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Journal articleMaitrallain A, Brunetti E, Streeter MJ, et al., 2022,
Parametric study of high-energy ring-shaped electron beams from a laser wakefield accelerator
, NEW JOURNAL OF PHYSICS, Vol: 24, ISSN: 1367-2630- Author Web Link
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- Citations: 3
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Journal articleMcIlvenny A, Doria D, Romagnani L, et al., 2021,
Selective Ion Acceleration by Intense Radiation Pressure
, PHYSICAL REVIEW LETTERS, Vol: 127, ISSN: 0031-9007- Author Web Link
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- Citations: 16
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Journal articleKettle B, Hollatz D, Gerstmayr E, et al., 2021,
A laser-plasma platform for photon-photon physics: the two photon Breit-Wheeler process
, New Journal of Physics, Vol: 23, ISSN: 1367-2630We describe a laser–plasma platform for photon–photon collision experiments to measure fundamental quantum electrodynamic processes. As an example we describe using this platform to attempt to observe the linear Breit–Wheeler process. The platform has been developed using the Gemini laser facility at the Rutherford Appleton Laboratory. A laser Wakefield accelerator and a bremsstrahlung convertor are used to generate a collimated beam of photons with energies of hundreds of MeV, that collide with keV x-ray photons generated by a laser heated plasma target. To detect the pairs generated by the photon–photon collisions, a magnetic transport system has been developed which directs the pairs onto scintillation-based and hybrid silicon pixel single particle detectors (SPDs). We present commissioning results from an experimental campaign using this laser–plasma platform for photon–photon physics, demonstrating successful generation of both photon sources, characterisation of the magnetic transport system and calibration of the SPDs, and discuss the feasibility of this platform for the observation of the Breit–Wheeler process. The design of the platform will also serve as the basis for the investigation of strong-field quantum electrodynamic processes such as the nonlinear Breit–Wheeler and the Trident process, or eventually, photon–photon scattering.
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Journal articleFinlay OJ, Gruse JN, Thornton C, et al., 2021,
Characterisation of a laser plasma betatron source for high resolution x-ray imaging
, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 63, ISSN: 0741-3335- Author Web Link
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- Citations: 1
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Journal articleBaggott RA, Rose S, Mangles SPD, 2021,
Temperature equilibration due to charge state fluctuations in dense plasmas
, Physical Review Letters, Vol: 27, ISSN: 0031-9007The charge states of ions in dense plasmas fluctuate due to collisionalionization and recombination. Here we show how, by modifying the ioninteraction potential, these fluctuations can mediate energy exchange betweenthe plasma electrons and ions. Moreover, we develop a theory for this novelelectron-ion energy transfer mechanism. Calculations using a random walkapproach for the fluctuations suggest that the energy exchange rate from chargestate fluctuations could be comparable to direct electron-ion collisions. Thismechanism is, however, predicted to exhibit a complex dependence on thetemperature and ionization state of the plasma, which could contribute to ourunderstanding of significant variation in experimental measurements ofequilibration times.
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Journal articleDanson CN, White M, Barr JRM, et al., 2021,
A history of high-power laser research and development in the United Kingdom
, High Power Laser Science and Engineering, Vol: 9, Pages: 1-86, ISSN: 2095-4719The first demonstration of laser action in ruby was made in 1960 by T. H. Maiman of Hughes Research Laboratories, USA. Many laboratories worldwide began the search for lasers using different materials, operating at different wavelengths. In the UK, academia, industry and the central laboratories took up the challenge from the earliest days to develop these systems for a broad range of applications. This historical review looks at the contribution the UK has made to the advancement of the technology, the development of systems and components and their exploitation over the last 60 years.
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Journal articleAlbert F, Couprie ME, Debus A, et al., 2021,
2020 roadmap on plasma accelerators
, New Journal of Physics, Vol: 23, Pages: 1-34, ISSN: 1367-2630Plasma-based accelerators use the strong electromagnetic fields that can be supported by plasmas to accelerate charged particles to high energies. Accelerating field structures in plasma can be generated by powerful laser pulses or charged particle beams. This research field has recently transitioned from involving a few small-scale efforts to the development of national and international networks of scientists supported by substantial investment in large-scale research infrastructure. In this New Journal of Physics 2020 Plasma Accelerator Roadmap, perspectives from experts in this field provide a summary overview of the field and insights into the research needs and developments for an international audience of scientists, including graduate students and researchers entering the field.
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Journal articleAssmann RW, Weikum MK, Akhter T, et al., 2021,
Erratum to: EuPRAXIA Conceptual Design Report
, European Physical Journal: Special Topics, Vol: 229, Pages: 11-31, ISSN: 1951-6355 -
Journal articleStreeter M, Najmudin Z, Shalloo R, et al., 2020,
Automation and control of laser wakefield accelerators using Bayesian optimisation
, Nature Communications, Vol: 11, Pages: 1-8, ISSN: 2041-1723Laser wakefield accelerators promise to revolutionize many areas of accelerator science. However, one of the greatest challenges to their widespread adoption is the difficulty in control and optimization of the accelerator outputs due to coupling between input parameters and the dynamic evolution of the accelerating structure. Here, we use machine learning techniques to automate a 100 MeV-scale accelerator, which optimized its outputs by simultaneously varying up to six parameters including the spectral and spatial phase of the laser and the plasma density and length. Most notably, the model built by the algorithm enabled optimization of the laser evolution that might otherwise have been missed in single-variable scans. Subtle tuning of the laser pulse shape caused an 80% increase in electron beam charge, despite the pulse length changing by just 1%.
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Journal articleGruse J-N, Streeter MJV, Thornton C, et al., 2020,
Application of compact laser-driven accelerator X-ray sources for industrial imaging
, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment, Vol: 983, Pages: 1-7, ISSN: 0168-9002X-rays generated by betatron oscillations of electrons in a laser-driven plasma accelerator were charac-terised and applied to imaging industrial samples. With a125TWlaser, a low divergence beam with5.2 ± 1.7 × 107photonsmrad−2per pulse was produced with a synchrotron spectrum with a critical energy of14.6 ± 1.3keV. Radiographs were obtained of a metrology test sample, battery electrodes, and a damage sitein a composite material. These results demonstrate the suitability of the source for non-destructive evaluationapplications. The potential for industrial implementation of plasma accelerators is discussed.
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Journal articleAssmann RW, Weikum MK, Akhter T, et al., 2020,
EuPRAXIA conceptual design report
, European Physical Journal: Special Topics, Vol: 229, Pages: 3675-4284, ISSN: 1951-6355This report presents the conceptual design of a new European research infrastructure EuPRAXIA. The concept has been established over the last four years in a unique collaboration of 41 laboratories within a Horizon 2020 design study funded by the European Union. EuPRAXIA is the first European project that develops a dedicated particle accelerator research infrastructure based on novel plasma acceleration concepts and laser technology. It focuses on the development of electron accelerators and underlying technologies, their user communities, and the exploitation of existing accelerator infrastructures in Europe. EuPRAXIA has involved, amongst others, the international laser community and industry to build links and bridges with accelerator science — through realising synergies, identifying disruptive ideas, innovating, and fostering knowledge exchange. The Eu-PRAXIA project aims at the construction of an innovative electron accelerator using laser- and electron-beam-driven plasma wakefield acceleration that offers a significant reduction in size and possible savings in cost over current state-of-the-art radiofrequency-based accelerators. The foreseen electron energy range of one to five gigaelectronvolts (GeV) and its performance goals will enable versatile applications in various domains, e.g. as a compact free-electron laser (FEL), compact sources for medical imaging and positron generation, table-top test beams for particle detectors, as well as deeply penetrating X-ray and gamma-ray sources for material testing. EuPRAXIA is designed to be the required stepping stone to possible future plasma-based facilities, such as linear colliders at the high-energy physics (HEP) energy frontier. Consistent with a high-confidence approach, the project includes measures to retire risk by establishing scaled technology demonstrators. This report includes preliminary models for project implementation, cost and schedule that would allow operation of the full Eu-PRAXIA facili
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Journal articleUnderwood CID, Baird CD, Murphy CD, et al., 2020,
Development of control mechanisms for a laser wakefield accelerator-driven bremsstrahlung x-ray source for advanced radiographic imaging
, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 62, ISSN: 0741-3335- Author Web Link
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- Citations: 9
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Journal articleDover NP, Nishiuchi M, Sakaki H, et al., 2020,
Demonstration of repetitive energetic proton generation by ultra-intense laser interaction with a tape target
, High Energy Density Physics, Vol: 37, Pages: 100847-100847, ISSN: 1574-1818 -
Journal articleBaggott R, Rose S, Mangles S, 2020,
Calculating opacity in hot, dense matter using second-order electron-photon and two-photon transitions to approximate line broadening
, Physical Review Letters, Vol: 125, Pages: 145002 – 1-145002 – 5, ISSN: 0031-9007Calculations of the opacity of hot, dense matter require models for plasma line broadening. How-ever, the most general theories are too complex to calculate directly and some approximation is inevitably required. The most widely-used approaches focus on the line centre, where a Lorentzian shape is obtained. Here, we demonstrate that in the opposite limit, far from the line centre, the opacity can be expressed in terms of second-order transitions, such as electron-photon and two-photon processes. We suggest that this insight could form the basis for a new approach to improve calculations of opacity in hot, dense matter. Preliminary calculations suggest that this approach could yield increased opacity away from absorption lines.
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Journal articleKondo K, Nishiuchi M, Sakaki H, et al., 2020,
High-intensity laser-driven oxygen source from CW laser-heated titanium tape targets
, Crystals, Vol: 10, Pages: 837-837, ISSN: 2073-4352The interaction of high-intensity laser pulses with solid targets can be used as a highly charged, energetic heavy ion source. Normally, intrinsic contaminants on the target surface suppress the performance of heavy ion acceleration from a high-intensity laser–target interaction, resulting in preferential proton acceleration. Here, we demonstrate that CW laser heating of 5 µm titanium tape targets can remove contaminant hydrocarbons in order to expose a thin oxide layer on the metal surface, ideal for the generation of energetic oxygen beams. This is demonstrated by irradiating the heated targets with a PW class high-power laser at an intensity of 5 × 1021 W/cm2, showing enhanced acceleration of oxygen ions with a non-thermal-like distribution. Our new scheme using a CW laser-heated Ti tape target is promising for use as a moderate repetition energetic oxygen ion source for future applications.
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Journal articleXu ZY, Xiao CF, Lu HY, et al., 2020,
New injection and acceleration scheme of positrons in the laser-plasma bubble regime
, PHYSICAL REVIEW ACCELERATORS AND BEAMS, Vol: 23, ISSN: 2469-9888- Author Web Link
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- Citations: 8
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Journal articleAymar G, Becker T, Boogert S, et al., 2020,
LhARA: The Laser-hybrid accelerator for radiobiological applications
, Frontiers in Physics, Vol: 8, Pages: 1-21, ISSN: 2296-424XThe “Laser-hybrid Accelerator for Radiobiological Applications,” LhARA, is conceived as a novel, flexible facility dedicated to the study of radiobiology. The technologies demonstrated in LhARA, which have wide application, will be developed to allow particle-beam therapy to be delivered in a new regimen, combining a variety of ion species in a single treatment fraction and exploiting ultra-high dose rates. LhARA will be a hybrid accelerator system in which laser interactions drive the creation of a large flux of protons or light ions that are captured using a plasma (Gabor) lens and formed into a beam. The laser-driven source allows protons and ions to be captured at energies significantly above those that pertain in conventional facilities, thus evading the current space-charge limit on the instantaneous dose rate that can be delivered. The laser-hybrid approach, therefore, will allow the radiobiology that determines the response of tissue to ionizing radiation to be studied with protons and light ions using a wide variety of time structures, spectral distributions, and spatial configurations at instantaneous dose rates up to and significantly beyond the ultra-high dose-rate “FLASH” regime. It is proposed that LhARA be developed in two stages. In the first stage, a programme of in vitro radiobiology will be served with proton beams with energies between 10 and 15 MeV. In stage two, the beam will be accelerated using a fixed-field alternating-gradient accelerator (FFA). This will allow experiments to be carried out in vitro and in vivo with proton beam energies of up to 127 MeV. In addition, ion beams with energies up to 33.4 MeV per nucleon will be available for in vitro and in vivo experiments. This paper presents the conceptual design for LhARA and the R&D programme by which the LhARA consortium seeks to establish the facility.
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Journal articleShalloo RJ, Mangles SPD, 2020,
Faster laser pulses boost plasma accelerators
, NATURE PHOTONICS, Vol: 14, Pages: 470-471, ISSN: 1749-4885- Author Web Link
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- Citations: 2
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Journal articleNishiuchi M, Dover NP, Hata M, et al., 2020,
Dynamics of laser-driven heavy-ion acceleration clarified by ion charge states
, Physical Review Research, Vol: 2, Pages: 033081 – 1-033081 – 13, ISSN: 2643-1564Motivated by the development of next-generation heavy-ion sources, we have investigated the ionization and acceleration dynamics of an ultraintense laser-driven high-Z silver target, experimentally, numerically, and analytically. Using a novel ion measurement technique allowing us to uniquely identify silver ions, we experimentally demonstrate generation of highly charged silver ions (Z∗=45+2−2) with energies of >20 MeV/nucleon (>2.2 GeV) from submicron silver targets driven by a laser with intensity 5×1021W/cm2, with increasing ion energy and charge state for decreasing target thickness. We show that although target pre-expansion by the unavoidable rising edge of state-of-the-art high-power lasers can limit proton energies, it is advantageous for heavy-ion acceleration. Two-dimensional particle-in-cell simulations show that the Joule heating in the target bulk results in a high temperature (∼10keV) solid density plasma, leading to the generation of high flux highly charged ions (Z∗=40+2−2, ≳10MeV/nucleon) via electron collisional ionization, which are extracted and accelerated with a small divergence by an extreme sheath field at the target rear. However, with reduced target thickness this favorable acceleration is degraded due to the target deformation via laser hole boring, which accompanies higher energy ions with higher charge states but in an uncontrollable manner. Our elucidation of the fundamental processes of high-intensity laser-driven ionization and ion acceleration provides a path for improving the control and parameters of laser-driven heavy-ion sources, a key component for next-generation heavy-ion accelerators.
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Journal articleStreeter MJV, Najmudin Z, 2020,
Compton recoil effects in staging of laser wakefield accelerators
, PHYSICAL REVIEW ACCELERATORS AND BEAMS, Vol: 23, ISSN: 2469-9888- Author Web Link
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- Citations: 1
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Journal articleMangles S, 2020,
Bright x-ray radiation from plasma bubbles in an evolving laser wakefield accelerator
, Physical Review Accelerators and Beams, Vol: 23, Pages: 061301 – 1-061301 – 6, ISSN: 2469-9888We show that the properties of the electron beam and bright x rays produced by a laser wakefield accelerator can be predicted if the distance over which the laser self-focuses and compresses prior to self-injection is taken into account. A model based on oscillations of the beam inside a plasma bubble shows that performance is optimized when the plasma length is matched to the laser depletion length. With a 200 TW laser pulse, this results in an x-ray beam with a median photon energy of 20 keV, >6×108 photons above 1 keV per shot, and a peak brightness of 3×1022 photons s−1 mrad−2 mm−2 (0.1% BW)−1.
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Journal articleBlackburn TG, Gerstmayr E, Mangles SPD, et al., 2020,
Model-independent inference of laser intensity
, PHYSICAL REVIEW ACCELERATORS AND BEAMS, Vol: 23, ISSN: 2469-9888- Author Web Link
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- Citations: 7
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Journal articleBehm K, Hussein AE, Zhao TZ, et al., 2020,
Demonstration of femtosecond broadband X-rays from laser wakefield acceleration as a source for pump-probe X-ray absorption studies
, High Energy Density Physics, Vol: 35, Pages: 1-5, ISSN: 1574-1818We present X-ray absorption measurements near the K-edge of laser heated aluminum in a pump-probe configuration using X-rays generated in a laser wakefield accelerator. A 30 fs duration laser pulse from the Herculeslaser system was split into two beamlines, with one used to heat a 4 µm thickness Al foil and the second to drive a laser wakefield accelerator. The laser-heated plasma was probed at various pump-probe delays using the femtosecond duration X-rays generated by betatron oscillations of the electrons in the wakefield. We observe an apparent blue-shift of the K-edge occurring on a sub-picosecond timescale in the transmission spectra.
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Journal articleSchwab MB, Siminos E, Heinemann T, et al., 2020,
Visualization of relativistic laser pulses in underdense plasma
, PHYSICAL REVIEW ACCELERATORS AND BEAMS, Vol: 23, ISSN: 2469-9888- Author Web Link
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- Citations: 6
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Journal articleHussein AE, Senabulya N, Ma Y, et al., 2020,
Author Correction: Laser-wakefield accelerators for high-resolution X-ray imaging of complex microstructures
, Scientific Reports, Vol: 10, ISSN: 2045-2322An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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Journal articlePassalidis S, Ettlinger OC, Hicks GS, et al., 2020,
Hydrodynamic computational modelling and simulations of collisional shock waves in gas jet targets
, HIGH POWER LASER SCIENCE AND ENGINEERING, Vol: 8, ISSN: 2095-4719- Author Web Link
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- Citations: 6
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Journal articleKettle B, Gerstmayr E, Streeter MJV, et al., 2019,
Single-shot multi-keV X-ray absorption spectroscopy using an ultrashort laser-wakefield accelerator source
, Physical Review Letters, Vol: 123, Pages: 254801-1-254801-6, ISSN: 0031-9007Single-shot absorption measurements have been performed using the multi-keV x rays generated by a laser-wakefield accelerator. A 200 TW laser was used to drive a laser-wakefield accelerator in a mode which produced broadband electron beams with a maximum energy above 1 GeV and a broad divergence of ≈15 mrad FWHM. Betatron oscillations of these electrons generated 1.2±0.2×106 photons/eV in the 5 keV region, with a signal-to-noise ratio of approximately 300∶1. This was sufficient to allow high-resolution x-ray absorption near-edge structure measurements at the K edge of a titanium sample in a single shot. We demonstrate that this source is capable of single-shot, simultaneous measurements of both the electron and ion distributions in matter heated to eV temperatures by comparison with density functional theory simulations. The unique combination of a high-flux, large bandwidth, few femtosecond duration x-ray pulse synchronized to a high-power laser will enable key advances in the study of ultrafast energetic processes such as electron-ion equilibration.
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Journal articleKurup A, Pasternak J, Taylor R, et al., 2019,
Simulation of a radiobiology facility for the Centre for the Clinical Application of Particles
, Physica Medica, Vol: 65, Pages: 21-28, ISSN: 1120-1797The Centre for the Clinical Application of Particles’ Laser-hybrid Accelerator for Radiobiological Applications (LhARA) facility is being studied and requires simulation of novel accelerator components (such as the Gabor lens capture system), detector simulation and simulation of the ion beam interaction with cells. The first stage of LhARA will provide protons up to 15 MeV for in vitro studies. The second stage of LhARA will use a fixed-field accelerator to increase the energy of the particles to allow in vivo studies with protons and in vitro studies with heavier ions.BDSIM, a Geant4 based accelerator simulation tool, has been used to perform particle tracking simulations to verify the beam optics design done by BeamOptics and these show good agreement. Design parameters were defined based on an EPOCH simulation of the laser source and a series of mono-energetic input beams were generated from this by BDSIM. The tracking results show the large angular spread of the input beam (0.2 rad) can be transported with a transmission of almost 100% whilst keeping divergence at the end station very low (<0.1 mrad). The legacy of LhARA will be the demonstration of technologies that could drive a step-change in the provision of proton and light ion therapy (i.e. a laser source coupled to a Gabor lens capture and a fixed-field accelerator), and a system capable of delivering a comprehensive set of experimental data that can be used to enhance the clinical application of proton and light ion therapy.
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Journal articleConsoli F, De Angelis R, Robinson TS, et al., 2019,
Generation of intense quasi-electrostatic fields due to deposition of particles accelerated by petawatt-range laser-matter interactions
, Scientific Reports, Vol: 9, ISSN: 2045-2322We demonstrate here for the first time that charge emitted by laser-target interactions at petawatt peak-powers can be efficiently deposited on a capacitor-collector structure far away from the target and lead to the rapid (tens of nanoseconds) generation of large quasi-static electric fields over wide (tens-of-centimeters scale-length) regions, with intensities much higher than common ElectroMagnetic Pulses (EMPs) generated by the same experiment in the same position. A good agreement was obtained between measurements from a classical field-probe and calculations based on particle-flux measurements from a Thomson spectrometer. Proof-of-principle particle-in-cell simulations reproduced the measurements of field evolution in time, giving a useful insight into the charging process, generation and distribution of fields. The understanding of this charging phenomenon and of the related intense fields, which can reach the MV/m order and in specific configurations might also exceed it, is very important for present and future facilities studying laser-plasma-acceleration and inertial-confinement-fusion, but also for application to the conditioning of accelerated charged-particles, the generation of intense electric and magnetic fields and many other multidisciplinary high-power laser-driven processes.
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Conference paperMcIlvenny A, Doria D, Romagnani L, et al., 2019,
Absolute calibration of microchannel plate detector for carbon ions up to 250 MeV
, 5th International Conference on Frontiers in Diagnostics Technologies, Publisher: IOP PUBLISHING LTD, ISSN: 1748-0221 -
Journal articleKing M, Butler NMH, Wilson R, et al., 2019,
Role of magnetic field evolution on filamentary structure formation in intense laser-foil interactions
, HIGH POWER LASER SCIENCE AND ENGINEERING, Vol: 7, ISSN: 2095-4719 -
Journal articlePapp D, Wood JC, Gruson V, et al., 2018,
Laser wakefield acceleration with high-power, few-cycle mid-IR lasers
, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, Vol: 909, Pages: 145-148, ISSN: 0168-9002 -
Journal articleWarwick JR, Alejo A, Dzelzainis T, et al., 2018,
General features of experiments on the dynamics of laser-driven electron-positron beams
, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol: 909, Pages: 95-101, ISSN: 0168-9002The experimental study of the dynamics of neutral electron–positron beams is an emerging area of research, enabled by the recent results on the generation of this exotic state of matter in the laboratory. Electron–positron beams and plasmas are believed to play a major role in the dynamics of extreme astrophysical objects such as supermassive black holes and pulsars. For instance, they are believed to be the main constituents of a large number of astrophysical jets, and they have been proposed to significantly contribute to the emission of gamma-ray bursts and their afterglow. However, despite extensive numerical modelling and indirect astrophysical observations, a detailed experimental characterisation of the dynamics of these objects is still at its infancy. Here, we will report on some of the general features of experiments studying the dynamics of electron–positron beams in a fully laser-driven setup.
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Journal articleBehm KT, Cole JM, Joglekar AS, et al., 2018,
A spectrometer for ultrashort gamma-ray pulses with photon energies greater than 10 MeV
, REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 89, ISSN: 0034-6748 -
Journal articleKrushelnick K, Dangor AE, Kaluza M, et al., 2018,
Observation of anomalous side-scattering in laser waketield accelerators
, LASER AND PARTICLE BEAMS, Vol: 36, Pages: 391-395, ISSN: 0263-0346 -
Journal articleWood JC, Chapman DJ, Poder K, et al., 2018,
Ultrafast imaging of laser driven shock waves using Betatron x-rays from a laser Wakefield accelerator
, Scientific Reports, Vol: 8, ISSN: 2045-2322Betatron radiation from laser wakefield accelerators is an ultrashort pulsedsource of hard, synchrotron-like x-ray radiation. It emanates from a centimetrescale plasma accelerator producing GeV level electron beams. In recent yearsbetatron radiation has been developed as a unique source capable of producinghigh resolution x-ray images in compact geometries. However, until now, theshort pulse nature of this radiation has not been exploited. This reportdetails the first experiment to utilise betatron radiation to image a rapidlyevolving phenomenon by using it to radiograph a laser driven shock wave in asilicon target. The spatial resolution of the image is comparable to what hasbeen achieved in similar experiments at conventional synchrotron light sources.The intrinsic temporal resolution of betatron radiation is below 100 fs,indicating that significantly faster processes could be probed in futurewithout compromising spatial resolution. Quantitative measurements of the shockvelocity and material density were made from the radiographs recorded duringshock compression and were consistent with the established shock response ofsilicon, as determined with traditional velocimetry approaches. This suggeststhat future compact betatron imaging beamlines could be useful in the imagingand diagnosis of high-energy-density physics experiments.
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Journal articleSchumaker W, Liang T, Clarke R, et al., 2018,
Making pions with laser light
, NEW JOURNAL OF PHYSICS, Vol: 20, ISSN: 1367-2630 -
Journal articlePoder K, Tamburini M, Sarri G, et al., 2018,
Experimental signatures of the quantum nature of radiation reaction in the field of an ultraintense laser
, Physical Review X, Vol: 8, ISSN: 2160-3308The description of the dynamics of an electron in an external electromagnetic field of arbitrary intensity is one of the most fundamental outstanding problems in electrodynamics. Remarkably, to date, there is no unanimously accepted theoretical solution for ultrahigh intensities and little or no experimental data. The basic challenge is the inclusion of the self-interaction of the electron with the field emitted by the electron itself—the so-called radiation reaction force. We report here on the experimental evidence of strong radiation reaction, in an all-optical experiment, during the propagation of highly relativistic electrons (maximum energy exceeding 2 GeV) through the field of an ultraintense laser (peak intensity of 4×1020 W/cm2). In their own rest frame, the highest-energy electrons experience an electric field as high as one quarter of the critical field of quantum electrodynamics and are seen to lose up to 30% of their kinetic energy during the propagation through the laser field. The experimental data show signatures of quantum effects in the electron dynamics in the external laser field, potentially showing departures from the constant cross field approximation.
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Journal articleStreeter M, Kneip S, Bloom M, et al., 2018,
Observation of laser power amplification in a self-injecting laser wakefield accelerator
, Physical Review Letters, Vol: 120, Pages: 254801-1-254801-6, ISSN: 0031-9007We report on the depletion and power ampli cation of the driving laser pulse in a strongly-drivenlaser wake eld accelerator. Simultaneous measurement of the transmitted pulse energy and temporalshape indicate an increase in peak power from 18711 TW to a maximum of 31812 TW after13 mm of propagation in plasma density of 0:91018cm3. The power ampli cation is correlatedwith the injection and acceleration of electrons in the non-linear wake eld. This process is modeledby including localized redshift and subsequent group delay dispersion at the laser pulse front.
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Journal articleCole JM, Symes DR, Lopes NC, et al., 2018,
High-resolution mu CT of a mouse embryo using a compact laser-driven X-ray betatron source
, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 115, Pages: 6335-6340, ISSN: 0027-8424 -
Journal articleStreeter M, Dann S, Scott JDE, et al., 2018,
Temporal feedback control of high-intensity laser pulses to optimize ultrafast heating of atomic clusters
, Applied Physics Letters, Vol: 112, Pages: 244101-1-244101-5, ISSN: 1077-3118We describe how active feedback routines can be applied at limited repetition rate (5 Hz) to optimize high-power (P>10 TW) laser interactions with clustered gases. Optimization of x-ray production from anargon cluster jet, using a genetic algorithm, approximately doubled the measured energy through temporalmodification of the 150 mJ driving laser pulse. This approach achieved an increased radiation yield throughexploration of a multi-dimensional parameter space, without requiring detailedaprioriknowledge of thecomplex cluster dynamics. The optimized laser pulses exhibited a slow rising edge to the intensity profile,which enhanced the laser energy coupling into the cluster medium, compared to the optimally compressedFWHM pulse (40 fs). Our work suggests that this technique can be more widely utilized for control of intensepulsed secondary radiation from petawatt-class laser systems.
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Journal articleYu JQ, Hu RH, Gong Z, et al., 2018,
The generation of collimated gamma-ray pulse from the interaction between 10 PW laser and a narrow tube target
, APPLIED PHYSICS LETTERS, Vol: 112, ISSN: 0003-6951 -
Journal articleMcGuffey C, Schumaker W, Matsuoka T, et al., 2018,
On the properties of synchrotron-like X-ray emission from laser wakefield accelerated electron beams
, PHYSICS OF PLASMAS, Vol: 25, ISSN: 1070-664X -
Conference paperSymes DR, Brenner CM, Rusby DR, et al., 2018,
Optimisation of compact laser driven accelerator X-ray sources for industrial imaging applications
Compact laser-driven electron accelerators can produce coherent x-ray beams with high brightness, small source-size and femtosecond duration. We will discuss the suitability of these sources to address challenges in industrial imaging.
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Journal articleCole JM, Behm KT, Blackburn TG, et al., 2018,
Experimental evidence of radiation reaction in the collision of a high-intensity laser pulse with a laser-wakefield accelerated electron beam
, Physical Review X, Vol: 8, ISSN: 2160-3308The dynamics of energetic particles in strong electromagnetic fields can be heavily influenced by the energy loss arising from the emission of radiation during acceleration, known as radiation reaction. When interacting with a high-energy electron beam, today’s lasers are sufficiently intense to explore the transition between the classical and quantum radiation reaction regimes. We present evidence of radiation reaction in the collision of an ultrarelativistic electron beam generated by laser-wakefield acceleration (ϵ>500 MeV) with an intense laser pulse (a0>10). We measure an energy loss in the postcollision electron spectrum that is correlated with the detected signal of hard photons (γ rays), consistent with a quantum description of radiation reaction. The generated γ rays have the highest energies yet reported from an all-optical inverse Compton scattering scheme, with critical energy ϵcrit>30 MeV.
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Journal articleWarwick J, Dzelzainis T, Dieckmann ME, et al., 2017,
Experimental observation of a current-driven instability in a neutral electron-positron beam
, Physical Review Letters, Vol: 119, ISSN: 0031-9007We report on the first experimental observation of a current-driven instability developing in a quasineutral matter-antimatter beam. Strong magnetic fields (≥1 T) are measured, via means of a proton radiography technique, after the propagation of a neutral electron-positron beam through a background electron-ion plasma. The experimentally determined equipartition parameter of εB≈10−3 is typical of values inferred from models of astrophysical gamma-ray bursts, in which the relativistic flows are also expected to be pair dominated. The data, supported by particle-in-cell simulations and simple analytical estimates, indicate that these magnetic fields persist in the background plasma for thousands of inverse plasma frequencies. The existence of such long-lived magnetic fields can be related to analog astrophysical systems, such as those prevalent in lepton-dominated jets.
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Journal articlePoder K, Cole JM, Wood JC, et al., 2017,
Measurements of self-guiding of ultrashort laser pulses over long distances
, Plasma Physics and Controlled Fusion, Vol: 60, ISSN: 0741-3335We report on the evaluation of the performance of self-guiding over extended distances with $f/20$ and $f/40$ focussing geometries. Guiding over $39\,\mathrm{mm}$ or more than 100 Rayleigh ranges was observed with the $f/20$ optic at ${n}_{e}=1.5\times {10}^{18}\,{\mathrm{cm}}^{-3}$. Analysis of guiding performance found that the extent of the exiting laser spatial mode closely followed the matched spot size predicted by 3D nonlinear theory. Self-guiding with an $f/40$ optic was also characterised, with guided modes observed for a plasma length of $90\,\mathrm{mm}$ and a plasma density of ${n}_{e}=9.5\times {10}^{17}\,{\mathrm{cm}}^{-3}$. This corresponds to self-guided propagation over 53 Rayleigh ranges and is similar to distances obtained with discharge plasma channel guiding.
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Journal articleRidgers CP, Blackburn TG, Del Sorbo D, et al., 2017,
Signatures of quantum effects on radiation reaction in laser-electron-beam collisions
, JOURNAL OF PLASMA PHYSICS, Vol: 83, ISSN: 0022-3778 -
Journal articleCowley J, Thornton C, Arran C, et al., 2017,
Excitation and control of plasma wakefields by multiple laser pulses
, Physical Review Letters, Vol: 119, ISSN: 1079-7114We demonstrate experimentally the resonant excitation of plasma waves by trains of laser pulses. We also take an important first step to achieving an energy recovery plasma accelerator by showing that a plasma wave can be damped by an out-of-resonance trailing laser pulse. The measured laser wakefields are found to be in excellent agreement with analytical and numerical models of wakefield excitation in the linear regime. Our results indicate a promising direction for achieving highly controlled, GeV-scale laser-plasma accelerators operating at multikilohertz repetition rates.
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Conference paperWalker PA, Alesini PD, Alexandrova AS, et al., 2017,
Horizon 2020 EuPRAXIA design study
, 8th International Particle Accelerator Conference (IPAC), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
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