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Springer Theses Recognizing Outstanding Ph.D. Research Fabien Niel Classical and Quantum Description of Plasma and Radiation in Strong Fields Springer Theses Recognizing Outstanding Ph.D. Research Aims and Scope The series “Springer Theses” brings together a selection of the very best Ph.D. theses from around the world and across the physical sciences. Nominated and endorsed by two recognized specialists, each published volume has been selected foritsscientificexcellenceandthehighimpactofitscontentsforthepertinentfield of research. For greater accessibility to non-specialists, the published versions includeanextendedintroduction,aswellasaforewordbythestudent’ssupervisor explainingthespecialrelevanceoftheworkforthefield.Asawhole,theserieswill provide a valuable resource both for newcomers to the research fields described, and for other scientists seeking detailed background information on special questions. 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More information about this series at http://www.springer.com/series/8790 Fabien Niel Classical and Quantum Description of Plasma and Radiation in Strong Fields Doctoral Thesis accepted by é Sorbonne Universit , Jussieu, Paris 123 Author Supervisor FabienNiel Prof. Caterina Riconda Laboratoire Utilisation Lasers Intenses Laboratoire Utilisation Lasers Intenses Sorbonne Université Sorbonne Université,Jussieu Paris, France Paris, France ISSN 2190-5053 ISSN 2190-5061 (electronic) SpringerTheses ISBN978-3-030-73546-3 ISBN978-3-030-73547-0 (eBook) https://doi.org/10.1007/978-3-030-73547-0 ©TheEditor(s)(ifapplicable)andTheAuthor(s),underexclusivelicense toSpringerNatureSwitzerlandAG2021 Thisworkissubjecttocopyright.AllrightsaresolelyandexclusivelylicensedbythePublisher,whether thewholeorpartofthematerialisconcerned,specificallytherightsoftranslation,reprinting,reuseof illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmissionorinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilar ordissimilarmethodologynowknownorhereafterdeveloped. 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ThisSpringerimprintispublishedbytheregisteredcompanySpringerNatureSwitzerlandAG Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland À mes parents et à ma soeur ’ Supervisor s Foreword The study of quantum electrodynamics (QED) processes and strong-field QED processes,inparticular,haslongbeenconsideredthedomainofelementaryparticle physics.Overthelastdecade,however,thestudyofQEDprocessesinplasmashas become a very hot research topic, at the cross-road of various disciplines and as such approached differently by various scientific communities. The motivation behindtheongoingresearchefforthascome,ontheonehand,fromtherealization that QED processes are important in various extreme astrophysical environments dominated by relativistic plasma flows, such as active galactic nuclei, pulsars or gamma ray bursts. On the other hand, it is encouraged by the advent of new research facilities, such as the x-ray free-electron lasers and multi-petawatt laser facilities under construction worldwide, which will soon allow to create, in the laboratory, electromagnetic fields of unprecedented amplitude together with ultra-relativistic particles and/or plasma flows. Interestingly, the strong research activityinthisfieldisalsosupportedandinmanywaysdrivenbythedevelopment of high-performance kinetic simulation tools that more and more allow to account foradditionalQEDprocessesinafullyconsistent,relativisticframeworkforplasma modelling. FabienNiel’sthesisisacontributiontothisresearcheffort,whichfocusesonthe study of two processes: (i) the emission of high-energy gamma photons by ultra-relativistic electrons in strong electromagnetic fields and its back reaction on the electrons’ dynamics; and (ii) the production of electron–positron pairs in the interactionofanultra-highintensitylaserbeamcarryingangularorbitalmomentum with a counter-propagating gamma-photon bunch. The treatment of high-energy (gamma) photon emission by ultra-relativistic electrons in strong electromagnetic fields and its back reaction on the electron dynamics is a very old problem known as radiation reaction (RR). Its description and study in Fabien Niel’s thesis have led to new results that are particularly relevant today. First, it presents in a self-consistent, mathematically clear and physically solid framework how classical RR—usually treated using a continuous vii viii Supervisor’sForeword radiation reaction force—emerges from a quantum description based on the sta- tisticaldescriptionof notasingle electron, butanensemble of electrons. By doing so, it is possible to understand and relate various treatments of RR whether in a theoreticalframework(linearBoltzmann,Fokker–Planckorradiationreactionforce descriptions) or in computer simulations (Monte Carlo and particle-in-cell simulations). The domains of validity of the various descriptions are also identified. In addition, the author presents an exhaustive analysis of the effects of RR on the distribution function of relativistic charged particles interacting with a strong background electromagnetic field, as well as on the emitted high-energy gamma-photon spectra. This second aspect has serious implications for future experiments on the forthcoming extreme light laser facilities such as the Apollon laser in construction on the Plateau de Saclay, South of Paris, and the European project Extreme Light Infrastructure (ELI) that aims at the construction of at least three multi-petawatt laser facilities in Central and Eastern Europe. Such laser facilities will indeed provide the scientific community with a new path towards a yet unexplored regime of laser–plasma interaction where the electron dynamics is not only ultra-relativistic but also of a quantum nature. The in-depth study of the resultingelectronandphotondistributionswillproveanimportantassetinthestudy of RR on these forthcoming lasers. ThemostexoticprocessandstrikingdemonstrationofQEDenvisionedonthese extremelightlasersis theso-callednonlinear Breit–Wheeler process. It consists in the production of an electron–positron pair via the interaction of an energetic (gamma) photon with the strong electromagnetic field of the laser. A chapter in Fabien Niel’s thesis is devoted to the study of this process in the interaction of a high-energy photon bunch colliding with a Laguerre–Gaussian beam carrying orbital angular momentum. This study clearly illustrates that QED processes in plasmasarenotonlyinterestingatthefundamentallevel,theycanalsohelpdesign new intense sources of radiation (gamma photons) and electron–positron pairs. Clearly,thethesisbyFabienNielhasthepotentialtohelpthenextgenerationof young scientists get acquainted with the emerging field of strong-field plasma interaction.Supportedbyanextensiveliterature,itanswersmanyquestionsaswell asposesnewones,thuspavingthewaytofurtherstudiesinthesubject.Wearealso confident that this thesis will make an excellent reference text for a much broader audience and a valuable textbook for both students or experienced researchers interested in the treatment of QED processes in plasmas. Indeed, beyond the pre- sentation of original results in Part II and III of the thesis, Part I is intended as an advanced tutorial moving from classical electrodynamics, through the classical theory of RR, to quantum electrodynamics and quantum RR, while finally intro- ducingthebasicsofthekineticdescriptionofasystemcomposedofalargenumber of particles at the basis of plasma physics. There the author presents in a concise, yet clear and self-contained framework the theoretical background necessary to a solid understanding of the inclusion of QED processes in plasmas. Beyond the pedagogical approach, we hope this thesis will offer the reader a glimpse of the Supervisor’sForeword ix excitementandnewideasbloominginthisveryactiveresearchfield,andthatitwill motivate advances in basic physics problems past the near future applications of intense laser–plasma interaction. Prof. Caterina Riconda Acknowledgements First of all, I would like to thank my thesis supervisor Caterina Riconda for her unwavering support during these three years from both a human and a scientific point of view. Thank you for always encouraging me, even during my periods of existential doubts and questions about my future. Thank you for your intellectual availability.Youwerealwaysreadytodiscussanyscientificidea,whetheritwasin relationwiththethesisornot.Finallythanksforhavingcontributedtothisfriendly and relaxed working atmosphere. I will remember, in particular, the typical dis- cussions about the latest movie you had seen, or other more “philosophical” questions(suchas“whowasnicer:KarlPopperorLudwigWittgenstein?”Or“who is the nice one in Death Note: L or Light?”). I would like to thank François Amiranoff for the trust you have placed in me during the “laser–plasma interaction at high flux” oral exam, at the end of which I toldyouIwishedtopursueathesisintheoreticalphysicsandyouproposedmethis thesis without hesitation. Thank you for all the cakes, chocolates and other dishes you constantly gratified us, for the greatest pleasure of our palates and highest displeasure of our bellies! Finally thanks for all the “physics of everyday life” questionsthatyousharedwithusandthatconstituteformeanimportantsourceof inspirationforanyphysicist(“howdoesadiverfeelthepressureofthewaterabove him?”). Last but not least, I would like to thank Mickaël Grech. Thank you for your rigour, always searching for the devil in the details, or as you would say, “á e****** des mouches”! The sessions on the board to try to clarify what had been done have contributed without a doubt to the quality of this thesis. Thank you as well forallthediscussionsonphysics(“whatwouldhappen tothetwin paradox if wehaveauniversethatfoldsinonitself?”),music(LeonardCohenvsBobDylan) or the questions of existential nature that often started with “I’m going to grab a sandwich, let’s go downstairs?”. Iwouldalsoliketothankallthemembersofthejury,Pr.MattiasMarklund,Pr. Luis O. Silva, Pr. Antonino Di Piazza, Dr. Laurent Gremillet and Pr. Jean-Michel Raimond, for taking the time to read and evaluate this work, and also for the numerous questions and remarks. Thanks, in particular, to Pr. Mattias Marklund xi