Publications
182 results found
Kononenko O, Lopes NC, Cole JM, et 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.
Behm KT, Zhao TZ, Cole JM, et 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
Cole JM, Wood JC, Lopes NC, et 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.
Turcu ICE, Negoita F, Jaroszynski DA, et al., 2016, HIGH FIELD PHYSICS AND QED EXPERIMENTS AT ELI-NP, ROMANIAN REPORTS IN PHYSICS, Vol: 68, Pages: S145-S231, ISSN: 1221-1451
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- Citations: 89
Cole JM, Wood J, Lopes NC, et 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.
Savert, Mangles SPD, Schnell M, et 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.
Needham J, Lewis H, McIndoe N, et al., 2015, Individualised treatment in haemophilia A - variability in factor VIII activity measurement for pharmacokinetic dosing, Publisher: WILEY-BLACKWELL, Pages: 587-587, ISSN: 1538-7933
Luo P-L, Austin S, Atwal S, et al., 2015, Achieving haemostatic control in acquired haemophilia a with plasma derived FVIII infusions, Publisher: WILEY-BLACKWELL, Pages: 757-757, ISSN: 1538-7933
Needham J, Lewis H, McMullen A, et al., 2015, Circulating concentration of rivaroxaban or dabigatran anticoagulants in clinically selected patients, Publisher: WILEY-BLACKWELL, Pages: 641-641, ISSN: 1538-7933
Sarri G, Poder K, Cole JM, et 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.
Siminos E, Skupin S, Sävert A, et al., 2015, Modeling few-cycle shadowgraphy of laser-wakefield accelerators
Ultrafast shadowgraphy utilizes few cycle probe pulses in order to image density gradients in a plasma allowing to probe structures, such as laser-driven wakes, moving close to the speed of light. Here we study the process of shadowgraphic image formation in the interaction of a few cycle probe pulse with a laser-driven wake using particle-in-cell (PIC) simulations. The output of the PIC code is then post-processed by means of Fourier optics in order to take into account the effect of a typical imaging setup. This allows to construct synthetic shadowgrams which can be compared with experimentally recorded ones. This facilitates the correct interpretation of such involved measurements.
Willingale L, Nagel SR, Thomas AGR, et 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
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- Citations: 1
Sarri G, Corvan DJ, Cole JM, et 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
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- Citations: 1
Hooker SM, Bartolini R, Mangles SPD, et 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
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- Citations: 32
Sarri G, Corvan DJ, Schumaker W, et 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.
Kamperidis C, Dimitriou V, Mangles SPD, et 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
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- Citations: 14
Hooker SM, Mangles S, Pattathil R, 2014, Laser and Plasma Accelerator Workshop 2013 Preface, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 56, ISSN: 0741-3335
Albert F, Thomas AGR, Mangles SPD, et al., 2014, Laser wakefield accelerator based light sources: potential applications and requirements, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 56, ISSN: 0741-3335
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- Citations: 70
Najmudin Z, Kneip S, Bloom MS, et 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
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- Citations: 28
, 2014, Producing bright X-rays for imaging applications using a laser wakefield accelerator
We report on the generation of bright multi-keV betatron X-ray radiation using a GeV laser wakefield accelerator and investigate the use of these X-rays for various imaging applications. © 2014 Optical Society of America.
Mangles SPD, Bloom MS, Bryant J, et al., 2014, Producing bright X-rays for imaging applications using a laser wakefield accelerator
We report on the generation of bright multi-keV betatron X-ray radiation using a GeV laser wakefield accelerator and investigate the use of these X-rays for various imaging applications.
Mangles SPD, 2014, An overview of recent progress in laser wakefield acceleration experiments, Pages: 289-300
The goal of this paper is to examine experimental progress in laser wakefield acceleration over the past decade (2004-2014), and to use trends in the data to understand some of the important physical processes. By examining a set of over 50 experiments, various trends concerning the relationship between plasma density, accelerator length, laser power and the final electron beam energy are revealed. The data suggest that current experiments are limited by dephasing and that current experiments typically require some pulse evolution to reach the trapping threshold.
Mangles SPD, Bloom MS, Bryant J, et al., 2014, Producing bright X-rays for imaging applications using a laser wakefield accelerator
We report on the generation of bright multi-keV betatron X-ray radiation using a GeV laser wakefield accelerator and investigate the use of these X-rays for various imaging applications. © 2014 Optical Society of America.
Mangles SPD, Bloom MS, Bryant J, et 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
Genoud G, Bloom MS, Vieira J, et 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
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- Citations: 5
Thaury C, Phuoc KT, Corde S, et al., 2013, Probing electron acceleration and x-ray emission in laser-plasma accelerators, PHYSICS OF PLASMAS, Vol: 20, ISSN: 1070-664X
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- Citations: 2
Walton B, Dangor AE, Mangles SPD, et al., 2013, Measurements of magnetic field generation at ionization fronts from laser wakefield acceleration experiments, NEW JOURNAL OF PHYSICS, Vol: 15, ISSN: 1367-2630
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- Citations: 5
Thomas AGR, Ridgers CP, Bulanov SS, et al., 2012, Strong Radiation-Damping Effects in a Gamma-Ray Source Generated by the Interaction of a High-Intensity Laser with a Wakefield-Accelerated Electron Beam, PHYSICAL REVIEW X, Vol: 2, ISSN: 2160-3308
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- Citations: 112
Kamperidis C, Bellei C, Bourgeois N, et al., 2012, Self-modulated wakefield acceleration in a centimetre self-guiding channel, JOURNAL OF PLASMA PHYSICS, Vol: 78, Pages: 433-440, ISSN: 0022-3778
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- Citations: 2
Palmer CAJ, Schreiber J, Nagel SR, et al., 2012, Rayleigh-Taylor instability of an ultrathin foil accelerated by the radiation pressure of an intense laser., Phys Rev Lett, Vol: 108
We report experimental evidence for a Rayleigh-Taylor-like instability driven by radiation pressure of an ultraintense (10(21) W/cm(2)) laser pulse. The instability is witnessed by the highly modulated profile of the accelerated proton beam produced when the laser irradiates a 5 nm diamondlike carbon (90% C, 10% H) target. Clear anticorrelation between bubblelike modulations of the proton beam and transmitted laser profile further demonstrate the role of the radiation pressure in modulating the foil. Measurements of the modulation wavelength, and of the acceleration from Doppler-broadening of back-reflected light, agree quantitatively with particle-in-cell simulations performed for our experimental parameters and which confirm the existence of this instability.
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