1. FSC 1 Electron Transport Experiments Farhat Beg Fusion Science Center Meeting Feb. 28, 2007 FSC RAC

2. FSC 2 Collaborators Lawrence Livermore National Laboratory H. Habara, R. Kodama R.R. Freeman, L. Van Woerkom, D. Offerman, K. Highbarger, R. Weber D. Hey M. H. Key, A.J. MacKinnon, A. MacPhee, S. Lepape, P. Patel, S. Wilks P.A. Norreys K. Lancaster, J. S. Green J. Pasley, Mingsheng Wei, J.King, Tammy Ma, Erik Shipton R. Stephens

3. FSC 3 Progress So Far Two sets of experiments on electron transport Nail and wire targets Warm dense targets Status: Analysis of the results is in progress Four weeks in summer have been allocated on Titan laser for FSC experiment (two weeks each for UCSD and OSU)

4. FSC 4 New targets were developed Rationale for wire/nail targets: Simple - no glue, simple geometry Large head so laser can reliably hit it Accessible to diagnostics Small - completely simulate Status: Experiments have been performed on both the Vulcan PW at RAL and the Titan laser at LLNL Experiments have been modeled using three codes, i.e., LSP, e-PLAS and PICLS 100 µm dia head 20 µm dia wire 1 mm to bend 50 µm dia Ti wire (only on Titan) 1 mm to bend Data analysis is in progress

5. FSC 5 Laser Parameters and Diagnostics Setup Vulcan Laser at RAL Energy ~ 500 J Pulse length ~ 1 ps Spot size ~ 10 µm Intensity ~ 6x10 20 Wcm -2 Titan Laser at LLNL Energy ~ 100 J Pulse length ~ 500 fs Spot size ~ 15 µm Intensity ~ 1x10 20 Wcm -2 45 O Imaging XUV - 68, 256 ev X-ray - 4.5, 8.0 keV

6. FSC 6 Initial fall-off is rather rapid: 1/e <200  m 1 mm Nail head Laser Cu K  images 100 µm Initial 1/e decay length is very similar for cone and nail head targets Small fraction has very long path length - very visible in cone-wire target

7. FSC 7 20060809s 2 XUV - 68 eV Extended heating seen in XUV images - mostly return current Hydro jets at every inside edge Non uniform emission along the wire Low level heating for entire length of wire Hotter for ~200  m - associated with hot electrons 1 mm Jet X-ray emission from 1 ps laser heated wire F. N. Beg et al., PRL 92, 095001 (2004) Jets JetLaser Data being analysed to obtain temperature

8. FSC 8 Evidence of Surface Heating from 256 eV images The nail head and wire exhibits limb brightening – mass thickness ~ 0.04  m – Physical thickness ~ 1  m  Surface current - is it from hot electrons?? 20060809s2 XUV - 256 eV jet 20 µm

9. FSC 9 20 micron Cu wire is coated with 2microns of Ti Simultaneous radiography shows surface and core current – similar decay length – Current through the wire 4.5keV 8.0keV Modified targets were used to study surface current on Titan laser 100 µm Quantitative analysis of current partition between surface and bulk is underway Actual target

10. FSC 10 K alpha emission has been observed even after 90 0 bend 660um Back of wire Front of wire Surface current with extremely long propagation range! Limb brightening after the bend

11. FSC 11 Cone-wire targets are much different in XUV XUV (256 eV) images show emission from the large area inside the cone Emission was also observed near the tip of the cone XUV emission was not observed from the wire glue 256 eV 1 mm KK LPI inside the cone is an interesting issue for the advanced Fast Ignition

12. FSC 12 Initial analysis shows change in propagation length with laser energy Both Titanium coated copper nail and bare Ti wire have similar 1/e lengths Cu K alpha -8 keV Ti K alpha -4.5 keV

13. FSC 13 SUMMARY Three different targets were used – Surface transport is noticeable in nail/wire – Energy localization in all three targets? – Ground connection causes more heating in nail/wire targets Future Work – Measurement of E & B field to better characterize currents – Improvement in modeling for benchmarking

14. FSC 14 Motivation for Electron Transport in Hot Dense Matter Cone guided FI DT FI Most experiments are performed far from FI conditions Electron transport in hot targets is different

15. FSC 15 Shock Heated Targets Shock heated –Long pulse accelerates pusher plate –Compresses & heats foam –Short pulse laser interacts with gold –Hot electrons produced are detected by copper plate  Measures electron transport into plasma  Mimics the cone tip shock interaction

16. FSC 16 Shock driven experiment shows foam compression to 1 g/cc Density, g/ccTemperature, eV Long pulse accelerates Al/Cu flyer plate Compresses foam to ~1 g/cc Shock wave penetrates Au foil on opposite side Electrons generated in Au cross the Au/interface and are counted in Cu Foam Cu Au 60 30 00 Temp, eV , g/cc 6 3 0 depth, mm 0.15 0.160.170.18 Radiograph gold

17. FSC 17 Various types of targets were used to understand transport Au/Cu/Al - measure electron generation in Au –short pulse laser, Cu-K  imager, single hit CCD and spectrometer Au/CRF/Cu/Al - measure losses in hot foam –Long pulse, check timing w backlight –Long & short pulse, Cu-K  imager, single hit CCD and spectrometer Au/CH/Cu/Al - measure losses in cold CH, same areal density –Long & short pulse, back-light, Cu-K  imager and spectrometer Aim was to produce large enough plasma to diagnose

18. FSC 18 Real target Is actually rectangular glue for cone A variety of diagnostics was used Target Schematic

19. FSC 19 X-ray backlit images show shocked compression of foam 0ns3.5ns 5ns7ns h2d 5.6ns Bremsstrahlung from long pulse interaction. Radiographs show shocked compressed foam between copper and gold surface Good agreement with 2D rad-hydro simulations #3 18 th Sept #5 18 th Sept #4 13 th Sept #5 14 th Sept 300 LPI mesh 200J @ 2 ,200  m spot,2ns Resolution 24 microns gold Shock 55 µm into foam Shock 90 µm into foam

20. FSC 20 Shock heated targets Timing of short pulse varied with respect to long pulse to examine transport through: - Cold Au/shocked foam - Cold Au /partially shocked foam - Shocked Au /shocked foam

21. FSC 21 Shot 2, 7 th September, 152J KK He  Ly  KK Al/Cu/Au 10ps Shot 2, 6 th Sept, 256J KK He  Ly  KK Shot 4, 6 th September, 140J KK KK Presence of He  shows heating of copper for both 1 and 10 ps laser pulses He  disappears with an addition of CH in the target Transport is significantly different in insulator targets More accurate information from a single CCD camera CPA 5  m Au 5  m Cu 20  m Al Target composition affects the electron transport Al/Cu/CH/Au, 1ps

22. FSC 22 Shot 4, 15 th September, 142 J, 1 ps Fully shocked, Delay : 6.5ns KK KK Reduction in copper K alpha counts with shocked targets He  is not observed with both plastic and shocked targets More careful analysis with a single hit CCD camera is required Shot 4, 6 th September, 140J KK KK Al/Cu/CH/Au, 1ps Fully shocked target shows reduction in Cu K alpha

23. FSC 23 Emission is dominated by bremsstrahlung 10 ps only (no long pulse) 25um Cu filter 1ps + Long pulse delayed by 6.5ns Be filter 1ps + Long pulse delayed by 5ns Be filter WDM package w/ 3.9um Au Cold sandwich Al/Cu/Au (5.1um Au) Cold fully shocked partially shocked CPA CRF Foam Au Cu Al

24. FSC 24 Bremsstrahlung (8keV) / Cu k-a radiograph of long pulse / short pulse driven WDM target 2ns green 1ps Short pulse 5ns after long pulse Radiograph with long pulse at 5ns (different shot)

25. FSC 25 SUMMARY Experiments have been performed to produce warm dense matter with shock compression. Rad-hydro simulations show compression of foam to 1 g/cc and temperature of 20-25 eV. The shock timing agrees with experimental results with 200 J, 2 ns, green long pulse laser. Laser with a pulse length 10 ps burns through 3-4 µm gold foils Shocked targets show reduction in copper K alpha counts

26. FSC 26 Future Work Use of CH as ablator will reduce bremsstrahlung More shots are required for 1 and 10 ps laser pulse lengths A detailed data analysis will shed light on the physics of electron transport in warm dense matter