2004 cleo/iqec, san francisco, may 15-21 optical properties of the output of a high-gain,...
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2004 CLEO/IQEC, San Francisco, May 15-21
Optical properties of the output of a high-gain, self-amplified
free-electron laser
Yuelin LiAdvanced Photon Source, Argonne National Laboratory
2004 CLEO/IQEC, San Francisco, May 15-21
Self Amplified free electron laser
• Continuously tunable
•Produce reliable coherent X-ray radiation
)2/1(
42
20
0 K
c
u
2004 CLEO/IQEC, San Francisco, May 15-21
The low-energy undulator test line FEL: future ALFF
6 Hz, 0.5 ps, 50 J @ 120-530 nmMilton et al., Science 292, 2037 (2001)
2004 CLEO/IQEC, San Francisco, May 15-21
The facility and application experimentSingle Photon Ionization or Resonant Ionization at ThresholdFEL undulator hall
0 2 4 6 8 10 12 1410-11
10-9
10-7
10-5
10-3
W (
J)
z (m)
Li et al., PRL 89 234801 (2002).
2004 CLEO/IQEC, San Francisco, May 15-21
The FROG experiment at 530 nm
0.0
0.5
1.0
0
1
2
3
0.0
0.5
1.0
0
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2
3
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0.5
1.0
-0.4 0.0 0.4 525 530 535
0
1
2
3
268
266
264
FrequencyTimeReconstructedRaw
(a) A065
268
266
264
(n
m)
I (
arb
. un
its)
(b) A771
(ra
d)
-0.4 0.0 0.4268
266
264
(ps)-0.4 0.0 0.4
(ps) t (ps)
(c) A454
(nm)
2004 CLEO/IQEC, San Francisco, May 15-21
.)3
1(4
)/())]((1[exp)(),(
2
2
000
eN
ij t
gjj
z
ivzttttttcizEztE
The field of a SASE FEL (by solving Green’s function) is
[S. Krinsky and Z. Huang, Phys. Rev. ST Accel. Beams 6, 050702 (2003).]
Temporal structure: Analysis
resonant frequency
t coherence length
/z electron beam energy chirp
4/1
02
1 eu
t nz
)2/1(
42
20
0 K
c
u
Goodman, Statistical Optics, (John Wiley & Sons, New York, 1985), p. 35.S. Krinsky, PRSTAB 6, 050701 (2003).
Summing of random phasors:Chaotic light
2004 CLEO/IQEC, San Francisco, May 15-21
Interest in temporal structure
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7.0
526 528 530 532 534 5360.0
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-600 -400 -200 0 200 400 600
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263 Raw
(fs)
(n
m)
-600 -400 -200 0 200 400 600
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263 Reconstructed
(fs)
Time
Inte
nsi
ty (
a. u
. )
t (fs)
Intensity Phase
Ph
ase
(rad
) (nm)
-600 -400 -200 0 200 400 600
'"
'"
I t
t (fs)
• Experimental data• Simulation• Analytical theory
2004 CLEO/IQEC, San Francisco, May 15-21
0 1 2 30.0
0.5
1.0
1.5
2.0
(a)
dp
()/d
=/‹›
0 4 8 12
0.0
0.1
0.2
0.3
0.4
(b)
dp
()/d
= t/‹›
0 1 2 30.0
0.5
1.0
1.5
2.0
(a)
dp
()/d
=/‹›
exp sim the
0 4 8 12
0.0
0.1
0.2
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0.4
(b)
dp
()/d
= t/‹›
0 1 2 30.0
0.5
1.0
1.5
2.0
(a)
dp
()/d
=/‹›
exp sim the
0 4 8 12
0.0
0.1
0.2
0.3
0.4
(b)
dp
()/d
= t/‹›Li et al., PRL 91 243602 (2003).
Temporal structure: spike width and spacing
= 52 fs
Follow statistics for chaotic light exactly.
2004 CLEO/IQEC, San Francisco, May 15-21
0 1 2 3 4
0.0
0.5
1.0
(a)
d
p+()
/d
='/
0 2 4 6 80.00
0.05
0.10 (b)
dp
-()/
d
='/
Li et al., PRL 91 243602 (2003).
0 1 2 3 4
0.0
0.5
1.0
(a)
d
p+()
/d
='/
exp sim
0 2 4 6 80.00
0.05
0.10 (b)
dp
-()/
d
='/
0 1 2 3 4
0.0
0.5
1.0
(a)
d
p+()
/d
='|/
exp sim the
0 2 4 6 80.00
0.05
0.10 (b)
dp
-()/
d
=|'|/
Derivative of phase (frequency)
=0.0094 rad/fs
Each intensity spike is a coherence mode.
2004 CLEO/IQEC, San Francisco, May 15-21
Frequency domain statistics correlation with time domain
0 5 10 15 20 25
0.0
0.1
0.2
0.3 Maxima
dp
+()
/d
0 20 40 60 80 100
0.00
0.01
0.02
0.03 Minima
dp
+()
/d
='/<>
Phase derivative Spike number correlation between time and frequency domain
• Each spike in freq domain is a coherence mode
• The number of spikes in the two domains are statistically one to one.
0 1 2 3 4 5
Mfr
eq
(b) Within I>0.05
Mtime
2004 CLEO/IQEC, San Francisco, May 15-21
Frequency domain statistics correlation with time domain
Envelope
0 2 4 6 8 10 12
0.0
0.2
0.4
Spike spacing
dp
()/d
<T>
0 1 2 3 4 5 6
0.0
0.5
<T>
dp
()/d
Spike width
2.42 2/Tmfreq (1/2t)/(2/T)
T/4t mtime
Number of spikes in time and frequency domain
T=4mt
T=2m/
0 1 2 3 4 5 M
freq
(b) Within I>0.05
Mtime
2004 CLEO/IQEC, San Francisco, May 15-21
SASE FEL output is chaotic: fully coherent transversely, but only partially coherent longitudinally
Through measurement of the spectra, one can statisticall determine the temporal domain property, the most important one is the pulse duration for the future X-ray sources.
Also the first time a chaotic light source is fully characterized.
Conclusion
2004 CLEO/IQEC, San Francisco, May 15-21
Chaotic light
Candles + incandescent lights
but with longer coherence length and a single spatial mode. Each time spike represents a coherence region.
The sun Stars
SASE FELs are chaotic light sources……
2004 CLEO/IQEC, San Francisco, May 15-21
Seeding a SASE for better …….
• Better longitudinal coherence/coherence control• Shorter pulse duration/Pulse shaping • Partly losing tunability……
FERMI@ELETTRA, scheme demonstrated at Brookhaven National Lab
2004 CLEO/IQEC, San Francisco, May 15-21
J. Lewellen, V. Sajaev, K.-J. Kim, S. V. Milton, O. Makarov, R. Dejus (ANL)
S. Krinsky (BNL)
Z. Huang (SLAC)
Work supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Contract No. W-31-109-ENG-38.
Acknowledgements