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

qq

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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