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Review of UK HiPER relevant experiments Kate Lancaster

Review of UK HiPER relevant experiments Kate Lancaster. 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: Absorption as a function of scale length, LULI April 2008

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Review of UK HiPER relevant experiments Kate Lancaster

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  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: • Absorption as a function of scale length, LULI April 2008 • 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. LULI 2008 – absorption experiment w0 ps laser beam 40J, 1ps (FWHM), 45° incidence 10-13µm diameter spot (f/4 OAP) 2 - 5 x 1019 W/cm2 Al 10 25 50 Cu 10 CH 5 Al 1 Plasma ablated by ASE pedestal Critical Surface

  5. LULI 2008 – Experimental layout 2D Cu Ka imager To CCD Heating was diagnosed time resolved rear side optical emission –HISAC 3rd 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 shadowgraphy Visible emisson diagnostic Pointing system up and down

  6. Best contrast Median contrast Worst contrast 200 µm LULI 2008 – Interferometry data • 2D Hydro simulations: • match the experimental density profiles in the range 1019-1020 cm-3 • the density scale-length presents no variations near the critical density

  7. LULI 2008 – Harmonics measurements 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 3w 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.

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

  9. LULI 2008 – Cu K-alpha measurements Curves were fitted to the k-alpha peak intensities as a function of thickness for each ASE level

  10. 2D Fiber Array 1D Fibre Array Target Filters (w0 & 2w0 filtered out) Laser Lens HISAC Time 40ps Time LULI 2008 – rear surface optical emission • Factor 2 increase in intensity with longer pre-pulse, but effect appears to reach saturation for the thickest targets • Double heating pulse structure (40 ps delay independent of the propagation layer thickness)

  11. LULI 2008 – Discussion of HISAC data • 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)

  12. CHANNEL FORMATION IN UNDERDENSE PLASMAS FOR FAST IGNITION INERTIAL FUSION P.A. Norreys1,2, K.L. Lancaster1, M. Borghesi3, H. Chen4, E.L. Clark5, S. Hassan5, J. Jiang6, N. Kageiwa7, N. Lopes6, Z. Najmudin2, C. Russo6, G. Sarri3, R.H.H. Scott1,2, R. Ramis8, A. Rehman2, K.A. Tanaka7, M. Temporal8, T. Tanimoto7, R. Trines1, and J.R. Davies6 1. STFC Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK 2. BlackettLaboratory, 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 eFusão 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 1019 to 1021 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. Evidence for relativistic self focusing Electron spectra Ar 1bar Ar 3bar

  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 2 mm laser Deuterium gas backing pressure 99 bar (~1020 electrons cm-3) Timing +30 ps

  21. Temporal evolution of channel Deuterium gas backing pressure 72 bar (~7×1019 electrons cm-3) Timing 0 ps and decay into turbulence after pulse 2 mm laser Timing +130 ps Timing +30 ps

  22. Decay into turbulence is also density dependent 4 MeV proton radiograph Deuterium gas backing pressure 1 bar (~1018 electrons cm-3) 3 mm laser Timing = 150 ps after interaction

  23. Deuterium gas backing pressure 10 bar (~1019 electrons cm-3) 3 mm laser Timing = 150 ps after interaction

  24. Deuterium gas backing pressure 100 bar (~1020 electrons cm-3) 3 mm laser Timing = 150 ps after interaction

  25. Channels also visible in X-ray images with Argon 100 bar ~1021 e- cm-3 0.45 mm 10 bar ~1020 e- cm-3 1.53 mm

  26. Characterise large scalelength plasma X-ray pinhole image 800 J / ns laser Shadowgram 800 J / ns laser 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. Future work • 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

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