Publications


Measurement of the dynamic response of compressed hydrogen by inelastic X-ray scattering

Journal of Physics: Conference Series 244 (2010)

K Falk, BJB Crowley, J Wark, G Gregori, AP Jephcoat, AK Kleppe, H Wilhelm, RR Fäustlin, S Toleikis, C Fortmann, FY Khattak, D Riley

Measurement of the dynamic properties of hydrogen and helium under extreme pressures is a key to understanding the physics of planetary interiors. The inelastic scattering signal from statically compressed hydrogen inside diamond anvil cells at 2.8 GPa and 6.4 GPa was measured at the Diamond Light Source synchrotron facility in the UK. The first direct measurement of the local field correction to the Coulomb interactions in degenerate plasmas was obtained from spectral shifts in the scattering data and compared to predictions by the Utsumi-Ichimaru theory for degenerate electron liquids. © 2010 IOP Publishing Ltd.


Controlling implosion symmetry around a deuterium-tritium target

Science 327 (2010) 1208-1210

PA Norreys

Fusion power is a step closer with the demonstration of control over the extreme thermal radiation pressure created by high-power laser beams within a cavity.


Relativistic quasimonoenergetic positron jets from intense laser-solid interactions.

Phys Rev Lett 105 (2010) 015003-

H Chen, SC Wilks, DD Meyerhofer, J Bonlie, CD Chen, SN Chen, C Courtois, L Elberson, G Gregori, W Kruer, O Landoas, J Mithen, J Myatt, CD Murphy, P Nilson, D Price, M Schneider, R Shepherd, C Stoeckl, M Tabak, R Tommasini, P Beiersdorfer

Detailed angle and energy resolved measurements of positrons ejected from the back of a gold target that was irradiated with an intense picosecond duration laser pulse reveal that the positrons are ejected in a collimated relativistic jet. The laser-positron energy conversion efficiency is ∼2×10{-4}. The jets have ∼20 degree angular divergence and the energy distributions are quasimonoenergetic with energy of 4 to 20 MeV and a beam temperature of ∼1  MeV. The sheath electric field on the surface of the target is shown to determine the positron energy. The positron angular and energy distribution is controlled by varying the sheath field, through the laser conditions and target geometry.


Design of the 10 PW OPCPA facility for the Vulcan laser

Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference: 2010 Laser Science to Photonic Applications, CLEO/QELS 2010 (2010)

I Musgrave, O Chekhlov, J Collier, R Clarke, A Dunne, S Hancock, R Heathcote, C Hernandez-Gomez, M Galimberti, A Lyachev, P Matousek, D Neely, P Norreys, I Ross, Y Tang, T Winstone, G New

We present the progress made in developing IOPW OPCPA facility for the Vulcan laser to produce pulses with focused intensities >1023 Wcm-2. This power level will be delivered by generating pulses with >300J in 30fs. These pulses will be delivered to two target areas: in one target area they will be combined with the existing Vulcan Petawatt beamline and a new target area will be created for high intensity interactions. © 2010 Optical Society of America.


Soft X-ray scattering using FEL radiation for probing near-solid density plasmas at few electron volt temperatures

High Energy Density Physics 6 (2010) 15-20

S Toleikis, RR Fäustlin, S Düsterer, T Laarmann, P Radcliffe, F Tavella, L Cao, E Förster, I Uschmann, U Zastrau, T Döppner, SH Glenzer, C Fortmann, S Göde, R Irsig, K-H Meiwes-Broer, A Przystawik, R Redmer, R Thiele, J Tiggesbäumker, NX Truong, G Gregori, J Mithen, HJ Lee, T Tschentscher, B Li

We report on soft X-ray scattering experiments on cryogenic hydrogen and simple metal samples. As a source of intense, ultrashort soft X-ray pulses we have used free-electron laser radiation at 92 eV photon energy from FLASH at DESY, Hamburg. X-ray pulses with energies up to 150 μJ and durations 15-50 fs provide interaction with the sample leading simultaneously to plasma formation and scattering. Experiments exploiting both of these interactions have been carried out, using the same experimental setup. Firstly, recording of soft X-ray inelastic scattering from near-solid density hydrogen plasmas at few electron volt temperatures confirms the feasibility of this diagnostics technique. Secondly, the soft X-ray excitation of few electron volt solid-density plasmas in bulk metal samples could be studied by recording soft X-ray line and continuum emission integrated over emission times from fs to ns. © 2009 Elsevier B.V.


Inferring the electron temperature and density of shocked liquid deuterium using inelastic X-ray scattering

Journal of Physics: Conference Series 244 (2010)

SP Regan, PB Radha, TR Boehly, VN Goncharov, RL McCrory, DD Meyerhofer, TC Sangster, VA Smalyuk, T Doeppner, SH Glenzer, OL Landen, P Neumayer, K Falk, G Gregori

An experiment designed to launch laser-ablation-driven shock waves (10 to 70 Mbar) in a planar liquid-deuterium target on the OMEGA Laser System and to diagnose the shocked conditions using inelastic x-ray scattering is described. The electron temperature (T ) is inferred from the Doppler-broadened Compton-downshifted peak of the noncollective (α = 1kλ > 1) x-ray scattering for T > T . The electron density (n ) is inferred from the downshifted plasmon peak of the collective (α > 1) x-ray scattering. A cylindrical layer of liquid deuterium is formed in a cryogenic cell with 8-μm-thick polyimide windows. The polyimide ablator is irradiated with peak intensities in the range of 10 to 10 W/cm and shock waves are launched. Predictions from a 1-D hydrodynamics code show the shocked deuterium has a thickness of ∼0.1 mm with spatially uniform conditions. For the drive intensities under consideration, electron density up to ∼5 × 10 cm and electron temperature in the range of 10 to 25 eV are predicted. A laser-irradiated saran foil produces Cl Ly emission. The spectrally resolved x-ray scattering is recorded at 90° for the noncollective scattering and at 40° for the collective scattering with a highly oriented pyrolytic graphite (HOPG) crystal spectrometer and an x-ray framing camera. © 2010 IOP Publishing Ltd.


X-ray polarization measurements of dense plasmas heated by fast electrons

AIP Conference Proceedings 1228 (2010) 79-85

N Booth, J Pasley, E Wagenaars, JN Waugh, NC Woolsey, G Gregori, B Li, LA Gizzi, P Koester, L Labate, T Levato, RJ Clarke, P Gallegos, PP Rajeev, M Makita, D Riley

The detailed knowledge of fast electron energy transport following interaction with high-intensity, ultra-short laser pulses is a key area for secondary source generation for ELI. We demonstrate polarization spectroscopy at laser intensities up to 10 Wcm . This is significant as it suggests that in situ emission spectroscopy may be used as an effective probe of fast electron velocity distributions in regimes relevant to electron transport in solid targets. Ly-α doublet emission of nickel (Z = 28) and sulphur (Z = 16) is observed to measure the degree of polarization from the Ly-α emission. Ly-α emission is unpolarized, and as such acts as a calibration source between spectrometers. The measured ratio of the X-ray σ-and π-polarization allows the possibility to infer the velocity distribution function of the fast electron beam. © 2010 American Institute of Physics.


New developments in energy transfer and transport studies in relativistic laser-plasma interactions

Plasma Physics and Controlled Fusion 52 (2010)

PA Norreys, JS Green, KL Lancaster, APL Robinson, RHH Scott, F Perez, H-P Schlenvoight, S Baton, S Hulin, B Vauzour, JJ Santos, DJ Adams, K Markey, B Ramakrishna, M Zepf, MN Quinn, XH Yuan, P McKenna, J Schreiber, JR Davies, DP Higginson, FN Beg, C Chen, T Ma, P Patel

Two critical issues related to the success of fast ignition inertial fusion have been vigorously investigated in a co-ordinated campaign in the European Union and the United States. These are the divergence of the fast electron beam generated in intense, PW laser-plasma interactions and the fast electron energy transport with the use of high intensity contrast ratio laser pulses. Proof is presented that resistivity gradient-induced magnetic fields can guide fast electrons over significant distances in (initially) cold metallic targets. Comparison of experiments undertaken in both France and the United States suggests that an important factor in obtaining efficient coupling into dense plasma is the irradiation with high intensity contrast ratio laser pulses, rather than the colour of the laser pulse itself. © 2010 IOP Publishing Ltd.


X-ray polarization spectroscopy from ultra-intense interactions

Journal of Physics: Conference Series 244 (2010)

N Booth, J Pasley, E Wagenaars, JN Waugh, NC Woolsey, G Gregori, B Li, L Gizzi, P Koester, L Labate, T Levato, R Clarke, P Gallegos, PP Rajeev, M Makita, D Riley

Detailed knowledge of fast electron energy transport following the interaction of ultrashort intense laser pulses is a key subject for fast ignition. This is a problem relevant to many areas of laser-plasma physics with particular importance to fast ignition and X-ray secondary source development, necessary for the development of large-scale facilities such as HiPER and ELI. Operating two orthogonal crystal spectrometers set at Bragg angles close to 45° determines the X-ray s- and p- polarization ratio. From this ratio, it is possible to infer the velocity distribution function of the fast electron beam within the dense plasma. We report on results of polarization measurements at high density for sulphur and nickel buried layer targets in the high intensity range of 10 - 10 Wcm . We observe at 45° the Ly-α doublet using two sets of orthogonal highly-orientated pyrolytic graphite (HOPG) crystals set in 1 order for sulphur and 3 order for nickel. © 2010 IOP Publishing Ltd.


Transport of laser accelerated proton beams and isochoric heating of matter

Journal of Physics: Conference Series 244 (2010)

M Roth, I Alber, M Günther, K Harres, F Nürnberg, A Otten, A Pelka, M Schollmeier, J Schütrumpf, V Bagnoud, A Tauschwitz, C Brown, G Gregori, J Mithen, R Clarke, R Heathcote, B Li, G Schaumann, H Daido, M Tampo, J Fernandez, K Flippo, S Gaillard, C Gauthier, D Offermann, S Glenzer, A Kritcher, N Kugland, S Lepape, M Makita, D Riley, C Niemann, AN Tauschwitz

The acceleration of intense proton and ion beams by ultra-intense lasers has matured to a point where applications in basic research and technology are being developed. Crucial for harvesting the unmatched beam parameters driven by the relativistic electron sheath is the precise control of the beam. We report on recent experiments using the PHELIX laser at GSI, the VULCAN laser at RAL and the TRIDENT laser at LANL to control and use laser accelerated proton beams for applications in high energy density research. We demonstrate efficient collimation of the proton beam using high field pulsed solenoid magnets, a prerequisite to capture and transport the beam for applications. Furthermore we report on two campaigns to use intense, short proton bunches to isochorically heat solid targets up to the warm dense matter state. The temporal profile of the proton beam allows for rapid heating of the target, much faster than the hydrodynamic response time thereby creating a strongly coupled plasma at solid density. The target parameters are then probed by X-ray Thomson scattering (XRTS) to reveal the density and temperature of the heated volume. This combination of two powerful techniques developed during the past few years allows for the generation and investigation of macroscopic samples of matter in states present in giant planets or the interior of the earth. © 2010 IOP Publishing Ltd.


Third harmonic order imaging as a focal spot diagnostic for high intensity laser-solid interactions

Laser and Particle Beams 27 (2009) 243-248

B Dromey, C Bellei, DC Carroll, RJ Clarke, JS Green, S Kar, S Kneip, K Markey, SR Nagel, L Willingale, P McKenna, D Neely, Z Najmudin, K Krushelnick, PA Norreys, M Zepf

As the state of the art for high power laser systems increases from terawatt to petawatt level and beyond, a crucial parameter for routinely monitoring high intensity performance is laser spot size on a solid target during an intense interaction in the tight focus regime (<10m). Here we present a novel, simple technique for characterizing the spatial profile of such a laser focal spot by imaging the interaction region in third harmonic order (3laser). Nearly linear intensity dependence of 3laser generation for interactions >1019Wcm2 is demonstrated experimentally and shown to provide the basis for an effective focus diagnostic. Importantly, this technique is also shown to allow in-situ diagnosis of focal spot quality achieved after reflection from a double plasma mirror setup for very intense high contrast interactions (>1020Wcm2) an important application for the field of high laser contrast interaction science. © Cambridge University Press 2009.


Soft x-ray free electron laser microfocus for exploring matter under extreme conditions.

Opt Express 17 (2009) 18271-18278

AJ Nelson, S Toleikis, H Chapman, S Bajt, J Krzywinski, J Chalupsky, L Juha, J Cihelka, V Hajkova, L Vysin, T Burian, M Kozlova, RR Fäustlin, B Nagler, SM Vinko, T Whitcher, T Dzelzainis, O Renner, K Saksl, AR Khorsand, PA Heimann, R Sobierajski, D Klinger, M Jurek, J Pelka, B Iwan, J Andreasson, N Timneanu, M Fajardo, JS Wark, D Riley, T Tschentscher, J Hajdu, RW Lee

We have focused a beam (BL3) of FLASH (Free-electron LASer in Hamburg: lambda = 13.5 nm, pulse length 15 fs, pulse energy 10-40 microJ, 5 Hz) using a fine polished off-axis parabola having a focal length of 270 mm and coated with a Mo/Si multilayer with an initial reflectivity of 67% at 13.5 nm. The OAP was mounted and aligned with a picomotor controlled six-axis gimbal. Beam imprints on poly(methyl methacrylate) - PMMA were used to measure focus and the focused beam was used to create isochoric heating of various slab targets. Results show the focal spot has a diameter of < or =1 microm. Observations were correlated with simulations of best focus to provide further relevant information.


Hybrid Simulations for the Ion Structure and Dynamics in Dense Plasmas

ATOMIC PROCESSES IN PLASMAS 1161 (2009) 280-285

G Gregori, J Vorberger, DO Gericke


Soft X-Ray Thomson scattering in warm dense hydrogen at FLASH

Proceedings of SPIE - The International Society for Optical Engineering 7451 (2009)

RR Fäustlin, S Toleikis, T Bornath, T Döppner, S Düsterer, E Förster, C Fortmann, SH Glenzer, S Göde, G Gregori, R Irsig, T Laarmann, HJ Lee, B Li, K-H Meiwes-Broer, J Mithen, A Przystawik, H Redlin, R Redmer, H Reinholz, G Röpke, F Tavella, R Thiele, J Tiggesbäumker, I Uschmann, U Zastrau, T Tschentscher

We present collective Thomson scattering with soft x-ray free electron laser radiation as a method to track the evolution of warm dense matter plasmas with ∼200 fs time resolution. In a pump-probe scheme an 800 nm laser heats a 20 ∼m hydrogen droplet to the plasma state. After a variable time delay in the order of ps the plasma is probed by an x-ray ultra violet (XUV) pulse which scatters from the target and is recorded spectrally. Alternatively, in a self-Thomson scattering experiment, a single XUV pulse heats the target while a portion of its photons are being scattered probing the target. From such inelastic x-ray scattering spectra free electron temperature and density can be inferred giving insight on relaxation time scales in plasmas as well as the equation of state. We prove the feasibility of this method in the XUV range utilizing the free electron laser facility in Hamburg, FLASH. We recorded Thomson scattering spectra for hydrogen plasma, both in the self-scattering and in the pump-probe mode using optical laser heating. © 2009 SPIE-.


Temperature profiles derived from transverse optical shadowgraphy in ultraintense laser plasma interactions at 6 × 10 W cm?

Physics of Plasmas 16 (2009)

KL Lancaster, J Pasley, JS Green, RG Evans, R Heathcote, C Hernandez Gomez, I Musgrave, PA Norreys, JN Waugh, NC Woolsey, D Batani, A Morace, S Baton, M Koenig, F Perez, L Gizzi, P Koester

A variety of targets with different dimensions and materials was irradiated using the VULCAN PW laser [C. N. Danson, Nucl. Fusion 44, S239 (2004)]. Using transverse optical shadowgraphy in conjunction with a one-dimensional radiation hydrodynamics code it was possible to determine a longitudinal temperature gradient. It was demonstrated for thick targets with a low Z substrate and a thin higher Z tracer layer at the rear that the boundary between the two materials was Rayleigh-Taylor unstable. By including a simple bubble growth model into the calculations it was possible to correct for the associated behavior with regard to temperature. The resulting temperature gradient was in good agreement with the previously published data using two different methods of determining the temperature. © 2009 American Institute of Physics.


Evolution of elastic x-ray scattering in laser-shocked warm dense lithium

Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 80 (2009)

NL Kugland, G Gregori, S Bandyopadhyay, CM Brenner, CRD Brown, C Constantin, SH Glenzer, FY Khattak, AL Kritcher, C Niemann, A Otten, J Pasley, A Pelka, M Roth, C Spindloe, D Riley

We have studied the dynamics of warm dense Li with near-elastic x-ray scattering. Li foils were heated and compressed using shock waves driven by 4-ns-long laser pulses. Separate 1-ns-long laser pulses were used to generate a bright source of 2.96 keV Cl Ly- α photons for x-ray scattering, and the spectrum of scattered photons was recorded at a scattering angle of 120° using a highly oriented pyrolytic graphite crystal operated in the von Hamos geometry. A variable delay between the heater and backlighter laser beams measured the scattering time evolution. Comparison with radiation-hydrodynamics simulations shows that the plasma is highly coupled during the first several nanoseconds, then relaxes to a moderate coupling state at later times. Near-elastic scattering amplitudes have been successfully simulated using the screened one-component plasma model. Our main finding is that the near-elastic scattering amplitudes are quite sensitive to the mean ionization state Z̄ and by extension to the choice of ionization model in the radiation- hydrodynamics simulations used to predict plasma properties within the shocked Li. © 2009 The American Physical Society.


International workshop on the fast ignition of fusion targets

Plasma Physics and Controlled Fusion 51 (2009)

P Norreys


Recent fast electron energy transport experiments relevant to fast ignition inertial fusion

Nuclear Fusion 49 (2009)

PA Norreys, RHH Scott, KL Lancaster, JS Green, APL Robinson, M Sherlock, RG Evans, MG Haines, S Kar, M Zepf, MH Key, J King, T Ma, T Yabuuchi, MS Wei, FN Beg, P Nilson, W Theobald, RB Stephens, J Valente, JR Davies, K Takeda, H Azechi, R Kodama, M Nakatsutsumi, T Tanimoto, KA Tanaka

A number of experiments have been undertaken at the Rutherford Appleton Laboratory that were designed to investigate the physics of fast electron transport relevant to fast ignition inertial fusion. The laser, operating at a wavelength of 1054 nm, provided pulses of up to 350 J of energy on target in a duration that varied in the range 0.5-5 ps and a focused intensity of up to 10 W cm. A dependence of the divergence of the fast electron beam with intensity on target has been identified for the first time. This dependence is reproduced in two-dimensional particle-in-cell simulations and has been found to be an intrinsic property of the laser-plasma interaction. A number of ideas to control the divergence of the fast electron beam are described. The fractional energy transfer to the fast electron beam has been obtained from calibrated, time-resolved, target rear-surface radiation temperature measurements. It is in the range 15-30%, increasing with incident laser energy on target. The fast electron temperature has been measured to be lower than the ponderomotive potential energy and is well described by Haines' relativistic absorption model. © 2009 IAEA, Vienna.


Proton acceleration experiments and warm dense matter research using high power lasers

Plasma Physics and Controlled Fusion 51 (2009)

M Roth, I Alber, M Günther, K Harres, F Nürnberg, A Otten, A Pelka, G Schaumann, M Schollmeier, J Schütrumpf, V Bagnoud, A Tauschwitz, CRD Brown, R Clarke, R Heathcote, B Li, H Daido, M Tampo, J Fernandez, K Flippo, S Gaillard, C Gauthier, D Offermann, M Geissel, S Glenzer, A Kritcher, N Kugland, S Lepape, G Gregori, J Mithen, M Makita, D Riley, C Niemann

The acceleration of intense proton and ion beams by ultra-intense lasers has matured to a point where applications in basic research and technology are being developed. Crucial for harvesting the unmatched beam parameters driven by the relativistic electron sheath is the precise control of the beam. In this paper we report on recent experiments using the PHELIX laser at GSI, the VULCAN laser at RAL and the TRIDENT laser at LANL to control and use laser accelerated proton beams for applications in high energy density research. We demonstrate efficient collimation of the proton beam using high field pulsed solenoid magnets, a prerequisite to capture and transport the beam for applications. Furthermore, we report on two campaigns to use intense, short proton bunches to isochorically heat solid targets up to the warm dense matter state. The temporal profile of the proton beam allows for rapid heating of the target, much faster than the hydrodynamic response time thereby creating a strongly coupled plasma at solid density. The target parameters are then probed by x-ray Thomson scattering to reveal the density and temperature of the heated volume. This combination of two powerful techniques developed during the past few years allows for the generation and investigation of macroscopic samples of matter in states present in giant planets or the interior of the earth. © 2009 IOP Publishing Ltd.


Design of a sub 100-femtosecond X-ray Streak Camera

2009 Conference on Lasers and Electro-Optics and 2009 Conference on Quantum Electronics and Laser Science Conference, CLEO/QELS 2009 (2009)

B Li, PP Rajeev, G Gregori, M Benetou, B Dobson, L Pickworth, D Neely, A Cavalleri, P Lau, J Lynn, P Jaanimagi, F Read

The temporal resolution of existing streak cameras are limited by electron transit time dispersion. Here we present a state-of-art design compensating this to achieve a breakthrough of 100fs time resolution. ©2009 IEEE.