Publications


Erratum: Emittance Preservation in an Aberration-Free Active Plasma Lens [Phys. Rev. Lett. 121, 194801 (2018)].

Physical review letters 122 (2019) 129901-129901

CA Lindstrøm, E Adli, G Boyle, R Corsini, AE Dyson, W Farabolini, SM Hooker, M Meisel, J Osterhoff, J-H Röckemann, L Schaper, KN Sjobak

This corrects the article DOI: 10.1103/PhysRevLett.121.194801.


Wakefields in a cluster plasma

Physical Review Special Topics: Accelerators and Beams American Physical Society 22 (2019) 113501

L Ceurvorst, N Bourgeois, R Pattathil, P Norreys, M Mayr, J Sadler, M Kasim, B Spiers, K Glize, A Savin, F Keeble, A Ross, R Wang, R Bingham, P Burrows, M Wing, D Symes, R Aboushelbaya, R Fonseca, J Holloway, N Ratan, R Trines

We report the first comprehensive study of large amplitude Langmuir waves in a plasma of nanometer-scale clusters. Using an oblique angle single-shot frequency domain holography diagnostic, the shape of these wakefields is captured for the first time. The wavefronts are observed to curve backwards, in contrast to the forwards curvature of wakefields in uniform plasma. Due to the expansion of the clusters, the first wakefield period is longer than those trailing it. The features of the data are well described by fully relativistic two-dimensional particle-in-cell simulations and by a quasianalytic solution for a one-dimensional, nonlinear wakefield in a cluster plasma.


EuPRAXIA - A compact, cost-efficient particle and radiation source

AIP Conference Proceedings AIP Publishing 2160 (2019)

MK Weikum, T Akhter, PD Alesini, AS Alexandrova, MP Anania, NE Andreev, A Bacci, IF Barna, A Beaton, F Brandi, O Bringer, R Brinkmann, E Bründermann, A Cianchi, J Cole, J Clarke, R Fedele, AF Pousa, J Fils, G Fiore, I Andriyash, A Aschikhin, RW Assmann, T Audet, A Beck

Plasma accelerators present one of the most suitable candidates for the development of more compact particle acceleration technologies, yet they still lag behind radiofrequency (RF)-based devices when it comes to beam quality, control, stability and power efficiency. The Horizon 2020-funded project EuPRAXIA ("European Plasma Research Accelerator with eXcellence In Applications") aims to overcome the first three of these hurdles by developing a conceptual design for a first international user facility based on plasma acceleration. In this paper we report on the main features, simulation studies and potential applications of this future research infrastructure.


Low-density hydrodynamic optical-field-ionized plasma channels generated with an axicon lens

PHYSICAL REVIEW ACCELERATORS AND BEAMS 22 (2019) ARTN 041302

RJ Shalloo, C Arran, A Picksley, A von Boetticher, L Corner, J Holloway, G Hine, J Jonnerby, HM Milchberg, C Thornton, R Walczak, SM Hooker


Energy absorption in the laser-QED regime

Scientific Reports Springer Nature 9 (2019) 8956

A Savin, B Spiers, R Wang, P Norreys, A Ross, R Aboushelbaya, M Mayr

A theoretical and numerical investigation of non-ponderomotive absorption at laser intensities relevant to quantum electrodynamics is presented. It is predicted that there is a regime change in the dependence of fast electron energy on incident laser energy that coincides with the onset of pair production via the Breit-Wheeler process. This prediction is numerically verified via an extensive campaign of QED-inclusive particle-in-cell simulations. The dramatic nature of the power law shift leads to the conclusion that this process is a candidate for an unambiguous signature that future experiments on multi-petawatt laser facilities have truly entered the QED regime.


Plasma Wakefield Accelerator Research 2019 - 2040: A community-driven UK roadmap compiled by the Plasma Wakefield Accelerator Steering Committee (PWASC)

(2019)

B Hidding, S Hooker, S Jamison, B Muratori, C Murphy, Z Najmudin, R Pattathil, G Sarri, M Streeter, C Welsch, M Wing, G Xia

The acceleration gradients generated in a laser- or beam-driven plasma wakefield accelerator are typically three orders of magnitude greater than those produced by a conventional accelerator, and hence plasma accelerators can open a route to a new generation of very compact machines. In addition, plasma-based accelerators can generate beams with unique properties, such as tens of kiloamp peak currents, attosecond bunch duration, ultrahigh brightness and intrinsic particle beam-laser pulse synchronization. In this roadmap we review the status of plasma accelerator research in the UK. We outline potential applications, describe the research and development required to enable those applications, and discuss synergies with related areas of research. We also set-out the resources required to realise these ambitions and provide a timeline for advances in the key areas.


Kinetic simulations of fusion ignition with hot-spot ablator mix

Physical Review E American Physical Society 100 (2019) 033206

J Sadler, Y Lu, M Mayr, B Spiers, A Savin, R Wang, R Aboushelbaya, K Glize, R Bingham, H Li, K Flippo, P Norreys

Inertial confinement fusion fuel suffers increased X-ray radiation losses when carbon from the capsule ablator mixes into the hot-spot. Here we present one and two-dimensional ion VlasovFokker-Planck simulations that resolve hot-spot self heating in the presence a localised spike of carbon mix, totalling 1.9 % of the hot-spot mass. The mix region cools and contracts over tens of picoseconds, increasing its alpha particle stopping power and radiative losses. This makes a localised mix region more severe than an equal amount of uniformly distributed mix. There is also a purely kinetic effect that reduces fusion reactivity by several percent, since faster ions in the tail of the distribution are absorbed by the mix region. Radiative cooling and contraction of the spike induces fluid motion, causing neutron spectrum broadening. This artificially increases the inferred experimental ion temperatures and gives line of sight variations.


Direct Observation of Plasma Waves and Dynamics Induced by Laser-Accelerated Electron Beams

PHYSICAL REVIEW X 9 (2019) ARTN 011046

MF Gilljohann, H Ding, A Doepp, J Goetzfried, S Schindler, G Schilling, S Corde, A Debus, T Heinemann, B Hidding, SM Hooker, A Irman, O Kononenko, T Kurz, AM de la Ossa, U Schramm, S Karsch


Orbital angular momentum coupling in elastic photon-photon scattering

Physical Review Letters American Physical Society 123 (2019) 113604

R Aboushelbaya, A Savin, K Glize, M Mayr, R Wang, B Spiers, M Marklund, J Collier, R Trines, R Bingham, P Norreys

In this Letter, we investigate the effect of orbital angular momentum (OAM) on elastic photon-photon scattering in a vacuum for the first time. We define exact solutions to the vacuum electromagnetic wave equation which carry OAM. Using those, the expected coupling between three initial waves is derived in the framework of an effective field theory based on the Euler-Heisenberg Lagrangian and shows that OAM adds a signature to the generated photons thereby greatly improving the signal-to-noise ratio. This forms the basis for a proposed high-power laser experiment utilizing quantum optics techniques to filter the generated photons based on their OAM state.


Quasi-phase-matched high-harmonic generation in gas-filled hollow-core photonic crystal fiber

Optica The Optical Society 6 (2019) 442-442

F Wiegandt, PN Anderson, F Yu, DJ Treacher, DT Lloyd, PJ Mosley, SM Hooker, IA Walmsley


First demonstration of ARC-accelerated proton beams at the National Ignition Facility

Physics of Plasmas 26 (2019)

D Mariscal, T Ma, SC Wilks, AJ Kemp, GJ Williams, P Michel, H Chen, PK Patel, BA Remington, M Bowers, L Pelz, MR Hermann, W Hsing, D Martinez, R Sigurdsson, M Prantil, A Conder, J Lawson, M Hamamoto, P Di Nicola, C Widmayer, D Homoelle, R Lowe-Webb, S Herriot, W Williams, D Alessi, D Kalantar, R Zacharias, C Haefner, N Thompson, T Zobrist, D Lord, N Hash, A Pak, N Lemos, M Tabak, C McGuffey, J Kim, FN Beg, MS Wei, P Norreys, A Morace, N Iwata, Y Sentoku, D Neely, GG Scott, K Flippo

© 2019 Author(s). New short-pulse kilojoule, Petawatt-class lasers, which have recently come online and are coupled to large-scale, many-beam long-pulse facilities, undoubtedly serve as very exciting tools to capture transformational science opportunities in high energy density physics. These short-pulse lasers also happen to reside in a unique laser regime: very high-energy (kilojoule), relatively long (multi-picosecond) pulse-lengths, and large (10s of micron) focal spots, where their use in driving energetic particle beams is largely unexplored. Proton acceleration via Target Normal Sheath Acceleration (TNSA) using the Advanced Radiographic Capability (ARC) short-pulse laser at the National Ignition Facility in the Lawrence Livermore National Laboratory is demonstrated for the first time, and protons of up to 18 MeV are measured using laser irradiation of >1 ps pulse-lengths and quasi-relativistic (∼10 18 W/cm 2 ) intensities. This is indicative of a super-ponderomotive electron acceleration mechanism that sustains acceleration over long (multi-picosecond) time-scales and allows for proton energies to be achieved far beyond what the well-established scalings of proton acceleration via TNSA would predict at these modest intensities. Furthermore, the characteristics of the ARC laser (large ∼100 μm diameter focal spot, flat spatial profile, multi-picosecond, relatively low prepulse) provide acceleration conditions that allow for the investigation of 1D-like particle acceleration. A high flux ∼ 50 J of laser-accelerated protons is experimentally demonstrated. A new capability in multi-picosecond particle-in-cell simulation is applied to model the data, corroborating the high proton energies and elucidating the physics of multi-picosecond particle acceleration.


Optimised XUV holography using spatially shaped high harmonic beams

Optics Express The Optical Society 27 (2019) 29016-29016

DJ Treacher, DT Lloyd, F Wiegandt, K O’Keeffe, SM Hooker


Comparison of Strong-field Ionization Models in the Wavelength-scaling of High Harmonic Generation.

Optics express 27 (2019) 6925-6935

DT Lloyd, K O'Keeffe, SM Hooker

We report the use of wavelength-tuneable laser pulses from an optical parametric amplifier to generate high-order harmonics in a range of noble gases. The variation of the harmonic cut-off wavelength and phasematching pressure with gas species and fundamental wavelength were recorded. The experimental results are compared to a phenomenological model of the harmonic generation process, incorporating two separate models of photo-ionization. While the calculated phasematching pressure is generally insensitive to the ionization model, for the harmonic cut-off we obtain superior agreement between experiment and theory when the Yudin-Ivanov (YI) ionization model is used, compared to the commonly utilised Ammosov-Delone-Krainov (ADK) model.


Observation of Laser Power Amplification in a Self-Injecting Laser Wakefield Accelerator

Physical Review Letters 120 (2018)

MJV Streeter, S Kneip, MS Bloom, RA Bendoyro, O Chekhlov, AE Dangor, A Döpp, CJ Hooker, J Holloway, J Jiang, NC Lopes, H Nakamura, PA Norreys, CAJ Palmer, PP Rajeev, J Schreiber, DR Symes, M Wing, SPD Mangles, Z Najmudin

© 2018 American Physical Society. We report on the depletion and power amplification of the driving laser pulse in a strongly driven laser wakefield accelerator. Simultaneous measurement of the transmitted pulse energy and temporal shape indicate an increase in peak power from 187±11 TW to a maximum of 318±12 TW after 13 mm of propagation in a plasma density of 0.9×1018 cm-3. The power amplification is correlated with the injection and acceleration of electrons in the nonlinear wakefield. This process is modeled by including a localized redshift and subsequent group delay dispersion at the laser pulse front.


Single-shot frequency-resolved optical gating for retrieving the pulse shape of high energy picosecond pulses

Review of Scientific Instruments AIP Publishing 89 (2018) 103509

A Savin, L Ceurvorst, J Sadler, R Aboushelbaya, PA Norreys, AS Davies, DH Froula, A Boyle, M Galimberti, P Oliveira, B Parry, Y Katzir, K Glize

Accurate characterization of laser pulses used in experiments is a crucial step to the analysis of their results. In this paper, a novel single-shot frequency-resolved optical gating (FROG) device is described, one that incorporates a dispersive element which allows it to fully characterize pulses up to 25 ps in duration with a 65 fs per pixel temporal resolution. A newly developed phase retrieval routine based on memetic algorithms is implemented and shown to circumvent the stagnation problem that often occurs with traditional FROG analysis programs when they encounter a local minimum.


Hydrodynamic optical-field-ionized plasma channels

Physical Review E American Physical Society 97 (2018) 053203

RJ Shalloo, C Arran, L Corner, J Holloway, J Jonnerby, R Walczak, HM Milchberg, S Hooker

We present experiments and numerical simulations which demonstrate that fully-ionized, lowdensity plasma channels could be formed by hydrodynamic expansion of plasma columns produced by optical field ionization (OFI). Simulations of the hydrodynamic expansion of plasma columns formed in hydrogen by an axicon lens show the generation of 200 mm long plasma channels with axial densities of order ne(0) = 1 × 1017 cm−3 and lowest-order modes of spot size WM ≈ 40 µm. These simulations show that the laser energy required to generate the channels is modest: of order 1 mJ per centimetre of channel. The simulations are confirmed by experiments with a spherical lens which show the formation of short plasma channels with 1.5 × 1017 cm−3 . ne(0) . 1 × 1018 cm−3 and 61 µm & WM & 33 µm. Low-density plasma channels of this type would appear to be well-suited as multi-GeV laser-plasma accelerator stages capable of long-term operation at high pulse repetition rates.


Emittance Preservation in an Aberration-Free Active Plasma Lens

Physical Review Letters American Physical Society (2018)

CA Lindstrøm, E Adli, G Boyle, R Corsini, AE Dyson, W Farabolini, SM Hooker, M Meisel, J Osterhoff, J-H Röckemann, L Schaper, KN Sjobak

Active plasma lensing is a compact technology for strong focusing of charged particle beams, which has gained considerable interest for use in novel accelerator schemes. While providing kT/m focusing gradients, active plasma lenses can have aberrations caused by a radially nonuniform plasma temperature profile, leading to degradation of the beam quality. We present the first direct measurement of this aberration, consistent with theory, and show that it can be fully suppressed by changing from a light gas species (helium) to a heavier gas species (argon). Based on this result, we demonstrate emittance preservation for an electron beam focused by an argon-filled active plasma lens.


Spatially-resolved common-path high-order harmonic interferometry

Optics Letters Optical Society of America 43 (2018) 5275-5278

MM Mang, DT Lloyd, PN Anderson, DJ Treacher, AS Wyatt, SM Hooker, IA Walmsley, K O'Keeffe

Spatially resolved interference is observed between high-order harmonics generated in two longitudinally separated gas targets. High-contrast modulations in the intensity of each harmonic order up to the cutoff are observed on-axis in the far field of the source as the separation between the gas targets is increased. For low-order harmonics, additional off-axis modulations are observed, which are attributed to the interference between the contributions from the long quantum trajectories from each gas target. The inherent synchronization of this setup offers the prospect for high-stability metrology of quantum states with ultrafast temporal resolutions.


Advantages to a diverging Raman amplifier

Communications Physics Nature Publishing Group 1 (2018) 19

J Sadler, LO Silva, RA Fonseca, K Glize, M Kasim, M Mayr, A Savin, R Aboushelbaya, B Spiers, RH-W Wang, R Bingham, RMGM Trines, P Norreys

The plasma Raman instability can efficiently compress a nanosecond long high power laser pulse to sub-picosecond duration. Although many authors envisaged a converging beam geometry for Raman amplification, here we propose the exact opposite geometry; the amplification should start at the intense focus of the seed. We generalise the coupled laser envelope equations to include this non-collimated case. The new geometry completely eradicates the usual trailing secondary peaks of the output pulse, which typically lower the efficiency by half. It also reduces, by orders of magnitude, the initial seed pulse energy required for efficient operation. As in the collimated case, the evolution is self-similar, although the temporal pulse envelope is different. A two-dimensional particle-in-cell simulation demonstrates efficient amplification of a diverging seed with only 0:3mJ energy. The pulse has no secondary peaks and almost constant intensity as it amplifies and diverges.


Reconstructing nonlinear plasma wakefields using a generalized temporally encoded spectral shifting analysis

Physical Review Accelerators and Beams 21 (2018) 103501-103501

C Arran, NH Matlis, R Walczak, SM Hooker

We generalize the temporally encoded spectral shifting (TESS) analysis for measuring plasma wakefields using spectral interferometry to dissimilar probe pulses of arbitrary spectral profile and to measuring nonlinear wakefields. We demonstrate that the Gaussian approximation used up until now results in a substantial miscalculation of the wakefield amplitude, by a factor of up to two. A method to accurately measure higher amplitude quasilinear and nonlinear wakefields is suggested, using an extension to the TESS procedure, and we place some limits on its accuracy in these regimes. These extensions and improvements to the analysis demonstrate its potential for rapid and accurate on-shot diagnosis of plasma wakefields, even at low plasma densities.

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