compact erl-fel/pulse stacker cavity configurations: new high rep rate, high intensity driver...
TRANSCRIPT
Compact ERL-FEL/Pulse Stacker Cavity configurations: new high rep rate, high intensity driver sourcesfor High Field Applications ?
Mufit TecimerTHz-FEL Group, University of Hawai’i at Manoa
KEK, Tsukuba, Japan
April 20, 2012
The rationale of the presented study is an old idea regarding electron beam based radiation sources:
To tap on the (high) power deposited in the electron beam by elaborating on schemes with high extraction efficiency,
Use of the generated radiation in Applications relevant to the current research/ technological development.
High Field Applications
I.) Upfrequency conversion in the x-ray region
• phase-matched High order Harmonic Generation (HHG) attosecond science
• x-ray Parametric Amplification (XPA)
II.) Laser driven plasma-based electron accelerators
• Laser Wake Field Accelerator (LWFA)
III.) Inverse Compton Scattering (ICS)
.....
Generation of coherent X-Ray pulses by HHG
Three-Step Model (Corkum 1993)
Popmintchev et al.,OSA/ CLEO 2011
2 lcutoff Ih (single atom HHG)
requirements imposed on drive lasers (Popmintchev et al.) :
Phase-matched HHG in keV region photons needs:
preferably few cycle (CEP stabilized) to ~10 cycle drive laser pulses in NIR/MIR ,
intensities in the range of 1-5x1014 W/cm2 ,
noble gas filled hollow waveguide apertures: ~100m-200m, (He) gas pressure: tens of atm)
Generation of coherent X-Ray pulses by HHG
OPCPA’s
•NIR sub-10 fs with 70 mJ energy at 100kHz.
• NIR sub-10 fs multi-kHz, multi-mJ
•Mid-IR (~3m) sub-100 fs with a few micro-Joule energy at 100kHz
•3.9 m sub-100 fs with ~9 mJ at 20Hz
The idea of using Mid-IR (ERL) FELs as drivers for HHG thought of or considered by Kapteyn /Murnane (JILA), Foehlisch (Bessy) and others …
Popmintchev et al.,PNAS 106, 10516 (2009)
Curves normalized to phase-matched HHG @ λ0=0.8µm
@ = 6µm, 10 MHz rep. rate (He)
estimated Photon flux : ~1013-14 ph/sec (1.0%BW)
@ = 3.9µm, 1 kHz rep. rate (35 - 40 atm. He) Photon flux : ~108 ph/sec (1.0%BW) (based on experiments)
Popmintchev et al.,OSA/ CLEO 2011
Phase matched HHG @3.9m, 6cycle, 20 Hz
HHG - Predictions & Measurements
2 lcutoff Ih (single atom HHG)
M. Tecimer, FHI-Berlin (FEL Seminar), Sep. 29, 2011
HHG - Predictions & Measurements
to be published by Kapteyn/Murnane Group (JILA) in Science
He driven by 20 μm mid-IR lasers may generate bright 25 keV beams.[Ref.: Kapteyn/Murnane, Quantum Physics and Nonlinear Optics at High Energy Densities]
XPA Experiments
synch
ronized FEL pulse
s
(figure modified from H.Kapteyn, Quantum Physics and Nonlinear Optics at High Energy Densities)
B. Aurand et al., NIM A 653, 130 (2011)
A claimed maximum gain of about 8000 at 50eV photon energy is demonstrated.
Amplified spontaneous emission
Amplifier with a seed
J. Seres et al., Nature Phys. 6, 455 (2010).
FEL pulse
FEL pulse FEL pulse
Tens of TWattsfew optical cycles
synchronized FEL pulses
Reference:C.B. Schroeder, E. Esarey, C.G.R. Geddes, C. Benedetti, and W.P. Leemans, Phys. Rev. ST Accel. Beams 13, 101301 (2010).
e- beamGeV
multiple stages
"Modified" Cascaded/Staged LWFA using FEL driver pulses
J. S. Liu et al., PRL 107, 035001 (2011)
(Figure modified from 'High Power Laser Technology',Wim Leemans, LBNL)
Joule level driver laser pulses @ ~1 m
n~1017-1018
cm-3
~ 3 - 6 m (?)
electrons are repeatedly accelerated by the laser wakefields in a manner similar to the conventional accelerators ...
.
Beam parameters FEL (~3-6m) Units
Beam Energy 100 (200) MeV Bunch charge 80 (200) pC _z rms bunch length 0.1 ps norm.Trans. Emittance 5 mm.mrad
_e rms energy spread 0.5%
Wiggler parameters
Type planar
Wiggler period 60 mm
Wiggler Krms 1.7-2.6
Periods 25 (23)
Trim Quads reading
Beam parameters FEL (1.6m) Units
Beam Energy 115 MeV
Bunch charge 110 (135) pC
_z rms 150 fs
Peak current ~300 A
_e rms(uncorrelated)
0.1%
_e rms (correlated)
0.5%
nor. trans. Emit. 8 rad
rep. rate ~75 MHz
Coherent OTR interferometer autocorrelationscans for bunch length measurements [S. Zhang et al., FEL 09 Conf. Proceedings]
System parameters used in the Simulations JLab IR FEL
M. Tecimer, Bessy-Berlin (Machine Group Seminar), Apr. 12, 2011
Outline of the project:
short term: carrying out the HHG experiments on an existing FEL facility that meets the requirements set on the mid-IR drive laser, verifying the theory throughout the mid-IR(particularly at around 6 m-7m) (JLab, FHI-FEL, …?)
long term: mid-IR ERL-FELs should be able to perform better than atomic lasers in terms of : tunability (throughout the nir/mid IR and beyond)- high rep rate (MHz) in generating mJ(s) of ultrafast pulses with high average power
Ongoing simulation work is mainly focused on the latter :(system requirements imposed on a compact ERL)M. Tecimer, Bessy-Berlin (Machine Group Seminar), Apr.
12, 2011
stretcher
compressor
PLE
dielectric mirrorNIR/MIR FELO
mode matching telescope
high-Q enhancement cavity (EC) smoothes out power and timing jitter of the injected pulses inherent to FEL interaction.
allows ~fs level synchronization of the cavity dumped mid-IR pulse with the mode-locked switch laser.
Mode-lockedNIR Laser
Depending on the recombination time of the fast switch, sequence of micropulses with several ns separation can be ejected from the EC !
Suggested (3-6m) MIR FEL & Pulse Stacker Cavities
II.)
I.)
M. Tecimer, Bessy-Berlin (Machine Group Seminar), Nov.04, 2010 & Apr. 12, 2011
Brewster W.
vacuum vessel
Opt. Switch mount
Folded cavity
FEL
Input Coupler
High Reflector
T. Smith @ Stanford IR-FEL achieved enhancement of ~70 - 80 using an external pls stacker cavity (1996)
Q ~ 40 (Finesse ~ 300 ) enhancement :~90
Q~ 50enhancement :~130-140
estimated enhancement @ JLab ~ 100
Enhancement Cavity @ JLab
M. Tecimer, Bessy-Berlin (Machine Group Seminar), Apr. 12, 2011
• Chirped pulse generation in a FEL oscillator using a chirped electron beam and pulse compression
• Mode-locking techniques in FELs
-Active mode-locking
- Passive mode-locking
• Generation of short electron pulses
Ultrashort (few cycles) Pulse Generation in (IR-THz) FELs
M. Tecimer, Bessy-Berlin (Machine Group Seminar), Nov. 04, 2010
Passive modelocking in conventional (atomic) laser :
- Kerr Lens modelocking
- Semiconductor Saturable Absorber Mirrors (SESAM)
- Does FEL have a self (passive) modelocking mechanism ? (for instance intensity dependent absorber)
Ultrashort Pulse Generation by passive modelocking
rs ESynchrotron Osc. Freq. :
M. Tecimer, Bessy-Berlin (Machine Group Seminar), Nov. 04, 2010
Nonlinear reflectivity data for a representative SESAM sample(figure added to the original)
FEL oscillator with perfectly synchronized cavity (single spike, high gain superradiant FEL oscillator)
• Chirped pulse generation in a FEL oscillator using a chirped electron beam and pulse compression (JLab)
• Mode-locking techniques in FELs
-Active mode-locking (multiple OK sections used in a cavity)
- Passive mode-locking (JAERI, lasing at ~22 m) (single spike, high gain superradiant FEL osc.)
Generation of short electron pulses (JLab)
Ultrashort Pulse Generation in (Mid-IR) FELs
M. Tecimer, Bessy-Berlin (Machine Group Seminar), Apr. 12, 2011
Further studies:
- cascaded oscillator schemes (problem: large momentum spread for the beam transport/energy recovery)
- use of (assistant) SESAM mirrors
- checking the results with other well established codes
High Gain (superradiant) FEL Oscillator operating at cavity synchronization
M. Tecimer, Bessy-Berlin (Machine Group Seminar), Nov. 04, 2010
coupled FEL oscillators
• U(1) = U(2) (better U(1) > U(2) )
• Mirror coupling ratios of are optimized
1u1u
2u2u
I.)
II.)
FEL oscillators with perfectly synchronized cavity
relatively large Outcoupling
• U(1) = U(2) > U(3) = U(4) …
• U(1) > U(2) > U(3) > U(4) …
• Mirror coupling ratios of are optimized
Amplifier stage follows the coupled FEL oscillators
I.)
II.)
Cascaded system of coupled oscillators
dxdytzxJeS
tzuvS
qqtn n
zn
nnqgz
tzki
*1 ,,2
1,
))((e
}{ ,,,,,)()(
yxetzuetzutzxE nqnn
qntzznki
q
tzznki qqqq
e)(
Re
rq Lqc /0 rLc /
dxdytzxJeS
tzuvS
t nzn
nngnz
tzki
*001 ,,
2
1,
))((e
q
tvziqqn
gqneuun/
Time domain multi-mode appraoch using SVEA
0 ),,(~
),,(~
2
1
),,(
),,(
dezx
zx
tzxJ
tzxE ti
J
ERe
yxezuezuzx nnn
nzikzik znzn ,,,,,
~ )()(
e)( E
dxdyyxzxeS
zuS
nzn zik
nnz
),(,,
~
2
1, *)( e J
Space-frequency representation of the electromagnetic fields and current sources
• Exact first order ordinary differential equations of the axial dimension without the need of introducing any approximations.
• Inverse Fourier Transform is necessary to construct the fields used to determine particle’s motion.
Contrasting approaches used for FEL simulation
First Stage (master oscillator)
0 100 200 300 400 500 600 700 800
0
50
100
150
200
250
Pass
Pu
lse
En
erg
y [
J]
5 6 7 8 9 10 11
0.0
0.2
0.4
0.6
0.8
1.0
wavelength [m]
norm
. S
pect
ral I
nten
sity
0 10 20 30 40 50
0.0
0.2
0.4
0.6
0.8
1.0
Radiation cycles
no
rm.
Po
we
r
a.) b.) c.)
5 6 7 8 9 10 11
0.0
0.2
0.4
0.6
0.8
1.0
wavelength [m]
norm
. S
pect
ral I
nten
sity
10 20 30 40 50 60
0.0
0.2
0.4
0.6
0.8
1.0
Radiation cycles
no
rm.
Po
we
r
0 100 200 300 400 500 600
0
50
100
150
200
250
Pass
Pul
se E
nerg
y [
J]
d.) e.) f.)
1D SVAE (complex field amplitude of a carrier wave)
3D non-averaged, multifrequency (multimode) code M. Tecimer, PRST-AB 15, 020703
(2012)
0 100 200 300 400 500
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Pass
Pu
lse
En
erg
y [m
J]
6 7 8 9 10
0.0
0.2
0.4
0.6
0.8
1.0
wavelength [m]
norm
. S
pect
ral I
nten
sity
10 20 30 40 50 60
0.0
0.2
0.4
0.6
0.8
1.0
no
rm. P
ower
Radiation cycles
0 100 200 300 400 500
0
50
100
150
200
250
Pass
Pul
se E
nerg
y [
J]
10 20 30 40 50 60
0.0
0.2
0.4
0.6
0.8
1.0
Radiation cycles
no
rm. P
ow
er
0 100 200 300 400 500
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Pass
Pu
lse
En
erg
y [m
J]
10 20 30 40 50 60
0.0
0.2
0.4
0.6
0.8
1.0
no
rm. P
ower
Radiation cycles6 7 8 9 10
0.0
0.2
0.4
0.6
0.8
1.0
wavelength [m]
norm
. S
pect
ral I
nten
sity
Simulated temporal/spectral characteristics of mid-IR pulses
I.)
II.)
III.)
5 6 7 8 9 10 11
0.0
0.2
0.4
0.6
0.8
1.0
wavelength [m]
norm
. S
pect
ral I
nten
sity
~ 5x10-4 ~5 – 10% of optimum output pulse energy
~10-7 feed back ~65-70% of optimum output,
•feed back reduced to less than 10-8 to reach nearly the optimum output,
• limit cycle oscillations reduce strongly
0 100 200 300 400 500
0.0
0.2
0.4
0.6
0.8
1.0
Pass
no
rm.
Pu
lse
En
erg
y
0 100 200 300 400
0.0
0.2
0.4
0.6
0.8
1.0
Pass
no
rm.
Pu
lse
En
erg
y
feedback ~5x10-4
feedback ~5x10-4
Beam & Optical Pulse locking
Optical Pulse locking
Partial bilateral Coupling of FEL Oscillators
2.50x10-5 5.00x10-5 7.50x10-5 1.00x10-4 1.25x10-4 1.50x10-4 1.75x10-4 2.00x10-4150
160
170
180
190
200
210
z
2.50x10-5 5.00x10-5 7.50x10-5 1.00x10-4 1.25x10-4 1.50x10-4 1.75x10-4 2.00x10-4170
180
190
200
210
z
Master Oscillator: beam longitudinal phase space
a.)
b.)
Undulator exit
2.50x10-5 5.00x10-5 7.50x10-5 1.00x10-4 1.25x10-4 1.50x10-4 1.75x10-4 2.00x10-4150
160
170
180
190
200
210
z
2.50x10-5 5.00x10-5 7.50x10-5 1.00x10-4 1.25x10-4 1.50x10-4 1.75x10-4 2.00x10-4
150
160
170
180
190
200
210
220 C
z
a.)
Slave FEL Oscillator: beam longitudinal phase space
b.)
Undulator entrance
Undulator exit
2.50x10-5 5.00x10-5 7.50x10-5 1.00x10-4 1.25x10-4 1.50x10-4 1.75x10-4 2.00x10-4150
160
170
180
190
200
210
z
5.0x10-5 1.0x10-4 1.5x10-4 2.0x10-4 2.5x10-4 3.0x10-4
150
160
170
180
190
200
210
220
z
?
Slave FEL Oscillator: beam longitudinal phase spaceUndulator
entrance
Undulator exit
: timing jitterL : cavity lengthL: cavity length detuningf : bunch rep. frequency (perfectly synchronized to L) : cavity roundtrip time ( 2L/c)
/ = L/L + f/f
e- bunch
FEL Osc. sensitivity to temporal jitter
Bunch time arrival variation effectively has the same effect as cavity length detuning.
effect of the timing jitter on the FEL performance In slippage dominated short pulse FEL oscillators cavity detuning is necessary to optimize the temporal overlap between optical and e- pulses (Lethargy effect).Timing jitter induces fluctuations on the operational cavity detuning.
M. Tecimer, Bessy-Berlin (Machine Group Seminar), Apr. 12, 2011
FEL Osc. sensitivity to temporal jitter ~ 6 m
jitter 2.5 fs rms
w/o initial jitter
jitter 2.5 fs rms
0 100 200 300 400 500 600
0
1x1010
2x1010
3x1010
4x1010
5x1010
6x1010
7x1010
8x1010
9x1010
time [fs]
Pow
er [W
atts
]
0 100 200 300 400 500 600-1x1010
0
1x1010
2x1010
3x1010
4x1010
5x1010
6x1010
7x1010
time [fs]
Po
we
r [W
atts
]
0 100 200 300 400 500 600
0
1x1010
2x1010
3x1010
4x1010
5x1010
6x1010
7x1010
time [fs]
0 100 200 300 400 500 600
0
1x1010
2x1010
3x1010
4x1010
5x1010
6x1010
7x1010
time [fs]
Pow
er [W
atts
]
0 100 200 300 400 500 600
0
1x1010
2x1010
3x1010
4x1010
5x1010
6x1010
7x1010
time [fs]
jitter 2.5 fs rms
M. Tecimer, Bessy-Berlin (Machine Group Seminar), Apr. 12, 2011
100 200 300 400 500 600
0.0
0.2
0.4
0.6
0.8
1.0 3rd5th
a.)
0.9997
Re
flect
an
ce
wavelength [microns]
4xSi
100 200 300 400 500
0.0
0.2
0.4
0.6
0.8
1.0
b.)
0.9976
wavelength [microns]
5xQ
The presented coupled oscillator scheme should be applicable to longer mid-IR (THz) wavelengths by using the low loss, high reflectivity dielectric mirrors developed for THz-FEL applications.
High Reflectivity Dielectric Mirrors for the mid-IR & THz regions
M. Tecimer, K. Holldack and L. Elias, PRST-AB 13, 030703 (2010)
Summary
100-200 MeV range superconducting ERL driven mid-IR FELs hold great promise in filling a unique niche for generating multi-mJ level (possibly much higher), ultrashort ( <10 cycles) pulses tunable within the entire mid-IR region (and beyond) with at least many tens of MHz repetition rates.
Because of their ability in providing high peak intensities with excellent temporal and transversal coherence characteristics at unprecedented high repetition rates across the entire NIR/MIR spectral range, they have the potential to become attractive tools in various strong field applications alone or in combination with high finesse enhancement cavities.
References:HHG:•T. Popmintchev et al., Nature Photon. 4, 822 (2010).•M.-C. Chen et al., Phys. Rev. Lett. 105, 173901 (2010).•G. Andriukaitis,T. Balciunas, S. Alisauskas, A. Pugzlys, A. Baltuska, T. Popmintchev, M. C. Chen, M. M. Murnane, and H. C. Kapteyn, Opt. Lett. 36, 2755 (2011).•Henry Kapteyn and Margaret Murnane, Quantum Physics and Nonlinear Optics at High Energy Densities - Applications in Plasma Imaging •R. J. Jones, K. D. Moll, M. J. Thorpe, and J. Ye, Phys.Rev. Lett. 94, 193201 (2005).XPA:•J. Seres et al., Nature Phys. 6, 455 (2010).•L. Gallman, Nature Phys. 6, 406 (2010).
LWFA:•J. S. Liu et al., PRL 107, 035001 (2011).•Wim Leemans, LBNL ,White Paper of the ICFA-ICUIL Joint Task Force – High Power Laser Technology for Accelerators. and references in M. Tecimer, PRST-AB 15, 020703 (2012)
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