1. Review of UK HiPER relevant experiments Kate Lancaster

2. Work presented here is part of HiPER WP10 which aims to de-risk some of the physics of HiPER through targeted experimental campaigns There are two sets of work presented here: 1)Absorption as a function of scale length, LULI April 2008 2)Channelling in under and near critical plasma, march 2009 Work here is new and still under analysis.....

3. R.H.H. Scott, J. J. Santos, K. L. Lancaster, J. R. Davies, S. D. Baton, F. Perez, F. Dorchies, C. Fourment, S. Hulin, J. Valente, J.-L. Feugeas, Ph. Nicolaï, M. Rabec Le Glohaec and P.A. Norreys

4. Critical Surface Plasma ablated by ASE pedestal Al 10 25 50 Cu 10 Al 1 CH 5  0 ps laser beam 40J, 1ps (FWHM), 45° incidence 10-13µm diameter spot (f/4 OAP) 2 - 5 x 10 19 W/cm 2 ASE width (ns) Energy contrast ratio Type 1.13x10 -3 best 1.96x10 -3 median 4.31x10 -2 worst LULI 2008 – absorption experiment

5. Heating was diagnosed time resolved rear side optical emission –HISAC 3 rd harmonic emission was used to diagnose scale length – as in Watts et al, PRE 66 Cu-Kalpha was used to image rear surface transport pattern Transverse probing was used to examine front surface expansion Target plane 2D Cu Ka imager To CCD shadowgraphy Visible emisson diagnostic Pointing system up and down LULI 2008 – Experimental layout

6. Median contrastWorst contrastBest contrast 200 µm 2D Hydro simulations: match the experimental density profiles in the range 10 19 -10 20 cm -3 the density scale-length presents no variations near the critical density LULI 2008 – Interferometry data

7. Best contrast FWHM = 21.28, Peak Wavelength = 350.24 Medium contrast FWHM = 20.52 Peak Wavelength = 335.0 Worst contrast FWHM = 25.08 Peak Wavelength = 343.0 3  Peaks correspond roughly to scale length of 6-8 microns (from Ian Watts paper, PRE 66, 2002) Peak signal and bandwidth don’t change linearly with ASE. Fluctuation probably due to shot to shot fluctuation. This supports the notion that the near critical density position did not change very much by varying the ASE duration. LULI 2008 – Harmonics measurements

8. 25° half angle divergence was observed for all contrast levels LULI 2008 – Cu K-alpha measurements

9. Curves were fitted to the k-alpha peak intensities as a function of thickness for each ASE level

10. Time Laser Target Lens Filters (   & 2   filtered out) HISAC 2D Fiber Array 1D Fibre Array 40ps Time Double heating pulse structure (40 ps delay independent of the propagation layer thickness) Factor 2 increase in intensity with longer pre- pulse, but effect appears to reach saturation for the thickest targets LULI 2008 – rear surface optical emission

11. Our data for the best contrast fit well with other data in literature Quantitative agreement with hybrid simulations by J. Davies: - best contrast data well fitted by 15% laser energy absorption - worst contrast data well fitted by 30% laser energy absorption (but only for the thinnest targets) LULI 2008 – Discussion of HISAC data

12. CHANNEL FORMATION IN UNDERDENSE PLASMAS FOR FAST IGNITION INERTIAL FUSION P.A. Norreys 1,2, K.L. Lancaster 1, M. Borghesi 3, H. Chen 4, E.L. Clark 5, S. Hassan 5, J. Jiang 6, N. Kageiwa 7, N. Lopes 6, Z. Najmudin 2, C. Russo 6, G. Sarri 3, R.H.H. Scott 1,2, R. Ramis 8, A. Rehman 2, K.A. Tanaka 7, M. Temporal 8, T. Tanimoto 7, R. Trines 1, and J.R. Davies 6 1. STFC Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK 2. Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BZ UK 3. School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN, UK 4. Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA 5. Technological Educational Institute of Crete, P.O. Box 1939 IRAKLIO, Crete, GR 710 04 Greece 6. GoLP, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, 1049-001 Lisbon, Portugal 7. Graduate School of Engineering, Osaka University, Osaka 565-0871, Japan 8. ETSI Industriales, Universidad Politécnica de Madrid, Spain

13. Hole boring in fast ignition Hole-boring is an alternative to cone-shell geometry Easier to implement (target fabrication) for inertial fusion energy No debris issues

14. 3D view of experiment layout Phase 1: Interact 30ps, ~200J beam with gas jet to image channel at 10 19 to 10 21 cm-3 Phase 2: Create plasma column with 800J, 1ns Interact 30ps ~200J beam with plasma column

15. Top view of experiment layout

16. Diagnostics Electron spectrometers Optical forward scatter spectrometer – 500 nm – 1100 nm Transverse optical probe – interferometry and shadowgraphy Transverse MeV proton probe X-ray pinhole cameras Thomson parabola Ion pinhole imaging camera

17. Ar 1bar Ar 3bar Electron spectra Evidence for relativistic self focusing

18. Temperature scaling Electron energy spectra close to 800 keV – pulse experiences relativistic self focusing

19. No evidence for self modulation Laser pulse pushes plasma aside

20. Channels clearly seen in shadowgram Deuterium gas backing pressure 99 bar (~10 20 electrons cm -3 ) 2 mm Timing +30 ps laser

21. Temporal evolution of channel Deuterium gas backing pressure 72 bar (~7×10 19 electrons cm -3 ) 2 mm Timing +130 ps Timing +30 ps Timing 0 ps laser and decay into turbulence after pulse

22. 4 MeV proton radiograph Deuterium gas backing pressure 1 bar (~10 18 electrons cm -3 ) Timing = 150 ps after interaction 3 mm laser Decay into turbulence is also density dependent

23. Deuterium gas backing pressure 10 bar (~10 19 electrons cm -3 ) Timing = 150 ps after interaction 3 mm laser

24. Deuterium gas backing pressure 100 bar (~10 20 electrons cm -3 ) Timing = 150 ps after interaction 3 mm laser

25. 0.45 mm 1.53 mm Channels also visible in X-ray images with Argon 100 bar ~10 21 e - cm -3 10 bar ~10 20 e - cm -3

26. 800 J / ns laser 800 J / ns laser X-ray pinhole image Shadowgram Characterise large scalelength plasma Need to reduce intensity in next injection experiment to avoid thermal filamentation

27. Channel formation observed in X-ray images, proton radiographs and shadowgrams Extend up to 2mm in length Laser pulse simply pushes the plasma sideways – no self-modulated forward scatter or high energy electrons Laser pulse experiences relativistic self focusing

28. For absorption: Need to repeat the experiment looking near to the critical density Need also to repeat with high contrast using 2w For channelling: Need to produce long scale length well characterised plasma in solids (without destroying optics!!) and repeat experiment under these conditions Future work