Publications


In-situ determination of dispersion and resolving power in simultaneous multiple-angle XUV spectroscopy

Journal of Instrumentation 6 (2011)

U Zastrau, V Hilbert, C Brown, T Döppner, S Dziarzhytski, E Förster, E Förster, H Glenzer, S Göde, G Gregori, M Harmand, D Hochhaus, T Laarmann, J Lee, KH Meiwes-Broer, P Neumayer, A Przystawik, P Radcliffe, M Schulz, S Skruszewicz, F Tavella, J Tiggesbäumker, S Toleikis, S Toleikis, T White

We report on the simultaneous determination of non-linear dispersion functions and resolving power of three flat-field XUV grating spectrometers. A moderate-intense short-pulse infrared laser is focused onto technical aluminum which is commonly present as part of the experimental setup. In the XUV wavelength range of 10-19 nm, the spectrometers are calibrated using Al-Mg plasma emission lines. This cross-calibration is performed in-situ in the very same setup as the actual main experiment. The results are in excellent agreement with ray-tracing simulations. We show that our method allows for precise relative and absolute calibration of three different XUV spectrometers. © 2011 IOP Publishing Ltd and SISSA.


Measuring fast electron distribution functions at intensities up to 1021 W cm-2

Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (2011)

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


Particle acceleration: Pushing protons with photons

Nature Photonics 5 (2011) 134-135

P Norreys, P Norreys


Extent of validity of the hydrodynamic description of ions in dense plasmas.

Phys Rev E Stat Nonlin Soft Matter Phys 83 (2011) 015401-

JP Mithen, J Daligault, G Gregori

We show that the hydrodynamic description can be applied to modeling the ionic response in dense plasmas for a wide range of length scales that are experimentally accessible. Using numerical simulations for the Yukawa model, we find that the maximum wave number k(max) at which the hydrodynamic description applies is independent of the coupling strength, given by k(max)λ(s)≃0.43, where λ(s) is the ionic screening length. Our results show that the hydrodynamic description can be used for interpreting x-ray scattering data from fourth generation light sources and high power lasers. In addition, our investigation sheds new light on how the domain of validity of the hydrodynamic description depends on both the microscopic properties and the thermodynamic state of fluids in general.


Saturated ablation in metal hydrides and acceleration of protons and deuterons to keV energies with a soft-x-ray laser.

Phys Rev E Stat Nonlin Soft Matter Phys 83 (2011) 016403-

J Andreasson, B Iwan, A Andrejczuk, E Abreu, M Bergh, C Caleman, AJ Nelson, S Bajt, J Chalupsky, HN Chapman, RR Fäustlin, V Hajkova, PA Heimann, B Hjörvarsson, L Juha, D Klinger, J Krzywinski, B Nagler, GK Pálsson, W Singer, MM Seibert, R Sobierajski, S Toleikis, T Tschentscher, SM Vinko, RW Lee, J Hajdu, N Tîmneanu

Studies of materials under extreme conditions have relevance to a broad area of research, including planetary physics, fusion research, materials science, and structural biology with x-ray lasers. We study such extreme conditions and experimentally probe the interaction between ultrashort soft x-ray pulses and solid targets (metals and their deuterides) at the FLASH free-electron laser where power densities exceeding 10(17) W/cm(2) were reached. Time-of-flight ion spectrometry and crater analysis were used to characterize the interaction. The results show the onset of saturation in the ablation process at power densities above 10(16) W/cm(2). This effect can be linked to a transiently induced x-ray transparency in the solid by the femtosecond x-ray pulse at high power densities. The measured kinetic energies of protons and deuterons ejected from the surface reach several keV and concur with predictions from plasma-expansion models. Simulations of the interactions were performed with a nonlocal thermodynamic equilibrium code with radiation transfer. These calculations return critical depths similar to the observed crater depths and capture the transient surface transparency at higher power densities.


Towards laboratory produced relativistic electron-positron pair plasmas

High Energy Density Physics 7 (2011) 225-229

H Chen, DD Meyerhofer, SC Wilks, R Cauble, F Dollar, K Falk, G Gregori, A Hazi, EI Moses, CD Murphy, J Myatt, J Park, J Seely, R Shepherd, A Spitkovsky, C Stoeckl, CI Szabo, R Tommasini, C Zulick, P Beiersdorfer

We review recent experimental results on the path to producing electron-positron pair plasmas using lasers. Relativistic pair-plasmas and jets are believed to exist in many astrophysical objects and are often invoked to explain energetic phenomena related to Gamma Ray Bursts and Black Holes. On earth, positrons from radioactive isotopes or accelerators are used extensively at low energies (sub-MeV) in areas related to surface science positron emission tomography and basic antimatter science. Experimental platforms capable of producing the high-temperature pair-plasma and high-flux jets required to simulate astrophysical positron conditions have so far been absent. In the past few years, we performed extensive experiments generating positrons with intense lasers where we found that relativistic electron and positron jets are produced by irradiating a solid gold target with an intense picosecond laser pulse. The positron temperatures in directions parallel and transverse to the beam both exceeded 0.5 MeV, and the density of electrons and positrons in these jets are of order 1016 cm-3 and 1013 cm-3, respectively. With the increasing performance of high-energy ultra-short laser pulses, we expect that a high-density, up to 1018 cm-3, relativistic pair-plasma is achievable, a novel regime of laboratory-produced hot dense matter. © 2011 Elsevier B.V.


Measuring fast electron distribution functions at intensities up to 10 21 W cm-2

Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 653 (2011) 137-139

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

Here we present results from ultra-intense experiments demonstrating the viability of polarization spectroscopy as a diagnostic of the electron return current and spatial anisotropy and distribution function of the fast electron beam. The measurements extend to ultra-relativistic intensities of 10 21 W cm-2, including laserplasma interaction regimes important for fast ignition studies, for example HiPER, and the development of secondary sources from next generation ultra-short pulse, ultra-intense laser facilities such as Astra-Gemini and ELI. As an in situ diagnostic, spectroscopic measurements are vital to understanding fast electron beams, enabling extrapolation of results to define fast ignition inertial confinement fusion and secondary source facilities. © 2011 Elsevier B.V.


High resolution X-ray spectroscopy in fast electron transport studies

Proceedings of SPIE - The International Society for Optical Engineering 8080 (2011)

P Koester, P Koester, N Booth, CA Cecchetti, CA Cecchetti, H Chen, RG Evans, G Gregori, L Labate, L Labate, T Levato, B Li, M Makita, J Mithen, C Murphy, M Notley, R Pattathil, D Riley, N Woolsey, LA Gizzia, LA Gizzia

A detailed knowledge of the physical phenomena underlying the generation and the transport of fast electrons generated in high-intensity laser-matter interactions is of fundamental importance for the fast ignition scheme for inertial confinement fusion. Here we report on an experiment carried out with the VULCAN Petawatt beam and aimed at investigating the role of collisional return currents in the dynamics of the fast electron beam. To that scope, in the experiment counter-propagating electron beams were generated by double-sided irradiation of layered target foils containing a Ti layer. The experimental results were obtained for different time delays between the two laser beams as well as for single-sided irradiation of the target foils. The main diagnostics consisted of two bent mica crystal spectrometers placed at either side of the target foil. High-resolution X-ray spectra of the Ti emission lines in the range from the Lyα to the Kα line were recorded. In addition, 2D X-ray images with spectral resolution were obtained by means of a novel diagnostic technique, the energy-encoded pin-hole camera, based on the use of a pin-hole array equipped with a CCD detector working in single-photon regime. The spectroscopic measurements suggest a higher target temperature for well-aligned laser beams and a precise timing between the two beams. The experimental results are presented and compared to simulation results. © 2011 SPIE.


Vibrational excitation induced by electron beam and cosmic rays in normal and superconductive aluminum bars

ArXiv (2011)

M Bassan, B Buonomo, G Cavallari, E Coccia, S D'Antonio, V Fafone, LG Foggetta, C Ligi, A Marini, G Mazzitelli, G Modestino, G Pizzella, L Quintieri, F Ronga, P Valente, SM Vinko

We report new measurements of the acoustic excitation of an Al5056 superconductive bar when hit by an electron beam, in a previously unexplored temperature range, down to 0.35 K. These data, analyzed together with previous results of the RAP experiment obtained for T > 0.54 K, show a vibrational response enhanced by a factor 4.9 with respect to that measured in the normal state. This enhancement explains the anomalous large signals due to cosmic rays previously detected in the NAUTILUS gravitational wave detector.


Vibrational excitation induced by electron beam and cosmic rays in normal and superconductive aluminum bars

Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 659 (2011) 289-298

M Bassan, M Bassan, B Buonomo, G Cavallari, E Coccia, E Coccia, S Dantonio, V Fafone, V Fafone, LG Foggetta, LG Foggetta, C Ligi, A Marini, G Mazzitelli, G Modestino, G Pizzella, G Pizzella, L Quintieri, F Ronga, P Valente, SM Vinko, SM Vinko

We report new measurements of the acoustic excitation of an Al5056 superconductive bar when hit by an electron beam, in a previously unexplored temperature range, down to 0.35 K. These data, analyzed together with previous results of a dedicated experiment obtained for T >0.54K, show a vibrational response enhanced by a factor ∼4.9 with respect to that measured in the normal state. This enhancement explains the anomalous large signals due to cosmic rays previously detected in the NAUTILUS gravitational wave detector. © 2011 Elsevier B.V. All rights reserved.


Vibrational excitation induced by electron beam and cosmic rays in normal and superconductive aluminum bars

Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (2011)

M Bassan, B Buonomo, G Cavallari, E Coccia, S D'Antonio, V Fafone, LG Foggetta, C Ligi, A Marini, G Mazzitelli, G Modestino, G Pizzella, L Quintieri, F Ronga, P Valente, SM Vinko


Decay of Cystalline Order and Equilibration during the Solid-to-Plasma Transition Induced by 20-fs Microfocused 92-eV Free-Electron-Laser Pulses

PHYSICAL REVIEW SPECIAL TOPICS-ACCELERATORS AND BEAMS 14 (2011) ARTN 164801

E Galtier, FB Rosmej, T Dzelzainis, D Riley, FY Khattak, P Heimann, RW Lee, AJ Nelson, SM Vinko, T Whitcher, JS Wark, T Tschentscher, S Toleikis, RR Faeustlin, R Sobierajski, M Jurek, L Juha, J Chalupsky, V Hajkova, M Kozlova, J Krzywinski, B Nagler


In situ x-ray diffraction measurements of the c/a ratio in the high-pressure ε phase of shock-compressed polycrystalline iron

Physical Review B - Condensed Matter and Materials Physics 83 (2011)

JA Hawreliak, B El-Dasher, H Lorenzana, G Kimminau, A Higginbotham, B Nagler, SM Vinko, WJ Murphy, T Whitcher, JS Wark, S Rothman, N Park

The structure of laser-shock-compressed polycrystalline iron was probed using in situ x-ray diffraction over a pressure range spanning the α-ε phase transition. Measurements were also made of the c/a ratio in the ε phase, which, in contrast with previous in situ x-ray diffraction experiments performed on single crystals and large-scale molecular dynamics (MD) simulations are close to those found in high-pressure diamond anvil cell experiments. This is consistent with the observation that significant plastic flow occurs within the nanosecond time scale of the experiment. Furthermore, within the sensitivity of the measurement technique, the fcc phase that had been predicted by MD simulations was not observed. © 2011 American Physical society.


Simulations of neon irradiated by intense X-ray laser radiation

High Energy Density Physics 7 (2011) 111-116

O Ciricosta, HK Chung, RW Lee, JS Wark

We present simulations of the charge states produced by the interaction of intense X-ray laser radiation with a neon gas. We model the results of a recent experiment (Young et al., Nature 466, 56 (2010)), where mJ pulses of X-rays, with photon energies ranging from 800 to 2000 eV and pulse lengths ranging from 70 to 340 fs were incident on neon atoms at intensities of up to 10 18 W cm -2. Simulations using an adapted version of the SCFLY collisional-radiative code, which included the effect of electron collisions and a simple self-consistent temperature model, result in charge state distributions that are in good agreement with the experimental data. We calculate the electron temperature of the system during the evolution of the plasma, and comment upon the role that collisions may play in determining the charge state distributions as a function of the neon ion number density. © 2011 Elsevier B.V.


Experimental results performed in the framework of the HiPER European Project

Proceedings of SPIE - The International Society for Optical Engineering 8080 (2011)

D Batani, D Batani, M Koenig, S Baton, F Perez, LA Gizzi, P Koester, L Labate, J Honrubia, A Debayle, J Santos, G Schurtz, S Hulin, X Ribeyre, C Fourment, P Nicolai, B Vauzour, L Gremillet, W Nazarov, J Pasley, G Tallents, M Richetta, K Lancaster, C Spindloe, M Tolley, D Neely, P Norreys, M Kozlová, J Nejdl, B Rus, L Antonelli, A Morace, L Volpe, J Davies, J Wolowski, J Badziak

This paper presents the goals and some of the results of experiments conducted within the Working Package 10 (Fusion Experimental Programme) of the HiPER Project. These experiments concern the study of the physics connected to "Advanced Ignition Schemes", i.e. the Fast Ignition and the Shock Ignition Approaches to Inertial Fusion. Such schemes are aimed at achieving a higher gain, as compared to the classical approach which is used in NIF, as required for future reactors, and making fusion possible with smaller facilities. In particular, a series of experiments related to Fast Ignition were performed at the RAL (UK) and LULI (France) Laboratories and were addressed to study the propagation of fast electrons (created by a short-pulse ultra-high-intensity beam) in compressed matter, created either by cylindrical implosions or by compression of planar targets by (planar) laser-driven shock waves. A more recent experiment was performed at PALS and investigated the laser-plasma coupling in the 1016 W/cm2 intensity regime of interest for Shock Ignition. © 2011 SPIE.


Density fluctuations in the Yukawa one-component plasma: An accurate model for the dynamical structure factor

Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 84 (2011)

JP Mithen, J Daligault, BJB Crowley, BJB Crowley, G Gregori

Using numerical simulations, we investigate the equilibrium dynamics of a single-component fluid with Yukawa interaction potential. We show that, for a wide range of densities and temperatures, the dynamics of the system are in striking agreement with a simple model of generalized hydrodynamics. Since the Yukawa potential can describe the ion-ion interactions in a plasma, our results have significant applicability for both analyzing and interpreting the results of x-ray scattering data from high-power lasers and fourth-generation light sources. © 2011 American Physical Society.


Studying ignition schemes on European laser facilities

Nuclear Fusion 51 (2011)

S Jacquemot, S Jacquemot, F Amiranoff, SD Baton, JC Chanteloup, C Labaune, M Koenig, DT Michel, F Perez, HP Schlenvoigt, B Canaud, C Cherfils Clérouin, G Debras, S Depierreux, J Ebrardt, D Juraszek, S Lafitte, P Loiseau, JL Miquel, F Philippe, C Rousseaux, N Blanchot, CB Edwards, P Norreys, S Atzeni, A Schiavi, J Breil, JL Feugeas, L Hallo, M Lafon, X Ribeyre, JJ Santos, G Schurtz, V Tikhonchuk, A Debayle, JJ Honrubia, M Temporal, D Batani, JR Davies, F Fiuza, RA Fonseca, LO Silva, LA Gizzi, P Koester, L Labate, J Badziak, O Klimo

Demonstrating ignition and net energy gain in the near future on MJ-class laser facilities will be a major step towards determining the feasibility of Inertial Fusion Energy (IFE), in Europe as in the United States. The current status of the French Laser MégaJoule (LMJ) programme, from the laser facility construction to the indirectly driven central ignition target design, is presented, as well as validating experimental campaigns, conducted, as part of this programme, on various laser facilities. However, the viability of the IFE approach strongly depends on our ability to address the salient questions related to efficiency of the target design and laser driver performances. In the overall framework of the European HiPER project, two alternative schemes both relying on decoupling target compression and fuel heating - fast ignition (FI) and shock ignition (SI) - are currently considered. After a brief presentation of the HiPER project's objectives, FI and SI target designs are discussed. Theoretical analysis and 2D simulations will help to understand the unresolved key issues of the two schemes. Finally, the on-going European experimental effort to demonstrate their viability on currently operated laser facilities is described. © 2011 IAEA, Vienna.


In-situ determination of dispersion and resolving power in simultaneous multiple-angle XUV spectroscopy

JOURNAL OF INSTRUMENTATION 6 (2011) ARTN P10001

U Zastrau, V Hilbert, C Brown, T Doeppner, S Dziarzhytski, E Foerster, SH Glenzer, S Goede, G Gregori, M Harmand, D Hochhaus, T Laarmann, HJ Lee, K-H Meiwes-Broer, P Neumayer, A Przystawik, P Radcliffe, M Schulz, S Skruszewicz, F Tavella, J Tiggesbaeumker, S Toleikis, T White


Controlling implosion symmetry around a deuterium-tritium target

Science 327 (2010) 1208-1210

PA Norreys, 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.


X-ray polarization spectroscopy from ultra-intense interactions

Journal of Physics: Conference Series 244 (2010)

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

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 1019 - 1021 Wcm-2. We observe at 45° the Ly-α doublet using two sets of orthogonal highly-orientated pyrolytic graphite (HOPG) crystals set in 1st order for sulphur and 3rd order for nickel. © 2010 IOP Publishing Ltd.