1. Ellipsoidal bunches by 2D laser shaping Bas van der Geer, Jom Luiten Eindhoven University of Technology DESY Zeuthen 30 November 2006 2) Experimental progress 1) Why pancakes do not work with 1nC and 40–60 MV/m Jom Luiten Bas van der Geer work as goodas 3D ellipsoids

2. Waterbags Transverse phase-space –No space-charge induced emittance degradation –No ‘slice’ dependence –O.J. Luiten, S.B. van der Geer et al, PRL 094802, (2004). –Confirmed by J. Rosenzweig and C. Limborg in NIM-A 557 (2006) Longitudinal phase-space –Ideal for linear compression –Manipulation possible at low energy –Energy spread can be recovered –S.B. van der Geer et al, PRST-AB, 9, 044203 (2006)

3. Transverse (5-D) brightness: Brightness

4. Source brightness Options (at fixed Q): Lower Temperature TUltra Cold Plasma cathode B.J. Claessens et al., PRL 95, (2005) 164801 Reduce Surface area ACarbon Nanotubes Needle cathodes … Reduce Pulse duration τ Pancake regime

5. Longitudinal phase space density Long pulsePancake 3 ps30 fs 1 nC 100 pC ~100 A/mm 2~ 1 kA/mm 2 (Both with A=π mm 2 ) z Energy Pancake Long pulse Thermal spread Longitudinal phase-space at cathode

6. The problem is not the high space charge density... Gaussian bunch Brightness degradation

7. pxpx x Gaussian bunch Space charge forces: Non-linear Slice-dependent... the real problem is the space charge density distribution.

8. pxpx x Gaussian bunch 1989 - 2003 Fighting the symptoms: Emittance compensation (B. Carlsten) Optimized transverse profile (L. Serafini) Uniform temporal & radial profile (DESY,...)...

9. Gaussian bunch Waterbag bunch pxpx x Space charge forces: Non-linear Slice-dependent Space charge forces: Linear Slice-independent Thermal-emittance-limited beam! 2004: Fundamental solution

10. History of uniformly charged ellipsoids 1929Have linear fields in all three coordinates O. D. Kellogg, Foundations of Potential Theory (Springer-Verlag, 1929). 1965Ellipsoids with uniform mass collapse into a disk (astrophysics) C.C. Lin et al., Astrophys. J. 142, 1431 (1965). Decades of use as idealized beams … 1997Pancakes evolve into approximate waterbags L. Serafini, AIP Conf. Proc. 413, 321 (1997) 2004Fundamental solution and practical recipe O.J. Luiten, S.B. van der Geer et al, PRL 094802, (2004). O.J. Luiten, S.B. van der Geer et al, EPAC (2004).

11. History of uniformly charged ellipsoids 1929Have linear fields in all three coordinates O. D. Kellogg, Foundations of Potential Theory (Springer-Verlag, 1929). 1965Ellipsoids with uniform mass collapse into a disk (astrophysics) C.C. Lin et al., Astrophys. J. 142, 1431 (1965). Decades of use as idealized beams … 1997Pancakes evolve into approximate waterbags L. Serafini, AIP Conf. Proc. 413, 321 (1997) 2004Fundamental solution and practical recipe O.J. Luiten, S.B. van der Geer et al, PRL 094802, (2004). O.J. Luiten, S.B. van der Geer et al, EPAC (2004). 2006Well received in the accelerator community J.B. Rosenzweig et al., NIM-A 557 (2006), Emittance compensation … C. Limborg et al., NIM-A 557 (2006), Optimum electron distributions … S.B. van der Geer et al, PRST-AB, 9, 044203 (2006), Longitudinal …...

12. 2D Waterbag bunch recipe Femtosecond photoexcitation of pancake bunch Half-sphere transverse laser intensity profile Temporal laser profile is irrelevant Automatic evolution into 3D, uniform ellipsoid fs laser

13. Ellipsoid creation How to Realize Uniform Three-Dimensional Ellipsoidal Electron Bunches O.J. Luiten, S.B. van der Geer et al, PRL 094802, (2004).

14. 1.5 cell, 3 GHz rf-photogun + focusing solenoid E acc = 92 MV/m Q = 100 pC Waterbag bunch in a realistic field z c = 0.9 m, E = 4.5 MeV O.J. Luiten, S.B. van der Geer et al, EPAC (2004).

15. Waterbag bunch in a realistic field Confirmed at higher energies –Compatible with SPARC emittance compensation, 85 MeV J. Rosenzweig et al., NIM-A 557 (2006), p. 87. –50% improvement on transverse emitance for LCLS, 63 MeV C. Limborg et al., NIM-A 557 (2006), p. 106. Thermal emittance! O.J. Luiten, S.B. van der Geer et al, EPAC (2004). 4 MeV

16. Thermal emittance! 10 fs First waterbag bunch in a realistic field O.J. Luiten, S.B. van der Geer et al, EPAC (2004). I=50 A

17. Longitudinal compression ~0.4 m Laser rf φ S.B. van der Geer et al, PRST-AB, 9, 044203 (2006), 3.5 MeV 0.7– 2.0 kA 30– 100 fs 0.7– 1.5 μm

18. 2D shaping @ PITZ Limitations of 2D ‘pancake’ shaping: Laser-pulse duration<< Asymptotic bunch length Fields of image charges<< Acceleration field PITZ: 1 nC, 50 MV/m, R=1 mm: Pulse duration: 30 fs<< 25 psOK Image charges: 36 MV/m<< 50 MV/mQuestionable

19. 2D shaping @ PITZ Settings: 50 MV/m uniform, 1 nC, R=1 mm, 2D shaping of 30 fs ‘pancake’ 0.10.20.51 GPT Charge [nC] 0.0 0.5 1.0 1.5 2.0 2.5 3.0 RMS Emittance [micron] Pancake

20. 3D shaping @ PITZ Settings: 50 MV/m uniform, 1 nC, R=1 mm, 3D shaping of 3 ps ellipsoid Pancake 3D

21. Emission:3D shaping2D shapingHighly non-linear fields! Lower charge densityMaintain short bunch Long pulse lengthHigh acceleration field 3D versus 2D shaping 1.5 ps: 10 μm15 fs: 1 nm

22. 3D shaping @ PITZ Settings: 50 MV/m uniform, 1 nC, R=1 mm, 3D shaping of 10 ps ellipsoid Pancake 3D: 3 ps 3D: 10 ps

23. 3D shaping @ PITZ Settings: 50 MV/m uniform, 1 nC, R=1 mm, 3D shaping of 10 ps ellipsoid Pancake 3D: 3 ps 3D: 10 ps 0.10.20.51 GPT Charge [nC] 0.0 0.5 1.0 1.5 2.0 2.5 3.0 RMS Emittance [micron] Pancake 100 MV/m

24. Next Experimental progress at Eindhoven University of Technology Experimental progress at Eindhoven University of Technology Jom Luiten

25. 2D ‘pancake’ shaping Ingredients: Ti:Sapphire 30 fs laser Transverse shaping only Ti:Saphire 30 fs laser Colinear THG 800nm → 266 nm Spatial filtering: 800 nm gaussian π shaper: Gauss → half-sphere UVSphereGauss

26. 800 nm after spatial filtering

27. ideal π Shaper Laser intensity radius 01 mm π shaper Input:Gaussian beam Output:Half-sphere laser intensity profile (without losses)

28. 0.15 mm BBO SHG 2.5 mm BBO Delay Zero order retardation plate 0.04 mm BBO THG RR+B R+B+UV Incident beam: 1 kHz, 30 fs pulse @ 800 nm, 1 mJ/pulse UV beam: 1 kHz, 30 fs pulse @ 266 nm Conversion efficiency ~ 10% Colinear 3 rd harmonic generation

29. Cooling channel bucking magnet Tube for thermoheater Stainless steel vacuum vessel 1.5 cell S-band cavity: Clamped design

30. f 0 =2.9918 GHz f 0 =2.9980 GHz Absorption > 96 % Q = 7600 0-mode  -mode 1.5 cell cavity: measured resonances Lorentzian fits

31. 1.5 cell cavity: field profile π-mode Superfish ♦ measured Design and machining precision better than 5 μm

32. Cavity training First results (November 2006) 15 hours @ 2 Hz, 10 5 rf pulses 65 MV/m

33. END