SPARC operation in seeded and

chirped mode

Luca Giannessi

ENEA C.R. Frascati

On behalf of the SPARC collaboration

32° International FEL Conference - Hilton Malmo City, Sweden, August 23-27 2010

Outline

• SASE FEL operation with a chirped beam– Lasing with chirped beam combined with tapered

undulator

• Seeded FEL operation– Seeded amplifier with the generation of high order

harmonics

– Cascaded FEL operating above saturation 400nm -> 200nm

– Cascaded FEL seeded with harmonics generated in gas

SASE with chirped & compressed beam

Compensation of the chirp with UM Taper

E. L. Saldin, E. A. Schneidmiller, and M.V. Yurkov, Self-amplified spontaneous emission FEL with energy-

chirped electron beam and its application for generation of attosecond x-ray pulses, PHYSICAL REVIEW

SPECIAL TOPICS - ACCELERATORS AND BEAMS 9, 050702 (2006)

• Compression with “Velocity Bunching”

– High peak current (up to 380A)

• Compression with “Velocity Bunching”

– High peak current (up to 380A)

• Compression with “Velocity Bunching”

– High peak current (up to 380A)

“Reconstruction” by D. Filippetto

Slippage length ~

e-bunch length

Projected r.m.s.

Energy spread ~ 1%

Strong chirp / energy spread in the longitudinal phase space

• Compression with “Velocity Bunching”

– High peak current (up to 380A)

Undulator

Resonance condition is a function of

Beam energy (chirp) / Undulator K

(untapered)

z

Radiation slips off resonance while

propagating along the undulator

δω

Initial

resonance

condition

ω

Wavelength range 45 nm

Spectr

om

ete

r slit

(vert

ical posititio

n)

Central Wavelength 540 nm

Spectrum

Average over 100 spectraEnergy 8 uJ (max 38 uJ)Rel Linewidth 1.6% rms

z

Resonance

condition

ω

u

u

ur

c

K

2

21

22

2

00)( sss

00)( zzKzKK k

Chirp

Taper

Resonance is maintained by tuning the

undulator taper

Compensation with Undulator taper

Average over 100 spectra:

Energy 140 uJ (max 380 uJ)

Rel Linewidth 0.8% rms

Single cooperation length observed in many spectra

(as the one shown above)

Average energy per pulse 18 times higher !!!

… in a narrower bandwidth (~1/2)

To see more: Poster sessions

ID: 1491 - TUPB18 FEL Experiments at SPARC

ID: 1642 - MOPB16 Energy Phase Correlation and FEL Efficiency

45 nm

Seeded Operation

Seed

FEL Amplifier

FEL Harmonic Generation

Seed 1

Modulator Radiator

2= 1/n, n=2

• Seed Sources:– 266 nm & 160 nm generated in gas

– 400 nm in BBO crystal (high seed energy)

• Cascaded FEL tested with both seed configurations

Direct seeding above saturation

Expected very efficient generation of high order harmonicsL. Giannessi, P. Musumeci, S. Spampinati, J. Appl. Phys. 98, 043110 (2005)

Seed Energy < 0.5 uJ

Direct seeding above saturation

Expected very efficient generation of high order harmonicsL. Giannessi, P. Musumeci, S. Spampinati, J. Appl. Phys. 98, 043110 (2005)

Seed Energy < 0.5 uJ

~ 0.7 uJ

Direct seeding above saturation

Expected very efficient generation of high order harmonicsL. Giannessi, P. Musumeci, S. Spampinati, J. Appl. Phys. 98, 043110 (2005)

Seed Energy < 0.5 uJ

~ 0.7 uJ

~ 3 uJ

Direct seeding above saturation

Expected very efficient generation of high order harmonicsL. Giannessi, P. Musumeci, S. Spampinati, J. Appl. Phys. 98, 043110 (2005)

385 390 395 400 405 410 415

4

6

8

5E8

7,25E8

9,5E8

1,175E9

1,4E9

1,625E9

1,85E9

2,075E9

2,3E9

2,525E9

2,75E9

2,975E9

3,2E9

3,425E9

3,65E9

3,875E9

4,1E9

4,325E9

4,55E9

4,775E9

5E9

lamda

Y Axis

Title

GENESIS

Simulation

Seed Energy < 0.5 uJ

~ 0.7 uJ

~ 3 uJ

~ 9 uJ

Harmonics down to 37 nm

Observation of 11° harmonic at 37nm

11h 10h 9h 8h 7h 6h 5h 4h 3h 2h 1h

To see more:

Poster session ID: 1491 - TUPB18

FEL Experiments at SPARC

Measured energy per pulse,

spot size & and bandwidth

of the first 11° harmonics

Cascaded configurations – Seed@400nm

Seed 1= 400nm

Modulator Radiator

2= 200 nm

Indication of saturation @200 nm

SPECTRUM @ 200 nm

Indication of saturation at 200nm

0.6 0.8 1 1.2 1.40

5 103

1 104

1.5 104

2 104

0

50

100

150

200

Total

Slit

Spot (rms mm)

Ener

gy (

nJ)

Correlation Energy – Spot size

0.3 0.35 0.4 0.450

5 103

1 104

1.5 104

2 104

0

50

100

150

200

Total

Slit

Rel. Linewidth (%)

Ener

gy (

nJ)

Correlation Energy – Linewidth

199.3 199.4 199.5 199.6 199.7 199.80

5 103

1 104

1.5 104

2 104

0

50

100

150

200

Total

Slit

Mean Wavelength (nm)

Ener

gy (

nJ)

Redshift

0.6 0.8 1 1.2 1.40

5 103

1 104

1.5 104

2 104

0

50

100

150

200

Total

Slit

Spot (rms mm)

Ener

gy (

nJ)

Correlation Energy – Spot size

0.3 0.35 0.4 0.450

5 103

1 104

1.5 104

2 104

0

50

100

150

200

Total

Slit

Rel. Linewidth (%)

Ener

gy (

nJ)

Correlation Energy – Linewidth

199.3 199.4 199.5 199.6 199.7 199.80

5 103

1 104

1.5 104

2 104

0

50

100

150

200

Total

Slit

Mean Wavelength (nm)

Ener

gy (

nJ)

Redshift

3° harmonic of the radiator

62 64 66 68

Wavelength (nm)

Inte

nsi

ty (

a.u.) Spectrum averaged over 30 shotsmax ~ 100 nJ,

average 30 nJ

0 1 2 3 4 50

10

20

30

Rel. Linewidth (%)

Pro

bab

ilit

y (

%)

FEL seeded with

harmonics generated in gas

Seed 266nm 1

Modulator Radiator

2= 133 nm

50 nJ 5-4-3 UM tuned @ 266 nm – 1-2-3 UM tuned @133 nm

Seed @ 266 nm → 133 nm

Studied the cascade changing the number of modulators/radiators

Direct seeding @ 160 nm

0 500 1 103

1.5 103

2 103

0

10

20

30

40

Energy (nJ)

Pro

bab

ility (

%)

Poster sessions

ID: 1491 - TUPB18 FEL Experiments at SPARC

ID: 1642 - MOPB16 Energy Phase Correlation and FEL Efficiency

Thank you !!!