Laser readiness for all optical EUV FEL

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Tyler Mitchell
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1 Laser readiness for all optical EUV FEL Akira Endo EUVA (Extreme Ultraviolet Lithography System Development Association) EUVL Source Workshop 19 October, 2006 Barcelona, Spain Acknowledgments This work was supported by the New Energy and Industrial Technology Development Organization -NEDO- Japan.

Intel Proposal(FEL-2005) M. Goldstein et al., FEL-2005.

with coherent enhancement transition radiation Compton scattering

2 Intel Proposal(FEL-2005) M. Goldstein et al., FEL Electron Beam Energy = 7-10 MeV EUV generation after acceleration with coherent enhancement transition radiation Compton scattering harmonic generation Micro bunching by optical wiggler (seed laser for efficient process)

3 Laser Compton X-ray Source Compact Hard and Soft X-ray Sources based on Laser Compton method : well established (NEDO FST Project ) Output average power increase is required for Medical Imaging 33keV, mw average power Lithography 13.5nm, >100W High repetition rate, high average power, short pulse laser required

4 Typical Experimental Parameters Electron parameters Energy Bunch charge Bunch width Beam size Normalized emittance 38 MeV 0.8 nc 3 ps (rms) 30-50μm (rms) 3 π mm mrad Laser parameters Pulse energy mj Pulse width 50 fs (FWHM) Wavelength 800 nm Beam size 10 μm (rms) Interaction angle 90, 165

5 General System Arrangement Gun: BNL type 1.6 cell Cu cathode Laser for gun: LD pumped Nd:YLF Linac: Standing Wave, 1.5mx2 Ti:sapphire or Yb:S-FAP Laser for interaction: LD pumped Yb:S-FAP (under development) or Ti:sapphire: 200mJ/pulse, 100fs Beam Dumper Focusing Magnet X-ray Nd:YLF 4ϖ Achromatic Bending Photocathode Linac

6 X-ray Generation Experimental results Interaction angle Energy* (max.) Number of total photons (photons/pulse)** Pulse width (rms)* Repetition rate *Estimated values with beam parameters **Using a MCP detector 34keV 17 kev ps 150 fs 10Hz Number of photons ( 10 6 photons/pulse) Number of X-rays 10 6 (photons/pulse) Laser Laser pulse energy (mj) Laser energy vs. number of X-ray photons

7 Spatial distributions of X-rays Spatial distributions of X-ray intensity and energy were measured with a X-ray CCD camera Polarized laser pulse Polarized laser Be Window (φ30mm) Be Window (30mm dia.) X-ray CCD camera X-ray CCD camera 36MeV Electron 38MeV Electron pulse Interaction point Interaction point 2.6m

2-D Profiles of X-ray Energy S-polarization 15.5 X-ray energy (kev) 15 14.5 14 X-ray Energy (kev) P-polarization Energy dispersion(%, rms) 13.5-15 5-10 -5 0 5 10 15 4.

8 2-D Profiles of X-ray Energy S-polarization 15.5 X-ray energy (kev) X-ray Energy (kev) P-polarization Energy dispersion(%, rms) fiiting curve calculated by 3π mm*mrad, 3.6% offset Distance from the beam center (mm) Distance from the beam center (mm) Energy Dispersion (%,rms) Solid-line: simulation

9 Low-jitter synchronization system Stabilization Stable RF oscillator 2856MHz mode-locked laser 2856 MHz 2856 MHz O/E Synchronization system Synchronization system 119 MHz Picosecond laser Klystron Femtosecond laser 119 MHz X-ray pulse Advantages No multiplier Phase detection by electrical (microwave phase detector) and optical (sumfrequency intensity ) methods. Deliverable by optical fibers (Less sensitive to environmental noise)

10 Top view of experimental apparatus 1200 mm 2856MHz laser Photo detector 119MHz laser SFG crystal

11 Performance Synchronization of two independent mode-locked lasers was achieved by dual PLL (Phase-Locked Loop). Accuracy RMS jitter < 6 fs ( bandwidth 300 khz max. ) Long-term Stability 1 hour operation with jitter of < 4 fs ( bandwidth 50 Hz) Synchronization system was used in the Laser-Compton X- ray system. The result was high X-ray stability.

12 Stability of X-ray X Intensity Shot-to-shot stability (15 min) % (rms) (* Laser intensity jitter was 5%(rms)) 11% (rms) 8 % (rms) ( *Each Data shows x-ray intensity in10sec ) Normalized X-ray intensity (arb. unit) Long time stability (7 hour) 90 Normalized X-ray intensity (arb. unit) Time (min) 1 0 Time (min) Time (hour) Time (hour)

13 LPP System Overview (EUVA Project )

14 Focusing of CO 2 Laser Beam (Focal Length of Lens:127 mm) No change of CO 2 laser focus spot size observed before and after amplification. No wavefront distortion was caused by amplification Horizontal Before Amp. Before Amp. After Amp. After Amp. 1/e2 Vertical Before Amp. Before Amp. After Amp. After Amp. 1/e2 Intensity Intensity Dimension [ m] Dimension [μm] Dimension [ [μm] - focus spot size observed before and after amplification (1/e 2 ) - Horizontal: 153μm Vertical: 138μm M 2 =1.2

15 Schematic Diagram of Multi-line Amplification

16 Multi line CO2 regenerative amplifier 1488nm 1μJ, 1kHz 800nm, 100fs 1730nm

17 Multi line (broadband) output with DFG Pulse Injection Stabilization of pulse rise up time Multi-line Operation w/o Seed Pulse with Seed Pulse

18 Intense High-order Harmonic Generation by loosely focusing geometry Differential Pumpi ng Chamber 0. 2 μm Al Filter Aper t ur e Focusi ng l ens f = 5 m Var i abl e Lengt h Gas Cel l XUV Spect r ogr aph 35 f s Ti : S Laser Pul se ω 0 = 200 μm z R = 140 mm MCP+CCD 5 m 3 m L = 100 mm, P~a few Torr Output Power nm (Xe) nm (Ar) Focused Intensity : ~10 15 W/cm nm (Ne) E. Takahashi et al., PRA 66, 02180(R) (2002).

[μm] Spot size [μm] 20 15 10 5 5 μm Horiz. Vert. M 2 = 1.4 μm 0.5 0-0.5-10 -5 0 0 60 60.5 61 61.

19 Focusing with a Off-Axial Parabolic Mirror at 29.6 nm (27th) Focused by OAP Mirror f= 60 mm OA angle= 24Þ Single shot ablation pattern Spot size [μm] Spot size [μm] μm Horiz. Vert. M 2 = 1.4 μm Distance from focusing mirror [mm] Distance from focusing mirror [mm] H. Mashiko et al. Opt. Lett. 29, 1927 (2004) μm

20 Experimental Setup of Regenerative Amplifier 4. Regenerative Amplification 352 fs, 3.1 ns ps Output Round-trip 10kHz

21 Amplified Pulse Spectra

22 Single Mode Output Further cavity optimization Insertion of a mechanical slit M 2 x : 1.47 M 2 y : W at 10kHz Filling factor: ~15% Scalable up to 100kHz

23 Expected Laser Specifications until 2010 Solid state laser: 100fs, 100kHz, 500W CO2 laser: 100ps, 100kHz-1MHz, 10kW HHG: 13.5nm, 100fs, <μj, 100kHz Laser requirement for all optical EUV FEL is to be studied to fix the final high average power laser specifications

High-Power Femtosecond Lasers

High-Power Femtosecond Lasers FEATURES 190 fs ps tunable pulse duration Up to 2 mj pulse energy Up to 20 W average power Single pulse 1 MHz tunable repetition rate Includes pulse picker for pulse-on-demand