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14 th HAPL Meeting San Diego, CA August 8th , 2006 Naval Research Laboratory

NRL J. Sethian M. Myers J. Giuliani M. Wolford R. Lehmberg S. Obenschain M. Levy Commonwealth Tech F. Hegeler M. Friedman RSI P. Burns SAIC R. Jaynes. Electra (KrF) Laser Development. 14 th HAPL Meeting San Diego, CA August 8th , 2006 Naval Research Laboratory

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14 th HAPL Meeting San Diego, CA August 8th , 2006 Naval Research Laboratory

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  1. NRL J. Sethian M. Myers J. Giuliani M. Wolford R. Lehmberg S. Obenschain M. Levy Commonwealth Tech F. Hegeler M. Friedman RSI P. Burns SAIC R. Jaynes Electra (KrF) Laser Development 14th HAPL Meeting San Diego, CA August 8th , 2006 Naval Research Laboratory Plasma Physics Division Washington, DC Presented by M. Wolford Work supported by DOE/NNSA/DP

  2. Summary Since Last HAPL Meeting • Cathode Rep-rate & Durability: • Installed Carbon Emitter • 2.5 Hz 24,978 shots (continuous) • Beginning Rep-Rate Focal Profile Experiments • Single shot Recovery of Recirculator less than 200 ms (Necessary Time for 5 Hz Operation) • First Light Electra Pre-Amplifier • 23 J laser output

  3. Review IA: CERAMIC HONEYCOMB CATHODE:Placing a ceramic honeycomb slab above the emitter significantly improves the cathode performance and lifetime Ceramic honeycomb cathode primary emitter: velvet ceramic honeycomb HAPL Meeting March 2006 Present Limit of Laser Durability • The continuous shot number is limited by gas buildup in the vacuum diode (forces us to briefly break up long runs) • Laser run duration is ultimately limited by foil failure. (due to cathode debris and/or excess plasma in the A-K gap) Cathode lifetime was limited to 10,000 continuous shots

  4. Review IB: CERAMIC HONEYCOMB CATHODE:Cathode Action Plan as of March 2006 • Conditioning of the cathode • Replace velvet primary emitter with graphite emitter • Cool the cathode • Modify the cathode construction to eliminate weak spots • Replace cordierite ceramic with more robust SiC or YZA (yttria stabilized zirconia-alumina) • Eliminate cathode shroud high voltage feedthrough for water cooling primary emitter: graphite cathode cathode cooling concept copper cooling plate

  5. New all Carbon Emitter has increased Cathode Lifetime …… 31 k shots total, 24,978 continuous @ 2.5 Hz Velvet Carbon 31 k shots...no change ESLI (Energy Sciences Laboratories Inc.) 10 k shots...lots of burn marks SEM SEM

  6. Motivation for Beginning Focal Profile Experiments • Nike Laser System (Single Shot) • ISI smooth focal profiles • Rep-Rate Considerations • Possible Additional Phase Aberrations • Recirculator baseline gas flow • Leftover energy (pressure gradients) from last shot • Foil Temperature (Boundary Layer) • Gas Temperature after one roundtrip of recirculator

  7. Focal Profile after E-Beam Single Shot with NO RECIRCULATOR FLOW E-Beam Fires at Time Zero 0 5 10 30 Time (s)

  8. Focal Profile Floor Layout Aperture May 2006 main amp 30 cm x 30 cm seed osc 1cm x 3 cm

  9. Schematic of “Pseudo ISI” Essential Optical Elements for focal profile studies Beam size: 15 cm x 15 cm Amplifier Pinhole NanoStar Camera Recorded Image LPX 305 i Not ISI Source Lineout Image 6 meter focal length lens 248 nm

  10. 30 shots 1 Hz Focal Profile Measurement (“Pseudo ISI”) E-Beam Probe 0 1 2 3 0 1.39 1 2.39 .39 2 Time (s) Time(s) Probe Beam with E-Beam 1 Hz 390 ms after Probe Beam No E-Beam Probe 500 microns

  11. E-Beam Probe 0 1.39 1 2.39 .39 2 Time(s) 1 Hz and 2.5 Hz Rep-Rate Focal Profile Lineouts (“Pseudo ISI”) 30 shot measurement bursts (gas cycle time of recirculator ~5 secs) E-Beam Probe 0 2 2.39 .8 .39 Time(s) E-Beam 1 Hz Probe Beam 390 ms after E-Beam 2.5 Hz Probe Beam 390 ms after 500 microns

  12. Focal Profile Single Shot Lineouts (“Pseudo ISI”) E-Beam Fires at Time Zero 200 ms 400 ms 10 s 0 25 ms 50 ms 1 s Time

  13. Electra Pre-Amplifier Laser Experiments Input 0.5 J 10 cm x 10 cm LPX 305 i 1 cm x 3 cm Cylindrical lens Pair 3 cm x 3 cm Telescope Calorimeter

  14. First light on Electra Pre-Amp 80% Ar, 0.3% Fluorine Orestes Prediction (0.5 J input) Measured Output (~0.5 J input)

  15. Summary Since Last HAPL Meeting • Cathode Rep-rate & Durability: • Installed Carbon Emitter • 2.5 Hz 24,978 shots (continuous) • Beginning Rep-Rate Focal Profile Experiments • Single shot Recovery of Recirculator less than 200 ms (Necessary Time for 5 Hz Operation) • First Light Electra Pre-Amplifier • 23 J laser output

  16. Next Steps Based on Results • Cathode Rep-rate & Durability: • Cool the cathode • Modify the cathode construction to eliminate weak spots • Replace cordierite ceramic with more robust SiC or YZA (yttria stabilized zirconia-alumina) • Eliminate cathode shroud • Rep-Rate Focal Profile Experiments • Interferometer • Examine all of Aperture • Pre-Amplifier Laser • Integrate into the full laser system

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