Get documents about "harmonic generation Source Development Laboratory
Shared by: alicejenny
-
Stats
- views:
- 1
- posted:
- 9/26/2012
- language:
- Unknown
- pages:
- 33
Document Sample
LUX
Linac/laser based Ultrafast X-ray facility
R&D objectives
DUV FEL Accelerator and FEL Physics Workshop
BNL, February 2004
John Corlett, February 19, 2004
LUX design contributors
W. Barry, W. A. Barletta, J. Byrd, J. N. Corlett, S. DeSantis, L. Doolittle,
W. M. Fawley, W. Graves7, M. A. Green, N. Hartman, P. Heimann, D.
Jones9, D. Kairan1, H. Kapteyn8, E. Kujawski, S. Leone, D. Li, S. Lidia, P.
Luft, R. McClure, H. Padmore, F. Parmigiani2, Y. Petroff, W. Pirkl3, M.
Placidi4, A. Ratti, D. Reavill, I. Reichel, R. Rimmer5, A. Ratti, L. Reginato,
K.E. Robinson, F. Sannibale, R. Schoenlein, J. Staples, J. Tanabe, D.
Truchlikova, S. Virostek, W. Wan, S. Wang6, R. Wells, R. Wilcox, A. Wolski,
A. Zholents, M. Zisman
Lawrence Berkeley National Laboratory, CA, USA
1Budker Institute of Nuclear Physics, Novosibirsk, Russia
2Università Cattolica del Sacro Cuore, Milano, Italy
3Geneva, Switzerland
4CERN, Geneva, Switzerland
5Thomas Jefferson National Accelerator Facility
6 Indiana University
7MIT-Bates
8JILA / Univ. of Colorado, Boulder
9 Univ. of British Columbia / JILA
John Corlett, February 19, 2004
LUX is a design study for a facility to
perform time resolved experiments
• Timescales of the order of an atomic vibrational period
1 Å/vsound ~ 100 fs
• Apply existing x-ray techniques to ultrafast dynamics experiments
• Combining diffraction and spectroscopy (nuclear positions and
electronic, chemical or structural probes)
Time-resolved x-ray diffraction Time-resolved EXAFS, NEXAFS, surface EXAFS
r f(r)
absorption
detector
time delay diffraction angle
• Access new science in the x-ray regime
delay
K edge energy
• Time dynamics parameters have not been widely exploited in the
x–ray, mostly due to lack of sources
John Corlett, February 19, 2004
We propose a facility for ultrafast dynamics
which is driven by scientific requirements
• Pulse duration 10-200 fs, variable, or shorter
• High flux per pulse ~106-1013 (ph/pulse/0.1%BW)
• Broad photon range 20 eV to 12 keV
• Tunability fully tunable on each beamline
• Repetition rate 10 kHz to match pump-probe experiments
• Synchronization 10’s fs pump laser – probe x-ray
• Polarization lhc, rhc soft x-ray / linear hard x-ray
• In addition to accelerator systems, the facility will include multiple short-
pulse laser systems
– Master oscillator
– Photocathode laser
– Harmonic generation seed laser
– Beamline endstation pump lasers
John Corlett, February 19, 2004
LUX based on a recirculating linac provides
a refined source of ultrafast x-ray pulses
• RF photocathode gun produces high-quality electron beam
• 2-3 mm-mrad, 1 nC, 30 ps, ± 20 keV
• Compress beam from the injector to 3 ps
• Accelerate in multiple passes through linac
• 1-3 GeV beam generates x-rays
• 10-100 fs duration
• Recirculating configuration
offers flexibility
• Manipulation of bunch
longitudinal phase space on
each pass
• Multiple experiemntal
beamlines in each pass
John Corlett, February 19, 2004
LUX provides tunable, ultrafast x-ray
pulses from ps electron bunches
• Soft x-rays
• “HGHG” (but low-gain)
• Laser-seeded cascaded
harmonic-generation in
FEL’s
• Strong modulation
• Low-gain FEL
– 20-1000 eV
– Spatial and temporal
coherence
– 10-100 fs
– 10’s - 100’s MW
• Hard x-rays
• Spontaneous emission
in narrow-gap short-
period insertion
devices
– 1-12 keV
– 50-100 fs
John Corlett, February 19, 2004
Cascaded harmonic generation scheme
seed laser pulse disrupted region
modulator radiator modulator radiator
tail head
Low e electron pulse Unperturbed electrons
sE ~ sE (0)
Delay bunch in micro-orbit-bump (~50 mm)
Seed laser pulse FEL modulator 3rd - 5th 3 - 5th harmonic 3rd - 5th
Tbunch >> TMO LW < LSAT harmonic FEL modulator / harmonic
PMO >> Pshot Strong bunching radiator low gain amplifier radiator
LW < LSAT
John Corlett, February 19, 2004
Multiple independent harmonic cascades –
independent wavelength tuning for each beamline
20 eV beamline - single stage (4th) harmonic generation
Endstation
100 eV beamline - two-stage (16th) harmonic generation
Endstation
500 eV beamline - three-stage (80th) harmonic generation
Endstation
1000 eV beamline - four-stage (200th) harmonic generation
Endstation
• Seed at shorter wavelengths if laser developments allow
– May eliminate some stages of harmonic generation
John Corlett, February 19, 2004
Harmonic cascades
John Corlett, February 19, 2004
Potential for attosecond x-ray production
spectral
800 nm broadening and
pulse compression
e-beam
e-beam
one period wiggler tuned 2 nm light from FEL
time delay for FEL interaction at
harmonic-cascade FEL chicane 800 nm
1 nm
coherent
chicane-buncher radiation dump
2 nm modulator
end
1 nm radiator station
end
station
John Corlett, February 19, 2004
LUX R&D goals
• Demonstrate essential accelerator physics, hardware, and techniques
– Cascaded harmonic generation
• Demonstrate cascaded harmonic-generation
– Collaborate in experiments at the DUV FEL
• Demonstrate control of nm-scale bunch modulation
– 10 kHz rf gun development
• Fabricate high-power, high-brightness, rf photocathode gun
– Demonstrate performance under demanding rf conditions
– Synchronization
• Demonstrate stable laser master oscillator and optical timing distribution systems
• Demonstrate synchronization of remote lasers
– Flat beam production (small vertical emittance, required for hard x-ray compression)
• Develop optimized scheme
– Accelerator physics studies
• Tracking with CSR, resistive wall, cavity wakefields, vacuum chamber wakefields, alignment errors,
strength errors, etc.
• X-ray production with realistic bunch phase space
– Lasers
• Develop concepts for photocathode laser, FEL seed laser, multiple endstation lasers locked to master
oscillator
• CW scrf and narrow-gap short-period insertion devices under development elsewhere
John Corlett, February 19, 2004
LUX R&D goals - harmonic cascade
combines several requirements
• Demonstrate essential accelerator physics, hardware, and techniques
– Cascaded harmonic generation
• Demonstrate cascaded harmonic-generation
– Collaborate in experiments at the DUV FEL
• Demonstrate control of nm-scale bunch modulation
– 10 kHz rf gun development
• Fabricate high-power, high-brightness, rf photocathode gun
– Demonstrate performance under demanding rf conditions
– Synchronization
• Demonstrate stable laser master oscillator and optical timing distribution systems
• Demonstrate synchronization of remote lasers
– Flat beam production (small vertical emittance, required for hard x-ray compression)
• Develop optimized scheme
– Accelerator physics studies
• Tracking with CSR, resistive wall, cavity wakefields, vacuum chamber wakefields, alignment errors,
strength errors, etc.
• X-ray production with realistic bunch phase space
– Lasers
• Develop concepts for photocathode laser, FEL seed laser, multiple endstation lasers locked to master
oscillator
John Corlett, February 19, 2004
LUX rf photocathode gun design optimized for
high-brightness and high-duty factor
• Energy 10 MeV
• Charge 1 nC
• Normalized RMS emittance 2-3 p mm-mrad
• Energy spread at 10 MeV ±20 keV
• Bunch length 30 ps
• Repetition rate 10 kHz
cathode • RF frequency 1.3 GHz
Laser pulse
• Peak E field on a cathode 64 MV/m
• Cathode material Cs2Te
• Laser wavelength 260 nm
• UV pulse energy at cathode 1 µJ
• Pulse length (FWHM) 35 ps
• Laser spot radius 1-2 mm
Excess stored energy
Phase flip at 5µsec
John Corlett, February 19, 2004
Collective effects and emittance control
• Wakefields 1-st pass
– Linac cavity modes and BBU p
• p betatron phase advance in first arc 2-nd pass
– Resistive wall
• Coherent synchrotron radiation 3-rd pass
• Longitudinal phase space control
– Bunch compression 4-th pass
– Correlated energy spread
1 1
Elegant model - at - at the end of the
the end of the linac
bunch compressor
DE (MeV) DE (MeV)
-1 -1
-0.4 0.4 red – head electrons -0.4 0.4
Z (mm) Z (mm)
blue – tail electrons
yellow – core electrons
John Corlett, February 19, 2004
4 nm modulation successfully propagated through
transport line
Output of 5° achromatic bend
Output of 4 nm modulating undulator - linear terms
Output of 5° achromatic bend
- up to 5th order terms
John Corlett, February 19, 2004
Master oscillator and timing distribution
• Mode-locked fiber laser serves as
Modelocked Laser Oscillator – RF Stabilized
17 dBm mixer
master oscillator
RF Clock • Active stabilization of optical master
1.3/n GHz oscillator distribution
• All rf signals derived from laser master
1/Trep f BPF 1.3 GHz 28 dB
AMP
LPF oscillator
Trep • All lasers synchronized to master
Amplifier
PZT driver oscillator
Modelocked Laser
1.3 GHz error signal • Synchronization x-ray pulse to
experimental pump laser of 20-50 fs
Master
Oscillator Agilent 5501B
Path Length Control
cw reference laser 210-9 one hour (Dl/l) DL= 2 mm
Dt= 7 fs
EDFA
(fiber amp)
interferometer 210-8 lifetime
L~100 m
PZT control
path length
EDFA
fiber-based system (fiber amp) Beamline 1
Beamline 2
John Corlett, February 19, 2004
FEL seed laser
• OPA provides controlled optical seed for the free electron laser
Q-switched
Nd:YAG (2w)
Ti:sapphire Ti:sapphire Optical
Oscillator grating Regenerative grating Parametric
<100 fs, 2 nJ stretcher Amplifier compressor Amplifier
<50 fs jitter
~1 mJ, 800 nm, 10 kHz >10% conv. efficiency
RF from
master
oscillator laser seed pulse undulator
harmonic
e-beam undulator undulator
• Wavelength tunable x-ray
n undulator stages
– 190-250 nm
• Pulse duration variable
– 10-200 fs
• Pulse energy Endstation synch.
– 10-25 µJ
• Pulse repetition rate
– 10 kHz
• Endstation lasers seeded or synchronized to Ti:sapphire oscillator
– Tight synchronization <20 fs
John Corlett, February 19, 2004
1.1 GeV, 2-stage cascade
Genesis simulations
Electron beam:
• 2 mm normalized transverse emittance
• 500 A peak current
• +/- 200 keV
Laser:
• 200 nm wavelength
• Peak power 100 MW
• Gaussian pulse, 100 fs RMS in power 450
seed power
400 50 nm
12.5 nm
350
Using harmonics 4 - 16
300
• 200 nm, 8 cm period, 4 m,
Power (MW)
a=4.695 250
• followed by R56 = 21 micron
• 50 nm, 5 cm period, 5 m & 2.5 m, 200
a=2.865 150
• followed by R56 = 7.7 micron
• 12.5 nm, 3.5 cm period, 10.5 m, 100
a=1.517
50
0
-200 -150 -100 -50 0 50 100 150 200
T (fs)
John Corlett, February 19, 2004
2.1 GeV, 3-stage cascade
Genesis simulations
Electron beam:
• 2 mm normalized transverse emittance
• 500 A peak current
• +/- 200 keV
Laser:
• 200 nm wavelength
• Peak power 100 MW
• Gaussian pulse, 100 fs RMS in power 350
seed power
40 nm
300
10 nm
2.5 nm
Using harmonics 5 - 20 - 80 250
• 200 nm, 14 cm period, 4.2 m,
Power (MW)
a=6.850 200
• followed by R56 = 38 micron
• 40 nm, 8 cm period, 5.5m & 6.0 m, 150
a=3.978
• followed by R56 = 3.2 micron 100
• 10 nm, 5 cm period, 7.5m & 4.0 m,
a=2.396 50
• followed by R56 = 2.0 micron
• 2.5 nm, 3.5 cm period, 8.75 m, 0
a=1.1878 -150 -100 -50 0 50 T (fs) 100 150
John Corlett, February 19, 2004
2508
1.0 GW
240-nm
Energy (MeV)
modulator
4-stage cascade Z=0 m Z=1.8 m Z=3.6 m
Ginger simulations Z (m)
2492
3.6 -p q (radians) +p
0.4 GW 2510
• At each modulator, 48-nm
radiation interacts with radiator
“virgin” e-
• At each harmonic
upshift l l/n Z=0 m Z=2.4 m Z=4.4 m
(modulator to 2490
radiator), macro- Z (m) 4.4 -5p q (radians) +5p
particle phase 0.4 GW 2504
multiplied by n 48-nm
48-nm
modulator
modulator
• Bunching effects of
dispersive section
visible in change from
Z=6 m in 48-nm Z=0 m Z=3 m Z=6 m
2496
modulator to Z=0.4m Z (m) 6.0 -p q (radians) +p
scatter plot in 12-nm 120 MW 2504
radiator 12-nm
radiator
Z=0.4 m Z=3.4 m Z=5.4 m
2496
5.4 -4p q (radians) +4p John Corlett, February 19, 2004
Z (m)
4- and 1-nm output power sensitivity to input
electron beam parameters
Base parameters:
2.5 GeV
500 Amps Note: 4-nm power scaled down 10X to fit on plots
200 keV uniform dE
2.0 mm-mrad
1.0 GW input P @240 nm
4-stage harmonic cascade
Time-steady simulations
Nominal output power:
138 MW @ 4 nm
11 MW @ 1 nm
Current (A) Norm. Emit. (mm-mrad)
Delta E (KeV) (E- E0)/ E0 Input power (GW)
John Corlett, February 19, 2004
A cascaded harmonic generation
experiment at the DUV FEL?
1000
First harmonic for 200 MeV beam
800 nm
800
DUV FEL modulator
8 cm period
X-ray wavelength (nm)
600
Demonstrated
NISUS
400 2.5 cm period
267 nm
Second section 200
Proposed scheme for DUV FEL
NISUS modulator 89 nm
267 nm
VISA
First section 1.8 cm period
0
NISUS radiator 0.0 0.5 1.0 1.5 2.0 2.5 3.0
267 nm Undulator K value
Modulator
800 nm laser seed
chicane
Achromatic bend beamline designed to
VISA ? allow demonstration of control of 266
Radiator nm modulated beam
89 nm
John Corlett, February 19, 2004
A cascaded harmonic generation
experiment at the DUV FEL?
1000
First harmonic for 200 MeV beam
Expensive and difficult 800
800 nm
to accommodate in the
DUV FEL modulator
8 cm period
X-ray wavelength (nm)
existing facility
600
Demonstrated
NISUS
400 2.5 cm period
267 nm
Second section 200
Proposed scheme for DUV FEL
NISUS modulator 89 nm
267 nm
VISA
First section 1.8 cm period
0
NISUS radiator 0.0 0.5 1.0 1.5 2.0 2.5 3.0
267 nm Undulator K value
Modulator
800 nm laser seed
chicane
Achromatic bend beamline designed to
VISA ? allow demonstration of control of 266
Radiator nm modulated beam
89 nm
John Corlett, February 19, 2004
A more realistic cascaded harmonic
generation experiment at the DUV FEL?
NISUS
Radiator HGHG demonstration to-date
266 nm
Modulator
800 nm laser seed
Propose a modified
facility
Second section
NISUS modulator
266 nm First section
NISUS radiator
Achromatic bend designed to allow 266 nm
demonstration of control of 266 nm Modulator
modulated beam 800 nm laser seed
chicane
Diagnostics measure modulation
at 266 nm John Corlett, February 19, 2004
LUX R&D goals and opportunities for collaborative
experiments at the DUV FEL facility
• R&D in critical technologies and accelerator and FEL physics
• Demonstrate essential accelerator physics, hardware, and techniques
– Cascaded harmonic generation
• Demonstrate cascaded harmonic-generation
• Demonstrate control of micro-bunched electron beam
– Synchronization
• Demonstrate stable laser/electron bunch synchronization
– Accelerator physics studies
• Tracking with CSR, resistive wall, cavity wakefields, vacuum chamber
wakefields, FEL interaction, achromat adjustments, alignment errors, strength
errors, etc.
– Lasers
• Develop photocathode laser systems
LBNL is keen to contribute in supporting accelerator physics and
collaborative experiments towards cascaded harmonic generation at
the DUV FEL
John Corlett, February 19, 2004
John Corlett, February 19, 2004
John Corlett, February 19, 2004
Simulation results - noise evolution from
imperfect master oscillator seed
RMS phase noise dF(t)/dt after removal of average component
• 4-stage cascade configuration
(240 nm 1 nm) Psignal
2 Psignal
N
• Input laser seed initialized Pnoise out Pnoise in
with broadband
(a) phase noise
dF(t)/dt (A.U.)
(b) amplitude noise (a)
(b)
• Fields resolved in simulation on
240 nm/c temporal resolution
or better
– Noise reaches minimum at 48-nm
stage (slippage averaging)
– In later stages noise increases
due to harmonic multiplication of
low frequency components
EXIT 48 nm 12 nm 4 nm 1 nm
240 nm
John Corlett, February 19, 2004
Shot noise effects
• Due to high input power to modulator stages, effects from random e-beam
shot noise microbunching appear small
– essentially no growth of bunching in absence of seed signal
– in presence of coherent seed, shot noise leads to small phase and amplitude
time variations
– db2½ ~ 8 10-4 « b
– At 4 nm , dP(t)/ P ~ 2 10-4
– At 1 nm, dP(t)/ P ~ 5 10-3
• Figure at right is a 1-nm output 10 kW
spectrum from a GINGER LUX
simulation including shot noise effects
– Power at fundamental (10 MW)
is not plotted
– Output noise dominated by low
temporal frequency components
10 W
John Corlett, February 19, 2004
Sophisticated short-pulse laser systems
are an integral component of the facility
HGHG seed lasers
Laser oscillator Amplifier &
conditioning
Laser oscillator Amplifier &
conditioning
Laser oscillator Amplifier &
conditioning Spatial
profiling
Amplitude
clipping
Photocathode laser
Multiply
Beamline endstation
Amplifier
lasers
Pulse
Laser oscillator shaping
Laser systems are existing state-of-the-art products
or reasonable extrapolations of future capabilities
RF signals John Corlett, February 19, 2004
LUX rf photocathode gun design optimized for
high-brightness and high-duty factor
• Re-entrant cell design maximizes accelerating
field at the cathode while minimizing peak
surface fields elsewhere
• Independent rf cavities allow freedom to tune
cell phases
• ANSYS rf heating and thermal modeling
cathode
Laser pulse • PARMELA and ASTRA beam dynamics modeling
• Multiple solenoid magnets fine-tune beam
transport and emittance compensation
• rf focusing with recessed cathode
• Active phase control reduces stored energy
• rf phase and amplitude synchronized to laser
Excess stored energy
Phase flip at 5µsec
John Corlett, February 19, 2004
LUX flux spectrum
18
10
17
10
16
10
Average flux (photons/sec/0.1%BW)
15
10 LCLS
14
10
13
10
12
Harmonic cascades
10
ESRF time-
ESRF resolved beamline
11
10
10
10 SPPS Compressed
spontaneous
10
9 emission
8
10
1 2 3 4 5
10 10 10 10 10
Photon energy (eV)
John Corlett, February 19, 2004
Photocathode laser pulse control essential for
electron bunch quality
RF from Ti:sapphire
master Oscillator Q-switched
oscillator 100 fs, 2 nJ Nd:YAG (2w)
<0.5 ps jitter
Ti:sapphire
grating Pulse grating
Regenerative
stretcher Shaper compressor
Amplifier
2w, 3w
>1 mJ, 800 nm, 10 kHz
photo- Pulse Amplitude Stabilizer
Pulse Shaper (A.M. Weiner) Patent:: LLNL (R. Wilcox)
switch
Pockels
polarizer
Cell
Dazzler - Fastlite Inc.
acousto-optic dispersive filter
(P. Tournois et al.)
spectral filter (computer controlled)
- spatial light modulator
- acousto-optic modulator
TeO2 crystal
• ~1 µJ acoustic wave (computer programmable)
- spectral amplitude
• 30 ps - temporal phase
• 10 kHz
• 266 nm
• Spatial and temporal control to provide low-emittance electron bunches
– Genetic algorithms for optimal performance
John Corlett, February 19, 2004
