The FERMI@Elettra Project The FERMI@Elettra Project John Adams - PowerPoint PPT Presentation

The FERMI@Elettra Project The FERMI@Elettra Project John Adams Institute for Accelerator Science John Adams Institute for Accelerator Science June 12, 2008 June 12, 2008 Stephen V. Milton Stephen V. Milton Sincrotrone Trieste, S.C.p.A. Sincrotrone Trieste, S.C.p.A. Italy Italy

The ELETTRA Labortory Put seeded FEL Here i.e. FERMI@Elettra 2.0 to 2.4 GeV 2.0 to 2.4 GeV Synchrotron Radiation Synchrotron Radiation Source Source Existing 1+ GeV Linac JAI - 12 June 2008 (S.V. Milton) 2 JAI 2

Some Source Properties of Interest Some Source Properties of Interest Brightness Photon Energy Brightness Photon Energy Pulse Length Tunability Pulse Length Tunability Flux Repetition Rate Flux Repetition Rate Coherence Costs Coherence Costs Energy/Pulse Size Energy/Pulse Size Complexity Complexity JAI - 12 June 2008 (S.V. Milton) 3 JAI 3

Science Drives the Machine? Science Drives the Machine?  Yes…But Yes…But • If you already have a machine and site then you need to determine what the capabilities of the machine is. • So in this case the machine partially drives the science and then one must make a determination if the science that the machine is capable of empowering is worth pursuing. JAI - 12 June 2008 (S.V. Milton) 4 JAI 4

Undulator Magnets: Resonant Condition Undulator Magnets: Resonant Condition “Resonance” occurs when the light wavefront “slips” ahead of the electron by one optical period in the time that it took the electron to traverse the distance of one undulator period λ rad = l o 2 g 2 1 + K 2 ( ) 2 Where γ is the normalized electron beam total energy and K = 0.934 λ rad [cm] B max [T] Is the normalized undulator field strength parameter JAI - 12 June 2008 (S.V. Milton) 5 JAI 5

Wavelength Reach Wavelength Reach The resonant condition gives a slope of -2 on the log-log graph (red -7 10 LambdaUnd = 6.5 cm 9 lines). 8 K = 3 7 6 Geometric emittance 5 1.2 GeV 1.2 GeV 1.5 GeV 1.7 GeV 4 decrease inversely with 3 beam energy in a linac. 2 micron Emittance 2 FELs work best if the geometric emittance is 1 micron Emittance less that the photon -8 10 LambdUnd = 3.0 cm 9 K = 1 beam emittance (TEM 00 8 7 mode) λ /4 π (green lines) 6 5 4 Ones need to 3 realistically assess the capabilities of the linac 2 and electron beam source 4 5 6 7 8 9 2 1000 Energy [MeV] JAI - 12 June 2008 (S.V. Milton) 6 JAI 6

FEL Types: Oscillator, Seeded FEL, SASE FEL Types: Oscillator, Seeded FEL, SASE

The Start of Microbunching The Start of Microbunching Coherent sum of radiation from N electrons 300 200 100 0 -100 -200 -300 0 2 4 6 8 10 12 s The SASE light consists of several coherent regions, also known as spikes, randomly distributed over the pulse length of the electron beam.

Self-Amplified Spontaneous Emission (SASE) Self-Amplified Spontaneous Emission (SASE) Exponential Growth Saturation Log Radiation Intensity Microbunching Begins Start up is from noise signal Distance

SASE FELs SASE FELs Since they are regularly spaced, the micro-bunches Saturation produce radiation with enhanced temporal coherence. This results in Exponential Gain a “smoothing out” of the Regime instantaneous synchrotron radiation power (shown in the three plots ) to the Undulator Regime right) as the SASE process develops. Electron Bunch Micro-Bunching

The LCLS The LCLS Linac Coherent Light Source The SLAC Site: Home of the LCLS JAI - 12 June 2008 (S.V. Milton) 11 JAI 11

The LCLS: An X-ray Laser (1.5 Å) The LCLS: An X-ray Laser (1.5 Å) JAI - 12 June 2008 (S.V. Milton) 12 JAI 12

Capabilities Capabilities Spectral coverage: 0.15-1.5 nm To 0.5 nm in 3 rd harmonic Peak Brightness: 10 33 Photons/pulse: 10 12 Average Brightness: 3 x 10 22 Pulse duration: <230 fs Pulse repetition rate: 120 Hz Upgrade – more bunches/pulse JAI - 12 June 2008 (S.V. Milton) 13 JAI 13

Benefits of a Seeded FEL Benefits of a Seeded FEL  A “seed” laser controls the distribution of electrons within a bunch: A “seed” laser controls the distribution of electrons within a bunch: Very high peak flux and brightness (comparable to SASE FELs) • • Temporal coherence of the FEL output pulse Control of the time duration and bandwidth of the coherent FEL pulse • Close to transform-limit pulse provides excellent resolving power without • monochromators Complete synchronization of the FEL pulse to the seed laser • Tunability of the FEL output wavelength, via the seed laser wavelength or a harmonic • thereof Reduction in undulator length needed to achieve saturation. •  Giving: Giving: Controlled pulses of 10-100 fs duration for ultrafast experiments in atomic and • molecular dynamics Temporally coherent pulses of 500-1000 fs duration for experiments in ultrahigh • resolution spectroscopy and imaging. Future possible attosecond capability with pulses of ~100 as duration for ultrafast • experiments in electronic dynamics JAI - 12 June 2008 (S.V. Milton) 14 JAI 14

High Gain Harmonic Generation - HGHG High Gain Harmonic Generation - HGHG compressor seed laser ΗΓΗΓ modulator radiator λ 5 λ planar APPLE II e-beam Bunching at harmonic λ More compact and fully temporally coherent source, control of pulse length and control of Li-Hua Yu spectral parameters. DUV-FEL JAI - 12 June 2008 (S.V. Milton) 15 JAI 15

FEL Seeding a Long Bunch FEL Seeding a Long Bunch SASE Seeded FEL Short bunch Seeded FEL Long bunch Courtesy of J. Corlett, LBNL JAI - 12 June 2008 (S.V. Milton) 16 JAI 16

FERMI FEL Output Parameters FERMI FEL Output Parameters Parameter FEL-1 FEL-2 (in discussion) Wavelength range [nm] 100 to 20 40 to 10 (to 3?) Output pulse length (rms) [fs] < 100 > 200 Bandwidth (rms) [meV] 17 (at 40 nm) 5 (at 10 nm) Polarization Variable Variable Repetition rate [Hz] 50 50 Peak power [GW] 1 to >5 0.5 to 1 Harmonic peak power (% of fundamental) ~2 ~0.2 (at 10 nm) 10 14 (at 40 nm) 10 12 (at 10 nm) Photons per pulse Pulse-to-pulse stability 30 % ~50 % Pointing stability [ rad] < 20 < 20 Virtual waist size [ m] 250 (at 40 nm) 120 Divergence (rms, intensity) [ rad] 50 (at 40 nm) 15 (at 10 nm) JAI - 12 June 2008 (S.V. Milton) 17 JAI 17

FERMI Brightness FERMI Brightness P ∼ N e 2 FERMI@Elettra FEL 10 10 Increase ELETTRA Storage Ring FEL ELETTRA P ~ N e JAI - 12 June 2008 (S.V. Milton) 18 JAI 18

FERMI Seed Laser: Phase I FERMI Seed Laser: Phase I Courtesy M. Danailov JAI - 12 June 2008 (S.V. Milton) 19 JAI 19

FERMI Seed Laser: Phase I FERMI Seed Laser: Phase I Courtesy M. Danailov JAI - 12 June 2008 (S.V. Milton) 20 JAI 20

Seeding with an HHG Source? • Complicated • Tunability tunable radiation in 120 nm-12 nm range not proven FEL BUT JAI - 12 June 2008 (S.V. Milton) 21 JAI 21

More Comments About an HHG Seed More Comments About an HHG Seed  Direct Seeding Option Direct Seeding Option • But now one is limited to the wavelength cutoff of the HHG system  10 nm perhaps a little shorter.  10 kw to 100 kw o Too low for HGHG seed  Pulse length Pulse length • Tends to be on the order of 10 fs to 20 fs, even shorter if needed, but difficult to make significantly longer. JAI - 12 June 2008 (S.V. Milton) 22 JAI 22

Seeded HHG Source Seeded HHG Source A “problem” with using a HHG source as a seed is that the power is not that high. The “problems” with using a plasma laser are the timing stability, pulse duration, and longitudinal coherence. Combined however they could make an ideal seed for future FELs. Wang et al., Phys. Rev Lett. 97 123901 (2006) JAI - 12 June 2008 (S.V. Milton) 23 JAI 23

User Requirements & Science User Requirements & Science User Requirements User Requirements 100 - 10 nm range (and less) - fully tuneable & polarised coherent radiation • 100’s MW to GW’s of peak power • 10 13 to 10 14 photons/pulse • 0.05 to > 1ps photon pulse lengths • good pointing stability • reasonable pulse to pulse timing jitter • good pulse reproducibility ~10% ∆ I/I • Science Science chemical reaction dynamics • study of the electronic structure of atoms, molecules and clusters • biological systems • inhomogeneous materials on a microscopic scale • geophysics and study of extra-terrestrial materials • material properties under extreme conditions (pressure, temperature, etc.) • surfaces and interfaces • nano-structures and semiconductors • polymers and organic materials • magnetism and magnetic materials • superconductors and highly correlated electronic materials • JAI - 12 June 2008 (S.V. Milton) 24 JAI 24

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Ultrafast coherent imaging at Fermi Spokesperson: H. Chapman (LLNL-CA) , J. Haidu (Stanford University and Uppsala University) JAI - 12 June 2008 (S.V. Milton) 26 JAI 26

Schematic layout of the FERMI accelerator Laser Heater x-band longitudinal linearizer Mostly FEL1 Mostly FEL2 Mostly FEL1 Mostly FEL2 JAI - 12 June 2008 (S.V. Milton) 27 JAI 27