Compact ERL-FEL/Pulse Stacker Cavity configurations:

1. Compact ERL-FEL/Pulse Stacker Cavity configurations: new high rep rate, high intensity driver sources for High Field Applications ? Mufit Tecimer THz-FEL Group, University of Hawai’i at Manoa KEK, Tsukuba, Japan April 20, 2012

2. 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 withhighextraction efficiency, • Use of the generated radiation in Applications relevant to the current research/ technological development.

3. 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) .....

4. Generation of coherent X-Ray pulses by HHG Three-Step Model (Corkum 1993) (single atom HHG) Popmintchev et al., OSA/ CLEO 2011

5. Generation of coherent X-Ray pulses by HHG • The idea of using Mid-IR (ERL) FELs as drivers for HHG thought of or considered by Kapteyn /Murnane (JILA), Foehlisch (Bessy)and others … • 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: ~100mm-200mm, (He) gas pressure: tens of atm) • OPCPA’s • NIR sub-10 fs with 70 mJ energy at 100kHz. • NIR sub-10 fs multi-kHz, multi-mJ • Mid-IR (~3mm) sub-100 fs with a few micro-Joule energy at 100kHz • 3.9 mm sub-100 fs with ~9 mJ at 20Hz

6. HHG - Predictions & Measurements Popmintchev et al., PNAS 106, 10516 (2009) (single atom HHG) Curves normalized to phase-matched HHG @ λ0=0.8µm @l= 6µm,10 MHz rep. rate (He) estimated Photon flux : ~1013-14ph/sec (1.0%BW) @l= 3.9µm,1 kHz rep. rate (35 - 40 atm. He) Photon flux : ~108 ph/sec (1.0%BW) (based on experiments) Phase matched HHG @3.9mm, 6cycle, 20 Hz Popmintchev et al., OSA/ CLEO 2011 M. Tecimer, FHI-Berlin (FEL Seminar), Sep. 29, 2011

7. HHG - Predictions & Measurements 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] to be published by Kapteyn/Murnane Group (JILA) in Science

8. XPAExperiments J. Seres et al., Nature Phys. 6, 455 (2010). Amplified spontaneous emission B. Aurand et al., NIM A 653, 130 (2011) Amplifier with a seed A claimed maximum gain of about 8000 at 50eV photon energy is demonstrated. synchronized FEL pulses (figure modified from H.Kapteyn, Quantum Physics and Nonlinear Optics at High Energy Densities)

9. Reference: C.B. Schroeder, E. Esarey, C.G.R. Geddes, C. Benedetti, and W.P. Leemans, Phys. Rev. ST Accel. Beams 13, 101301 (2010). GeV e- beam "Modified" Cascaded/Staged LWFA using FEL driver pulses electrons are repeatedly accelerated by the laser wakefields in a mannersimilar to the conventional accelerators ... • . J. S. Liu et al., PRL 107, 035001 (2011) n~1017-1018cm-3 l~ 3 - 6 mm (?) Joule level driver laser pulses @ ~1 mm multiple stages FEL pulse Tens of TWatts few optical cycles FEL pulse FEL pulse synchronized FEL pulses (Figure modified from 'High Power Laser Technology',Wim Leemans, LBNL)

10. Trim Quads reading System parameters used in the Simulations JLab IR FEL Coherent OTR interferometer autocorrelation scans for bunch length measurements [S. Zhang et al., FEL 09 Conf. Proceedings] M. Tecimer, Bessy-Berlin (Machine Group Seminar), Apr. 12, 2011

11. 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 mm-7mm) (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 mainlyfocused on the latter : • (system requirements imposed on a compact ERL) M. Tecimer, Bessy-Berlin (Machine Group Seminar), Apr. 12, 2011

12. compressor stretcher mode matching telescope PLE dielectric mirror NIR/MIR FELO Suggested (3-6mm) MIR FEL & Pulse Stacker Cavities I.) II.) Mode-locked NIR Laser • 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. • Depending on the recombination time of the fast switch, sequence of micropulses with several ns separation can be ejected from the EC ! M. Tecimer, Bessy-Berlin (Machine Group Seminar), Nov.04, 2010 & Apr. 12, 2011

13. Folded cavity vacuum vessel Input Coupler FEL Opt. Switch mount High Reflector Brewster W. Enhancement Cavity @ JLab Q ~ 40 (Finesse ~ 300 ) enhancement :~90 Q~ 50 enhancement :~130-140 estimated enhancement @ JLab ~ 100 T. Smith @ Stanford IR-FEL achieved enhancement of ~70 - 80 using an external pls stacker cavity (1996) M. Tecimer, Bessy-Berlin (Machine Group Seminar), Apr. 12, 2011

14. 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

15. Ultrashort Pulse Generation by passive modelocking • 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) Synchrotron Osc. Freq. : FEL oscillator with perfectly synchronizedcavity(single spike, high gain superradiant FEL oscillator) Nonlinear reflectivity data for a representative SESAM sample (figure added to the original) M. Tecimer, Bessy-Berlin (Machine Group Seminar), Nov. 04, 2010

16. Ultrashort Pulse Generation in (Mid-IR) FELs • 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 l~22 mm) • (single spike, high gain superradiant FEL osc.) • Generation of short electron pulses (JLab) M. Tecimer, Bessy-Berlin (Machine Group Seminar), Apr. 12, 2011

17. High Gain (superradiant) FEL Oscillator operating at cavity synchronization • 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 M. Tecimer, Bessy-Berlin (Machine Group Seminar), Nov. 04, 2010

18. coupled FEL oscillators FEL oscillators with perfectly synchronized cavity I.) relatively large Outcoupling II.) • U(1) = U(2) (better U(1) > U(2) ) • Mirror coupling ratios of are optimized

19. Cascaded system of coupled oscillators I.) II.) • 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

20. Time domain multi-mode appraoch using SVEA 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.

21. a.) b.) c.) d.) e.) f.) Contrasting approaches used for FEL simulation First Stage (master oscillator) 1D SVAE (complex field amplitude of a carrier wave) 3D non-averaged, multifrequency (multimode) code M. Tecimer, PRST-AB 15, 020703 (2012)

22. Simulated temporal/spectral characteristics of mid-IR pulses I.) II.) III.)

23. Partial bilateral Coupling of FEL Oscillators Beam&Optical Pulse locking Optical Pulse locking feedback ~5x10-4 feedback ~5x10-4 • ~ 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 nearlythe optimum output, • limit cycle oscillations reduce strongly

24. Master Oscillator: beam longitudinal phase space a.) Undulator exit b.)

25. Slave FEL Oscillator: beam longitudinal phase space Undulator entrance a.) Undulator exit b.)

26. Slave FEL Oscillator: beam longitudinal phase space Undulator entrance Undulator exit ?

27. e- bunch Dt/t = dL/L + df/f FEL Osc. sensitivity to temporal jitter • Dt: timing jitter • L : cavity length • dL: cavity length detuning • f : bunch rep. frequency (perfectly synchronized to L) • : cavity roundtrip time ( 2L/c) • 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

28. jitter 2.5 fs rms FEL Osc. sensitivity to temporal jitter ~ 6 mm jitter 2.5 fs rms w/o initial jitter jitter 2.5 fs rms M. Tecimer, Bessy-Berlin (Machine Group Seminar), Apr. 12, 2011

29. High Reflectivity Dielectric Mirrors for the mid-IR & THz regions 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. M. Tecimer, K. Holldack and L. Elias, PRST-AB 13, 030703 (2010)

30. Summary 100-200 MeV range superconducting ERLdriven mid-IR FELs hold great promise in filling aunique niche for generating multi-mJ level (possibly much higher), ultrashort( <10 cycles) pulses tunable within the entire mid-IRregion (and beyond) with at least many tens of MHzrepetition rates. Because of their ability in providing highpeak intensities with excellent temporal and transversalcoherence characteristics at unprecedented high repetitionrates across the entire NIR/MIR spectral range, theyhavethe potential to become attractive tools in various strongfieldapplications alone or in combination with high finesse enhancement cavities.

31. 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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