1. Update on LLNL FI activities on the Titan Laser A.J.Mackinnon Feb 28, 2007 Fusion Science Center Meeting Chicago

2. Titan laser provides a capability for combined high energy SP and LP beam experiments Existing Janus Target Area (2x 1kJ LP beams) Short-pulse: 300J in 400fs Long-pulse: 1kJ in 3ns Laser Bay Titan Target Area Switchyard upgrade will allow simultaneous Titan and Janus 2 beam

3. Titan operating reliably - @5-7 shots per day Max irradiance = 3x10 20 Wcm -2 at 200J, 500fs. Prepulse levels low and appear reproducible - working to verify shot to shot diagnostic capability Pointing accuracy appears to be very good (5-10  m) Proton beams with slope T p ~ 4MeV, E max ~ 40MeV routinely produced with 10  m gold targets Fast Ignition relevant experiments to take place in April will study: laser to hot e coupling proton conversion from hydride targets Proton focusing Aim for 80 shots in 5 week run Outline

4. Titan long-pulse arm has been operational since Aug 06, enabling 2-beam combined SP-LP experiments Short pulse F/3 focusing optic Long pulse periscope

5. The long pulse beam can be moved to any of 6 ports in Horizontal plane

6. Titan short pulse has very good pointing and target alignment accuracy 150µm square foil target 150µm Laser and target alignment accuracy and laser pointing stability is 5-10µm 20µm diameter wire target 500µm

7. Low power images of focal region gives a peak intensity of 1x10 20 W/cm 2 in 200J, 500fs pulse -400µm-200µm0µm+400µm+200µm 300µm Best focus 4.9µm FWHM containing 14% of total energy  3x10 20 W/cm 2 15µm diameter spot encircles 50% of total energy  1x10 20 W/cm 2 Best focus 14% 50% 80µm

8. On-line fast diode and 2  optical probing are used to monitor the laser contrast and preformed plasma Diode and preformed plasma measurements can be obtained to examine shot to shot variations 500µm Interferogram at -25ps Fast diode pre-pulse measurement 0.18ns 1.38ns 3.18ns Density map

9. Titan data proton beams from gold targets give 2% conversion from laser to protons above 3MeV Conversion efficiency, peak proton energy, proton slope all reduce with increasing target thickness and pulse length Data being used to benchmark PIC and LSP simulations Good proton beam obtained at 10ps - encouraging for proton FI Titan E max vs target thickness Target thickness (  m) Peak Proton Energy, E p (MeV) Best fit to data Titan data Titan  lp vs target thickness Target thickness (  m) Laser to Proton conversion % 1/L scaling Titan data

10. LSP simulations show very similar behavior to experiments with plausible laser to electron coupling LSP shows slightly higher than 1/L scaling - very similar trend to data Conversion from hot electrons to protons peaks at 8% for 10  m Gold Implies ~ 30% coupling from laser to 1MeV electron source Future work will couple PIC code results as input to LSP Gold substrate 1000 A CHO layer 50J, 1MeV electrons

11. 1D simulations predict that High Z hydrides could result in higher conversion efficiency Fraction of energy in heavy ion Fraction of energy in H + Heavy ions are left behind at back surface during ion separation Current experiments with contaminant layers Hot electron to proton conversion eff (%)

12. Erbium Hydride will be tested on Titan in April 07 ** M. Allen, P. K. Patel, et al., PRL 93 265004 (2004) Surface contaminants and barrier layers will be removed by ion sputtering** Films 100nm thick have been manufactured by reactive sputtering* Oxide and hydrogen barriers may be necessary to maximize hydrogen content ErH 2 and ErH 3 10-15 um gold layer ~1 um Er or U layer 10-30 nm Pd oxidation protective layer Laser * Sandia National lab

13. Main focus of April 07 experiment will be to characterize laser MeV electron coupling 2. Prepulse effect inside cones 3. Pointing and effect of defocus (start) 1. Compare coupling for slabs vs cones Spring expt: Laser to hot E coupling Long pulse preform beam

14. The long pulse beam will be used to generate FI scale prepulse inside cones = 1 , E = 1 to 100J,  = 3ns, Spot ~ 30  m

15. Titan operating reliably - @5-7 shots per day (depending on experiment) Max irradiance = 3x10 20 Wcm -2 at 200J, 500fs. Prepulse levels low and appear reproducible - working to verify shot to shot diagnostic capability Pointing accuracy appears to be very good (5-10  m) Proton beams with slope T p ~ 4MeV, E max ~ 40MeV routinely produced with 10  m gold targets Fast Ignition relevant experiments to take place in April will study: laser to hot e coupling proton conversion from hydride targets Proton focusing Aim for 80 shots in 5 week run Summary