generation of ultrafast mid-ir pulses using a 100 mev erl-fel (drivers for tunable hhg based...
TRANSCRIPT
Generation of Ultrafast Mid-IR pulses using a 100 MeV ERL-FEL
(Drivers for tunable HHG based coherent X-Ray sources ?)
T. Popmintchev, nature photonics | VOL 4 | DECEMBER 2010
Phase matched HHG using mid-IR lasers (Experiments)
Idea (A.Foehlisch): Can we drive HHG by a compact ERL(FEL)?
requirements imposed on drive lasers :
- HHG (phase matched) needs preferably few cycle to ~10 cycle drive laser pulses in NIR/MIR and intensities in the range of 1-5x1014 W/cm2 (noble gas filled hollow waveguide apertures: ~100m-200m )
Generation of coherent X-Ray pulses by HHG
OPCPA’s
•NIR sub-10 fs with 70 J 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 6 mJ at 10-20Hz
Outline :
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 (and beyond 10 m if necessary) (JLab ???)
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)- rep rate (MHz) in generating mJ(s) of ultrafast pulses with high average power (problems in CEP stabilization???)
simulation study has been and still is mainly focused on the latter and on the question:What system requirements will be imposed on a compact ERL, (particularly concerning timing jitter budget)
• 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
E ~ 60 MeV (NIR/MIR)E ~ 13 MeV (FIR)135 pC pulsesz ~ 0.5 – 4 ps10.7 MHz (21.4 MHz FIR)
Parameter NIR FEL MIR FEL FIR FELWavelength (μm) 2.5 to 27 8 to >150 100 to 1100Wawenum (cm−1) 400 to 4000 < 70 to 1300 9 to 100
FSU-NHMFL NIR/MIR/FIR (&broadband THz) FEL Proposal
X
MIR/FIR
FIR
NIR
inclusion of a HHG based coherent X-Ray source ?
Beam parameters FEL (~3-6m) Units
Beam Energy 100 MeV Bunch charge 80 pC _z rms bunch length 0.1 ps norm.Trans. Emittance 5 mm.mrad
_e rms energy spread 0.5% Beam pulse rate 40 (?) MHz Macropulse form 100s (?) Average current 0.30 - 1.9(?) mA
Wiggler parameters
Type planar
Wiggler period 60 mm
Wiggler Krms 1.7-2.6
Periods 25 (30)
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
system parametersBERLinPro JLab IR FEL
stretcher
compressor
PLE
dielectric mirrorNIR/MIR FELO
mode matching telescope
- Beam Energy: 100 MeV
- Bunch Charge: 80 pC
- Rep rate: 40 MHz
- Outcpl.Pls. Energy: 50-70J
- Cav. Enhancement: 80-100
-Pulse width: ~100-200fs (fwhm)
-IL ~ 1x1014 – 3.5x1014W/cm2
- high-Q enhancement cavity (EC) smoothes out power and timing jitter of the injected pulses inherent to FEL interaction.
- allows fs (10 -100 ?) 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 Cavity
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
5.6 5.8 6.0 6.2 6.4 6.6 6.8 7.0 7.2
0.0
0.2
0.4
0.6
0.8
1.0
200th pass after Saturation
wavelength [m]
no
rm. S
pe
ctra
l In
ten
sity
-200 0 200 400 600 800 1000 1200-5.0x108
0.0
5.0x108
1.0x109
1.5x109
2.0x109
2.5x109
3.0x109
3.5x109
Intracavity Power (overlap over 200 pulses after Saturation)
time [fs]
Po
we
r [W
atts
]
2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6
0.0
0.2
0.4
0.6
0.8
1.0
200th pass after Saturation
no
rm.
Sp
ect
ral I
nte
nsi
ty
wavelength [m]
0 200 400 600 800
0
1x109
2x109
3x109
4x109
5x109
6x109 Intracavity Power (overlap over 200 pulses after Saturation)
Po
we
r [W
atts
]
time [fs]
~ 3 m
/~ 4%-5%
100fs (fwhm)
200fs (fwhm)
3 m - 6 m Short Pulse FEL (cavity detuning)
/~ 4%-5%
- low time jitter
- low peak to peak power deviations
- Outcoupled Pulse Enegies: ~ 50-70 J
~ 10 cycle pulses (HHG drive laser)
~ 6 m
Talk in Nov. 2010
150 200 250 300 350 400 450 500 550
0.0
5.0x1010
1.0x1011
1.5x1011
2.0x1011
Intracavity power level in superradiance mode
P
ow
er
[Wa
tts]
time [fs]
High Gain (superradiant) FEL Oscillator operating at cavity synchronization
rs ESynchrotron Osc. Freq.
• nearly an order of magnitude higher outcoupled pulse intensity (despite low outcoupling ratios)
• FEL efficiency in superradiance mode more than doubled
2.5 3.0 3.5 4.0 4.5 5.0
0.0
0.2
0.4
0.6
0.8
1.0
chirped pulse spectrum in superradiance mode
wavelength [m]
no
rm. S
pe
ctra
l In
ten
sity
0 1000 2000 3000 4000
0.000
0.002
0.004
0.006
0.008
0.010Intracavity pulse energy in superradiance mode
Pu
lse
En
erg
y [J
]
roundtrip #
35 - 40fs (fwhm)
lc ~ 45fs
Talk in Nov. 2010
Comparison between two FEL simulation methods
3 4 5 6 7 8
0.0
2.0x102
4.0x102
6.0x102
8.0x102
1.0x103
1.2x103
1.4x103
1.6x103
1.8x103
spec
tral
inte
nsity
[a.
u.]
wavelength [m]
3.1m 6.2m
3 4 5 6 7 8 9 10
0.0
2.0x103
4.0x103
6.0x103
8.0x103
1.0x104
1.2x104
1.4x104
spec
tral
inte
nsity
[a.
u.]
wavelength [m]
3.1m 6.2m
3D (semi-)frequency domain
3 4 5 6 7 8 9
0.0
2.0x1012
4.0x1012
6.0x1012
8.0x1012
1.0x1013
1.2x1013
1.4x1013
1.6x1013
1.8x1013
spec
tral
inte
nsity
[a.
u.]
wavelength [m]
3.1m 6.2m
1½D - SVEA time domain
(superradiant) FEL Oscillator@ synchr.' case ‘FEL oscillator-cav. detuning' case
good agreement between the models in 'FEL oscillator with cavity detuning' case
(in terms of outcoupled pulse energy, temporal and spectral pulse profiles)
Disagreements in the 'superradiant operation at cavity synchronism' in obtaining self similar pulses following saturation, differences in temporal and spectral pulse profiles.
: 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.
~ 6 m
• Peak power fluctuations ~4-5% rms
• Pulse width fluctuations limited to a few %
• timing jitter ~ ±20 fs (optical pulse)
0 100 200 300 400 500 600 700 800
0.0
5.0x108
1.0x109
1.5x109
2.0x109
2.5x109
3.0x109
time [fs]
Pow
er
[Wa
tts]
Jitter 5 fs rms
0 100 200 300 400 500 600 700 800
0.0
5.0x108
1.0x109
1.5x109
2.0x109
2.5x109
3.0x109
3.5x109
time [fs]
Po
wer
[W
att
s]
Jitter 10 fs rms
0 100 200 300 400 500 600 700 800
0.0
5.0x108
1.0x109
1.5x109
2.0x109
2.5x109
3.0x109
time [fs]
Po
we
r [W
att
s]
w/o initial Jitter
FEL Osc. sensitivity to temporal jitter ~ 6 m
Simulation using BERLinPro parameters, 'FEL oscillator with cavity detuning'
0 100 200 300 400 500 600
0
1x109
2x109
3x109
4x109
5x109
time [fs]
Po
we
r [W
att
s]
P~2% rms
100fs (fwhm)
• Pulse width fluctuations limited to a few % rms
• Timing jitter ~ ±20 fs (optical pulse)
~ 3 m
• Peak power fluctuations ~8 -10% rms
0 100 200 300 400 500 600
0
1x109
2x109
3x109
4x109
5x109
6x109
time [fs]
Po
we
r [W
att
s]
jitter 5 fs rms w/o initial jitter
FEL Osc. sensitivity to temporal jitter
Simulation using BERLinPro parameters, 'FEL oscillator with cavity detuning'
Timing jitter measurements @ JLab IR-FEL
• phase noise spectra measured in the vicinity of the wiggler-entrance (behind the bunch compressor)
• e- bunch length: 150 fs rms
• average current : 0.5 mA to 4.5 mA (bunch charge ~135 pC kept constant, bunch rep rate varied)
• measured timing jitter : ~25 fs rms @ 1.5 mA - ~80 fs rms @ 4.5 mA
• estimated FEL spec (to keep pp-power fluct. below 10 % @ l = 1.6 m ) on arrival time jitter : L/L < 3.8x10-8
( P. Evtushenko , ELECTRON BEAM TIMING JITTER AND ENERGY MODULATION MEASUREMENTS AT THE
JLAB ERL )(Beam Current Monitor (cavities) and Signal Source Analyzer employed for power spectrum measurements at harmonics to characterize phase noise)
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
jitter 2.5 fs rms
1D-SVEA Simulation using BERLinPro parameters, 'superradiant operation at cavity synchronism'
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.060
0.005
0.01
0.015
0.02
0.025
~5E
r
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0
0.005
0.01
0.015
0.02
0.025
~E
r
• 8% -10% spent beam momentum spread (full) generated by the FEL interaction
• large energy spread acceptance is required for beam transport/energy recovery(JLab IR Upgrade acceptance :~15 %)
Calculated spent beam energy distribution @FEL saturation
=3 m
=6 m