mode allows to tune - the radiation pulse energy (3-4 mj) - the pulse width (FWHM -7 fs). Acknowledgements to my colleagues from DSY Beam Dynamics Group.