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Issues and Challenges for Short Pulse Radiation Production Paul Emma

Issues and Challenges for Short Pulse Radiation Production Paul Emma Stanford Linear Accelerator Center July 8, 2004. Several FEL proposals go beyond even this:. sub-femtosecond pulses 1- Å radiation GW power levels unprecedented brightness. How Short?.

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Issues and Challenges for Short Pulse Radiation Production Paul Emma

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  1. Issues and Challenges for Short Pulse Radiation Production Paul Emma Stanford Linear Accelerator Center July 8, 2004

  2. Several FEL proposals go beyond even this: • sub-femtosecond pulses • 1-Å radiation • GW power levels • unprecedented brightness How Short? …defined by New York Traffic Commissioner T.T. Wiley in 1950 as: “…the time between the light turning green and the guy behind you honking.” -W. Safire, NY Times, March 7, 2004 why so short…

  3. E. Muybridge at L. Stanford in 1878 disagree whether all feet leave the ground during gallop… E. Muybridge used spark photography to freeze this ‘ultra-fast’ process E. Muybridge, Animals in Motion, ed. L. S. Brown (Dover Pub. Co., New York 1957).

  4. Coulomb Explosion of Lysozyme (50 fs) Single Molecule Imaging with Intense X-rays Atomic and molecular dynamics occur at the fsec-scale J. Hajdu, Uppsala U.

  5. In Neils Bohr’s 1913 model of the Hydrogen atom it takes about 150 as for an electron to orbit the proton. – Nature, 2004 Time Scales Dt 1 sec 1 femto-second (fs) = 10-15 sec  0.3 mm 1 atto-second (as) = 10-18sec  0.3 nm

  6. Outline • Electron bunch limitations • Photon pulse limitations • Schemes for short pulse generation • SPPSresults(Sub-psec Pulse Source) Just a tick: Scientists are using ever-shorter time scales to investigate chemical reactions. Nature, February 26, 2004

  7. Try to compress sz in LCLS to 1 mm… 1 nC CSR:e/e0= 1 CSR:e/e0 14 brightness destroyed Electron bunch length is limited by… • Coherent synch. rad. (CSR) in compressors • Longitudinal wakefields in linac & undulator • Space-charge forces in accelerator • System jitter (RF, charge, etc)

  8. lr DE/E = 0 bend-plane emittance is ruined  DE/E < 0 Coherent Synchrotron Radiation in Bends sz e– Coherent radiation for lr > sz lr R (= L/q) R A. Kabel: MOPKF081 

  9. r extreme wake Resistive-Wall Wakefields in Undulator Copper tube

  10. Micro-Bunching Instabilities current modulation Gain=10 1% 10% Z(k) t LCLS simulations (M. Borland) CSR m-bunching Saldin, Schneidmiller, Yurkov TESLA-FEL-2003-02 • FEL ‘instability’ needs very “cold” e- beam (small ex,y & E-spread) • Cold beam is subject to “undesirable” instabilities in accelerator (CSR, Longitudinal Space-Charge, wakefields) Can be Landau damped with energy spread

  11. TTF measurement M. Hüning,H. Schlarb, PAC’03. simulation measured 3 keV, accelerated to 14 GeV, & compressed 36  110-5 Too small to be useful in FEL (no effect on FEL gain when <10-4) How cold is the photo-injector beam? Parmela Simulation 3 keV DE/E Dt (sec)

  12. 40 keV rms ‘Laser Heater’ in LCLS for Landau Damping Ti:saph 800 nm 1.2 MW Injector at 135 MeV ‘Laser heater’ suggested by Saldin et al. • Laser-e- interaction 800-nmE-modulation (40 keV rms) • Heater in weak chicane for time-coordinate smearing • Energy spread in next compressors smears m-bunching Huang: WEPLT156,Limborg: TUPLT162, Carr: MOPKF083

  13. heater OFF heater ON 0.01 % 0.1% In LCLS tracking, final energy spread blows up without ‘Laser-Heater’ Final longitudinal phase space at 14 GeV for initial 15-mm, 1% modulation at 135 MeV Z. Huang et al., SLAC-PUB-10334, 2004 ...accepted in PR ST AB, June 2004

  14. Outline • Electron bunch limitations • Photon pulse limitations • Schemes for short pulse generation • SPPSresults(Sub-psec Pulse Source) Just a tick: Scientists are using ever-shorter time scales to investigate chemical reactions. Nature, February 26, 2004

  15. FEL pulse duration limited by intrinsic bandwidth • For shorter pulses: • shorter wavelength, lr • largerr (smallerex,y) • low-gain (large Dw) • seeded start-up For X-ray FEL: lr 1 Å, sw/w0 0.04%, st 100 as

  16. w sw h t monochromator bandwidth sm sw/h Monochromator Pulse Slicing sm/w0 = 10-4, sw/w0 = 510-4, h 2% st 5 fs S. Krinsky, Z. Huang, PR ST AB, 6, 050702 (2003).

  17. Outline • Electron bunch limitations • Photon pulse limitations • Schemes for short pulse generation • SPPSresults(Sub-psec Pulse Source) Just a tick: Scientists are using ever-shorter time scales to investigate chemical reactions. Nature, February 26, 2004

  18. pulse length control with seed laser 0.9 ps 0.4 ps 0.3 ps HGHG Saturation at DUVFEL 266 nm Li-Hua Yu et al. PRL91, 074801 (2003). Ipk = 300 A, sE/E0 = 0.01% Pin = 1.8 MW: sz = 0.6 ps, ge = 2.7 mm, dy/dg = 8.7 Pin = 30 MW: sz = 1.0 ps, ge = 4.7 mm, dy/dg = 3.0

  19. I8I18 8 Å 1 Å 300 as Statistical Single-Spike Selection Un-seeded single-bunch HGHG (8  4  2  1 Å ) Saldin et al., Opt. Comm.,212, 377 (2002).

  20. coulomb scattered e- e- unspoiled e- coulomb scattered e- 15-mm thick Be foil LCLS Add thin slotted foil in center of chicane y 2Dx x DE/E  t PRL92, 074801 (2004). P. Emma, M. Cornacchia, K. Bane, Z. Huang, H. Schlarb, G. Stupakov, D. Walz (SLAC)

  21. 200 fs DE/E cold e- core passing through slot Track 200k macro-particles through entire LCLS up to 14.3 GeV No design changes to FEL – only foil added in chicane

  22. 2 fs FWHM z 60 m Genesis 1.3 FEL code ~1010 photons x-ray Power (<1 fs possible) Power (GW)

  23. Mod. tuned so only high energy e- interact with 2-nm HC FEL radiation 800 nm Chicane Modulator 2 nm 1 nm ~2x106 photons 110 as 2 nm, 100 MW, 100 fs LUX electron beam parameters: e- energy = 3 GeV emittance = 2 mm-mrad energy spread = 0.3 MeV peak current = 500 A Generation of Attosecond Pulses… A. Zholents, W. Fawley PRL92, 224801 (2004). MOPKF072

  24. Ti:saph: 800 nm, 2-4 mJ, 5 fs 300 as Ge monochromator to select single pulse monochromator is broadband Ge crystal diffracting from the (1 1 1) lattice planes (pre-monochromator to reduce power) 1 GW Saldin et al., Opt. Comm.,237, 153 (2004).

  25. short pulse train 800-nm modulation (few GW) 24 kA peak current enhanced x7 70 as SASE FEL 4 GeV 14 GeV Allows synchronization between laser pulse and x-ray pulse E-SASE(applied to LCLS) A. Zholents (submitted to PRL)

  26. Outline • Electron bunch limitations • Photon pulse limitations • Schemes for short pulse generation • SPPSresults(Sub-psec Pulse Source) Just a tick: Scientists are using ever-shorter time scales to investigate chemical reactions. Nature, February 26, 2004

  27. add 14-meter chicane in linac at 1/3-point (9 GeV) Existing bends compress to 80 fsec 1.5% 1.5 Å 30 kA compression by factor of 500 80 fs FWHM 28.5 GeV Short Bunch Generation in the SLAC Linac 1-GeV Damping Ring sz 6 mm SLAC Linac FFTB sz 1.1 mm sz 40 mm 30 GeV sz12 mm P. Emma et al., PAC’01

  28. Source comparisons * streak camera resolution 1 psec, DQe 0.01 ** photons/sec/mm2/mrad2/0.1%-BW J. Hastings, SLAC

  29. Undulator, view upstream Dave Fritz, Soo Lee, David Reis Undulator parameters:Lu 2.5 m,lu= 8.5 cm, K 4.3, B 0.55 T, Np 30

  30. R&D at SPPS Towards X-Ray FELs Measurewakefields of micro-bunch  Develop bunch length diagnostics StudyRF phase stability of linac  Measure emittance growth in chicane (CSR)  X-ray optics and transport

  31. theory meas. sz  40 mm Wakefield energy-loss used to set and confirm minimum bunch length K. Bane et al., PAC’03

  32. Transition radiation is coherent for/2p > sz(CTR) P. Muggli, M. Hogan

  33. minimum bunch length (with j-jitter) Mylar resonances Gaussian bunch:sz 18 mm CTR Autocorrelation sz 9 mm Dz (mm) P. Muggli, M. Hogan

  34. FWHM/2.35  40 mm 9 kA SPPS chicane CSR simulations with 1D model (unshielded) (good agreement with 3D-model studied by F. Stulle - DESY) 3.4 nC, 9 GeV 1 mm 0.3 kA

  35. Bend-Plane Emittance: Chicane ON and OFF Bend-plane emittance is consistent with calculations and sets upper limit on CSR effect P. Emma et al., PAC’03

  36. Concluding Remarks • Very short x-ray pulses are key to exploring ultra-fast science at future light sources • Linac-based FEL’s offer high power, very high brightness, and possibly sub-femtosecond pulses at ~1-Å wavelengths • Advances in ultra-short, high-power table-top lasers will greatly influence future LS designs, as will e-gun development (gex,y < 1 mm) • Thanks to the many who contributed to this presentation… Z. Huang, W. Fawley, and A. Zholents

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