1. 17 th HAPL Meeting Washington, DC October 30, 2007 Naval Research Laboratory Plasma Physics Division Washington, DC Presented by M. Wolford Work supported by DOE/NNSA/DP Electra (KrF) Laser Development NRL J. SethianM. Myers S. ObenschainJ. Giuliani J. DubingerM. Wolford Commonwealth Tech F. HegelerM. Friedman T. AlbertJ. Parish R. JonesP. Howard RSI P. BurnsR. Lehmberg S. SearlesW. Webster SAIC R. Jaynes A. Mangassarian PLEX M. McGeoch APP S. GliddenH. Sanders Georgia Tech S. Abdel-KhalikD. Sadowski K. Schoonover

2. Angularly Multiplexed Electra Laser System –452 J Single Shot –1.585 kJ, 5 shots @ 5 Hz for 1 second Less expensive solid state switch based on commercial product (APP). Plex LLC has tested in 3 stage Marx: 1M shots @ 5 Hz. Demo 89% efficiency. Georgia Tech has designed and bench tested Jet Foil Cooling Technique (Scalable, less power consumption) Cathode & Rep-Rate Durability –Averaged 270 J for 16,619 shots @ 2.5 Hz over two hour period –Far Less Debris with Silica Coating on Cordierite –No Debris with All Carbon Cathode after 4000 shots @ 2.5 Hz Summary Since December HAPL Meeting

3. LPX Pre-AMPMain AMP Completed Electra Laser System

4. LPX PLCC Cylindrical Optics f ~ 6 m Lens Beamsplitter Calorimeter Photodiode Combo PD 2 PD1 Angularly Multiplex Preamplifier 25 J Output Beam 1 Beam 2 INPUT OUTPUT

5. 452 J Single Shot Yield 12 34 56 Big 33 x 33 cm 2 Small 18 x 18 cm 2 Output Beams 15 x 15 cm 2 Calorimeter Array Main Amp 30 x 30 cm 2 PRE AMP OSC 12 Split Beam 26 Split Each Beam into 3

6. Total Yield 1.585 kJ in One Second 5 Hz Burst 12 34 56 PHOTODIODE Energy Drops Due To Pre-Amplifier (Phase Aberrations) Pre-Amplifier Recirculator ( Designed)

7. Pre-Amp Recirculator Allow rep-rate runs, improve beam quality Improved Coupling &Timing, Pre-Amp to Main Amp More energy into main amp More diagnostics for KrF Code Comparison Strip Cathode for Pre-Amp 25% more energy deposited in the Laser Gas On going Improvements in Laser System See Laser Posters: J. Giuliani et al. “KrF Laser Amplification in the MultiStage Electra Facility” For Code Comparison & R. Lehmberg “Pulse Shaping and Energy Storage Capabilities in Angularly Multiplexed KrF Laser Amplifiers” & M. Wolford et al. “Optical System and staging of the Electra KrF laser facility”

8. We have made advances with existing durable switches that will be less expensive, and will come close to efficiency PLEX LLC PREVIOUSNEW ADVANCE LASER GATED SWITCH High Efficiency But, potentially more expensive requires further development p n+ n- n++ p++ Diode Laser D Laser USE EXISTING Specs 30 kA/usec, >> 10 8 shots Tested to 50 kA/usec PLEX LLC has demonstrated 96 kA/usec @ 40 kV with SMA # S33 Solid State (45 kV) Switch Applied Pulsed Power, Ithaca, NY

9. PLEX corporation has built a 3 stage Marx using modified APP switches and magnetic assist Demonstrated 1 M shots @ 5 Hz 3 stage Marx Rep-rate/duration:10 6 @ 5 Hz 10 5 @ 10 Hz dI/dt 60 kA/us Voltage60 kV Pulse length320 nsec Total Current7 kA Switch efficiency: 89% Circuit efficiency: 84% PLEX Corporation We will build a 12 stage e-beam system to demonstrate all solid state, durable architecture

10. foil Tubes Main Gas Flow Jets VIEW FROM GAS INTO THE DIODE "Jet" foil cooling technique developed by Georgia Tech Keeps foil (uniformly) cool Scalable to large apertures Low power consumption (minimal efficiency penalty) Should not mess up the focal profile TOP VIEW Rib tube Jet foil Gas Side e-beam side

11. Jet Foil Cooling Technique Successfully Demonstrated on Bench

12. Hypothesis: Foil is lifetime not limited by thermal management Debris from Cordierite honeycomb Causes Foil Failure Evidence of Debris e-beam Ceramic Honeycomb* "Primary" emitter 3 mm gap

13. Silica Coated (Far Less Debris) Cordierite Improvement Average 270 J @ 2.5 Hz Over Two Hour Time Period

14. All Carbon Cathode Shows Potential for Greater Durability (4000 shots @ 2.5 Hz No Debris, No Foil Damage, 50x lower vacuum) See Poster: M. Myers & M. Friedman “Development of a Large Area, Durable Electron Emitter For High Average Power KrF Lasers”

15. Angularly Multiplexed Electra Laser System –452 J Single Shot –1.585 kJ, 5 shots @ 5 Hz for 1 second Less expensive solid state switch based on commercial product (APP). Plex LLC has tested in 3 stage Marx: 1M shots @ 5 Hz. Demo 89% efficiency. Georgia Tech has designed and bench tested Jet Foil Cooling Technique (Scalable, less power consumption) Cathode & Rep-Rate Durability –Averaged 270 J for 16,619 shots @ 2.5 Hz over two hour period –Far Less Debris with Silica Coating on Cordierite –No Debris with All Carbon Cathode after 4000 shots @ 2.5 Hz Summary Since December HAPL Meeting