Publications


Transport of laser accelerated proton beams and isochoric heating of matter

Journal of Physics: Conference Series 244 (2010)

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


Phonon instabilities in uniaxially compressed fcc metals as seen in molecular dynamics simulations

PHYSICAL REVIEW B 81 (2010) ARTN 092102

G Kimminau, P Erhart, EM Bringa, B Remington, JS Wark


A proposal for testing subcritical vacuum pair production with high power lasers

ArXiv (2010)

G Gregori, DB Blaschke, PP Rajeev, H Chen, RJ Clarke, T Huffman, CD Murphy, AV Prozorkevich, CD Roberts, G Röpke, SM Schmidt, SA Smolyansky, S Wilks, R Bingham

We present a proposal for testing the prediction of non-equilibrium quantum field theory below the Schwinger limit. The proposed experiments should be able to detect a measurable number of gamma rays resulting from the annihilation of pairs in the focal spot of two opposing high intensity laser beams. We discuss the dependence of the expected number of gamma rays with the laser parameters and compare with the estimated background level of gamma hits for realistic laser conditions.


The strength of single crystal copper under uniaxial shock compression at 100 GPa.

J Phys Condens Matter 22 (2010) 065404-

WJ Murphy, A Higginbotham, G Kimminau, B Barbrel, EM Bringa, J Hawreliak, R Kodama, M Koenig, W McBarron, MA Meyers, B Nagler, N Ozaki, N Park, B Remington, S Rothman, SM Vinko, T Whitcher, JS Wark

In situ x-ray diffraction has been used to measure the shear strain (and thus strength) of single crystal copper shocked to 100 GPa pressures at strain rates over two orders of magnitude higher than those achieved previously. For shocks in the [001] direction there is a significant associated shear strain, while shocks in the [111] direction give negligible shear strain. We infer, using molecular dynamics simulations and VISAR (standing for 'velocity interferometer system for any reflector') measurements, that the strength of the material increases dramatically (to approximately 1 GPa) for these extreme strain rates.


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

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.


Hot electron generation and transport using Kα emission

Journal of Physics: Conference Series 244 (2010)

KU Akli, RB Stephens, MH Key, T Bartal, FN Beg, S Chawla, CD Chen, R Fedosejevs, RR Freeman, H Friesen, E Giraldez, JS Green, DS Hey, DP Higginson, J Hund, LC Jarrott, GE Kemp, JA King, A Kryger, K Lancaster, S Lepape, A Link, T Ma, AJ MacKinnon, AG MacPhee, HS McLean, C Murphy, PA Norreys, V Ovchinnikov, PK Patel, Y Ping, H Sawada, D Schumacher, W Theobald, YY Tsui, LD Van Woerkom, MS Wei, B Westover, T Yabuuchi

We have conducted experiments on both the Vulcan and Titan laser facilities to study hot electron generation and transport in the context of fast ignition. Cu wires attached to Al cones were used to investigate the effect on coupling efficiency of plasma surround and the pre-formed plasma inside the cone. We found that with thin cones 15% of laser energy is coupled to the 40μm diameter wire emulating a 40μm fast ignition spot. Thick cone walls, simulating plasma in fast ignition, reduce coupling by x4. An increase of pre-pulse level inside the cone by a factor of 50 reduces coupling by a factor of 3. © 2010 IOP Publishing Ltd.


Bragg diffraction using a 100 ps 17.5 keV x-ray backlighter and the Bragg diffraction imager

REVIEW OF SCIENTIFIC INSTRUMENTS 81 (2010)

BR Maddox, H-S Park, J Hawreliak, A Elsholz, R Van Maren, BA Remington, A Comley, JS Wark


Observation of ultrafast nonequilibrium collective dynamics in warm dense hydrogen.

Phys Rev Lett 104 (2010) 125002-

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

We investigate ultrafast (fs) electron dynamics in a liquid hydrogen sample, isochorically and volumetrically heated to a moderately coupled plasma state. Thomson scattering measurements using 91.8 eV photons from the free-electron laser in Hamburg (FLASH at DESY) show that the hydrogen plasma has been driven to a nonthermal state with an electron temperature of 13 eV and an ion temperature below 0.1 eV, while the free-electron density is 2.8x10{20} cm{-3}. For dense plasmas, our experimental data strongly support a nonequilibrium kinetics model that uses impact ionization cross sections based on classical free-electron collisions.


Probing near-solid density plasmas using soft x-ray scattering

Journal of Physics B: Atomic, Molecular and Optical Physics 43 (2010)

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

X-ray scattering using highly brilliant x-ray free-electron laser (FEL) radiation provides new access to probe free-electron density, temperature and ionization in near-solid density plasmas. First experiments at the soft x-ray FEL FLASH at DESY, Hamburg, show the capabilities of this technique. The ultrashort FEL pulses in particular can probe equilibration phenomena occurring after excitation of the plasma using ultrashort optical laser pumping. We have investigated liquid hydrogen and find that the interaction of very intense soft x-ray FEL radiation alone heats the sample volume. As the plasma establishes, photons from the same pulse undergo scattering, thus probing the transient, warm dense matter state. We find a free-electron density of (2.6 ± 0.2) × 1020 cm-3 and an electron temperature of 14 ± 3.5 eV. In pump-probe experiments, using intense optical laser pulses to generate more extreme states of matter, this interaction of the probe pulse has to be considered in the interpretation of scattering data. In this paper, we present details of the experimental setup at FLASH and the diagnostic methods used to quantitatively analyse the data. © 2010 IOP Publishing Ltd.


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.


Electron energy deposition to the fusion target core for fast ignition

Journal of Physics: Conference Series 244 (2010)

WM Wang, ZM Sheng, PA Norreys, M Sherlock, R Trines, APL Robinson, YT Li, B Hao, J Zhang

Heating of the target core for fast ignition by electron beams is investigated by two-dimensional collisional particle-in-cell simulations. It is found that the electron beams emitted from the core surface with the initial energy of 1.4MeV, 2.4MeV, and 4.2MeV can heat most efficiently the core with ρr = 0.75g/cm2, 1.5g/cm2, and 3g/cm2, respectively, when taking ρ 300g/cm3, where ρ and r are the mass density and radius of the core, respectively. © 2010 IOP Publishing Ltd.


Laser-driven fast electron collimation in targets with resistivity boundary

Physical Review Letters 105 (2010)

B Ramakrishna, S Kar, APL Robinson, DJ Adams, K Markey, MN Quinn, XH Yuan, P McKenna, KL Lancaster, JS Green, RHH Scott, PA Norreys, J Schreiber, M Zepf

We demonstrate experimentally that the relativistic electron flow in a dense plasma can be efficiently confined and guided in targets exhibiting a high-resistivity-core-low-resistivity-cladding structure analogous to optical waveguides. The relativistic electron beam is shown to be confined to an area of the order of the core diameter (50μm), which has the potential to substantially enhance the coupling efficiency of electrons to the compressed fusion fuel in the Fast Ignitor fusion in full-scale fusion experiments. © 2010 The American Physical Society.


Experimental detection of post-soliton structures following high intensity laser interaction with a sub-critical gas jet

37th EPS Conference on Plasma Physics 2010, EPS 2010 3 (2010) 1960-1963

G Sarri, DK Singh, JR Davies, KL Lancaster, EL Clark, S Hassan, J Jiang, N Kageiwa, N Lopes, A Rehman, C Russo, RHH Scott, T Tanimoto, Z Najmudin, KA Tanaka, M Tatarakis, M Borghesi, P Norreys


Static ion structure factor for dense plasmas: Semi-classical and ab initio calculations

High Energy Density Physics 6 (2010) 305-310

V Schwarz, B Holst, T Bornath, C Fortmann, W-D Kraeft, R Thiele, R Redmer, G Gregori, HJ Lee, T Döppner, SH Glenzer

We calculate the static structure factor of dense multi-component plasmas. Large scale ab initio finite-temperature DFT molecular dynamics simulations are performed in order to cover the region where a consistent quantum treatment for the electrons is inevitable. Especially, the behavior at small wave numbers k can be inferred from the relation to the isothermal compressibility. Alternatively, the static structure factor is obtained by solving the integral equations for the pair correlation functions within the hypernetted chain (HNC) scheme. For this purpose we derive new effective two-particle quantum potentials for the interactions between the charge carriers from the full two-particle Slater sum by accounting for bound states. Comparison to the ab initio molecular dynamics simulations enables us to determine the short-range behavior of the effective electron-ion quantum potentials. Results for the static structure factor are presented for beryllium plasmas at solid density and at threefold compression. © 2009 Elsevier B.V.


Electron trapping and acceleration on a downward density ramp: A two-stage approach

New Journal of Physics 12 (2010)

RMGM Trines, R Bingham, Z Najmudin, S Mangles, LO Silva, R Fonseca, PA Norreys

In a recent experiment at Lawrence Berkeley National Laboratory (Geddes et al 2008 Phys. Rev. Lett. 100 215004), electron bunches with about 1 MeV mean energy and small absolute energy spread (about 0.3 MeV) were produced by plasma wave breaking on a downward density ramp. It was then speculated that such a bunch might be accelerated further in a plasma of low constant density, while mostly preserving its small absolute energy spread. This would then lead to a bunch with a high mean energy and very low relative energy spread. In this paper, trapping of a low-energy, low-spread electron bunch on a downward density ramp, followed by acceleration in a constant-density plasma, has been explored through particle-in-cell simulations. It has been found that the scheme works best when it is used as a separate injection stage for a laserwakefield accelerator, where the injection and acceleration stages are separated by a vacuum gap. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.


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.


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.


The Vulcan 10 PW project

Journal of Physics: Conference Series 244 (2010)

C Hernandez-Gomez, SP Blake, O Chekhlov, RJ Clarke, AM Dunne, M Galimberti, S Hancock, R Heathcote, P Holligan, A Lyachev, P Matousek, IO Musgrave, D Neely, PA Norreys, I Ross, Y Tang, TB Winstone, BE Wyborn, J Collier

The aim of this project is to establish a 10 PW facility on the Vulcan laser system capable of being focussed to intensities of at least 10 23 Wcm-2 and integrate this into a flexible and unique user facility This paper will present progress made in Phase one developing the 10PW Front End as well as the concept for the new Vulcan 10 PW facility. The new facility will be configured in a unique way to maximise the scientific opportunities presented through a combination with the existing capabilities already established on Vulcan. This ground breaking development will open up a range of new scientific opportunities. © 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.


Electron bunch length measurements from laser-accelerated electrons using single-shot thz time-domain interferometry

Physical Review Letters 104 (2010)

AD Debus, M Bussmann, U Schramm, R Sauerbrey, CD Murphy, Z Major, R Hörlein, L Veisz, K Schmid, J Schreiber, K Witte, SP Jamison, JG Gallacher, DA Jaroszynski, MC Kaluza, B Hidding, S Kiselev, R Heathcote, PS Foster, D Neely, EJ Divall, CJ Hooker, JM Smith, K Ertel, AJ Langley, P Norreys, JL Collier, S Karsch

Laser-plasma wakefield-based electron accelerators are expected to deliver ultrashort electron bunches with unprecedented peak currents. However, their actual pulse duration has never been directly measured in a single-shot experiment. We present measurements of the ultrashort duration of such electron bunches by means of THz time-domain interferometry. With data obtained using a 0.5 J, 45 fs, 800 nm laser and a ZnTe-based electro-optical setup, we demonstrate the duration of laser-accelerated, quasimonoenergetic electron bunches [best fit of 32 fs (FWHM) with a 90% upper confidence level of 38 fs] to be shorter than the drive laser pulse, but similar to the plasma period. © 2010 The American Physical Society.