UCLA Claudio Pellegrini UCLA Department of Physics and Astronomy X-ray Free-electron Lasers Ultra-fast Dynamic Imaging of Matter II Ischia, Italy, 4/30-5/3/ 2009

UCLA Ischia 5/1/2009C. Pellegrini2 Outline 1.Present status of X-ray free-electron lasers (FELs). 2.Near future developments, using existing accelerator technology, electron/radiation pulses manipulation, HHG seeding, to produce: shorter pulses; improved longitudinal coherence; higher average brightness; wavelengths<0.1 nm; more compact, less costly FELs. 3Further future developments, will use new electron sources, advanced laser-plasma accelerator, novel short period undulators for very compact, table-top FELs. 4Conclusions.

UCLA Ischia 5/1/2009C. Pellegrini3 Peak brightness of existing X-ray FELs, Flash and LCLS An old plot with superimposed FLASH and the very new LCLS data. Good predictions. Peak power in the 1-10 GW range.

UCLA Ischia 5/1/2009C. Pellegrini4 LCLS first lasing at SLAC, April 2009, at 0.15 nm Courtesy LCLS group, SLAC

UCLA Ischia 5/1/2009C. Pellegrini5 LCLS: FEL parameters Wavelength151.5 Å FEL parameter Cooperation length28257 nm Peak saturation power48 GW Average saturation power W Coherent photons/pulse Peak photon flux Ph/s Peak brightness* Average brightness* Instantaneous photon ΔE/E % Beam radius, rms µm Beam divergence, rms µrad Pulse duration, rms,7070fs *Ph./s/mm 2 /mrad 2 /.1%bw

UCLA Ischia 5/1/2009C. Pellegrini6 LCLS: Other parameters Pulse repetition rate120 Hz Single spike duration(0.15 nm)1 fs Number of spikes200 Spike line width3x10 -4 … and, mostly important, more than10 9 photons per coherent volume (compare with less than 1 for spontaneous synchrotron radiation sources). This, and the FEL attribute of simultaneous short wavelength and short pulse length, nanometer to sub-nanometer, sub-picosecond to femtosecond, will lead us to explore a new range of phenomena.

UCLA Ischia 5/1/2009C. Pellegrini7 Pulse trains of up to 800 µs duration Up to 10 Hz repetition rate (currently 5 Hz) Fixed gap undulators (Tune with electron beam energy) Wavelength range (fundamental): 6-47 nm Pulse energy average: 100 µJ Peak power: ~ 5 GW Pulse duration (FWHM): fs Spectral width (FWHM): % Courtesy Siegfried Schreiber, DESY Electron beam pulse train (30 bunches, 1 µs spacing, 5 Hz rep rate) FLASH OPERATING FACILITY, PULSED SCRF LINAC, SASE FEL

UCLA Ischia 5/1/2009C. Pellegrini8 Transverse coherence at FLASH Double-slit diffraction pattern at 25.5 nm indicates good level of transverse coherence. (from XFEL TDR)

UCLA Ischia 5/1/2009C. Pellegrini9 UV to X-ray FEL next developments Photon energy, keV Pulse repetition rate, Hz Pulse duration, fs< Coherence, transverseVery good Coherence lengthL Bunch to L Cooperation ( μm) Peak Brightness ph/mm 2 mrad 2 s 0.1%bw Average brightness ph/mm 2 mrad 2 s 0.1%bw PolarizationVariable, linear to circular Flash, LCLS, and the next FELs, like XFEL, SCSS, Fermi, are only the beginning of the road. Present and next generation FEL capabilities can be extended to these parameters:

UCLA Two examples As an example of FELs development I will discuss two examples: Very short radiation pulses at about 1 and 0.15 nm High energy photon FELs, E>10keV Ischia 5/1/2009C. Pellegrini10

UCLA Ischia 5/1/2009C. Pellegrini11 Example of developments: from 100fs to ultra-short X-ray pulses Many methods have been proposed to reduce the pulse length to the fs range: slotted spoiler; ESASE; two stage undulator with energy chirped pulse. All these methods select and use part of the electron bunch to lase. Pulse length can be as short as 1fs or less. The number of photons in the pulse is reduce by the number of electron lasing to the total number of electrons. There is a spontaneous radiation pedestal. Another possibility studied recently is to operate the FEL at low charge[1,2]. I use this case to illustrate what can be achieved. [1] Rosenzweig et al. ”, Nuclear Instruments and Methods, A 593, (2008). [2] Reiche, Rosenzweig, Musumeci, Pellegrini, Nucl. Instr. And Methods, A 593, (2008).

UCLA Ischia 5/1/2009C. Pellegrini12 Recent studies show that a smaller emittance (x 0.1), larger electron beam brightness (x ) and very short, ~ 1fs or less, electron bunches can be produced by reducing the bunch charge from about 1nC to few, 1 to 10 pC, and using velocity and magnetic bunching. Low charge electron bunches for ultra-short X-ray pulses SPARX: E=2 GeV, λ=3 nm, Single spike σ B =0.48 µm (1.6 fsec), 2x10 10 photons in the pulse.

UCLA Ischia 5/1/2009C. Pellegrini13 LCLS 1pC example: attosecond pulses. Beam current profile Single spike at saturation, with photons. Beam brightness~ 4x10 17 A/m 2 rad 2 compared to 6x10 15 A/m 2 rad 2 for the 1 nC design case. Peak power vs. z

UCLA LCLS at low charge, short pulses Ischia 5/1/2009C. Pellegrini14 20 pC Y. Ding and the LCLS group, SLAC, and C. Pellegrini, UCLA, 2009 Part. Acc. Conf.

UCLA Ischia 5/1/2009C. Pellegrini15 LCLS at low charge, short pulses Y. Ding and the LCLS group, SLAC, and C. Pellegrini, UCLA, 2009 Part. Acc. Conf.

UCLA Ischia 5/1/2009C. Pellegrini16 60 KeV, short pulse FEL, using low emittance electron bunches FEL Parameters Wavelength0.02 nm FEL parameter Gain Length2.7 m Saturation power1 GW Coherent Photons10 8 Pulse length0.5 fs The small emittance at 1pC can be used to obtain high energy photons at low beam energy with a short period undulator. Beam Parameters Energy =11.5 GeV I P =800 A ε N =6.x10 -8 m  E = Undulator  U =0.015 m K=1

UCLA Ischia 5/1/2009C. Pellegrini nm, short pulse FEL Pulse duration~0.5 fs Power vs undulator length Spectrum

UCLA Ischia 5/1/2009C. Pellegrini18 ….. or a Compact soft X-ray FEL Beam energy 1.4 GeV S-band injector+X or C-band linac, length <35 m 1.5 cm period, K=1, undulator, length 15 m Bunch charge, 1-20 pC Pulse length, 1 to few fs Number of coherent photons/pulse, Linac repetition rate, 120 Hz X-ray Pulses in one linac pulse, 1 to 100 Synchronization to external laser using the signals from the photoinjector laser and the coherent radiation from the electron bunch after compression.

UCLA Ischia 5/1/2009C. Pellegrini19 Optical manipulations techniques (1) Bunching Acceleration SASE Modulation A. Zholents, Phys. Rev. ST Accel. Beams 8, (2005) Precise synchronization of x-ray output with the modulating laser Variable output pulse train duration Increased peak current and shorter x-ray undulator Solitary ~100-attosecond duration x-ray pulse Peak current, I/I 0 z /l L kA < fs section ESASE

UCLA Ischia 5/1/2009C. Pellegrini20 Example with seed at 30 nm, radiating in the water window First stage amplifies low-power seed with “optical klystron” More initial bunching than could be practically achieved with a single modulator Output at 3.8 nm (8 th harmonic) 300 MW output at 3.8 nm (8 th harmonic) from a 25 fs FWHM seed 1 GeV beam 500 A 1.2 micron emittance 75 keV energy spread Modulator =30 nm, L=1.8 m Modulator =30 nm, L=1.8 m Radiator =3.8 nm, L=12 m 100 kW =30 nm Lambert et al., FEL04 Optical manipulations techniques HHG LASER SEED

UCLA Ischia 5/1/2009C. Pellegrini21 Future developments II Plasma laser accelerators, 1 GeV/m or more, would greatly decrease the linac length. Novel electron sources, using plasmas or ultra-cold gases or.?., reducing the emittance below 0.1 mm mrad, and increasing the beam 6-D phase space density would give: –Reduced beam energy for same wavelength –Larger FEL parameter -> larger efficiency, photon number/electron, shorter pulse duration Undulators with small period, and large gap/period ratio, like microwave undulator or other new ideas, would also reduce the beam energy for the same wavelength.

UCLA Ischia 5/1/2009C. Pellegrini22 Conclusions  FLASH and LCLS are only the beginning of a new class of photon sources which will: –Allow the exploration and manipulation of matter at the Angstrom-femtosecond level and the study of nonlinear phenomena –Give fully longitudinal and transverse coherence –Provide order of magnitudes larger peak and average brightness –Reduce the cost and size of the sources while extending their performance