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:

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.....

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

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

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

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

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

25° half angle divergence was observed for all contrast levels

LULI 2008 – Cu K-alpha measurements

LULI 2008 – Cu K-alpha measurements

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

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

• 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

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

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

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

Top view of experiment layout

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

Ar 1bar

Ar 3bar

Electron spectra

Evidence for relativistic self focusing

Temperature scaling

Electron energy spectra close to 800 keV – pulse experiences relativistic

self focusing

No evidence for self modulation

Laser pulse pushes plasma aside

Channels clearly seen in shadowgram

Deuterium gas backing pressure 99 bar (~1020 electrons cm-3)

2 mm

Timing +30 ps

laser

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

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

Deuterium gas backing pressure 10 bar (~1019 electrons cm-3)

Timing = 150 ps after interaction

3 mm

laser

Deuterium gas backing pressure 100 bar (~1020 electrons cm-3)

Timing = 150 ps after interaction

3 mm

laser

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

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

• 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

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