Publications


Prospects for high gain inertial fusion energy: an introduction to the second edition

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences The Royal Society 379 (2020) 20200028

P Norreys, C Ridgers, K Lancaster, M Koepke, G Tynan

Part II of this special edition contains the remaining eleven papers arising from a Hooke discussion meeting held in March 2020 devoted to exploring the current status of inertial confinement fusion research worldwide and its application to electrical power generation in the future, via the development of an international inertial fusion energy programme. It builds upon increased coordination within Europe over the past decade by researchers supported by the EUROFusion Enabling Research grants, as well as collaborations that have arisen naturally with some of America’s and Asia’s leading researchers’ both in the universities and national laboratories. The articles are devoted to informing an update to the European roadmap for an inertial fusion energy demonstration reactor, building upon the commonalities between the magnetic and inertial fusion communities’ approaches to fusion energy. A number of studies devoted to understanding the physics barriers to ignition on current facilities are then presented. The special issue concludes with four state of-the-art articles describing recent significant advances in fast ignition inertial fusion research.


One-dimensional hydrodynamic simulations of low convergence ratio direct-drive inertial confinement fusion implosions

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences The Royal Society 379 (2020) 20200224

R Paddock, H Martin, R Ruskov, R Scott, W Garbett, B Haines, A Zylstra, R Aboushelbaya, M Mayr, B Spiers, R Wang, P Norreys

Indirect drive inertial confinement fusion experiments with convergence ratios below 17 have been previously shown to be less susceptible to Rayleigh-Taylor hydrodynamic instabilities, making this regime highly interesting for fusion science. Additional limitations imposed on the implosion velocity, in-flight aspect ratio and applied laser power aim to further reduce instability growth, resulting in a new regime where performance can be well represented by one-dimensional (1D) hydrodynamic simulations. A simulation campaign was performed using the 1D radiation-hydrodynamics code HYADES to investigate the performance that could be achieved using direct drive implosions of liquid layer capsules, over a range of relevant energies. Results include potential gains of 0.19 on LMJ-scale systems and 0.75 on NIF-scale systems, and a reactor-level gain of 54 for an 8.5 MJ implosion. While the use of 1D simulations limits the accuracy of these results, they indicate a sufficiently high level of performance to warrant further investigations and verification of this new low-instability regime. This potentially suggests an attractive new approach to fusion energy.


Collisionless shock acceleration in the corona of an inertial confinement fusion pellet with possible application to ion fast ignition.

Philosophical transactions. Series A, Mathematical, physical, and engineering sciences 379 (2021) 20200039-

E Boella, R Bingham, RA Cairns, P Norreys, R Trines, R Scott, M Vranic, N Shukla, LO Silva

Two-dimensional particle-in-cell simulations are used to explore collisionless shock acceleration in the corona plasma surrounding the compressed core of an inertial confinement fusion pellet. We show that an intense laser pulse interacting with the long scale-length plasma corona is able to launch a collisionless shock around the critical density. The nonlinear wave travels up-ramp through the plasma reflecting and accelerating the background ions. Our results suggest that protons with characteristics suitable for ion fast ignition may be achieved in this way. This article is part of a discussion meeting issue 'Prospects for high gain inertial fusion energy (part 2)'.


Whole-beam self-focusing in fusion-relevant plasma

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences Royal Society 379 (2020) 20200159

B Spiers, M Hill, C Brown, L Ceurvorst, N Ratan, A Savin, P Allan, E Floyd, J Fyrth, L Hobbs, S James, J Luis, M Ramsay, N Sircombe, J Skidmore, R Aboushelbaya, M Mayr, R Paddock, R Wang, P Norreys

Fast ignition inertial confinement fusion requires the production of a low-density channel in plasma with density scale-lengths of several hundred microns. The channel assists in the propagation of an ultra-intense laser pulse used to generate fast electrons which form a hot spot on the side of pre-compressed fusion fuel. We present a systematic characterisation of an expanding laser-produced plasma using optical interferometry, benchmarked against three-dimensional hydrodynamic simulations. Magnetic fields associated with channel formation are probed using proton radiography, and compared to magnetic field structures generated in fullscale particle-in-cell simulations. We present observations of long lived, straight channels produced by the Habara-Kodama-Tanaka (HKT) wholebeam self-focusing mechanism, overcoming a critical barrier on the path to realising fast ignition.


Preparations for a European R&D roadmap for an inertial fusion demo reactor

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences The Royal Society 379 (2020) 20200005

P Norreys, L Ceurvorst, J Sadler, B Spiers, M Mayr, N Ratan, A Savin, K Glize, R Trines, B Bingham, M Hill, N Sircombe, P Allan, L Hobbs, S James, J Skidmore, J Fyrth, J Luis, E Floyd, C Brown, B Haines, R Olson, S Yi, A Zylstra, R Peterson

A European consortium of 15 laboratories across nine nations have worked together under the EUROFusion Enabling Research grants for the past decade with three principle objectives. These are: (a) investigating obstacles to ignition on megaJoule-class laser facilities; (b) investigating novel alternative approaches to ignition, including basic studies for fast ignition (both electron and ion-driven), auxiliary heating, shock ignition, etc.; and (c) developing technologies that will be required in the future for a fusion reactor. A brief overview of these activities, presented here, along with new calculations relates the concept of auxiliary heating of inertial fusion targets, and provides possible future directions of research and development for the updated European Roadmap that is due at the end of 2020.


First demonstration of ARC-accelerated proton beams at the National Ignition Facility (vol 26, 043110, 2019)

PHYSICS OF PLASMAS 27 (2020) ARTN 129901

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 Hoemoelle, 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, M Gatu-Johnson, B Lahmann


Prospects for high gain inertial fusion energy: an introduction to the first special edition

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences The Royal Society 378 (2020) 20200006

P Norreys, K Lancaster, C Ridgers, M Koepke, G Tynan


Nonlinear wakefields and electron injection in cluster plasma

Physical Review Accelerators and Beams American Physical Society 23 (2020) 093501

M Mayr, B Spiers, R Aboushelbaya, R Paddock, J Sadler, C Sillett, R Wang, K Krushelnick, P Norreys

Laser and beam driven wakefields promise orders of magnitude increases in electric field gradients for particle accelerators for future applications. Key areas to explore include the emittance properties of the generated beams and overcoming the dephasing limit in the plasma. In this paper, the first in-depth study of the self-injection mechanism into wakefield structures from nonhomogeneous cluster plasmas is provided using high-resolution two dimensional particle-in-cell simulations. The clusters which are typical structures caused by ejection of gases from a high-pressure gas jet have a diameter much smaller than the laser wavelength. Conclusive evidence is provided for the underlying mechanism that leads to particle trapping, comparing uniform and cluster plasma cases. The accelerated electron beam properties are found to be tunable by changing the cluster parameters. The mechanism explains enhanced beam charge paired with large transverse momentum and energy which has implications for the betatron x-ray flux. Finally, the impact of clusters on the high-power laser propagation behavior is discussed.


Bright x-ray radiation from plasma bubbles in an evolving laser wakefield accelerator

Physical Review Accelerators and Beams 23 (2020)

MS Bloom, MJV Streeter, S Kneip, RA Bendoyro, O Cheklov, JM Cole, A Döpp, CJ Hooker, J Holloway, J Jiang, NC Lopes, H Nakamura, PA Norreys, PP Rajeev, DR Symes, J Schreiber, JC Wood, M Wing, Z Najmudin, SPD Mangles

© 2020 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. 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.


Measuring the orbital angular momentum of high-power laser pulses

Physics of Plasmas AIP Publishing 27 (2020) 053107

R Aboushelbaya, K Glize, A Savin, M Mayr, B Spiers, R Wang, N Bourgeois, C Spindloe, R Bingham, P Norreys

In this article, we showcase the experimental results of methods to produce and characterize orbital angular momentum (OAM) carrying high-power lasers. The OAM pulses were produced on the ASTRA laser of the Central Laser Facility using a continuous spiral phase plate. Three different characterization methods were then used to measure the OAM content of the beam. The methods that were used were a cylindrical lens diagnostic, an interferometric diagnostic, and a projective diagnostic. We further discuss the relative advantages and disadvantages of each method in the context of high-power laser experiments.


Energy absorption in the laser-QED regime

Scientific Reports Springer Nature 9 (2019) 8956

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

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.


Wakefields in a cluster plasma

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

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

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.


Orbital angular momentum coupling in elastic photon-photon scattering

Physical Review Letters American Physical Society 123 (2019) 113604

R Aboushelbaya, K Glize, A Savin, M Mayr, B Spiers, R Wang, J Collier, M Marklund, 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.


Kinetic simulations of fusion ignition with hot-spot ablator mix

Physical Review E American Physical Society 100 (2019) 033206

J Sadler, Y Lu, B Spiers, M Mayr, 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.


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.


Advantages to a diverging Raman amplifier

Communications Physics Nature Publishing Group 1 (2018) 19

J Sadler, LO Silva, RA Fonseca, K Glize, M Kasim, A Savin, R Aboushelbaya, M Mayr, 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.


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

R Aboushelbaya, A Savin, L Ceurvorst, J Sadler, 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.


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.


Channel optimization of high-intensity laser beams in millimeter-scale plasmas

Physical Review E American Physical Society 97 (2018) 043208

L Ceurvorst, A Savin, N Ratan, J Sadler, P Norreys, H Habara, KA Tanaka, S Zhang, Wei, S Ivancic, D Froula, W Theobald

Channeling experiments were performed at the OMEGA EP facility using relativistic intensity ( > 10 18 W / cm 2 ) kilojoule laser pulses through large density scale length ( ∼ 390 – 570 μ m ) laser-produced plasmas, demonstrating the effects of the pulse's focal location and intensity as well as the plasma's temperature on the resulting channel formation. The results show deeper channeling when focused into hot plasmas and at lower densities, as expected. However, contrary to previous large-scale particle-in-cell studies, the results also indicate deeper penetration by short (10 ps), intense pulses compared to their longer-duration equivalents. This new observation has many implications for future laser-plasma research in the relativistic regime.


AWAKE readiness for the study of the seeded self-modulation of a 400GeV proton bunch

PLASMA PHYSICS AND CONTROLLED FUSION 60 (2017) ARTN 014046

P Muggli, E Adli, R Apsimon, F Asmus, R Baartman, A-M Bachmann, MB Marin, F Batsch, J Bauche, VKB Olsen, M Bernardini, B Biskup, EB Vinuela, A Boccardi, T Bogey, T Bohl, C Bracco, F Braunmuller, S Burger, G Burt, S Bustamante, B Buttenschoen, A Butterworth, A Caldwell, M Cascella, E Chevallay, M Chung, H Damerau, L Deacon, A Dexter, P Dirksen, S Doebert, J Farmer, V Fedosseev, T Feniet, G Fior, R Fiorito, R Fonseca, F Friebel, P Gander, S Gessner, I Gorgisyan, AA Gorn, O Grulke, E Gschwendtner, A Guerrero, J Hansen, C Hessler, W Hofle, J Holloway, M Huther, M Ibison, MR Islam, L Jensen, S Jolly, M Kasim, F Keeble, S-Y Kim, F Kraus, A Lasheen, T Lefevre, G LeGodec, Y Li, S Liu, N Lopes, KV Lotov, M Martyanov, S Mazzoni, DM Godoy, O Mete, VA Minakov, R Mompo, J Moody, MT Moreira, J Mitchell, C Mutin, P Norreys, E Oz, E Ozturk, W Pauw, A Pardons, C Pasquino, K Pepitone, A Petrenko, S Pitmann, G Plyushchev, A Pukhov, K Rieger, H Ruhl, J Schmidt, IA Shalimova, E Shaposhnikova, P Sherwood, L Silva, AP Sosedkin, R Speroni, RI Spitsyn, K Szczurek, J Thomas, PV Tuev, M Turner, V Verzilov, J Vieira, H Vincke, CP Welsch, B Williamson, M Wing, G Xia, H Zhang, AWAKE Collaboration

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