TWO COLOR OPERATION AT THE FERMI SEEDED FEL: ONE SEED PULSE One - - PowerPoint PPT Presentation

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TWO COLOR OPERATION AT THE FERMI SEEDED FEL: ONE SEED PULSE One - - PowerPoint PPT Presentation

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TWO COLOR OPERATION AT THE FERMI SEEDED FEL: ONE SEED PULSE One seed pulse > two color zero-delay FEL pulses using the split undulator scheme 2 colors Seed pulse (344 nm) H9 of 344nm (38 nm) MOD radiators DS possible applications

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SLIDE 1

TWO COLOR OPERATION AT THE FERMI SEEDED FEL: ONE SEED PULSE

H9 of 344nm (38 nm) H8 of 344nm (43 nm) Seed pulse (344 nm)

38 43 Wavelength (nm)

2 colors

MOD

DS

radiators

One seed pulse –> two color “zero-delay” FEL pulses using the split undulator scheme

Seed pulse Pulse 1st stage Pulses 1st stage and 2nd stage 1st stage H7 2nd stage H(7x3)

MOD

DS

radiators MOD

DS

radiators

possible applications in FWM possible applications in pump-probe experiments (when combined with an appropriate split-and-delay stage) One seed pulse –> two color “zero-delay” FEL pulses using the two-stage FEL2

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SLIDE 2

SPLIT AND DELAY

Courtesy of E. Principi Courtesy of F. Bencivenga

“mini-TIMER”@DiProI …and soon maxi-TIMER @EIS-TIMER beamline

FEL-stimulated transient grating

PADReS delay line

Bencivenga et al., Nature 2015

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SLIDE 3

TWO COLOR OPERATION AT THE FERMI SEEDED FEL: TWO SEED PULSES

Two seed pulses

MOD

DS

radiators

4me!delay!!<!800!fs!

Two color seed pulses –> two color FEL pulses inside the FEL bandwidth

  • E. Allaria et al., Nat. Commun., 2013

261.8nm 260.4nm

Two FEL pulses (max wavelength separation below 1%)

37.4nm 37.2nm

H7 + tunability inside the FEL gain bandwidth

time modulator bandwidth (1/N)

4me!delay!!<!800!fs!

37.1 (nm) ∆t ∆t ∆t Undulator FEL amplifier Twin seed laser pulses Twin FEL pulses Online spectrometer K–B focusing

  • ptics

Ti dispersive grating C C D d e t e c t

  • r

ΘProbe ΘPump 1 µ m 37.5 37.4 37.3 37.2 –500 500 1,000 1,500 2,000 2,500 37.0 37.1 37.2 37.3 37.4 37.5 37.6 (nm) Delay (fs) 3,000 3,000 15,000 1,000 39 100 Angle ccd pixels ccd pixels ccd pixels ccd pixels Probe Pump Pump probe low - F Pump probe high - F 50 42 41 40 39 42 40 39 42 40 100 50 100 50 100 50 39 42 41 40

probing structural dynamics in solid samples using diffraction

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SLIDE 4

TWO COLOR OPERATION AT THE FERMI SEEDED FEL: TWO SEED PULSES

Two seed pulses Two FEL pulses τ!<!800!!fs! H14 of 261nm (18 nm) H11 of 255nm (23 nm)

MOD

DS

radiators 261nm 255nm

τ!<!800!fs!

23nm 18nm

wide tunability

  • E. Ferrari et al., Nat. Commun., 2016

Two color seed pulses –> split undulator scheme

probing demagnetization dynamics in magnetic compounds

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SLIDE 5

EXOTIC TWO COLOR SCHEMES AND FULL SPECTRO-TEMPORAL SHAPING OF FEL PULSES AT FERMI

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SLIDE 6

bn(t)~Jn[−nBA(t)]exp{in[φs(t)+φe(t)]}

Bessel!func4on! Dispersive!sec4on!strength! Seed!laser!envelope! Seed!phase! Electron!energy!profile! Bunching!envelope!! FEL!temporal!profile!

φs(t)+φe(t)

FEL!phase!

Energy' Time''

The!FEL!pulse!can!be!shaped!through!the!manipula4on!of!the! seed!envelope!A(t)!and!phase!!!!

φs(t)

BUNCHING IN A SEEDED FEL

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SLIDE 7

Bunching!at!the!nth!harmonic!

Amplitude'profile!

bn(t)~Jn[−nBA(t)]exp{in[φs(t)+φe(t)]}

FEL PULSE ENVELOPE

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SLIDE 8

Amplitude'profile!

Bunching!at!the!nth!harmonic!

bn(t)~Jn[−nBA(t)]exp{in[φs(t)+φe(t)]}

FEL SPECTRUM

Phase'profile!

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SLIDE 9

FEL'intensity' 9me' Spectrum' wavelength'

λ" moderate dispersive strength

SEEDED FELs AS SELF-STANDING SOURCES FOR X-RAY PUMP – X-RAY PROBE EXPERIMENTS

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SLIDE 10

FEL'intensity' 9me'

λ1"

Spectrum' wavelength'

λ2" moderate dispersive strength strong dispersive strength

G.!De!Ninno#et#al.,!!PRL,#2013#

λ"

SEEDED FELs AS SELF-STANDING SOURCES FOR X-RAY PUMP – X-RAY PROBE EXPERIMENTS

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SLIDE 11

GENERATION OF TRANSFORM LIMITED FEL PULSES

Amplitude'profile! Phase'profile!

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SLIDE 12

Experiment! Theory!

Strong'chirp' Compensated'chirp'

First!demonstra4on!of!the!possibility!to!generate!a!transform[limited!FEL!pulse!

Gauthier et al., PRL, 2015

EXPERIMENTAL DEMONSTRATION

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SLIDE 13

Gauthier et al., PRL, 2016

GENERATION OF TIME-DELAYED PHASE-LOCKED PULSES

Twin#seed#pulses#

spectrometer# RADIATOR! MODULATOR!

DISPERSIVE!

SECTION!

Twin#FEL#pulses#

to#beamlines#

τ#

µ[controlled!! birefringent!plate!

τ#

Laser#pulse#

e[!beam!!

τ# ΔϕSEED" Twin'seeds'?'e+'beam'interac9on'

Two phase-locked seed pulses generate two phase-locked FEL pulses:

wavelength ΔϕFEL"="2k"π" ΔϕFEL"="(2k+1)"π" Spectral intensity

Interferogram

Control the phase difference between the carrier waves of the two time-delayed FEL pulses.

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SLIDE 14

Possible applications: nonlinear coherent transient interferometry and spectroscopy, spectral holography, quantum state holography, highly resolved spectroscopy, …

ΔϕFEL"+"2π Interferograms'vs.'phase'varia9on'

Step!phase!varia4on!ΔϕFEL"="2π"/5.67#

Sequence'of'single?shot'spectra'

phase stability: λFEL/12 RMS tuning of the twin-seed phase

Gauthier et al., PRL, 2016

precise control of the twin-FEL phase locking in phase better than 15 attoseconds

TIME-DELAYED PHASE-LOCKED PULSES: EXPERIMENTAL RESULTS

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SLIDE 15

w = 63nm

Proof[of[principle!experiment:!! Two[path!quantum!interference!experiment!(Brumer[Shapiro).! Interferences!between!2!pathways!for!Ne!ioniza4on:! Ioniza4on!of!Ne!with!1!photon!at!2w!vs.!2!photons!at!w.! Phase locking between two harmonics of the seed, controlled by means of an electron phase shifter.

2w = 31.5nm

“ZERO-DELAY” PHASE-LOCKED PULSES FOR COHERENT CONTROL

K.!C.!Prince!et#al.,#Nature#Photonics,!2016!

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SLIDE 16

THERE ARE MANY MORE THINGS YOU CAN DO IN THE TEMPORAL DOMAIN BY USING AN EXTERNAL SEED TO TRIGGER THE FEL EMISSION...

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SLIDE 17

BUT LET’S SWITCH TO THE TRANSVERSE PLANE...

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SLIDE 18

FUL DESCRIPTION OF THE FEL RADIATION MECHANISM

E.!L.!Saldin,!E!.A.!Schneidmiller!and!M.!V.!Yurkov,!New#J.#Phys.,!2010!

3D FEL theory: Eigenmode expansion of the radiation field: eigenmode growth rate At saturation the fundamental (TEM00) mode, which has the highest growth rate, dominates.

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SLIDE 19

ORBITAL ANGULAR MOMENTUM (OAM) OF LIGHT

Optical vortices, i.e., helically phased beams with a field dependence , carry orbital angular momentum* Classically: Analogy with quantum mechanics:

*Allen et al., Phys. Rev. A, 1992 image by Ebrahim Karimi

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SLIDE 20

SO, WHAT CAN WE DO WITH OPTICAL VORTICES?

Visible wavelengths: XUV and X-rays:

  • H. He et al., Direct Observation of

Transfer of Angular Momentum to Absorptive Particles from a Laser Beam with a Phase Singularity, Phys.

  • Rev. Lett. 75, 826 (1995).
  • M. P. J. Lavery et al., Detection of a

Spinning Object Using Light’s Orbital Angular Momentum, Science 341, 537 (2013).

  • A. Jesacher et al., Shadow Effects in

Spiral Phase Contrast Microscopy,

  • Phys. Rev. Lett. 94, 233902 (2005).
  • J. Wang et al., Terabit free-space data

transmission employing orbital angular momentum multiplexing, Nature Photonics 6, 488 (2012).

  • M. van Veenendaal et al., Prediction
  • f Strong Dichroism Induced by X

Rays Carrying Orbital Momentum,

  • Phys. Rev. Lett. 98, 157401 (2007).
  • A. Picón et al., Photoionization with
  • rbital angular momentum beams,
  • Opt. Express 18, 3660 (2010).
  • A. S. Rury et al., Examining

resonant inelastic spontaneous scattering of classical Laguerre- Gauss beams from molecules,

  • Phys. Rev. A 87, 043408 (2013).
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SLIDE 21

HOW CAN WE GENERATE OAM?

Using optical elements, e.g., a spiral phase plate: Not practical at XUV and X-ray wavelengths and FEL intensities in situ generation preferred

image by Ebrahim Karimi

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SLIDE 22

WHAT CAN WE DO AT FERMI?

Use a phase-mask to modify the transverse profile of the seed:

Use a spiral phase plate as the phase- mask? It doesn‘t work! Using a 4-quadrant staircase-like phase modulation of the seed:

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SLIDE 23

MICROBUNCHING CONSTRUCTION IN THE MODULATOR

Modification of the transverse seed profile using a phase mask: Formation of microbunching in the modulator: transverse profile at a) the fundamental (260 nm) and b) 7th harmonic (37 nm)

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SLIDE 24

EVOLUTION OF THE RADIATION PROFILE

Transverse radiation profile in the undulator (7th harmonic) Evolution of the FEL power and bunching factors (Ibeam = 1 kA, Pseed = 1 GW, normalized emittance = 5 x 10-6 m)

P.R. Ribič et al., PRL 112, 2014

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SLIDE 25

EXPERIMENTAL (ALMOST) DEMONSTRATION

seed transverse intensity profile FEL intensity profile Shaping FEL radiation in the transverse plane is much more difficult compared to shaping in the temporal domain!

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SLIDE 26

WHAT HAVE WE JUST LEARNED?

  • compared to synchrotrons FELs produce more poweful

(orders of magnitude higher peak brilliance) and shorter (femtosecond) pulses with laser-like properties

  • self seeding and HGHG improve FEL performance

(spectral brightness, central wavelength and pulse energy stability)

  • different schemes for SASE and seeded FELs can

deliver two color pulses with tunable properties for pump-probe experiments

  • HGHG offers full control over the spectro-temporal

and spatial properties of FEL light

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SLIDE 27

Acknowledgements:

Giovanni De Ninno, Elettra/UNG David Gauthier, Elettra FERMI comissioning team Giorgio Margaritondo, EPFL