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Phto -injector laser chain NEWS

Phto -injector laser chain NEWS. Massimo Petrarca & Marta Divall V. Fedosseev, K. Elsener, E. Chevallay,. History:. June July 2008 Amp1 problems (pulses train instability , ASE, parasitic lasing). 1 Amp1 Problems (Over most of the other problems):. 1 Amp2 Problems (for energy).

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Phto -injector laser chain NEWS

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  1. Phto-injector laser chain NEWS Massimo Petrarca & Marta Divall V. Fedosseev, K. Elsener, E. Chevallay,

  2. History: June July 2008 Amp1 problems (pulses train instability , ASE, parasitic lasing) 1 Amp1 Problems (Over most of the other problems): 1 Amp2 Problems (for energy) 1->2 Amp2 Problems (for energy) 1 Synch. Problems (Laser -> Gun) 1->2 Synch. Problems (Laser -> Gun) Major issues in January 2008 When NO Harmonic generation was performed! 2 Harmonic Conversion Efficiency &Stability 2->3 Harmonic Conversion Efficiency &Stability May June 2008 Harmonic generation Performed with Amp1 only: New Problems discovered!

  3. Micro pulses at 1.5 GHz ~666ps; 10W 400us amplification window for AMP1 Macro pulse 200us amplification window for AMP2 Macro pulse Dt Dt Dt UV Green Laser overview 1.5 GHz Nd:YLF Oscillator + Nd:YLF Preamplifier 1047nm 3-pass Nd:YLF amplifier 2 pass Nd:YLF amplifier Optical gate (Pockels cell) PC 4 2 Pulse picker IR Drive Beam (PHIN); Probe beam ~600ps=<Dt=<DtPC

  4. F1 = +1146mm Preamp. beam M4 21cm M2 Nd:Ylf rod M6 2.5cm 3.5cm M3 M1 M5 5cm 54cm 58cm 1st pass 2nd pass 3rd pass First Amplifier layout Power Measurements Amp1: Unamplified  ~ 5.6 W @ 50 amps  ~ 6.7 W @ 60 amps  ~ 7.4 W @ 70 amps  ~ 8.1 W @ 80 amps  ~ 8.8 W @ 90 amps  ~ 9.7 W  ~3.0 KW -Final configuration: 3passages trough the rod with F1 to ~ compensate for the beam divergence: X(3rd pass)-X(1st pass)~1.2mm; Y(3rd pass)-Y(1st pass)~1mm . Nominal power ~3KW has been reached Satisfactory trace pulse stability has been reached Transverse beam parameters:M2x~2.38; M2x~1.94

  5. Amp2: layout M6 Amp1 3rd pass. 122cm M12 Nd:Ylf rod M10 2.5cm 2.5cm 75cm M9 M11 7cm 29.5cm 14.5cm 22cm 156cm F5 = +402mm F4 = +802mm Pericope+Farady M8 M7 F2 = +300mm F3 = -114mm 29.5cm 20cm 20.5cm 57.5cm Way to Harmonic G. crystal Tot:48cm 94cm 1st pass -Present configuration: 2passages trough the rod with F3 and F2 for the matching: “beam size rod size” Satisfactory trace pulse stability has been achieved Power ~6.3KW has been reached with 90A (Amp1@90A) 26cm 25cm 2nd pass Pockels Cell 7cm

  6. Amp1 + Amp2 @ 90A Power Measurements Amp1: Unamplified  ~ 5.6 W @ 50 amps  ~ 6.7 W @ 60 amps  ~ 7.4 W @ 70 amps  ~ 8.1 W @ 80 amps  ~ 8.8 W @ 90 amps  ~ 9.7 W  ~3.0 KW Power Measurements Amp1 @90A +Amp2 ..: @ 50 amps  ~ 10.0W @ 60 amps  ~ 10.5 W @ 70 amps  ~ 11.2 W @ 80 amps  ~ 11.6 W @ 90 amps  ~ 12.3 W  ~6.3 KW

  7. Amp1+Amp2 Harmonic Generation A decrease on the conversion efficiency has been observed when both amplifiers are @90A Optimization of the beam size onto the conversion crystals has to be done; nevertheless the conversion efficiency is still acceptable yielding a micropulse energy of ~230nJ (nominal 730nJ) Collaboration with Guy Cheymol “CEA”

  8. On site synchronization meas.: After on site investigation, oscillator cavity perturbations due to thermal effects were suspected HighQ expert came and fixed the settings of the oscillator end-cavity mirror (semiconductor saturable absorber mirror “SESAM”): 50C Degree Problem has been fixed Lecroy SDA (16GHz, 60GS/s+ NewFocus Photodetector25GHz) JNF: jitter noise floor ~ 350 fs Jmeas: 724fs Jreal ~ 634 fs (rms jitter required <1ps)

  9. HighQ Jitter behavior (over a day) HighQ company provided the unit to synchronize the laser to the ext. rf master clock (~1.499):“Synch” From this unit it is possible to monitories the jitter “Laser vs Ext-rf”

  10. Open Issues: • Even more difficult (it takes time!!): • The rod probably has to be changed to improve transverse beam profile (poor quality now!). • Third passage has to installed to extract more energy and to compensate for thermal effect introduced by Amp1 . • Lenses system for the matching “rod -beam” size along the 3 passages has to be installed …… …..(optimization of the whole beam line that comes after!!!!!) • Coupling: “Pumping beam vs Nd:Ylf rod” has to be study (no cylindrical lenses installed now; it could be necessary to replaced those lenses to focus pumping beam into the rod.) • Conversion efficiency studies (saturation, best size onto crystals….) • Collaboration (starting) with Russian people from ‘Institute of Applied Physics ’, they will help us performing the changes required to improve the laser performances: Amp2 layout modification + Harmonic Generation scheme modification  Higher IR energy, conversion efficiency & better beam profile

  11. The end

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