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The Quest for Ultra-Short X-ray Pulses. Alexander Zholents ANL. Fermilab , 03/09/2011. J. Levesque and P.B. Corkum , Can. J. Phys. 84: 1–18 (2006) . 2010. X-ray pulses. Thomson. Slicing. SPPS. LCLS. Expected. - PowerPoint PPT Presentation
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1Zholents, 03-09-2011
The Quest for Ultra-Short X-ray Pulses
Alexander ZholentsANL
Fermilab, 03/09/2011
2Zholents, 03-09-2011
J. Levesque and P.B. Corkum, Can. J. Phys. 84: 1–18 (2006)
2010
“…shorter and shorter laser pulses were obtained since discovery of mode locking in 1964. Each advance in technology opened a new field of science and each advance in science strengthened the motivation for even shorter laser pulses.”
Thomson Slicing
SPPS
LCLS
X-ray pulses
Expected
3Zholents, 03-09-2011
Scientific drivers. Why ultra-short pulses?· Phase transitions in solids
· Surface dynamics
· Making and braking of bonds during chemical reactions
· Chemical dynamics in proteins
· Correlated behavior of electrons in complex solids
… for showing that it is possible with rapid laser technique to see how atoms in a molecule move during a chemical reaction
t ~1Å / (speed of sound) ~ 100 fs
Femtochemistry
Ahmed Zewail,Nobel Prize, 1999
The vibration period between the two hydrogen atoms in a hydrogen molecule is about 8 fs
4Zholents, 03-09-2011
Molecule of rhodopsin before …
CH N
1) R.W. Schoenlein, L.A. Peteanu, R.A. Mathies, C.V. Shank, Science, 254, 412 (1991).
… and after absorption of a photon
First step in vision1)
How living systems function using smallest amount of energy?
5Zholents, 03-09-2011
Charles Shank
In 1981 Charles Shank and coworkers at Bell Labs redefined the term “ultrafast” when they reported the demonstration of 90 fs long pulses from colliding-pulse dye laser 1
1) R.L. Fork, B.I. Greene, C.V. Shank, Appl. Phys. Lett., 38, 671(1981).
Probe valence electrons with optical laser
Probe core electrons with x-rays
6Zholents, 03-09-2011
Laser assisted techniques: 90o Thomson scattering1
1) S. Chattopadhyay, K.-J. Kim, C. Shank, Nucl. Instr. Meth., A341, 351 (1994). 2) R.W. Schoenlein et. al., Science, 274(11), 236 (1996).
300 fs
7Zholents, 03-09-2011
90o Thomson scattering (2)
300 fs
1) A.H. Chin, R.W. Schoenlein, T.E. Glover, P. Balling, W. P. Leemans, C. V. Shank, “Ultrafast Structural Dynamics in InSb Probed by Time-Resolved X-Ray Diffraction”, Phys. Rev. Lett. 83, 336 - 339 (1999).
Lattice expansion dynamics in InSb as a function of time delay between laser and x-ray pulses1
X-ray probe before the laser pump
X-ray probe after the laser pump
8Zholents, 03-09-2011Femtosecond X-ray Beamline
First Light2000
In-vacuum Undulator
Femtosecond Laser ~50 W
“Slicing” source of fs x-ray pulses at the ALS1
1) R.W.Schoenlein et al , Science, March 24, (2000)
wiggler
100 fs electron slice
undulator beamline
70 ps electronbunch
100 fslaser pulse
spatial separationby dispersive bend
lW
Laser - ebeam interaction in wiggler
100 fs x-ray pulse
synchronous to laser
9Zholents, 03-09-2011
Electron trajectory through wiggler
22/ zw llWiggler period
Magnetic field in the wiggler
B B0sin(kuz)
Laser wavelengthFEL resonance condition
While propagating one wiggler period, the electron is delayed with respect to the light on one optical wavelength
=
Light interaction with relativistic electron*)
E
k
B
E
k
B V
V 0)(2 dtVEmc
e
Elaser N
S
S
NS
SN
N
e-
lu
light
*) Motz 1953; Phillips 1960, Madey 1971
Energy modulation of electrons in the wiggler magnet by the laser lightenergy modulation over the length of one optical cycle
10Zholents, 03-09-2011
Interference term defines energy gain/loss
Alternative approach to find energy modulation
Far field observer
Far field observer sees the field: )()()( tEtEtE sL
laser spontaneous emission
dEEdEdEdE LsLs *222 2
spontaneous emission
)sin(2 sL AAE laser
Electronbeam
11Zholents, 03-09-2011
Selection of fs x-ray pulses
DE
z
100 fs
2sE
Electron beam energy modulation
DX
z
100 fs
2sx
In dispersive placeDX=D•DE/E
Radiation of these electrons is selected
12Zholents, 03-09-2011
Other means to select fs pulse besides coordinate separation
spectral selection (works only with undulator source)2
Nn1)(
0
Bandwidth of the
undulator radiation at a high harmonic number n
1) R.W. Schoenlein, et al., Appl. Phys. B71, 1 (2000).2) H. Padmore, private discussion
Selection of fs x-ray pulses1
time-off-flight selection
-
+
angular selection
modulator dipole magnet
radiator
fs laser pulse fs x-ray pulseelectron bunch
aperturewiggler undulatorbend
magnet
electron bunchlaser pulse
subps x-ray pulse
mask
BESSY: courtesy S. Khan Select before first x-ray mirror
13Zholents, 03-09-2011
bend magnet visible radiation
Ti:Sa laser
Ti:Sa amplifier
BBOe-
slit
hn2 = ~2 eV
hn1 = 1.55 eV
hn =hn1+hn2
Measurement of a short pulse of synchrotron radiation via cross-correlation with a short laser pulse
intermediate focus
PMT
filter
e-beam
fs pulsefs pulse
light
Diagnostics
-60 -40 -20 0 20 40 600
50100150200250300350
# ph
oton
s
delay (ps)
s = 16.6 ps
14Zholents, 03-09-2011
-1200-1000 -800 -600 -400 -200 0 20060
80
100
120
140
160
180
delay (fs)
coun
ts
-1200-1000 -800 -600 -400 -200 0 200
100
150
200
250
coun
ts
-1500 -1000 -500 0 500 1000 1500
2000
2500
coun
tsElectron Density Distribution
time (ps) 0.3-0.3
x/s x
+3sx to +8sx
+4sx to +8sx
-3sx to +3sx
Diagnostics (2)ALS bend magnet
beamline
Modulation amplitude extracted from experimental data is 6.4 MeV
(expected ~ 10 MeV)
15Zholents, 03-09-2011
Diagnostics (3)
Electron loss rate versus scraper position
Deducing energy modulation amplitude from beam lifetime measurements using scraper in dispersive location (BESSY)
Energy modulation amplitude versus laser pulse energy
Approximately two times more laser pulse energy was used than it was predicted (same problem at ALS)
Not explained so far !
theory
experiment
laser pulse energy, (mJ)
LAEE ~D
without laser
withlaser
courtesy S. Khanscraper position, (mm)
16Zholents, 03-09-2011
“Slicing” at BESSY 1)
0 1 2 3 m
x-raypump pulse
e
1) S. Khan, et al., PRL, 97, 074801 (2006)
Detected photon rate per 0.1% bandwidth versus cutoff angle
phot
ons/
(s 0
.1%
bw
)
sign
al-to
-bac
kgro
undwithlaser
without laser
signal/background
angle, (mrad)
17Zholents, 03-09-2011
l1l2
wiggler detuning form
FEL resonance
Gain, %
I ≈ 25A
2EdEd
D
bunch train and a gap
Measurement of FEL gain through wiggler at ALS
Small-signal FEL gain
Madey’s theorem
FEL gain ~
laser spectrum gain
function
laser
e-beam
0.4
0.2
measured with laser oscillator
FEL resonance
-60 -40 -20 0 20 40 60 80
0
1
2
3
4
5
gain
(x10
-3)
delay (ps)
electron bunch laser pulse
s = 16.6 ps
Gain follows peak current distribution
18Zholents, 03-09-2011
first turn
second turn
1.2
time (ps) frequency (THz)
Rel
ativ
e ch
arge
den
sity A
mplitude (arb. units)
0.4
1.04
0.92
Laser-induced coherent fs THz radiation1-4
dtetI ti )(~
e-beam density distribution
Dip in the electron density distribution expands and dries out as the electron bunch travels along the ring
e-beam density distribution
time (ps) 0.3-0.3
x/s x
1) R.W.Schoenlein et al , Appl. Physics, B71, 1 (2000).2) J. Byrd et al , Phys. Rev. Lett., 96, 164801(2006).3) K. Holldack et al , Phys. Rev. Lett., 96, 054801 (2006).4) J. Byrd et al , Phys. Rev. Lett., 97, 074802 (2006).
Large, medium and
small modulationamplitudes
19Zholents, 03-09-2011
Dip reconstruction from THz spectra1
1) K. Holldack et al , Phys. Rev. Lett., 96, 054801 (2006).
wave number, (1/cm) time, (ps)
P coh
/Pin
c, (a
rb. u
nits
)
elec
tron
den
sity
, (ar
b. u
nits
)
THz signal is now routinely used for tuning of laser e-beam interaction and to maintain it with a feedback on mirrors – BESSY, ALS, SLS
20Zholents, 03-09-2011
Black: measurementRed: theoretical fit
Alternative approach to find energy modulation*
LaserSpontaneous emission An example of a poor
overlapping: wiggler is detuned too far away from the laser frequency
*) A. Zholents, K. Holldack, Proc. FEL’06, Berlin (2006).
In the experiment, wiggler gap was adjusted such as to change the central frequency of spontaneous emission from 200 nm to 1000 nm laser
21Zholents, 03-09-20111) A. Zholents, P. Heimann, M. Zolotorev, J. Byrd, NIM A, 425, 385 (1999).2) M. Katoh, Japan. J. Appl. Phys, 38, L547(1999)
Radiation from tail electrons
angle >> beam divergence + x-ray diffraction
Radiation from head electrons
undulator
Storage Ring
Deflecting cavity delivers a time-dependent vertical kick to the beam
Compression using
asymmetrically cut crystal
Trading brightness to a short pulse
Ideally, second cavity cancels effect of first cavity
~1 ps
High repetition rate source of ps x-ray pulses1,2
22Zholents, 03-09-2011
Application to the Advanced Photon Source1
Part of the APS upgrade pursued in an active collaboration with JLab
Pulse length versus transmission through aperture calculated for 10 keV photons
courtesy M. Borland
6 MV deflection
rf harmonicnumber
Obtaining short x-ray pulses at APS1-3
1) K. Harkay et al, Proc. PAC’05, 668(2005).2) M. Borland, Phys. Rev. ST – AB, 8, 074001(2005).3) M. Borland et al, Proc. PAC’07, (2007).
diffraction limited
Pulse length versus photon energy
emittance limited
rfz
rfy
z
rayx
zy )()(s
ss
sD
saturated at
rf kick
23Zholents, 03-09-2011
Synchronization between laser pump and x-ray probe pulses
LASER OSCILLATOR(passively modelocked)
Dt Dt3.0 GHz
(RF Kick)electron bunch
laser pulse
x-rays
Synchronous bunch
Jitter in the e-beam arrival time is converted into position
jitter of compressed x-ray pulse
Early bunchAsymmetrically cut crystal
Late bunch
Sensitivity to electron bunch timing jitter is significantly reduced
aperture
or intensity jitter behind the aperture
24Zholents, 03-09-2011
add 14-meter chicane in linac at 1/3-point (9 GeV)
1-GeV Damping Ring
sz 1.1 mm sz 40 mm sz 12 mm
sz 6 mmSLAC Linac
30 GeVFFTB
Short Bunch Generation with the SLAC Linac - SPPS
Existing bends compress to 80 fsec
1.5 Å
compression by factor of 500
P. Emma et al., PAC’01
1.5%
28.5 GeV
80 fs FWHM
30 kA
measurement < 300fs
Single pass, low rep. rate
25Zholents, 03-09-2011
New Scientists
Coherent emission of x-rays using Free Electron Lasers: a road to attosecond x-ray pulses
nm30sec10100sec/m103 188 sec10100
137sec/m103 18
8
2 Å
Zholents, Avalon, 10/2010E. Goulielmakis et al., Nature, 466, 739(2010).
Probing intra-atomic electron motion by attosecond absorption spectroscopy.
80 attoseconds !
June 19, 2008
Attosecond XUV pulses had been obtained
27Zholents, 03-09-2011
Attosecond x-ray pulses is a powerful tool for addressing Grand Challenges in Science and BES Research Needs
• How do we control materials and processes at the level of electrons?
• How do we design and perfect atom-and energy-efficient synthesis of new forms of matter with tailored properties?
• How do remarkable properties of matter emerge from complex correlations of atomic and electronic constituents and how can we control these properties?
• Can we master energy and information on the nanoscale to create new technologies with capabilities rivaling those of living systems?
• How do we characterize and control matter away—especially very far away—from equilibrium?
2007G. Fleming
Zholents, Avalon, 10/2010
Short EUV/x-ray pulses are routinely produced at FLASH (10 – 70 fs), SCSS (~ 30 fs) , LCLS (<10 – 80 fs)
All future x-ray FEL projects consider ultra-short x-ray pulse capabilities
Zholents, Avalon, 10/201029
20-pC bunch operation at LCLS1
Photo-diode signal on OTR screen after BC21) Y. Ding et. al, PRL 2009
FEL gas detector measurements
BL signal
+1deg-1 deg
soft x-rayh=840 eV
Simulated signal
Simulated bunch length
X-ray pulse duration should be <10 fs, but no direct
measurement yet possible
(9/29/2009)
~ 1mm
Soft x-rays at 1.5 nm (simulations for LCLS)1
Under-compression: +1 deg off Full-compression Over-compression: -1 deg off
z = 40m z = 40mz = 40m
Actual measurements qualitatively confirm simulations. Direct measurement of ultra-short x-ray pulse duration remains to be difficult.
At undulator entrance, 4.3 GeV, Laser heater off1) Y. Ding ,LBNL workshop, 08/2010
~ 3 fs ~ 3 fsFEL peak power is ~ 3 orders lower
Too narrow pulse: slippage larger than pulse duration
31
~1 fs
at 70 m~150 mJ
L1 = -22 deg
Simulation at 13.6 GeV At 1.5 Å FEL performs well at full compression (slippage just right)
Not short enough for FT limited pulse
Y. Ding ,LBNL workshop, 08/2010
Gain length =2.74 m
140 mJ FEL energy
J. Frish et. al., talk at FEL’09
Measurement
deflecting angle
SUB-FEMTOSECOND X-RAY PULSES USING THE SLOTTED FOIL METHODP. Emma, M. Cornacchia, K. Bane, Z. Huang, H. Schlarb ,G. Stupakov, D. Walz , PRL, 2004
BC24.3 GeV
14 GeVBC1250 MeV
135 MeV
gun 4 wirescanners to FEL
h=8 keV
Linac Coherent Light Source, SLAC
200 fs
7 M
eV
Only bright spot will lase
z
DE
energy chirp
X-ray pulse width ~ 400 asecBunch arrival time jitter ~ 50 fs~ 109 photons/pulse -> 7 GW
Courtesy P. Emma
Simulation using Elegant
time (fs)
Pow
er (G
W)
0
10
5
0-150 fs
2 fs
2-Pulse Productionwith 2 slots
0-6 mm
0.25 mm
pulses not coherent
Double X-Ray Pulses from a Double-Slotted Foil
Courtesy P. Emma
FEMTOSECOND X-RAY PULSES IN THE LCLS USING THE SLOTTED FOIL METHOD
Precise controlled time delay between x-ray pump and x-ray probe pulses
Slotted Foil in at -6000 um
Slotted Foil in at -34000 um
Slotted Foil in at -37000 um
Over-compressed bunch introduces e- energy chirp on dump screen… ~time
~time
~time
time
dumpscreen
sing
le s
lot
doub
le s
lot
doub
le s
lot
HEAD
TAIL
Courtesy P. Emma
Initial results (very preliminary), June 17, 2010
X-ray pulse energy
slots e-bunch
Wider slot gives more energy
Zholents, Avalon, 10/2010
Pump – probe studies using ultra-fast x-ray pulses
Stop-motion photography E. Muybridge, 1878
Pellet hits a strawberry
delay
x-ray probe
visible pump
36Zholents, 03-09-2011
Options for experiment utilizing synchronized pump and probe signals when electron bunch arrival time has a “large” jitter
Chicane Undulator
IR pump, ~100 MW
X-ray probe
Single color x-ray pump – x-ray probe experiment
Split single x-ray pulse into two and adjust delay
Create pump signal using cohrent undulator radiation and adjust delay1 (in case of an ultra-short e-bunch, ~ 1 fs)
1) U. Fruhling et al., Nature photonics, 3, 523(2009); F. Tavella et al., Nature photonics, 5, 162(2011)
Use double slotted foil
37Zholents, 03-09-2011
Precision synchronization of pump and probe pulses Seeded FELs naturally posses precise synchronization
if electron bunch length > laser pulse + jitter
Current-enhanced SASE FEL --> same conclusion (Zholents, 2004) BunchingAccelerationModulation
Pea
k cu
rren
t
t
20-25 kA 10 fsAfter bunching
This part will lase
~50 fs
laser
e-bunch
10 fs
Require synchronization of the seed and pump lasers 1)
1) J. Kim et. al., Nature Photonics, 2, 733, 2008;
R. Wilcox, Opt. Lett. 34, 3050, 2009
38Zholents, 03-09-2011
e-beam ~ 50 fs
e-beam ~ 50 fs
Laser pulse ~ 5 fs
)t(E
Attosecond pulse generation via electron interaction with a few cycle carrier-envelop phase stabilized
laser pulse
Basic idea:Take an ultra-short slice of electrons from a longer electron bunch to produce a dominant x-ray radiation
Small jitter in the electron bunch arrival time is not important – good for pump-probe experiments using variety of pump sources derived from initial laser signal
39Zholents, 03-09-2011
Electron trajectory through wiggler
22/)2/21( ll KwL Wiggler period
Laser wavelengthFragment of the electron bunch
While propagating one wiggler period, the electron is delayed with respect to the light on one optical wavelength
Light interaction with relativistic electron
E
k
B
E
k
B V
V 0)(2 dtVEmc
e
Elaser N
S
S
NS
SN
N
e-
lu
light
Laser pulse: 1 mJ, 5-fs
at 800 nm wave length with CEP stabilization
sE
Sin-wave Cos-wave
40Zholents, 03-09-2011
Energy modulation induced in the electron bunch during interaction with a ~1 mJ, 5 fs, 800 nm wave length laser pulse in a two period wiggler magnet with K value and period length matched to FEL resonance at 800 nm
Current enhancement
Pea
k cu
rren
t This spike gives a dominant signal
41Zholents, 03-09-2011
Energy modulation of electrons produced in interaction with two lasers
Current enhancement method *)
Combined field of two lasers:increases one laser bandwidth
t (fs)
Elec
tric
fiel
d
*) Zholents, Penn, PRST-AB, 8, (2005); Y. Ding et al., Phys. Rev. ST-AB, 12, (2009).
800 – 1000 nm laser; 7.5 – 25 fs; 0.2 – 0.5 mJ
Undulator with ~ 1% taper
1300 – 1600 nm laser; 10 – 45 fs; 0.07 – 0.2 mJ
42Zholents, 03-09-2011
one lasertwo lasers
Selection of attosecond x-ray pulse:regions with higher peak current reach saturation earlier
Contrast ≈ 1 (assuming 100 fs long bunch ) Nearly Fourier transform limited pulse
t (fs)
curr
ent,
(kA
)
t (fs)
10 mJ1010ph
Pow
er, (
GW
)
250 asec
X-ray wavelength = 0.15 nm
Current enhancement method (2)
43Zholents, 03-09-2011
[1] A. A. Zholents and W. M. Fawley, Phys. Rev. Lett. 92, 224801 (2004).[2] E.L. Saldin, E.A. Schneidmiller, M.V. Yurkov, Opt. Commun. 237,153 (2004).[3] E.L. Saldin, E.A. Schneidmiller, M.V. Yurkov, Opt. Commun. 239,161 (2004).[4] A. A. Zholents and G. Penn, Phys. Rev. ST-AB 8, 050704 (2005).[5] E.L. Saldin, E.A. Schneidmiller, M.V. Yurkov, Phys. Rev. ST-AB 9, 050702 (2006).[6] A. A. Zholents and M.S. Zolotorev, New J. Phys. 10, 025005 (2008).[7] W.M. Fawley, Nucl. Inst. and Meth. A 593, 111(2008).[8] Y. Ding, Z. Huang, D. Rather, P. Bucksbaum, H. Maerdji, Phys. Rev. ST-AB 12, 060703 (2009).[9] D. Xiang, Z. Huang, G. Stupakov, Phys. Rev. ST-AB 12, 060701 (2009).[10] A. A. Zholents and G. Penn, Nucl. Inst. and Meth. A 612, 254(2010).
Publications exploring generation of attosecond x-ray pulses using a few-cycle laser pulse with a carrier envelop phase stabilization:
Zholents, Avalon, 10/2010
~ 200 as
Contrast ≈ 1
Energy modulation
lx=0.15 nm
cdtd
KK
dzKd
u
x ll ln
2/2/1ln
2
2
Tapered undulator method1
Energy chirp is compensated by the undulator taper in the central slice
1) E.L. Saldin, E.A. Schneidmiller, M.V. Yurkov, Phys. Rev. ST-AB 9, 050702 (2006).
2)/( tt s
Frequency chirp definition
Wigner transformof the on-axis far field
-2.5 0-5t, fs
7.9
7.6
7.8
Wav
elen
gth,
nm Chirp
≈ 0.57.7
2.5
W.M. Fawley, Nucl. Inst. and Meth. A 593, 111(2008).
Fourier transform limited pulse ~ 1.5 fs (FWHM)
Hard x-rays Soft x-rays
With two laser one can manipulate the energy chirp and, thus, the frequency chirp
Zholents, Avalon, 10/2010
Photoelectron probability
Pho
toel
ectro
n m
omen
ta
“Sudden” photoionization creates a coherent superposition of electronic states, G. Yudin, PRL, (2006)
The figure-of-merit is broad bandwidth of attosecond pulses
Zholents, Avalon, 10/2010
Artist’s (Denis Han) view of excited electron wavepackets in molecule created by core excitation with attosecond x-ray pulses (courtesy S. Mukamel)
Intense attosecond x-ray pulses from FELs provide the opportunity to probe the matter on atomic scale in space and time
Stimulated X-ray Raman spectroscopy *)
X-ray pump, X-ray probe;element specific
ener
gy
v-bandEF
core level
phot
on in
photon out
DE~10eV
hnout, kout
300 asec -> 6 eV, i.e. “sudden” excitation reveals multi-electrondynamics
*) Schweigert, Mukamel, Phys. Rev. A 76, 012504 (2007)
In molecules all electrons move in a combined potential of ion core and other electrons
x-rays
UndulatorWigglerLinac
e-beam2 mm laser
TEM00
TEM10
Selection of attosecond x-ray pulses via angular modulation of electrons*)
*) Zholents, Zolotorev, New Journal of Physics, 10, 025005 (2008).
Hermite-Gaussian laser modes
)cos()( 0 zkxzx DD
)sin()( 0 zkEzE DD2 mm laser
10-1
0 Px-
ray
(W)
t (fs)
X-ray peak power as a function of time
Combining angular and energy modulations for improved contrast of attosecond x-ray pulses
100 GW 115 as, 10 mJ~100mJ/cm2
Central peak
Contrast > 100
X-ray wavelength = 0.15 nm
Obtaining attosecond pulses at 1 nm using echo effect*)
*) D. Xiang, Z. Huang, G. Stupakov, Phys. Rev. ST-AB 12, 060701 (2009).
Adding energy chirp via interaction with ultra short laser pulse; needs sub-fs synchronization
radiator has only 12 periods
x-ray pulse
20 asec
2 2
wiggler1chicane1
radiator11
wiggler2 wiggler3 radiator2chicane2 chicane3
Two color attosecond pump and attosecond probe x-ray pulses*)
DT
*) Zholents, Penn, Nucl. Inst. and Meth. A 612, 254(2010).
z/l
DE/s
E
Fragment of the longitudinal phase space
z/l
DE/s
E
Adjustable time delay with better than 100 asec precision
zoom
Zoom into the main peak shows microbunching at 2.28 nm
DT
ħ=410 eV ħ=543 eV
7.2 eV FWHM
6.4 eV FWHM
543 eV210 asec FWHM
410 eV480 asec FWHM
DT
Simulation results using 1D code and GENESIS for two color scheme
time, (fs)
photon energy, (eV)
adjustable
Molecule structure of 5-quinolinol
Zholents, 03-09-2011 52
Three synchrotron light sources ALS, BESSY, SLS routinely operate with 100 – 200 fs x-ray pulses
SOLEIL, SPring8, APS pursuing plans to add ulrafast x-ray science capacities
X-ray FELs FLASH, SCSS and LCLS routinely work with ultra-short XUV/x-ray pulses.
Summary
53Zholents, 03-09-2011
Summary: FELs – the light fantastic
We are at the threshold of a new era of science, where for the first time, the new instruments, the x-ray FELs, are capable to study the matter with a single atom time and space resolution.
Remarkably, adding attosecond capabilities to existing FELs require rather modest modifications.
P. Bucksbaum, Science, 317, 766(2007).
Conical intersection
pump
Attosecond probe
Expected soon:X-ray pulses million times brighter and thousand times shorter than anything can be done using spontaneous emission
54Zholents, 03-09-2011
Acknowledgement
I greatly benefited from discussions with many people including:
M. Borland, J. Byrd, J. Corlett, P. Emma, W. Fawley, E. Glover, P. Hiemann, K. Holldack, Z. Huang, S. Khan, M. Martin, B. McNeil, C. Pellegrini, G. Penn, V. Sajaev, F. Sannibale, R. Schoenlein, J. Staples, G. Stupakov, M. Venturini, J. Wurtele, M. Zolotorev
,
Zholents, Avalon, 10/2010
Thank you for your attention
Zholents, Avalon, 10/2010
Back-up slides
57Zholents, 03-09-2011
Recent studies show that a smaller emittance (by a factor of 10), and very short, ~ 1 fs or less, electron bunches can be produced if the electron bunch charge is dropped to 1 -10 pC
Ultra-short X-ray pulses with low charge electron bunches 1- 10 pC *)
UCLA
*) J.B. Rosenzweig et al., NIM A 593, 39 (2008); C. Pellegrini, seminar at LBNL, 07/11/08
peak current
s 2
IB
Normalized slice emittance Slice energy spread
Electron beam brightness can be increased by a factor 10 - 100
Road to compact FELs
58Zholents, 03-09-2011
Example of simulations for LCLS with 1 pC*)
*) J.B. Rosenzweig, talk at FEL workshop, LBNL, November 2008
Improved brightness -> reduced saturation length
saturation at ~70 m
~350 asec
Difficult to synchronize to external source due to electron bunch arrival time jitter
59Zholents, 03-09-2011*) Saldin, Schneidmiller, Yurkov, Optics, Com., 239 (2004)
Chicane
x-rays
UndulatorUndulatorWigglerLinac
e-beam x-rays
0 + 0
• seed signal interacts with “virgin” electrons in the second undulator
• second undulator is tuned to favor SASE for electrons at the offset frequency 0+
• Contrast >> 1 (assuming 100 fs long electron bunch)
no saturation
~300 asec, ~5-25 mJ
Attosecond x-ray pulse
Spectral separation plus seeding *)
seed 0 +
X-ray wavelength = 0.15 nm
Selection of attosecond x-ray pulse
60Zholents, 03-09-2011
Echo effect for harmonic generation of x-rays*)
DE/sE
z/l*) G. Stupakov, PRL, 102, 074801(2009).
FEL undulator