Laser for SPARCLaser for SPARC

Carlo VicarioCarlo Vicario

Ilario BoscoloIlario Boscolo

Simone CialdiSimone Cialdi

Andrea GhigoAndrea Ghigo

Franco TazzioliFranco Tazzioli

SPARC Step 1

14.5 m1.5m

20º1.5 m

5.0 m D

10.0 m 6 m6.0 m

photo injectorRF sections

Undulator

Plan of SPARC BunkerPlan of SPARC Bunker

SPARC BunkerSPARC Bunker

Laser cleaningLaser cleaningRoomRoom

Parameter Requirement

Operating wavelength < 266 nm (3a harmonic Ti:Sa)

Repetition rate 10 Hz

Pulse energy on cathode 500µJ (Q.E.=10-5)

Energy jitter (in UV) 5 % rms

Pulse length 2-10 ps FWHM

Pulse rise time (10-90%) 1 ps

Temporal pulse shape Uniform (10% ptp)

Transverse pulse shape Uniform (10% ptp)

Laser-RF jitter 1 ps rms

Spot dimension on cathode Circular 1 mm radius

Spot diameter jitter 1% rms

Pointing Stability 1% radius rms

LaserLaser RequirementsRequirements

LaserLaserlayoutlayout

Zoom on Oscillator Zoom on Oscillator

Zoom on Amplifier Zoom on Amplifier

Emittance simulation with Parmela code with Emittance simulation with Parmela code with different risetime of square pulsedifferent risetime of square pulse

Input Parameters:•Pulse duration 11.66 FWHM •0.3 mm mrad εth•Epeak=120 MV/m, B=.27 T

94% of bunch for no rise time,81% of bunch for 1 ps rise time

achieve sase saturation with undulator length<10m

0,4

0,5

0,6

0,7

0,8

0,9

1

1,1

1,2

0,7 0,8 0,9 1 1,1 1,2 1,3

ENX_[MMMRAD]ENY_[MMMRAD]

εnx,εny

Ellipticity

Circular spot can be obtain with conventional optics (cylindrical lens)

EmittanceEmittance simulation with Homdyn code simulation with Homdyn code for elliptic spot on cathodefor elliptic spot on cathode

0,48

0,49

0,5

0,51

0,52

0,53

0,54

0,55

0,94 0,96 0,98 1 1,02 1,04 1,06

EnX_[mm mrad]

En

X_

[mm

mra

d]

Q_[nC]

Working point: nominal charge Q=1nC, RF phase = 27.5°

EmittanceEmittance simulation with Homdyn code for simulation with Homdyn code for energy and time jitterenergy and time jitter

Other Simulation for time jitter shows that: Other Simulation for time jitter shows that:

∆∆ t = ± 1ps (1˚RF) t = ± 1ps (1˚RF) ∆∆ εε n n = + 4%= + 4%

∆∆ Q= + 5% Q= + 5% ∆∆ εε n n = + 4.45%= + 4.45%

∆∆ Q= - 5% Q= - 5% ∆∆ εε n n = + 7.51%= + 7.51%

Transport to the RF-gun Transport to the RF-gun

•Spatial flattener: pinhole + position-dependent attenuatorSpatial flattener: pinhole + position-dependent attenuator

•Frequency triplerFrequency tripler

• Transport Optics in evacuated pipeTransport Optics in evacuated pipe

•72° Incidence compensation: grating+cylindrical lens72° Incidence compensation: grating+cylindrical lens

Energy Losses:Energy Losses:FlattenerFlattener 62%62%

Transport opticsTransport optics 38%38%

33thth harmonic generation harmonic generation 90%90%

20 mJ20 mJ in IR needed to obtain in IR needed to obtain 500 500 µµJJ on cathode @ 266 nm for Q.E.=10 on cathode @ 266 nm for Q.E.=10 -5-5

to extract to extract 1 nC1 nC

Transport to the RF-gun Transport to the RF-gun

Time pulse shaperTime pulse shaper

Ti:Sa large bandwidth allows the square pulse Ti:Sa large bandwidth allows the square pulse shaping via frequency manipulation.shaping via frequency manipulation.

With amplitude and phase control an arbitrary With amplitude and phase control an arbitrary shape can be produced.shape can be produced.

The pulse shaper must be inserted before the The pulse shaper must be inserted before the amplifier to avoid damage.amplifier to avoid damage.

Time pulse shaperTime pulse shaper

Phase-only modulation preserves optical band Phase-only modulation preserves optical band to perform pulse stretching! to perform pulse stretching!

Specified flat top can be obtained by phase-only Specified flat top can be obtained by phase-only modulation.modulation.

No control on phase of shaped pulse: but no problem No control on phase of shaped pulse: but no problem for photoemission!for photoemission!

Liquid crystal spatial light phase Liquid crystal spatial light phase modulator in Fourier planemodulator in Fourier plane

Collinear Acousto-Optic Collinear Acousto-Optic modulatormodulator (AOM) (AOM)

F. Verluise and al, Opt. Lett.25,8 (2000)

Comparison between optical modulatorsComparison between optical modulators

Dynamically addressableDynamically addressable

Phase-shift variablePhase-shift variable

Results (Sumitomo, amplified pulse )

Not tested for requested pulse

15 nm bandwidth200 nm bandwidth

Crucial LC positionNo critical alignment

Discrete, interpixel gapsContinuos modulation

LC-SLMCollinear AOM

Parameter Requirement Performances

Operating wavelength <266 nm OK

Repetition rate 10 Hz OK

Pulse energy on cathode 500µJ OK

Energy jitter (in UV) 5 % rms > 6%

Pulse length 2-10 ps FWHM Achievable

Pulse rise time (10-90%) 1 ps Requires developments

Temporal pulse shape Uniform (10% ptp) Requires developments

Transverse pulse shape Uniform (10% ptp) Requires developments

Laser-RF jitter 1 ps rms Achievable

Spot dimension on cathode Circular 1 mm radius OK

Spot diameter jitter 1% rms ?

Pointing Stability 1% radius rms ?

Conclusion 1Conclusion 1

To be studied:To be studied:

•Time Pulse Time Pulse ShapingShaping..

•Effects of the uniform time distribution on Effects of the uniform time distribution on amplification and next pulse handling.amplification and next pulse handling.

•Optical transfer line to preserve transverse Optical transfer line to preserve transverse and longitudinal distribution.and longitudinal distribution.

Conclusion 2Conclusion 2

•Stability of high energy amplified pulses is Stability of high energy amplified pulses is an issue.an issue.

•Improvements in cathodes quantum Improvements in cathodes quantum efficiency simplifies the problem.efficiency simplifies the problem.

Conclusion 3Conclusion 3

AcknowledgmentsAcknowledgments

S. De Silvestri, M. Nisoli, S. Stagira.S. De Silvestri, M. Nisoli, S. Stagira.

M. Ferrario, M. Boscolo, V. Fusco, M. Ferrario, M. Boscolo, V. Fusco, F. Sgamma. F. Sgamma.