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  • Journal article
    Mangles SPD, Smid M, Gallardo Gonzalez I, Ekerfelt H, Bjorklund Svensson J, Hansson M, Wood JC, Persson A, Lundh O, Falk Ket al., 2017,

    Highly efficient angularly resolving x-ray spectrometer optimized for absorption measurements with collimated sources

    , Review of Scientific Instruments, Vol: 88, ISSN: 1089-7623

    Highly collimated betatron radiation from a laser wakefield accelerator is a promising tool for spectroscopic measurements. Therefore, there is a requirement to create spectrometers suited to the unique properties of such a source. We demonstrate a spectrometer which achieves an energy resolution of <5 eV at 9 keV (E∕ΔE>1800) and is angularly resolving the x-ray emission allowing the reference and spectrum to be recorded at the same time. The single photon analysis is used to significantly reduce the background noise. Theoretical performance of various configurations of the spectrometer is calculated by a ray-tracing algorithm. The properties and performance of the spectrometer including the angular and spectral resolution are demonstrated experimentally on absorption above the K-edge of a Cu foil backlit by a laser-produced betatron radiation x-ray beam.

  • Journal article
    Alejo A, Krygier AG, Ahmed H, Morrison JT, Clarke RJ, Fuchs J, Green A, Green JS, Jung D, Kleinschmidt A, Najmudin Z, Nakamura H, Norreys P, Notley M, Oliver M, Roth M, Vassura L, Zepf M, Borghesi M, Freeman RR, Kar Set al., 2017,

    High flux, beamed neutron sources employing deuteron-rich ion beams from D2O-ice layered targets

    , PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 59, ISSN: 0741-3335
  • Journal article
    Robinson TS, Consoli F, Giltrap S, Eardley S, Hicks G, Ditter E, Ettlinger O, Stuart N, Notley M, De Angelis R, Najmudin Z, Smith Ret al., 2017,

    Low-noise time-resolved optical sensing of electromagnetic pulses from petawatt laser-matter interactions

    , Scientific Reports, Vol: 7, ISSN: 2045-2322

    We report on the development and deployment of an optical diagnostic for single-shot measurement of the electric-field components of electromagnetic pulses from high-intensity laser-matter interactions in a high-noise environment. The electro-optic Pockels effect in KDP crystals was used to measure transient electric fields using a geometry easily modifiable for magnetic field detection via Faraday rotation. Using dielectric sensors and an optical fibre-based readout ensures minimal field perturbations compared to conductive probes and greatly limits unwanted electrical pickup between probe and recording system. The device was tested at the Vulcan Petawatt facility with 1020 W cm−2 peak intensities, the first time such a diagnostic has been used in this regime. The probe crystals were located ~1.25 m from target and did not require direct view of the source plasma. The measured signals compare favourably with previously reported studies from Vulcan, in terms of the maximum measured intra-crystal field of 10.9 kV/m, signal duration and detected frequency content which was found to match the interaction chamber’s horizontal-plane fundamental harmonics of 76 and 101 MHz. Methods for improving the diagnostic for future use are also discussed in detail. Orthogonal optical probes offer a low-noise alternative for direct simultaneous measurement of each vector field component.

  • Conference paper
    Martin P, Doria D, Romagnani L, Ahmed H, McIlvenny A, Scullion C, Williamson SDR, Ditter EJ, Hicks G, Ettlinger OC, Scott GG, Symes DR, Booth N, Sgattoni A, Macchi A, Kar S, McKenna P, Najmudin Z, Neely D, Zepf M, Borghesi Met al., 2017,

    Transition to light sail acceleration using ultraintense femtosecond pulses

    Presented are results from experimental campaigns undertaken on the Gemini laser system at the Central Laser Facility in the UK. In these experiments amorphous carbon targets ranging in thickness from 10nm to 100nm were irradiated with high contrast 40fs pulses with an intensity up to 1021 W/cm2, for both circular and linear polarisations and the resulting proton and ion spectra compared. Examining the highest energies achieved for a given polarisation and target thickness, allows to identify the transition from TNSA to LS. Observations of the optimal target thickness for ion acceleration are compared to analytical predictions from LS theory, in addition to results from Particle in Cell modelling.

  • Journal article
    Sarri G, Warwick J, Schumaker W, Poder K, Cole J, Doria D, Dzelzainis T, Krushelnick K, Kuschel S, Mangles SPD, Najmudin Z, Romagnani L, Samarin GM, Symes D, Thomas AGR, Yeung M, Zepf Met al., 2016,

    Spectral and spatial characterisation of laser-driven positron beams

    , PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 59, ISSN: 0741-3335
  • Conference paper
    Scullion C, Doria D, Romagnani L, Ahmed H, Alejo A, Ettlinger OC, Gray RJ, Green J, Hicks GS, Jung D, Naughton K, Padda H, Poder K, Scott GG, Symes DR, Kar S, McKenna P, Najmudin Z, Neely D, Zepf M, Borghesi Met al., 2016,

    Angularly resolved characterization of ion beams from laser-ultrathin foil interactions

    , 4th International Conference on Frontiers in Diagnostics Technologies, Publisher: IOP PUBLISHING LTD, ISSN: 1748-0221
  • Conference paper
    Ting A, Hafizi B, Helle M, Chen Y-H, Gordon D, Kaganovich D, Polyanskiy M, Pogorelsky I, Babzien M, Miao C, Dover N, Najmudin Z, Ettlinger Oet al., 2016,

    Staging and Laser Acceleration of Ions in Underdense Plasma

    , 17th Advanced Accelerator Concepts Workshop (AAC), Publisher: AMER INST PHYSICS, ISSN: 0094-243X
  • Conference paper
    Chen Y-H, Helle M, Ting A, Gordon D, Dover N, Ettlinger O, Najmudin Z, Polyanskiy M, Pogorelsky I, Babzien Met al., 2016,

    Laser Acceleration of Protons with an Optically Shaped, Near-Critical Hydrogen Gas Target

    , 17th Advanced Accelerator Concepts Workshop (AAC), Publisher: AMER INST PHYSICS, ISSN: 0094-243X
  • Journal article
    Smyth AG, Sarri G, Vranic M, Amano Y, Doria D, Guillaume E, Habara H, Heathcote R, Hicks G, Najmudin Z, Nakamura H, Norreys PA, Kar S, Silva LO, Tanaka KA, Vieira J, Borghesi Met al., 2016,

    Erratum: “Magnetic field generation during intense laser channelling in underdense plasma” [Phys. Plasmas 23, 063121 (2016)]

    , Physics of Plasmas, Vol: 23, ISSN: 1089-7674
  • Journal article
    Smyth AG, Sarri G, Vranic M, Amano Y, Doria D, Guillaume E, Habara H, Heathcote R, Hicks G, Najmudin Z, Nakamura H, Norreys PA, Kar S, Silva LO, Tanaka KA, Vieira J, Borghesi Met al., 2016,

    Magnetic field generation during intense laser channelling in underdense plasma

    , Physics of Plasmas, Vol: 23, ISSN: 1089-7674

    Channel formation during the propagation of a high-energy (120 J) and long duration (30 ps) laser pulse through an underdense deuterium plasma has been spatially and temporally resolved via means of a proton imaging technique, with intrinsic resolutions of a few μm and a few ps, respectively. Conclusive proof is provided that strong azimuthally symmetric magnetic fields with a strength of around 0.5 MG are created inside the channel, consistent with the generation of a collimated beam of relativistic electrons. The inferred electron beam characteristics may have implications for the cone-free fast-ignition scheme of inertial confinement fusion.

  • Conference paper
    Bracco C, Amorim LD, Assmann R, Batsch F, Bingham R, Burt G, Buttenschoen B, Butterworth A, Caldwell A, Chattopadhyay S, Cipiccia S, Deacon LC, Doebert S, Dorda U, Feldbaumer E, Fonseca RA, Fedossev V, Goddard B, Grebenyuk J, Grulke O, Gschwendtner E, Hansen J, Hessler C, Hofle W, Holloway J, Jaroszynski D, Jenkins M, Jensen L, Jolly S, Jones R, Kasim MF, Lopes N, Lotov K, Mandry SR, Martyanov M, Meddahi M, Mete O, Minakov V, Moody J, Muggli P, Najmudin Z, Norreys PA, Oez E, Pardons A, Petrenko A, Pukhov A, Rieger K, Reimann O, Seryi AA, Shaposhnikova E, Sherwood P, Silva LO, Sosedkin A, Tarkeshian R, Trines RMGM, Velotti FM, Vieira J, Vincke H, Welsch C, Wing M, Xia Get al., 2016,

    AWAKE: A Proton-Driven Plasma Wakefield Acceleration Experiment at CERN

    , 37th International Conference on High Energy Physics (ICHEP), Publisher: ELSEVIER SCIENCE BV, Pages: 175-180, ISSN: 2405-6014
  • Journal article
    Siminos E, Skupin S, Savert A, Cole JM, Mangles SPD, Kaluza MCet al., 2016,

    Modeling ultrafast shadowgraphy in laser-plasma interaction experiments

    , Plasma Physics and Controlled Fusion, Vol: 58, ISSN: 1361-6587

    Ultrafast shadowgraphy is a new experimental technique that uses few cycle laser pulses to imagedensity gradients in a rapidly evolving plasma. It enables structures that move at speeds close tothe speed of light, such as laser driven wakes, to be visualized. Here we study the process of shadowgraphicimage formation during the propagation of a few cycle probe pulse transversely througha laser-driven wake using three-dimensional particle-in-cell simulations. In order to construct syntheticshadowgrams a near-field snapshot of the ultrashort probe pulse is analyzed by means ofFourier optics, taking into account the effect of a typical imaging setup. By comparing syntheticand experimental shadowgrams we show that the generation of synthetic data is crucial for the correctinterpretation of experiments. Moreover, we study the dependence of synthetic shadowgramson various parameters such as the imaging system aperture, the position of the object plane andthe probe pulse delay, duration and wavelength. Finally, we show that time-dependent informationfrom the interaction can be recovered from a single shot by using a broadband, chirped probe pulseand subsequent spectral filtering.

  • Journal article
    Kononenko O, Lopes NC, Cole JM, Kamperidis C, Mangles SPD, Najmudin Z, Osterhoff J, Poder K, Rusby D, Symes DR, Warwick J, Wood JC, Palmer CAJet al., 2016,

    2D hydrodynamic simulations of a variable length gas target for density down-ramp injection of electrons into a laser wakefield accelerator

    , Nuclear Instruments & Methods in Physics Research Section A - Accelerators Spectrometers Detectors and Associated Equipment, Vol: 829, Pages: 125-129, ISSN: 0168-9002

    In this work, two-dimensional (2D) hydrodynamic simulations of a variable length gas cell were performed using the open source fluid code OpenFOAM. The gas cell was designed to study controlled injection of electrons into a laser-driven wakefield at the Astra Gemini laser facility. The target consists of two compartments: an accelerator and an injector section connected via an aperture. A sharp transition between the peak and plateau density regions in the injector and accelerator compartments, respectively, was observed in simulations with various inlet pressures. The fluid simulations indicate that the length of the down-ramp connecting the sections depends on the aperture diameter, as does the density drop outside the entrance and the exit cones. Further studies showed, that increasing the inlet pressure leads to turbulence and strong fluctuations in density along the axial profile during target filling, and consequently, is expected to negatively impact the accelerator stability.

  • Journal article
    Behm KT, Zhao TZ, Cole JM, Maksimchuk A, Mangles SPD, Nees J, Wood JC, Yanovsky V, Krushelnick K, Thomas AGRet al., 2016,

    Ionization injection effects in x-ray spectra generated by betatron oscillations in a laser wakefield accelerator

    , Plasma Physics and Controlled Fusion, Vol: 58, ISSN: 1361-6587
  • Conference paper
    Symes DR, Najmudin Z, Cole JM, Wood JC, Lopes NC, Poder K, Abel P, Abel RL, Alatabi S, Kneip S, Mecseki K, Winkler M, Foster PS, Norris DP, Teboul L, Johnson S, Szoke-Kovacs Z, Sandholzer M, Botchway S, Gratton S, Hill MA, De Lazzari M, Thomson Jet al., 2016,

    High-resolution tomographic imaging using coherent hard x-rays from compact laser driven accelerators

    , Compact EUV & X-ray Light Sources 2016, Publisher: OSA Publishing

    Extremely bright coherent femtosecond x-ray pulses are generated in compact laserdriven electron accelerators. Micro-tomography obtained with the Gemini laser indicates the usefulness of these sources in research and clinical applications.

  • Journal article
    Pogorelsky IV, Babzien M, Ben-Zvi I, Polyanskiy MN, Skaritka J, Tresca O, Dover NP, Najmudin Z, Lu W, Cook N, Ting A, Chen Y-Het al., 2016,

    Extending laser plasma accelerators into the mid-IR spectral domain with a next-generation ultra-fast CO<sub>2</sub> laser

    , PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 58, ISSN: 0741-3335
  • Conference paper
    Gschwendtner E, Adli E, Amorim L, Apsimon R, Assmann R, Bachmann A-M, Batsch F, Bauche J, Olsen VKB, Bernardini M, Bingham R, Biskup B, Bohl T, Bracco C, Burrows PN, Burt G, Buttenschoen B, Butterworth A, Caldwell A, Cascella M, Chevallay E, Cipiccia S, Damerau H, Deacon L, Dirksen R, Doebert S, Dorda U, Farmer J, Fedosseev V, Feldbaumer E, Fiorito R, Fonseca R, Friebel F, Gorn AA, Grulke O, Hansen J, Hessler C, Hofle W, Holloway J, Huether M, Jaroszynski D, Jensen L, Jolly S, Joulaei A, Kasim M, Keeble F, Li Y, Liu S, Lopes N, Lotov KV, Mandry S, Martorelli R, Martyanov M, Mazzoni S, Mete O, Minakov VA, Mitchell J, Moody J, Muggli P, Najmudin Z, Norreys R, Oez E, Pardons A, Pepitone K, Petrenko A, Plyushchev G, Pukhov A, Rieger K, Ruhl H, Salveter E, Savard N, Schmidt J, Seryi A, Shaposhnikova E, Sheng ZM, Sherwood R, Silva L, Soby L, Sosedkin AP, Spitsyn RI, Trines R, Tuev PV, Turner M, Verzilov V, Vieira J, Vincke H, Wei Y, Welsch CP, Wing M, Xia G, Zhang Het al., 2016,

    AWAKE, The Advanced Proton Driven Plasma Wakefield Acceleration Experiment at CERN

    , 2nd Workshop on European Advanced Accelerator Concepts (EAAC), Publisher: ELSEVIER SCIENCE BV, Pages: 76-82, ISSN: 0168-9002
  • Conference paper
    King M, Gray RJ, Powell HW, MacLellan DA, Gonzalez-Izquierdo B, Stockhausen LC, Hicks GS, Dover NP, Rusby DR, Carroll DC, Padda H, Torres R, Kar S, Clarke RJ, Musgrave IO, Najmudin Z, Borghesi M, Neely D, McKenna Pet al., 2016,

    Ion acceleration and plasma jet formation in ultra-thin foils undergoing expansion and relativistic transparency

    , 2nd Workshop on European Advanced Accelerator Concepts (EAAC), Publisher: Elsevier, Pages: 163-166, ISSN: 0168-9002

    At sufficiently high laser intensities, the rapid heating to relativistic velocities and resulting decompression of plasma electrons in an ultra-thin target foil can result in the target becoming relativistically transparent to the laser light during the interaction. Ion acceleration in this regime is strongly affected by the transition from an opaque to a relativistically transparent plasma. By spatially resolving the laser-accelerated proton beam at near-normal laser incidence and at an incidence angle of 30°, we identify characteristic features both experimentally and in particle-in-cell simulations which are consistent with the onset of three distinct ion acceleration mechanisms: sheath acceleration; radiation pressure acceleration; and transparency-enhanced acceleration. The latter mechanism occurs late in the interaction and is mediated by the formation of a plasma jet extending into the expanding ion population. The effect of laser incident angle on the plasma jet is explored.

  • Journal article
    Dover N, Cook N, Tresca O, Ettlinger O, Maharjan C, Polyanskiy M, Shkolnikov P, Pogorelsky I, Najmudin Zet al., 2016,

    Optical shaping of gas targets for laser plasma ion sources

    , Journal of Plasma Physics, Vol: 82, ISSN: 1469-7807

    We report on the experimental demonstration of a technique to generate steep densitygradients in gas jet targets of interest to laser plasma ion acceleration. By using anintentional low energy prepulse, we generated a hydrodynamic blast wave in the gas toshape the target prior to the arrival of an intense CO2 (λ ≈ 10 µm) drive pulse. Thistechnique has been recently shown to facilitate the generation of ion beams by shockwaveacceleration (Tresca et al. 2015). Here, we discuss and introduce a model to understandthe generation of these blast waves and discuss in depth the experimental realisationof the technique, supported by hydrodynamics simulations. With appropriate prepulseenergy and timing, this blast wave can generate steepened density gradients as short asl ≈ 20 µm (1/e), opening up new possibilities for laser-plasma studies with near-criticalgaseous targets.

  • Journal article
    Dover N, Palmer CAJ, Streeter MJV, Ahmed H, Albertazzi B, Borghesi M, Carroll DC, Fuchs J, Heathcote R, Hilz P, Kakolee KF, Kar S, Kodama R, Kon A, MacLellan DA, McKenna P, Nagel SR, Neely D, Notley MM, Nakatsutsumi M, Prasad R, Scott G, Tampo M, Zepf M, Schreiber J, Najmudin Zet al., 2016,

    Buffered high charge spectrally-peaked proton beams in the relativistic-transparency regime

    , New Journal of Physics, Vol: 18, ISSN: 1367-2630

    Spectrally-peaked proton beams of high charge (Ep ≈ 8 MeV, ∆E ≈4 MeV, N ≈ 50 nC ) have been observed from the interaction of an intense laser(> 1019 Wcm−2) with ultrathin CH foils, as measured by spectrally-resolved full beamprofiles. These beams are reproducibly generated for foil thicknesses 5-100 nm, andexhibit narrowing divergence with decreasing target thickness down to ≈ 8◦for 5 nm.Simulations demonstrate that the narrow energy spread feature is a result of bufferedacceleration of protons. The radiation pressure at the front of the target results inasymmetric sheath fields which permeate throughout the target, causing preferentialforward acceleration. Due to their higher charge-to-mass ratio, the protons outrun acarbon plasma driven in the relativistic transparency regime.

  • Journal article
    Caldwell A, Adli E, Amorim L, Apsimon R, Argyropoulos T, Assmann R, Bachmann AM, Batsch F, Bauche J, Berglyd Olsen VK, Bernardini M, Bingham R, Biskup B, Bohl T, Bracco C, Burrows PN, Burt G, Buttenschön B, Butterworth A, Cascella M, Chattopadhyay S, Chevallay E, Cipiccia S, Damerau H, Deacon L, Dirksen P, Doebert S, Dorda U, Elsen E, Farmer J, Fartoukh S, Fedosseev V, Feldbaumer E, Fiorito R, Fonseca R, Friebel F, Geschonke G, Goddard B, Gorn AA, Grulke O, Gschwendtner E, Hansen J, Hessler C, Hillenbrand S, Hofle W, Holloway J, Huang C, Hüther M, Jaroszynski D, Jensen L, Jolly S, Joulaei A, Kasim M, Keeble F, Kersevan R, Kumar N, Li Y, Liu S, Lopes N, Lotov KV, Lu W, Machacek J, Mandry S, Martin I, Martorelli R, Martyanov M, Mazzoni S, Meddahi M, Merminga L, Mete O, Minakov VA, Mitchell J, Moody J, Müller AS, Najmudin Z, Noakes TCQ, Norreys P, Osterhoff J, Öz E, Pardons A, Pepitone K, Petrenko Aet al., 2016,

    Path to AWAKE: Evolution of the concept

    , Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol: 829, Pages: 3-16, ISSN: 0168-9002

    This paper describes the conceptual steps in reaching the design of the AWAKE experiment currently under construction at CERN. We start with an introduction to plasma wakefield acceleration and the motivation for using proton drivers. We then describe the self-modulation instability - a key to an early realization of the concept. This is then followed by the historical development of the experimental design, where the critical issues that arose and their solutions are described. We conclude with the design of the experiment as it is being realized at CERN and some words on the future outlook. A summary of the AWAKE design and construction status as presented in this conference is given in Gschwendtner et al. [1].

  • Journal article
    Cole JM, Wood JC, Lopes NC, Poder K, Abel RL, Alatabi S, Bryant JSJ, Jin A, Kneip S, Mecseki K, Parker S, Symes DR, Sandholzer MA, Mangles SPD, Najmudin Zet al., 2016,

    Tomography of human trabecular bone with a laser-wakefield driven x-ray source

    , Plasma Physics and Controlled Fusion, Vol: 58, ISSN: 1361-6587

    A laser-wakefield driven x-ray source is used for the radiography of human bone. The betatron motion of accelerated electrons generates x-rays which are hard (critical energy ${{E}_{\text{crit}}}>30$ keV), have small source size (<3 μm) and high average brightness. The x-rays are generated from a helium gas cell which is near-instantly replenishable, and thus the average photon flux is limited by the repetition rate of the driving laser rather than the breakdown of the x-ray source. A tomograph of a human bone sample was recorded with a resolution down to 50 μm. The photon flux was sufficiently high that a radiograph could be taken with each laser shot, and the fact that x-ray beams were produced on 97% of shots minimised failed shots and facilitated full micro-computed tomography in a reasonable time scale of several hours, limited only by the laser repetition rate. The x-ray imaging beamline length (not including the laser) is shorter than that of a synchrotron source due to the high accelerating fields and small source size. Hence this interesting laboratory-based source may one day bridge the gap between small microfocus x-ray tubes and large synchrotron facilities.

  • Journal article
    Turcu ICE, Negoita F, Jaroszynski DA, Mckenna P, Balascuta S, Ursescu D, Dancus I, Cernaianu MO, Tataru MV, Ghenuche P, Stutman D, Boianu A, Risca M, Toma M, Petcu C, Acbas G, Yoffe SR, Noble A, Ersfeld B, Brunetti E, Capdessus R, Murphy C, Ridgers CP, Neely D, Mangles SPD, Gray RJ, Thomas AGR, Kirk JG, Ilderton A, Marklund M, Gordon DF, Hafizi B, Kaganovich D, Palastro JP, D'Humieres E, Zepf M, Sarri G, Gies H, Karbstein F, Schreiber J, Paulus GG, Dromey B, Harvey C, Di Piazza A, Keitel CH, Kaluza MC, Gales S, Zamfir NVet al., 2016,

    HIGH FIELD PHYSICS AND QED EXPERIMENTS AT ELI-NP

    , ROMANIAN REPORTS IN PHYSICS, Vol: 68, Pages: S145-S231, ISSN: 1221-1451
  • Conference paper
    Cook N, Tresca O, Dover NP, Maharjan C, Polyanskiy MN, Najmudin Z, Shkolnikov P, Pogorelsky Iet al., 2016,

    Hydrodynamic Shaping of Gas Jets for Laser Driven Shock Acceleration of Helium Ions

    , 16th Advanced Accelerator Concepts Workshop, Publisher: AMER INST PHYSICS, ISSN: 0094-243X
  • Conference paper
    Najmudin Z, Fiuza F, Fernandez JC, 2016,

    Summary of Working Group 6: Ion Acceleration with Lasers

    , 16th Advanced Accelerator Concepts Workshop, Publisher: AMER INST PHYSICS, ISSN: 0094-243X
  • Journal article
    Deas RM, Wilson LA, Rusby D, Alejo A, Allott R, Black PP, Black SE, Borghesi M, Brenner CM, Bryant J, Clarke RJ, Collier JC, Edwards B, Foster P, Greenhalgh J, Hernandez-Gomez C, Kar S, Lockley D, Moss RM, Najmudin Z, Pattathil R, Symes D, Whittle MD, Wood JC, McKenna P, Neely Det al., 2015,

    A laser driven pulsed X-ray backscatter technique for enhanced penetrative imaging

    , Journal of X-Ray Science and Technology, Vol: 23, Pages: 791-797, ISSN: 1095-9114

    X-ray backscatter imaging can be used for a wide range of imaging applications, in particular for industrial inspection and portal security. Currently, the application of this imaging technique to the detection of landmines is limited due to the surrounding sand or soil strongly attenuating the 10s to 100s of keV X-rays required for backscatter imaging. Here, we introduce a new approach involving a 140 MeV short-pulse (< 100 fs) electron beam generated by laser wakefield acceleration to probe the sample, which produces Bremsstrahlung X-rays within the sample enabling greater depths to be imaged. A variety of detector and scintillator configurations are examined, with the best time response seen from an absorptive coated BaF2 scintillator with a bandpass filter to remove the slow scintillation emission components. An X-ray backscatter image of an array of different density and atomic number items is demonstrated. The use of a compact laser wakefield accelerator to generate the electron source, combined with the rapid development of more compact, efficient and higher repetition rate high power laser systems will make this system feasible for applications in the field.

  • Journal article
    Doria D, Kar S, Ahmed H, Alejo A, Fernandez J, Cerchez M, Gray RJ, Hanton F, MacLellan DA, McKenna P, Najmudin Z, Neely D, Romagnani L, Ruiz JA, Sarri G, Scullion C, Streeter M, Swantusch M, Willi O, Zepf M, Borghesi Met al., 2015,

    Calibration of BAS-TR image plate response to high energy (3-300 MeV) carbon ions

    , REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 86, ISSN: 0034-6748
  • Journal article
    Powell HW, King M, Gray RJ, MacLellan DA, Gonzalez-Izquierdo B, Stockhausen LC, Hicks G, Dover NP, Rusby DR, Carroll DC, Padda H, Torres R, Kar S, Clarke RJ, Musgrave IO, Najmudin Z, Borghesi M, Neely D, McKenna Pet al., 2015,

    Proton acceleration enhanced by a plasma jet in expanding foils undergoing relativistic transparency

    , New Journal of Physics, Vol: 17, ISSN: 1367-2630

    Ion acceleration driven by the interaction of an ultraintense (2 × 1020 W cm−2) laser pulse with an ultrathin ($\leqslant 40$ nm) foil target is experimentally and numerically investigated. Protons accelerated by sheath fields and via laser radiation pressure are angularly separated and identified based on their directionality and signature features (e.g. transverse instabilities) in the measured spatial-intensity distribution. A low divergence, high energy proton component is also detected when the heated target electrons expand and the target becomes relativistically transparent during the interaction. 2D and 3D particle-in-cell simulations indicate that under these conditions a plasma jet is formed at the target rear, supported by a self-generated azimuthal magnetic field, which extends into the expanded layer of sheath-accelerated protons. Electrons trapped within this jet are directly accelerated to super-thermal energies by the portion of the laser pulse transmitted through the target. The resulting streaming of the electrons into the ion layers enhances the energy of protons in the vicinity of the jet. Through the addition of a controlled prepulse, the maximum energy of these protons is demonstrated experimentally and numerically to be sensitive to the picosecond rising edge profile of the laser pulse.

  • Journal article
    Tresca O, Dover NP, Cook N, Maharjan C, Polyanskiy MN, Najmudin Z, Shkolnikov P, Pogorelsky Iet al., 2015,

    Spectral Modification of Shock Accelerated Ions Using a Hydrodynamically Shaped Gas Target

    , PHYSICAL REVIEW LETTERS, Vol: 115, ISSN: 0031-9007
  • Journal article
    Cole JM, Wood J, Lopes NC, Poder K, Abel RL, Alatabi S, Bryant JSJ, Jin A, Kneip S, Mecseki K, Symes DR, Mangles SPD, Najmudin Zet al., 2015,

    Laser-wakefield accelerators as hard x-ray sources for 3D medical imaging of human bone

    , Scientific Reports, Vol: 5, ISSN: 2045-2322

    A bright μm-sized source of hard synchrotron x-rays (critical energy Ecrit > 30 keV) based on the betatron oscillations of laser wakefield accelerated electrons has been developed. The potential of this source for medical imaging was demonstrated by performing micro-computed tomography of a human femoral trabecular bone sample, allowing full 3D reconstruction to a resolution below 50 μm. The use of a 1 cm long wakefield accelerator means that the length of the beamline (excluding the laser) is dominated by the x-ray imaging distances rather than the electron acceleration distances. The source possesses high peak brightness, which allows each image to be recorded with a single exposure and reduces the time required for a full tomographic scan. These properties make this an interesting laboratory source for many tomographic imaging applications.

  • Journal article
    Savert, Mangles SPD, Schnell M, Siminos E, Cole JM, Leier M, Reuter M, Schwab MB, Moller M, Poder K, Jackel O, Paulus GG, Spielmann C, Skupin S, Najmudin Z, Kaluza MCet al., 2015,

    Direct observation of the injection dynamics of a laser wakefield accelerator using few-femtosecond shadowgraphy

    , Physical Review Letters, Vol: 115, ISSN: 1079-7114

    We present few-femtosecond shadowgraphic snapshots taken during the non-linear evolution of the plasma wave in a laser wakefield accelerator with transverse synchronized few-cycle probe pulses. These snapshots can be directly associated with the electron density distribution within the plasma wave and give quantitative information about its size and shape. Our results show that self-injection of electrons into the first plasma wave period is induced by a lengthening of the first plasma period. Three dimensional particle in cell simulations support our observations.

  • Journal article
    Mirfayzi SR, Kar S, Ahmed H, Krygier AG, Green A, Alejo A, Clarke R, Freeman RR, Fuchs J, Jung D, Kleinschmidt A, Morrison JT, Najmudin Z, Nakamura H, Norreys P, Oliver M, Roth M, Vassura L, Zepf M, Borghesi Met al., 2015,

    Calibration of time of flight detectors using laser-driven neutron source

    , REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 86, ISSN: 0034-6748
  • Journal article
    Krygier AG, Morrison JT, Kar S, Ahmed H, Alejo A, Clarke R, Fuchs J, Green A, Jung D, Kleinschmidt A, Najmudin Z, Nakamura H, Norreys P, Notley M, Oliver M, Roth M, Vassura L, Zepf M, Borghesi M, Freeman RRet al., 2015,

    Selective deuterium ion acceleration using the Vulcan petawatt laser

    , Physics of Plasmas, Vol: 22, ISSN: 1089-7674

    We report on the successful demonstration of selective acceleration of deuterium ions by targetnormalsheath acceleration (TNSA) with a high-energy petawatt laser. TNSA typically produces amulti-species ion beam that originates from the intrinsic hydrocarbon and water vapor contaminantson the target surface. Using the method first developed by Morrison et al. [Phys. Plasmas 19,030707 (2012)], an ion beam with >99% deuterium ions and peak energy 14 MeV/nucleon is producedwith a 200 J, 700 fs, >1020W=cm2 laser pulse by cryogenically freezing heavy water (D2O)vapor onto the rear surface of the target prior to the shot. Within the range of our detectors(0!–8.5!), we find laser-to-deuterium-ion energy conversion efficiency of 4.3% above 0.7 MeV/nucleon while a conservative estimate of the total beam gives a conversion efficiency of 9.4%.

  • Journal article
    Sarri G, Poder K, Cole JM, Schumaker W, Di Piazza A, Reville B, Dzelzainis T, Doria D, Gizzi LA, Grittani G, Kar S, Keitel CH, Krushelnick K, Kuschel S, Mangles SP, Najmudin Z, Shukla N, Silva LO, Symes D, Thomas AG, Vargas M, Vieira J, Zepf Met al., 2015,

    Generation of neutral and high-density electron-positron pair plasmas in the laboratory

    , Nature Communications, Vol: 6, ISSN: 2041-1723

    Electron-positron pair plasmas represent a unique state of matter, whereby there exists an intrinsic and complete symmetry between negatively charged (matter) and positively charged (antimatter) particles. These plasmas play a fundamental role in the dynamics of ultra-massive astrophysical objects and are believed to be associated with the emission of ultra-bright gamma-ray bursts. Despite extensive theoretical modelling, our knowledge of this state of matter is still speculative, owing to the extreme difficulty in recreating neutral matter-antimatter plasmas in the laboratory. Here we show that, by using a compact laser-driven setup, ion-free electron-positron plasmas with unique characteristics can be produced. Their charge neutrality (same amount of matter and antimatter), high-density and small divergence finally open up the possibility of studying electron-positron plasmas in controlled laboratory experiments.

  • Conference paper
    Seely J, Feldman U, Hudson L, Glover J, Henins A, Neely D, Rusby D, Najmudin Z, Lopes N, Wood Jet al., 2015,

    Betatron x-ray spectra recorded by a transmission crystal spectrometer in the 10 keV to 70 keV photon energy range

  • Journal article
    Willingale L, Nagel SR, Thomas AGR, Bellei C, Clarke RJ, Dangor AE, Heathcote R, Kaluza MC, Kamperidis C, Kneip S, Krushelnick K, Lopes N, Mangles SPD, Nazarov W, Nilson PM, Najmudin Zet al., 2015,

    Characterization of laser-driven proton beams from near-critical density targets using copper activation

    , JOURNAL OF PLASMA PHYSICS, Vol: 81, ISSN: 0022-3778
  • Conference paper
    Sarri G, Corvan DJ, Cole JM, Schumaker W, Di Piazza A, Ahmed H, Yeung M, Zhao Z, Harvey C, Keitel CH, Krushelnick K, Mangles SPD, Najmudin Z, Thomas AGR, Zepf Met al., 2015,

    Laser-driven Thomson scattering for the generation of ultra-bright multi-MeV gamma-ray beams

    , Conference on Laser Acceleration of Electrons, Protons, and Ions III and Medical Applications of Laser-Generated Beams of Particles III, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
  • Journal article
    Hooker SM, Bartolini R, Mangles SPD, Tuennermann A, Corner L, Limpert J, Seryi A, Walczak Ret al., 2014,

    Multi-pulse laser wakefield acceleration: a new route to efficient, high-repetition-rate plasma accelerators and high flux radiation sources

    , JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 47, ISSN: 0953-4075
  • Journal article
    Sarri G, Corvan DJ, Schumaker W, Cole JM, Di Piazza A, Ahmed H, Harvey C, Keitel CH, Krushelnick K, Mangles SPD, Najmudin Z, Symes D, Thomas AGR, Yeung M, Zhao Z, Zepf Met al., 2014,

    Ultrahigh brilliance multi-MeV gamma-Ray beams from nonlinear relativistic Thomson scattering

    , Physical Review Letters, Vol: 113, Pages: 1-5, ISSN: 0031-9007

    We report on the generation of a narrow divergence (θγ<2.5  mrad), multi-MeV (Emax≈18  MeV) and ultrahigh peak brilliance (>1.8×1020  photons s−1 mm−2  mrad−2 0.1% BW) γ-ray beam from the scattering of an ultrarelativistic laser-wakefield accelerated electron beam in the field of a relativistically intense laser (dimensionless amplitude a0≈2). The spectrum of the generated γ-ray beam is measured, with MeV resolution, seamlessly from 6 to 18 MeV, giving clear evidence of the onset of nonlinear relativistic Thomson scattering. To the best of our knowledge, this photon source has the highest peak brilliance in the multi-MeV regime ever reported in the literature.

  • Journal article
    Alejo A, Kar S, Ahmed H, Krygier AG, Doria D, Clarke R, Fernandez J, Freeman RR, Fuchs J, Green A, Green JS, Jung D, Kleinschmidt A, Lewis CLS, Morrison JT, Najmudin Z, Nakamura H, Nersisyan G, Norreys P, Notley M, Oliver M, Roth M, Ruiz JA, Vassura L, Zepf M, Borghesi Met al., 2014,

    Characterisation of deuterium spectra from laser driven multi-species sources by employing differentially filtered image plate detectors in Thomson spectrometers

    , REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 85, ISSN: 0034-6748
  • Journal article
    Kamperidis C, Dimitriou V, Mangles SPD, Dangor AE, Najmudin Zet al., 2014,

    Low energy spread electron beams from ionization injection in a weakly relativistic laser wakefield accelerator

    , PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 56, ISSN: 0741-3335
  • Journal article
    Albert F, Thomas AGR, Mangles SPD, Banerjee S, Corde S, Flacco A, Litos M, Neely D, Vieira J, Najmudin Z, Bingham R, Joshi C, Katsouleas Tet al., 2014,

    Laser wakefield accelerator based light sources: potential applications and requirements

    , PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 56, ISSN: 0741-3335
  • Journal article
    Green JS, Dover NP, Borghesi M, Brenner CM, Cameron FH, Carroll DC, Foster PS, Gallegos P, Gregori G, McKenna P, Murphy CD, Najmudin Z, Palmer CAJ, Prasad R, Romagnani L, Quinn KE, Schreiber J, Streeter MJV, Ter-Avetisyan S, Tresca O, Zepf M, Neely Det al., 2014,

    Enhanced proton beam collimation in the ultra-intense short pulse regime

    , PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 56, ISSN: 0741-3335
  • Journal article
    Najmudin Z, Kneip S, Bloom MS, Mangles SPD, Chekhlov O, Dangor AE, Doepp A, Ertel K, Hawkes SJ, Holloway J, Hooker CJ, Jiang J, Lopes NC, Nakamura H, Norreys PA, Rajeev PP, Russo C, Streeter MJV, Symes DR, Wing Met al., 2014,

    Compact laser accelerators for X-ray phase-contrast imaging

    , PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 372, ISSN: 1364-503X
  • Conference paper
    Mangles SPD, Bloom MS, Bryant J, Cole JM, Doepp A, Kneip S, Nakamura H, Poder K, Streeter MJV, Wood J, Najmudin Z, Bendoyro R, Jiang J, Lopes NC, Russo C, Cheklov O, Ertel K, Hawkes SJ, Hooker CJ, Neely D, Norreys PA, Rajeev PP, Rusby DR, Scott RHH, Symes DR, Holloway J, Wing M, Seely JFet al., 2014,

    Producing bright X-rays for imaging applications using a laser wakefield accelerator

    , Conference on Lasers and Electro-Optics (CLEO), Publisher: IEEE, ISSN: 2160-9020
  • Conference paper
    Sarri G, Schumaker W, Di Piazza A, Poder K, Cole JM, Vargas M, Doria D, Kushel S, Dromey B, Grittani G, Gizzi L, Dieckmann ME, Green A, Chvykov V, Maksimchuk A, Yanovsky V, He ZH, Hou BX, Nees JA, Kar S, Najmudin Z, Thomas AGR, Keitel CH, Krushelnick K, Zepf Met al., 2013,

    Laser-driven generation of collimated ultra-relativistic positron beams

    , 40th Conference of the European-Physical-Society on Plasma Physics, Publisher: IOP PUBLISHING LTD, ISSN: 0741-3335
  • Journal article
    Thaury C, Phuoc KT, Corde S, Brijesh P, Lambert G, Mangles SPD, Bloom MS, Kneip S, Malka Vet al., 2013,

    Probing electron acceleration and x-ray emission in laser-plasma accelerators

    , PHYSICS OF PLASMAS, Vol: 20, ISSN: 1070-664X
  • Journal article
    Genoud G, Bloom MS, Vieira J, Burza M, Najmudin Z, Persson A, Silva LO, Svensson K, Wahlstrom C-G, Mangles SPDet al., 2013,

    Increasing energy coupling into plasma waves by tailoring the laser radial focal spot distribution in a laser wakefield accelerator

    , PHYSICS OF PLASMAS, Vol: 20, ISSN: 1070-664X
  • Journal article
    Palmer CAJ, Schreiber J, Nagel SR, Dover NP, Bellei C, Beg FN, Bott S, Clarke RJ, Dangor AE, Hassan SM, Hilz P, Jung D, Kneip S, Mangles SPD, Lancaster KL, Rehman A, Robinson APL, Spindloe C, Szerypo J, Tatarakis M, Yeung M, Zepf M, Najmudin Zet al., 2012,

    Rayleigh-Taylor Instability of an Ultrathin Foil Accelerated by the Radiation Pressure of an Intense Laser

    , PHYSICAL REVIEW LETTERS, Vol: 108, ISSN: 0031-9007
  • Journal article
    Kneip S, McGuffey C, Dollar F, Bloom MS, Chvykov V, Kalintchenko G, Krushelnick K, Maksimchuk A, Mangles SPD, Matsuoka T, Najmudin Z, Palmer CAJ, Schreiber J, Schumaker W, Thomas AGR, Yanovsky Vet al., 2011,

    X-ray phase contrast imaging of biological specimens with femtosecond pulses of betatron radiation from a compact laser plasma wakefield accelerator

    , APPLIED PHYSICS LETTERS, Vol: 99, ISSN: 0003-6951

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