1. 16 th HAPL Meeting Princeton, New Jersey December 12, 2006 Naval Research Laboratory Plasma Physics Division Washington, DC Presented by M. Wolford Work supported by DOE/NNSA/DP Electra (KrF) Laser Development NRL J. Sethian M. Myers J. Giuliani M. Wolford S. Obenschain Commonwealth Tech F. Hegeler M. Friedman T. Albert J. Parrish K. Gunlicks RSI P. Burns R. Lehmberg S. Searles SAIC R. Jaynes

2. Starting Integration of Electra Laser System –First Stages of Construction Pre-Amplifier Laser Energy Measurements –Increased laser yield to 25 J –Time-Dependent characterization of laser pulse –Near-Field Profile Cathode & Rep-Rate Durability –Anode Mesh (1 st Implementation 12,363 shots) Summary Since August HAPL Meeting

3. LPX Electra ISI Source Options Electra Laser System Pre-AMP Main AMP

4. Pinhole Amplifier Focus A. V. Deniz, S. P. Obenschain Opt. Comm. 106 (1994) 113-122 LPX ff Diffuser T. Lehecka et al., Opt. Comm. 117 (1995) 485-491 External Cavity Diffuser w/ additional amplifier Electra ISI Laser Source Options See NRL Poster: Large Aperture KrF Discharge Amplifier Initial experiments and will continue with LPX as is, non ISI

5. LPX Large Amplifier optical architecture Electra Laser System Pre-AMP Main AMP

6. Pinhole Amplifier Focus AMP Closely Packed Convex Mirror Array Large Concave Mirror Double Pass Large Amp Architecture

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

8. Review: First light on Electra Pre-Amp 80% Ar, 0.3% Fluorine

9. 25 J Electra Pre-Amplifier Output 80% Ar, 0.3% F 2

10. Timing Electron Beam to Laser, 10 J Yield Voltage OutputInput 64.8 ns

11. Output Time Dependent Intensity 1 23 4 5 6 Input Output

12. Pre-Amplifier Energy Function of Input Timing Cause of Discrepancy

13. Progress in realizing long duration laser runs ceramic honeycomb primary emitter Gas buildup in the diode Degradation of the emitter Foil failure due to debris and/or plasma arcs in A-K gap Previous Limits to Laser Durability (< 10 k shots) March 2006 HAPL meeting Hibachi Solved with new all-carbon emitter. As much as 25 k shots (reported at Aug 2006 meeting) Foil MAY have been solved with high transparency anode screen Screen

14. One Possible mechanism limiting foil durability Electron emission from Anode HypothesisRationale Micro particles can stick to the foilEmission is an explosive process. See marks on foil Voltage reverses in diodeSeen on Voltage monitors after the main pulse Voltage reversal causes microSee what may be "cathode spots" on particles to emit electronspressure foil Emission can be an explosive processKnown fact. Can puncture hole in highly stressedExperiments with an anode foil show pressure foilevolution of this process First experiments with mesh, (90%-95% effective transmission) show a) Minimal degradation in laser energy (i.e. transmission OK) b) First Implementation lasted several multi-thousand shot runs

15. Starting Integration of Electra Laser System –First Stages of Construction Pre-Amplifier Laser Energy Measurements –Increased laser yield to 25 J –Time-Dependent characterization of laser pulse –Near-Field Profile Cathode & Rep-rate Durability –Anode Mesh (1 st Implementation 12,363 shots) Summary Since August HAPL Meeting