Experimental Path to Echo-75 at NLCTA

Experimental Path to Echo-75 at NLCTA Erik Hemsing on behalf of the ECHO group at SLAC NLCTA ICFA Workshop on Future Light Sources March 5-9, 2012 Thomas Jefferson National Accelerator Facility

Motivation Ultimate goal: Seeding to generate transform limited x-ray pulses Several seeding approaches: High Harmonic Generation (HHG) High Gain Harmonic Generation (HGHG) Various Self-seeding techniques (HXRSS and SXRSS) Echo-Enabled Harmonic Generation (EEHG) Echo is a new approach where laser challenges are traded for beam manipulation challenges Has advantage in that bunching is weak function of harmonic number and only small relative energy modulations required Echo (EEHG) demonstration to benchmark critical accelerator and laser physics issues Find optimal combination of high-harmonics and short wavelength seeds

Echo-Enabled Harmonic Generation (EEHG) G. Stupakov, PRL, 2009; D. Xiang, G. Stupakov, PRST-AB, 2009 (Courtesy of D. Xiang)

Echo-Enabled Harmonic Generation (EEHG) G. Stupakov, PRL, 2009; D. Xiang, G. Stupakov, PRST-AB, 2009 First laser generates energy modulation in electron beam (Courtesy of D. Xiang)

Echo-Enabled Harmonic Generation (EEHG) G. Stupakov, PRL, 2009; D. Xiang, G. Stupakov, PRST-AB, 2009 First laser generates energy modulation in electron beam First strong chicane stratifies the longitudinal phase space Second laser imprints energy modulation (Courtesy of D. Xiang)

EEHG FEL: Advantages and Challenges Advantages Excellent frequency up-conversion efficiency High harmonics from small energy modulation UV laser up-converted to soft x-rays in a single stage Tunable through dispersion Challenges Preservation of fine-grained phase-space correlations Sensitive to SR and SC instabilities in transport, higher-order transport coupling effects, and b h h 1/3 laser quality and stability (x-verse mode purity, ~π/h phase control (A. Fry))

Echo experiment at NLCTA Existing Main echo beam line constructed after 10/2009 C-1 TCAV1 X2 TCAV2 C1 U1 U2 spectrometer (Courtesy of D. Xiang)

First ECHO signal (2010) D. Xiang et al., PRL, 2010; Featured in Nature Photonics News & Views (a) 1590 nm laser on k E = nk 1 + mk 2 (b) H2 795 nm laser on (c) Both lasers on n = 1 m = 5 H2 Echo k E = 3k 2 350 400 450 500 550 Radiation wavelength (nm) 600

First ECHO signals (2010) 1590 nm laser on (a) (a) H4 1590 nm laser on 1590 nm laser on H3 Observation of multiple harmonics due to EEHG. Confirmed by varying beam chirp 795 nm laser H2 on H2 (b) (b) simulation 795 nm laser on 795 nm laser on H2 Both lasers on (c) H4 H2 H3 E1 E2 E3 350 400 450 500 550 600 Radiation wavelength (nm) In good agreement with theory

Pushing EEHG to realistic scenarios Advantage of EEHG lies in efficient upconversion even for E σ E Typically a laser heater is used to increase beam slice energy spread RF transverse cavity used to increase slice energy spread Reversible heater: C. Behrens, Z. Huang and D. Xiang, PRSTAB 15, 022802 (2012) (Courtesy of D. Xiang)

ECHO-7 (2011) k E = 2k 1 + 11k 2 = 7k 2 7th 6th 1590 nm only, V=0 5th 4th 1590 nm only, V=85 kv 4th to 7th harmonics from HGHG suppressed with increased beam slice energy spread from TCAV 1590 nm only, V=170 kv 1590 nm only, V=255 kv 795 nm +1590 nm, V=255 kv 7th harmonic reappears with the first laser on, like an echo 7th harmonic generated when energy modulation is about 2~3 times the beam slice energy spread D. Xiang, et al, PRL 108, 024802 (2012).

ECHO Publications thus far (11 Journal articles; 9 conference Proceedings) Journal Articles: Evidence of High Harmonics from Echo-Enabled Harmonic Generation for Seeding X-ray Free Electron Lasers, PRL 108, 024802 (2012). A novel diagnostic for measuring the laser modulation of the longitudinal phase space, Phys. Rev. ST Accel. Beams 14, 112801 (2011). Triple modulator-chicane scheme for seeding sub-nanometer x-ray free electron lasers.submitted to: New Journal of Physics (2011). Laser assisted emittance transfer for storage ring lasing. Submitted to: Phys. Rev. ST Accel.B eams (2011). Longitudinal profile diagnostic scheme with subfemtosecond resolution for high-brightness electron beams. Phys. Rev. ST Accel.B eams 14 (2011) 072802. Demonstration of the Echo-Enabled Harmonic Generation Technique for Short-Wavelength Seeded Free Electron Lasers. Phys. Rev. Lett. 105 (2010) 114801. Longitudinal-to-transverse mapping for femtosecond electron bunch length measurement. Phys. Rev. ST Accel. Beams 13 (2010) 094001. Laser Assisted Emittance Exchange: Downsizing the X-ray Free Electron Laser. Phys.Rev.ST Accel. Beams 13 (2010) 010701. Generation of intense attosecond x-ray pulses using ultraviolet laser induced microbunching in electron beams. Phys.Rev. ST Accel. Beams 12 (2009) 060701. Enhanced tunable narrow-band THz emission from laser-modulated electron beams. Phys. Rev. ST Accel. Beams 12 (2009) 080701. Echo-enabled Harmonic Generation Free Electron Laser. Phys.Rev.ST Accel. Beams 12 (2009) 030702. Conference Proceedings: Observation and Characterization of Coherent Optical Radiation and Microbunching Instability in the SLAC Next Linear Collider Test Accelerator. PAC 11, SLAC-PUB-14451. (2011). Commissioning the Echo-Seeding Experiment Echo-7 at SLAC. FEL 10, SLAC-PUB-14450. (2011). Laser assisted emittance exchange. AIP Conf.Proc. 1299, 620-625 (2010). Echo-Enabled Harmonic Generation. IPAC 10, SLAC-PUB-14438 (2010). A Proof-of-principle Echo-enabled Harmonic Generation FEL Experiment at SLAC. IPAC 10, SLAC-PUB-14448, (2010). Preliminary results of the echo-seeding experiment ECHO-7 at SLAC. IPAC 10, SLAC-PUB-14450, (2010). Effects of energy chirp on echo-enabled harmonic generation free-electron lasers. SLAC-PUB-13547. (2009). Tolerance Study for the Echo-Enabled Harmonic Generation Free Electron Laser. SLAC-PUB-13644. (2009). Feasibility study for a seeded hard x-ray source based on a two-stage echo-enabled harmonic generation FEL. SLAC-PUB-13818. (2009). (Courtesy of T. Raubenheimer)

Pushing towards higher harmonics Goal: Seeding to generate transform limited x-ray pulses In going from UV to hard x-rays, beam manipulation and laser challenges suggest a dual path: EEHG+HHG For EEHG: 1) must be able to generate highharmonics 2) and must be able to reliably reach x-ray wavelengths of interest

Parallel R&D on laser driven multiplicative seeding (example: N=100, 200nm laser 2nm x-rays) e - momentum Linac GeV e - HGHG, EEHG 2 nm bunched GeV e - Seeded FEL 2 nm FEL 200 nm laser Seeding laser system Oscillator Transform Limited Pulse Amplifier Harmonics Chirped Pulse Need to measure and control laser spectral phase to better than ~!/N (From of A. Fry, Laser phase control for FEL seeding, LBNL Workshop on seeding 2011)

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Phase-1: Echo-11 at 217nm! "#$%&'(%)*%+,*-./#%0##/%120#,%2)%34567%89%! :8;#%<3%=.;>,#20#%?%@,*9%34AB%)*%34CDE%! '2,29#)#,.F#%GGHI%-#,080%01.>#%#9.J2;>#K%01.>#%#;#,LM%0+,#2/% 2385 nm laser Bunching Spectrum 0.0035 0.0030 n = 1, m = 14 0.0025 b 2 0.0020 0.0015 0.0010 0.0005 0.0000 160 180 200 220 240 260 280 300 Λ nm

Phase-1: Echo-11 at 217nm! "#$%&'(%)*%+,*-./#%0##/%120#,%2)%34567%89%! :8;#%<3%=.;>,#20#%?%@,*9%34AB%)*%34CDE%! '2,29#)#,.F#%GGHI%-#,080%01.>#%#9.J2;>#K%01.>#%#;#,LM%0+,#2/% 2385 nm laser b 2 0.008 0.006 0.004 mφ = 0 Bunching Spectrum mφ = 2π mφ = 4π mφ = 8π n = 1, m = 14 Laser phase error issues are relaxed for e-beam laser pulse length 0.002 0.000 216.2 216.4 216.6 216.8 217.0 217.2 217.4 Λ nm φ = accumulated phase error over FWHM pulse of second laser

Phase-2: Echo-21 at 114 nm! "#$%&'()*+%,-./0-/.#%-1%2*0.#),#%(#)3%#*#.45%-1%678%9#:%! "#$%:;:%,<#0-.13#-#.% X3 2385 nm laser 165 MeV b 2 0.006 0.005 0.004 0.003 0.002 0.001 0.000 mφ = 0 Bunching Spectrum 113.3 113.4 113.5 113.6 113.7 113.8 113.9 Λ nm mφ = 2π mφ = 4π mφ = 8π b 2 0.006 0.005 0.004 0.003 0.002 0.001 0.000 Bunching Spectrum n = 1, m = 24 105 110 115 120 125 Λ nm

Phase-3: Echo-32 at 75 nm! "#$%&'()*+%,-./0-/.#%-1%2*0.#),#%(#)3%#*#.45%-1%678%9#:% X3 X4 b 2 0.004 0.003 0.002 0.001 mφ = 0 Bunching Spectrum 0.000 74.3 74.4 74.5 74.6 74.7 Λ nm 2385 nm laser mφ = 2π mφ = 4π mφ = 8π b 2 0.0035 0.0030 0.0025 0.0020 0.0015 0.0010 0.0005 165 MeV 205 MeV Bunching Spectrum n = 1, m = 35 0.0000 70 72 74 76 78 80 Λ nm

Phase-4: Echo-75 at 32 nm! "#$%&'(&)*#%$(+'%, -. %/0%+1%2-%33%! "#$%/*4/5)+16%+1%7#*#6)+#%8/*4)3#*+)5%6)4()91*%)+%:.%*3;%$(+'%)305#%< 64 % ')631*(&%)+%<=%*3% X3 X4 0.0015 mφ = 0 Bunching Spectrum 2385 nm laser 0.005 165 MeV 205 MeV Bunching Spectrum n = 1, m = 78 b 2 0.0010 0.0005 mφ = 8π b 2 0.004 0.003 0.002 0.0000 31.74 31.76 31.78 31.80 31.82 31.84 31.86 0.001 0.000 Λ nm McPhearson EUV to soft x-ray spectrometer with <0.1 nm resolution, iccd, MCP 31.0 31.5 32.0 32.5 Λ nm

Summary EEHG is a promising scheme to generate fully coherent soft x- rays directly from UV lasers in a single stage EEHG s enhanced frequency up-conversion efficiency at the 7th harmonic has been demonstrated at SLAC s NLCTA Existing echo beamline, RF, and laser systems, provide firmlyestablished launching point to examine higher-harmonics in EEHG through a series of staged facility upgrades and dedicated experiments Parallel R&D in HHG and laser spectral phase effects and tolerances Use necessary upgrades to also benchmark collective effects, phase space manipulation and transport limitations Thanks to Dao, Tor and to the Echo team!

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