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, T Doeppner, K Falk, SH Glenzer, VN Goncharov, G Gregori, OL Landen, RL McCrory, DD Meyerhofer, P Neumayer, TC Sangster, VA Smalyuk

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 (Te) is inferred from the Doppler-broadened Compton-downshifted peak of the noncollective (αs = 1kλD > 1) x-ray scattering for Te > T Fermi. The electron density (ne) is inferred from the downshifted plasmon peak of the collective (αscatter > 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 1013 to 10 15 W/cm2 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 × 1023 cm -3 and electron temperature in the range of 10 to 25 eV are predicted. A laser-irradiated saran foil produces Cl Ly αemission. 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.

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.

The HiPER experimental road map

AIP Conference Proceedings 1209 (2010) 129-133

D Batani, S Baton, J Badziak, J Davies, L Gizzi, L Hallo, P Norreys, M Roth, J Santos, V Tickhoncuk, N Woolsey

WP10 is one of the working packages of the HiPER project and it has the goal of addressing, in a systematic and programmatic way, some of the key experimental uncertainties on the way towards fast ignition (and shock ignition) in a perspective of risk reduction, so to contribute to the definition of the basic characteristics of the HiPER project. The paper describes the key points contained in the short term HiPER experimental road map, as well as the results of two first experiments performed in "HiPER dedicated time slots" in European Laser Facilities. © 2010 American Institute of Physics.

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

Journal of Physics: Conference Series 244 (2010)

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

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.

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.

Screening of ionic cores in partially ionized plasmas within linear response

Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 81 (2010)

DO Gericke, J Vorberger, K Wünsch, G Gregori

We employ a pseudopotential approach to investigate the screening of ionic cores in partially ionized plasmas. Here, the effect of the tightly bound electrons is condensed into an effective potential between the (free) valence electrons and the ionic cores. Even for weak electron-ion coupling, the corresponding screening clouds show strong modifications from the Debye result for elements heavier than helium. Modifications of the theoretically predicted x-ray scattering signal and implications on measurements are discussed. © 2010 The American Physical Society.

Measurement of fast electrons spectra generated by interaction between solid target and peta watt laser

Journal of Physics: Conference Series 244 (2010)

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

Fast electron energy spectra have been measured for a range of intensities between 1018 Wcm-2 and 1021 Wcm-2 and for different target materials using electron spectrometers. Several experimental campaigns were conducted on peta watt laser facilities at the Rutherford Appleton Laboratory and Osaka University. In these experimental campaigns, the pulse duration was varied from 0.5 ps to 5 ps. The laser incident angle was also changed from normal incidence to 40° in p-polarized. The results show a reduction from the ponderomotive scaling on fast electrons over 1020 Wcm-2. © 2010 IOP Publishing Ltd.

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.

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.

Magnetic collimation of petawatt driven fast electron beam for prospective fast ignition studies

Journal of Physics: Conference Series 244 (2010)

S Kar, D Adams, M Borghesi, K Markey, B Ramakrishna, M Zepf, K Lancaster, P Norreys, APL Robinson, DC Carroll, P McKenna, M Quinn, X Yuan, C Bellei, J Schreiber

Collimated transport of fast electron beam through solid density matter is one of the key issues behind the success of the fast ignition scheme by means of which the required amount of ignition energy can be delivered to the hot spot region of the compressed fuel. Here we report on a hot electron beam collimation scheme in solids by tactfully using the strong magnetic fields generated by an electrical resistivity gradient according to Faraday's law. This was accomplished by appropriately fabricating the targets in such a way that the electron beam is directed to flow in a metal which is embedded in a much lower resistivity and atomic number metal. Experimental results showed guided transport of hot electron beam over hundreds of microns length inside solid density plasma, which were obtained from two experiments examining the scheme for petawatt laser driven hot electron beam while employing various target configurations. © 2010 IOP Publishing Ltd.

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.

Micron-scale fast electron filaments and recirculation determined from rear-side optical emission in high-intensity laser-solid interactions

New Journal of Physics 12 (2010)

C Bellei, SR Nagel, S Kar, A Henig, S Kneip, C Palmer, A Sävert, L Willingale, D Carroll, B Dromey, JS Green, K Markey, P Simpson, RJ Clarke, H Lowe, D Neely, C Spindloe, M Tolley, MC Kaluza, SPD Mangles, P McKenna, PA Norreys, J Schreiber, M Zepf, JR Davies, K Krushelnick, Z Najmudin

The transport of relativistic electrons generated in the interaction of petawatt class lasers with solid targets has been studied through measurements of the second harmonic optical emission from their rear surface. The high degree of polarization of the emission indicates that it is predominantly optical transition radiation (TR). A halo that surrounds the main region of emission is also polarized and is attributed to the effect of electron recirculation. The variation of the polarization state and intensity of radiation with the angle of observation indicates that the emission of TR is highly directional and provides evidence for the presence of μm-size filaments. A brief discussion on the possible causes of such a fine electron beam structure is given. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

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.

Observation of postsoliton expansion following laser propagation through an underdense plasma

Physical Review Letters 105 (2010)

G Sarri, DK Singh, JR Davies, F Fiuza, 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, PA Norreys

The expansion of electromagnetic postsolitons emerging from the interaction of a 30? ps, 3×1018Wcm⊃-2 laser pulse with an underdense deuterium plasma has been observed up to 100? ps after the pulse propagation, when large numbers of postsolitons were seen to remain in the plasma. The temporal evolution of the postsolitons has been accurately characterized with a high spatial and temporal resolution. The observed expansion is compared to analytical models and three-dimensional particle-in-cell results, revealing a polarization dependence of the postsoliton dynamics. © 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

Applications of the wave kinetic approach: From laser wakefields to drift wave turbulence

Journal of Plasma Physics 76 (2010) 903-914

RMGM Trines, R Bingham, LO Silva, JT Mendonça, PK Shukla, CD Murphy, MW Dunlop, JA Davies, R Bamford, A Vaivads, PA Norreys

Nonlinear wave-driven processes in plasmas are normally described by either a monochromatic pump wave that couples to other monochromatic waves, or as a random phase wave coupling to other random phase waves. An alternative approach involves a random or broadband pump coupling to monochromatic and/or coherent structures in the plasma. This approach can be implemented through the wave-kinetic model. In this model, the incoming pump wave is described by either a bunch (for coherent waves) or a sea (for random phase waves) of quasi-particles. This approach has been applied to both photon acceleration in laser wakefields and drift wave turbulence in magnetized plasma edge configurations. Numerical simulations have been compared to experiments, varying from photon acceleration to drift mode-zonal flow turbulence, and good qualitative correspondences have been found in all cases. © 2010 Cambridge University Press.

Metal deformation and phase transitions at extremely high strain rates

MRS BULLETIN 35 (2010) 999-1006

RE Rudd, TC Germann, BA Remington, JS Wark

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.

Design of the 10 PW OPCPA facility for the vulcan laser

Optics InfoBase Conference Papers (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 10PW 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.

Design of the 10 PW OPCPA facility for the vulcan laser

Optics InfoBase Conference Papers (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 10PW 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.