X-Ray Free Electron Lasers

1. X-Ray Free Electron Lasers Lecture 6. New FEL Schemes and Challenges Igor Zagorodnov DeutschesElektronen Synchrotron TU Darmstadt, Fachbereich 18 22. June 2014

2. Contents • Motivation • Self-seeding scheme • Nonlinear harmonic generation • High-gain harmonic generation (HGHG) • Echo-enabled harmonic generation (EEHG) • Harmonic lasing • Purified SASE scheme (pSASE) • Energy spread cooling scheme • Table-top FEL • Outlook

3. Motivation Coherence Longitudinal profile with large statical fluctuations radiation electrons Transverse profile is coherent

4. Motivation Coherence Cooperation length: lc~ /4πρ (slippage length within one gain length) lb c/2πlc seed c/lb 2πlc FEL power FEL spectrum

5. Self-seeding scheme radiation amplifier SASE-FEL monochromator electronen SASE • SASE in the first undulator • monochromator filters the radiation • „seeded“ amplification in the second undulator • Grating monochromator J. Feldhaus et al, Opt.Comm. 140, p.341 (1997) • Gas cell monochromator G.Geloni et al, DESY 10-033 (2010)

6. Non-linear harmonic generation Higher harmonics in undulator (spontaneous radiation) Spectral density in forward direction. The absolute bandwidthisthe same

7. Non-linear harmonic generation Higher harmonics in FEL radiation Coupling factor in Lecture 3?

8. Non-linear harmonic generation A steady energy transfer? The electron energy changes as described by the equation

9. Nonlinear harmonic generation

10. Nonlinear harmonic generation A steady energy transfer?

11. Nonlinear harmonic generation Effective coupling factors

12. Nonlinear harmonic generation K = 1 K = 3 K = 10 Ratio of power gain length at the n-th harmonic to that at the fundamental:

13. Nonlinear harmonic generation Normalized high-gain FEL model

14. Nonlinear harmonic generation

15. Nonlinear harmonic generation

16. Nonlinear harmonic generation • Near saturation, roughly 1% of the power of fundamental is emitted in the third harmonic • Spectrum has the same width as that of the fundamental • The maximal power is decreasing function of harmonic number • Nonlinear harmonics have larger statistical power fluctuations from shot to shot

17. High-gain harmonic generation (HGHG) large energy spread • energy modulation with frequency ω • conversion in density modulations • coherent radiation with frequency nω in radiator section

18. High-gain harmonic generation (HGHG) • in modulator energy changes • phase remains approx. the same

19. High-gain harmonic generation (HGHG) • in chicane higher energy particles are bent less than lower energy particles • energy of particles remains approx. the same

20. High-gain harmonic generation (HGHG)

21. High-gain harmonic generation (HGHG)

22. High-gain harmonic generation (HGHG) L.H.Yu et al, PRL 91, 074801 (2003) temporally coherent radiation HGHG was demonstrated at the third harmonic of 800 nm

23. Echo-enabled harmonic generation G. Stupakov, PRL 102, 074801 (2009)

24. Echo-enabled harmonic generation

25. Echo-enabled harmonic generation

26. Echo-enabled harmonic generation For HGHG For EEHG

27. Echo-enabled harmonic generation G. Stupakov, PRL 102, 074801 (2009) • the first laser produces energy modulation • the first chicane is strong, rotates phase space • the second laser produces again energy modulation • The second chicane converts the energy modulation in density modulation

28. Echo-enabled harmonic generation only the second laser ON experiment for EEHG both lasers ON D.Xiang et al, PRL 108, 024802 (2012)

29. Harmonic lasing harmonic lasing non-linear harmonic generation

30. Harmonic lasing retuned to fundamental harmonic only

31. Harmonic lasing harmonic only retuned to fundamental

32. Harmonic lasing

33. Purified SASE scheme U13 … U18 U1 U2 U3 … … U7 U8 U9 U10 U11 U12 λ1 =0.6 nm K = 2, λ1 =0.6 nm K=6.3,λ1 =4.2 nm 6 GeV

34. Purified SASE scheme U13 … U18 U1 U2 U3 … … U7 U8 U9 U10 U11 U12 λ1 =0.6 nm K = 2, λ1 =0.6 nm K=6.3,λ1 =4.2 nm 6 GeV At the exit of U10 At the exit of U11 At the exit of U12 At the exit of U9 2πlc≈ 4~ 5 fs 2πlc≈1 fs

35. Energy spread cooling scheme H.Deng , arXiv:1305.7041 (2013)

36. Energy spread cooling scheme

37. Energy spread cooling scheme Two electrons through modulator

38. Energy spread cooling scheme H.Deng , arXiv:1305.7041 (2013)

39. Energy spread cooling scheme H.Deng , arXiv:1305.7041 (2013)

40. Energy spread cooling scheme 1D simulations 3D simulations H.Deng , arXiv:1305.7041 (2013)

41. Table-top FEL External injection

42. Table-top FEL “Bubble” regime

43. Table-top FEL • λ=740 nm H.-P. Schlenvoigt et al, Nature Physics 4, 130 (2008) • λ=17 nm spontaneous undulator radiation with laser-plasma accelerator M.Fuchs et al, Nature Physics 5, 826(2009)

44. Table-top FEL M.Fuchs et al, Nature Physics 5, 826(2009) no FEL radiation so far

45. Outlook Growth of brillance of X-ray and growth of computer power European XFEL 3rd SR generation 2nd SR generation 1st SRs

46. Outlook Wavelength of radiation Saturation? λ=0.5 A λ= 0.25 A MaRIE (Los Alamos) concept Q. R. Marksteiner, FEL 2011, TUPA28, 2011

47. Outlook „Meine Vision für DESY ist dass wir die deutsche Nobelpreisschmiede werden.“ Professor Helmut Dosch (Film „Licht der Zukunft“) • shorter wave length • shorter radiation pulses • higher brilliance • longitudinal coherence • compact facilities