review of uk hiper relevant experiments kate lancaster
TRANSCRIPT
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Review of UK HiPER
relevant experiments
Kate Lancaster
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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 20082)Channelling in under and near critical plasma, march 2009
Work here is new and still under analysis.....
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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
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Critical Surface
Plasma ablated by ASE pedestal
Al102550
Cu 10
Al1
CH5
0 ps laser beam
40J, 1ps (FWHM), 45° incidence10-13µm diameter spot (f/4 OAP)2 - 5 x 1019 W/cm2
ASE width(ns)
Energy contrast ratio
Type
1.1 3x10-3 best
1.9 6x10-3 median
4.3 1x10-2 worst
LULI 2008 – absorption experiment
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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
2D Cu Ka imagerTo CCD
shadowgraphy
Visible emisson diagnostic
Poi
ntin
g sy
stem
up a
nd d
own
LULI 2008 – Experimental layout
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1019
1020
1021
1022
1023
1024
-150 -100 -50 0 50
10-2
energy contrastt=4ns
#34: t=t0+4ns+-0.2ns
ne [c
m-3
]
z [µm]
1019
1020
1021
1022
1023
1024
-150 -100 -50 0 50
6x10-3
energy contrastt=1.6ns
#27: t=1.6ns+-0.2ns
ne [c
m-3
]
z [µm]
1019
1020
1021
1022
1023
1024
-150 -100 -50 0 50
2x10-3
energy contrastt=0.8ns
2.5x10-3
energy contrastt=0.9ns
3.1x10-3
energy contrastt=1ns
#07: t=t0+0.8ns+-0.2ns
ne [c
m-3
]
z [µm]
Median contrast Worst contrastBest contrast
200 µm
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
LULI 2008 – Interferometry data
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Best contrast FWHM = 21.28, Peak Wavelength = 350.24
Medium contrastFWHM = 20.52 Peak Wavelength = 335.0
Worst contrastFWHM = 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
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25° half angle divergence was observed for all contrast levels
LULI 2008 – Cu K-alpha measurements
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LULI 2008 – Cu K-alpha measurements
Curves were fitted to the k-alpha peak intensities as a function of thickness for each ASE level
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Tim
e
Laser
Target
Lens
Filters ( & 2filtered out)
HISAC
2D Fiber Array1D Fibre Array
40
ps
Tim
e
• 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
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• 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
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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, UK2. Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BZ UK3. School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN, UK4. Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA5. Technological Educational Institute of Crete, P.O. Box 1939 IRAKLIO, Crete, GR 710 04 Greece6. GoLP, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, 1049-001 Lisbon, Portugal7. Graduate School of Engineering, Osaka University, Osaka 565-0871, Japan8. ETSI Industriales, Universidad Politécnica de Madrid, Spain
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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
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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
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Top view of experiment layout
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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
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Ar 1bar
Ar 3bar
Electron spectra
Evidence for relativistic self focusing
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Temperature scaling
Electron energy spectra close to 800 keV – pulse experiences relativistic
self focusing
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No evidence for self modulation
Laser pulse pushes plasma aside
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Channels clearly seen in shadowgram
Deuterium gas backing pressure 99 bar (~1020 electrons cm-3)
2 mm
Timing +30 ps
laser
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Temporal evolution of channel
Deuterium gas backing pressure 72 bar (~7×1019 electrons cm-3)
2 mm
Timing +130 ps
Timing +30 ps
Timing 0 ps
laser
and decay into turbulence after pulse
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4 MeV proton radiograph
Deuterium gas backing pressure 1 bar (~1018 electrons cm-3)
Timing = 150 ps after interaction
3 mm
laser
Decay into turbulence is also density dependent
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Deuterium gas backing pressure 10 bar (~1019 electrons cm-3)
Timing = 150 ps after interaction
3 mm
laser
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Deuterium gas backing pressure 100 bar (~1020 electrons cm-3)
Timing = 150 ps after interaction
3 mm
laser
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0.45 mm
1.53 mm
Channels also visible in X-ray images with Argon
100 bar ~1021 e- cm-3
10 bar ~1020 e- cm-3
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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
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• 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
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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