First Seeding experiment SPARC Luca Giannessi On behalf

First Seeding experiment @ SPARC Luca Giannessi On behalf of the SPARC collaboration: LIFE Meeting - Frascati - 11. 03. 2010

Outline l SPARC Layout l Why seeding an FEL amplifier l First results l Simulations

Seeded SPARC Layout + MUR Ti: Sa Regenerative Amplifier HHG generation Chamber Periscope & injection chicane In vacuum spectrometer 550 -40 nm

Why seeding an FEL amplifier: Longitudinal coherence Slippage length independent processes ζ l The radiation “slips” over the electrons for a distance N 0 l SPARC: l l l N ~ 500 0 ~500 nm N 0 ~ 250 μm Bunch length 2. 6 - 2. 8 ps (rms) → 7 - 8 independent regions (the gain process increases this number)

Phase space at saturation

SPARC Spectra measurements July 22 2009 Orbit kicks to selectively inhibit SASE in the first undulators 6 UM 4 UM 2 UM 5 UM Spectrometer 3 UM 1 UM

Seeded FEL – Phase space @ exit of modulator Coherence length determined by the seed 5 th 3 rd 1 st

2 days of beam l 1° day l synchronization e-beam & laser l Commissioning of the chicane l 2° day - first seeding tests: FEL Amplifier Seed FEL Harmonic Generation Seed 1 2= 1/n, n=2 Modulator Very preliminary results Radiator

1° Day Adjust delay line 1. Align seed to reference in UM (1. 5 u. J) 2. Tune resonance @400 nm 3. Adjust electronic delay better than 1 ns (photodiode) 4. Move the delay line until amplification is observed Adjustable delay up to 4 m

Synchronization (11 -02 -2010) SASE SEED SASE + SEED Beam energy tuning SASE + SEED @ resonance 4 x brightness SEEDED FEL !!! Delay line tuning

2° Day FEL Amplifier Seed FEL Harmonic Generation Seed 1 Modulator 2= 1/n, n=2 Radiator

Beam parameters Emittance (mm-mrad) 3 -4 Slice En. Spread (x 10 -4) 2 -3

SASE @ 400 nm typical spectrum No attenuation

Seed only Attenuation x 0. 1

Seeded FEL Structure in the spectrum Attenuation x 0. 01 Seeded Amplifier

3° harmonic No attenuation

FEL Harmonic Generation Seed 1 Modulator No attenuation 2= 1/n, n=2 Radiator

Problems of the first 2 days l Spectrometer slit locked at (? ) 100 um (solved) l Fast photodiode in place of the J-meter. No absolute energy measurements. l Misplaced mirror holder in the vacuum chamber, cutting the beam (solved) l Laser pointing stability (solved)

Simulations

SASE

Z Undulator coordinate (a. u. ) Seeded SPARC Pulse evolution ζ bunch coordinate (a. u. )

FEL Harmonic Generation Seed 1 Modulator 2= 1/n, n=2 Radiator

Thank you