Publications
303 results found
Arran C, Bradford P, Dearling A, et al., 2023, Measurement of Magnetic Cavitation Driven by Heat Flow in a Plasma., Phys Rev Lett, Vol: 131
We describe the direct measurement of the expulsion of a magnetic field from a plasma driven by heat flow. Using a laser to heat a column of gas within an applied magnetic field, we isolate Nernst advection and show how it changes the field over a nanosecond timescale. Reconstruction of the magnetic field map from proton radiographs demonstrates that the field is advected by heat flow in advance of the plasma expansion with a velocity v_{N}=(6±2)×10^{5} m/s. Kinetic and extended magnetohydrodynamic simulations agree well in this regime due to the buildup of a magnetic transport barrier.
Chen YH, Ting AC, Hafizi B, et al., 2023, Proton acceleration in an overdense hydrogen plasma by intense CO<inf>2</inf> laser pulses with nonlinear propagation effects in the underdense pre-plasma, Physics of Plasmas, Vol: 30, ISSN: 1070-664X
We report on proton acceleration from intense CO2 laser-irradiated hydrogen plasmas at near-critical densities, with the density gradient steepened by Nd:YAG laser ablation-driven hydrodynamic shocks. While the experimental results, such as the quasi-monoenergetic proton spectra and their scaling with respect to the laser energy, are generally in agreement with the simulations, certain laser shots produced significantly higher proton energies than anticipated during the experiment. The increased proton energy may be linked to nonlinear propagation effects in the steepened plasma density ramp before the critical surface, including relativistic self-focusing and, for the case of temporally-structured laser pulses observed in the experiment, focusing of the trailing pulse through the plasma channel formed by the leading pulse 25 ps ahead. The occurrence of channel focusing in the underdense hydrogen plasma is supported by a subsequent pump-probe experiment with a dark-field imaging technique, where the formation of ion channels was observed after the passage of an intense CO2 laser pulse.
Streeter MJV, Ma Y, Kettle B, et al., 2022, Characterization of laser wakefield acceleration efficiency with octave spanning near-IR spectrum measurements, PHYSICAL REVIEW ACCELERATORS AND BEAMS, Vol: 25
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- Citations: 1
Dickson LT, Underwood CID, Filippi F, et al., 2022, Mechanisms to control laser-plasma coupling in laser wakefield electron acceleration, Physical Review Accelerators and Beams, Vol: 25, Pages: 1-12, ISSN: 2469-9888
Experimental results, supported by precise modeling, demonstrate optimization of a plasma-based injector with intermediate laser pulse energy (<1 J), corresponding to a normalized vector potential a0=2.15, using ionization injection in a tailored plasma density profile. An increase in electron bunch quality and energy is achieved experimentally with the extension of the density downramp at the plasma exit. Optimization of the focal position of the laser pulse in the tailored plasma density profile is shown to efficiently reduce electron bunch angular deviation, leading to a better alignment of the electron bunch with the laser axis. Single peak electron spectra are produced in a previously unexplored regime by combining an early focal position and adaptive optic control of the laser wavefront by optimizing the symmetry of the prefocal laser energy distribution. Experimental results have been validated through particle-in-cell simulations using realistic laser energy, phase distribution, and temporal envelope, allowing for accurate predictions of difficult to model parameters, such as total charge and spatial properties of the electron bunches, opening the way for more accurate modeling for the design of plasma-based accelerators.
Alejo A, Ahmed H, Krygier AG, et al., 2022, Stabilized Radiation Pressure Acceleration and Neutron Generation in Ultrathin Deuterated Foils, PHYSICAL REVIEW LETTERS, Vol: 129, ISSN: 0031-9007
Martin P, Ahmed H, Doria D, et al., 2022, Absolute calibration of Fujifilm BAS-TR image plate response to laser driven protons up to 40 MeV, REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 93, ISSN: 0034-6748
Maitrallain 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
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- Citations: 3
McIlvenny A, Doria D, Romagnani L, et al., 2021, Selective Ion Acceleration by Intense Radiation Pressure, PHYSICAL REVIEW LETTERS, Vol: 127, ISSN: 0031-9007
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- Citations: 11
Finlay 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
Danson 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: 2095-4719
The 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.
Assmann 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
Gruse 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: 0168-9002
X-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.
Streeter 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: 2041-1723
Laser 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%.
Underwood 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
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- Citations: 5
Assmann RW, Weikum MK, Akhter T, et al., 2020, EuPRAXIA conceptual design report, European Physical Journal: Special Topics, Vol: 229, Pages: 3675-4284, ISSN: 1951-6355
This 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
Dover 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
Kondo 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: 2073-4352
The 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.
Xu 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
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- Citations: 3
Aymar 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: 2296-424X
The “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.
Nishiuchi 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: 2643-1564
Motivated 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.
Streeter MJV, Najmudin Z, 2020, Compton recoil effects in staging of laser wakefield accelerators, PHYSICAL REVIEW ACCELERATORS AND BEAMS, Vol: 23, ISSN: 2469-9888
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- Citations: 1
Mangles 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: 2469-9888
We 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.
Bloom MS, Streeter MJV, Kneip S, et al., 2020, Bright X-ray radiation from plasma bubbles in an evolving laser wakefield accelerator
We show that the properties of the electron beam and bright X-rays producedby a laser wakefield accelerator can be predicted if the distance over whichthe laser self-focuses and compresses prior to self-injection is taken intoaccount. A model based on oscillations of the beam inside a plasma bubble showsthat performance is optimised when the plasma length is matched to the laserdepletion length. With a 200~TW laser pulse this results in an X-ray beam withmedian photon energy of 20 keV, $> 10^{9}$ photons per shot and a peakbrightness of $4 \times 10^{23}$ photons s$^{-1}$ mrad$^{-2}$ mm$^{-2}$ (0.1 %BW)$^{-1}$.
Hussein 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: 2045-2322
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Passalidis 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
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- Citations: 4
Kurup 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: 1120-1797
The 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.
Consoli 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: 2045-2322
We 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.
Dann SJD, Baird CD, Bourgeois N, et al., 2019, Laser wakefield acceleration with active feedback at 5 Hz, Physical Review Accelerators and Beams, Vol: 22, ISSN: 2469-9888
We describe the use of a genetic algorithm to apply active feedback to a laser wakefield accelerator at a higher power (10 TW) and a lower repetition rate (5 Hz) than previous work. The temporal shape of the drive laser pulse was adjusted automatically to optimize the properties of the electron beam. By changing the software configuration, different properties could be improved. This included the total accelerated charge per bunch, which was doubled, and the average electron energy, which was increased from 22 to 27 MeV. Using experimental measurements directly to provide feedback allows the system to work even when the underlying acceleration mechanisms are not fully understood, and, in fact, studying the optimized pulse shape might reveal new insights into the physical processes responsible. Our work suggests that this technique, which has already been applied with low-power lasers, can be extended to work with petawatt-class laser systems.
McIlvenny 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
King 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
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