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L. Lancia, J-R. Marquès, J. Fuchs, A. Mancic, P. Antici, P. Audebert,

Experimental investigation of short light pulse amplification using stimulated Brillouin backscattering. L. Lancia, J-R. Marquès, J. Fuchs, A. Mancic, P. Antici, P. Audebert, C. Riconda, S. Weber, V.T. Tikhonchuck, S. H ü ller, J-C. Adam, A. Héron. CPHT. OUTLINE. CONTEXT

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L. Lancia, J-R. Marquès, J. Fuchs, A. Mancic, P. Antici, P. Audebert,

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  1. Experimental investigation of short light pulse amplificationusing stimulated Brillouin backscattering L. Lancia, J-R. Marquès, J. Fuchs, A. Mancic, P. Antici, P. Audebert, C. Riconda, S. Weber, V.T. Tikhonchuck, S. Hüller, J-C. Adam, A. Héron CPHT

  2. OUTLINE • CONTEXT • EXPERIMENTAL SET UP • DIAGNOSTICS • RESULTS • MODELLING • CONCLUSION -general result -analysis of parameters

  3. Short seed Longer pump IAW EPW Context: interaction and energy exchange of laser beams ► Study of non linear processes in plasmas when coupling beams • - Energy coupling • - Light distribution • Symmetry • Amplification ICF CPA pulses ►Phenomenon: resonant 3 waves coupling Kruer 95 Baldis 96 & Labaune 2000 Kirkwood 96 , 02, 05 Wharton 98 Long pulses SBS Shvets PRL 98 Malkin PRL 99,2000, Mardahl P.Lett.A 02, Fisch PoP 03, Malkin PoP 05 Cheng PRL 05 Short pulses SRS

  4. Interaction of quasi-counterpropagating CPA laser beams • Goal: Compression and light amplification in a plasma at high intensities • Why with plasma?: medium capable of bearing high power densities (>>GW/cm2) and heat loads • Methods: - SRS limitations: precise frequency tuning, kinetic effects, long amplifier lengths • - SBS: first study, (Milroy 77,79) in the weak coupling regime ..or Short-Pulse Amplification in the Strong-Coupling Regime (Andreev, Riconda, Tikhonchuk, Weber, PoP 2006) Advantages • Quasi-mode, robustness wrt frequency-mismatch and plasma inhomogeneities • absence of kinetic effects during amplification • very short interaction length • pump depletion easily attained • Low Temperatures (hundreds of eV) • High laser intensities (yet not relativistic)

  5. IONIZATION BEAM • - wavelenght: 1057 nm • 30J • 450ps • - ~ 1013W/cm2 rpp • PUMP BEAM • - wavelength 1057nm • - 2 J • - 0.4-30 ps • ~ 1016 W/cm2 • - beam waist ~10-100mm • SEED BEAM • - wavelength: 1057nm- 50 mJ • - 400fs • ~ 1015 W/cm2 • - beam waist ~20mm Gas Jet ~ 20° BEAMS CONFIGURATION

  6. 20 1 10 -3 n(cm ) 19 8 10 19 6 10 19 4 10 19 2 10 0 x (mm) 19 -2 10 -1 -0,5 0 0,5 1 PLASMA CHARACTERISTICS Avalanche ionization of a gas jet (supersonic, high pressure) Dim. beam section at focus: 0.7mm 0.12mm rpp ~1 mm 1 mm IONIZATION BEAM Gas Jet Gas: Ar,N2,He Pressures: 5 to 100 bar 1ns before interaction beams to allow homogeneous plasma

  7. lt space time DIAGNOSTICS Seed Pump 20° Pump:Focal spot (transmission/refraction) Spectrum+ Interferometer(coherence) Seed: Focal spot (energy gain/ transmission/refraction) Spectrum (gain) Auto-correlator (temporal length) space lt

  8. Without pump Log scale 70 mm Lin scale Typical seed beam amplification Focal spot Typical shot. Ar 50 bar 3.5 ps pump Seed/pump coincident

  9. Without pump With pump Log scale Log scale 70 mm 70 mm Lin scale Lin scale Typical seed beam amplification Focal spot Typical shot. Ar 50 bar 3.5 ps pump Seed/pump coincident

  10. Without pump With pump Log scale Log scale 70 mm 70 mm Lin scale Lin scale With pump 7 8 10 8 Spectrum 7 7 10 7 w/o pump 7 6 10 6 7 5 10 Amplitude (A.U.) 5 7 4 10 4 7 3 10 3 7 2 10 2 7 1 10 1 l(nm) 0 1040 1050 1060 1070 1080 Typical seed beam amplification Focal spot Typical shot. Ar 50 bar 3.5 ps pump Seed/pump coincident

  11. 100 mm 100 mm Pump beam is depleted Focal spot With seed Without seed interaction Log scale Log scale Total signal 6 times less Typical shot. Ar 50 bar 3.5 ps pump Seed/pump coincident Same conditions, same colorbar

  12. 1.2 Transmission level without pump beam 1 0.8 Gain: 1-10 Normalized seed amplitude 0.6 0.4 0.2 -5 0 5 10 15 20 Delay (ps) Amplification peaks at zero pump / seed delay Ar 50 bar (pump 3.5 ps)

  13. Pump+seed No seed Gain:1.5-5 Gain: 1-10 Dependence of seed transmission on plasma density (Gas pressure) 2 No pump 1.5 Normalized seed amplitude 1 0.5 0 0 20 40 60 80 100 (bar) pressure Argon, zero delay pump-seed

  14. Proof of electromagnetic coupling: dependence on polarization 35 30 25 20 15 amplification 10 5 0 1040 1048 1056 1064 1072 1080 l(nm) Seed spectrum signal Pressure 50 bar Ar Seed/pump coincident

  15. MODELLING CPHT  In progress…

  16. Simulation KOLIBRI (Electromagnetic+hydro)

  17. CONCLUSION & PERSPECTIVES • We demonstrated the feasibility of light amplification using SBS-sc • Energy amplification is observed for a number of different gas and • for various plasma densities • Maximum amplification is observed for coincident beams, • parallel polarizations • Modelling (PIC, hybrid) in progress • Perspective: we’ll explore varying the intensity ratios

  18. I14l02 > 10-2 Te3/2[keV] nc/ne√1- ne/nc 2 w0 vosc > 4k0cs 1/3 wpi 1+ i√3 2 ve wpe wpe √ ne vosclo √ Ip ve √ Te 2 2 ko2 vosc wsc= wo 2 Strong coupling regime: Low Temperatures (hundreds of eV) High laser intensities (yet not relativistic) Plasma response: quasi-mode

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