Temporal contrast-dependent modeling of laser-driven solids - studying femtosecond-nanometer interactions and probing

Establishing precise control over the unique beam parameters of laser-accelerated ions from relativistic ultra-short pulse laser-solid interactions has been a major goal for the past 20 years. While the spatio-temporal coupling of laser-pulse and target parameters create transient phenomena at femtosecond-nanometer scales that are decisive for the acceleration performance, these scales have also largely been inaccessible to experimental observation. Computer simulations of laser-driven plasmas provide valuable insight into the physics at play. Nevertheless, predictive capabilities are still lacking due to the massive computational cost to perform these in 3D at high resolution for extended simulation times. This thesis investigates the optimal acceleration of protons from ultra-thin foils following the interaction with an ultra-short ultra-high intensity laser pulse, including realistic contrast conditions up to a picosecond before the main pulse. Advanced ionization methods implemented into the highly scalable, open-source particle-in-cell code PIConGPU enabled this study. Supporting two experimental campaigns, the new methods led to a deeper understanding of the physics of Laser-Wakefield acceleration and Colloidal Crystal melting, respectively, for they now allowed to explain experimental observations with simulated ionization- and plasma dynamics. Subsequently, explorative 3D3V simulations of enhanced laser-ion acceleration were performed on the Swiss supercomputer Piz Daint. There, the inclusion of realistic laser contrast conditions altered the intra-pulse dynamics of the acceleration process significantly. Contrary to a perfect Gaussian pulse, a better spatio-temporal overlap of the protons with the electron sheath origin allowed for full exploitation of the accelerating potential, leading to higher maximum energies. Adapting well-known analytic models allowed to match the results qualitatively and, in chosen cases, quantitatively. However, despite complex 3D plasma dynamics not being reflected within the 1D models, the upper limit of ion acceleration performance within the TNSA scenario can be predicted remarkably well. Radiation signatures obtained from synthetic diagnostics of electrons, protons, and bremsstrahlung photons show that the target state at maximum laser intensity is encoded, previewing how experiments may gain insight into this previously unobservable time frame. Furthermore, as X-ray Free Electron Laser facilities have only recently begun to allow observations at femtosecond-nanometer scales, benchmarking the physics models for solid-density plasma simulations is now in reach. Finally, this thesis presents the first start-to-end simulations of optical-pump, X-ray-probe laser-solid interactions with the photon scattering code ParaTAXIS. The associated PIC simulations guided the planning and execution of an LCLS experiment, demonstrating the first observation of solid-density plasma distribution driven by near-relativistic short-pulse laser pulses at femtosecond-nanometer resolution

Temporal contrast-dependent modeling of laser-driven solids: studying femtosecond-nanometer interactions and probing

Establishing precise control over the unique beam parameters of laser-accelerated ions from relativistic ultra-short pulse laser-solid interactions has been a major goal for the past 20 years. While the spatio-temporal coupling of laser-pulse and target parameters create transient phenomena at femtosecond-nanometer scales that are decisive for the acceleration performance, these scales have also largely been inaccessible to experimental observation. Computer simulations of laser-driven plasmas provide valuable insight into the physics at play. Nevertheless, predictive capabilities are still lacking due to the massive computational cost to perform these in 3D at high resolution for extended simulation times. This thesis investigates the optimal acceleration of protons from ultra-thin foils following the interaction with an ultra-short ultra-high intensity laser pulse, including realistic contrast conditions up to a picosecond before the main pulse. Advanced ionization methods implemented into the highly scalable, open-source particle-in-cell code PIConGPU enabled this study. Supporting two experimental campaigns, the new methods led to a deeper understanding of the physics of Laser-Wake eld acceleration and Colloidal Crystal melting, respectively, for they now allowed to explain experimental observations with simulated ionization- and plasma dynamics. Subsequently, explorative 3D3V simulations of enhanced laser-ion acceleration were performed on the Swiss supercomputer Piz Daint. There, the inclusion of realistic laser contrast conditions altered the intra-pulse dynamics of the acceleration process significantly. Contrary to a perfect Gaussian pulse, a better spatio-temporal overlap of the protons with the electron sheath origin allowed for full exploitation of the accelerating potential, leading to higher maximum energies. Adapting well-known analytic models allowed to match the results qualitatively and, in chosen cases, quantitatively. However, despite complex 3D plasma dynamics not being reflected within the 1D models, the upper limit of ion acceleration performance within the TNSA scenario can be predicted remarkably well. Radiation signatures obtained from synthetic diagnostics of electrons, protons, and bremsstrahlung photons show that the target state at maximum laser intensity is encoded, previewing how experiments may gain insight into this previously unobservable time frame. Furthermore, as X-ray Free Electron Laser facilities have only recently begun to allow observations at femtosecond-nanometer scales, benchmarking the physics models for solid-density plasma simulations is now in reach. Finally, this thesis presents the first start-to-end simulations of optical-pump, X-ray-probe laser-solid interactions with the photon scattering code ParaTAXIS. The associated PIC simulations guided the planning and execution of an LCLS experiment, demonstrating the first observation of solid-density plasma distribution driven by near-relativistic short-pulse laser pulses at femtosecond-nanometer resolution.Die Erlangung präziser Kontrolle über die einzigartigen Strahlparameter von laserbeschleunigten Ionen aus relativistischen Ultrakurzpuls-Laser-Festkörper-Wechselwirkungen ist ein wesentliches Ziel der letzten 20 Jahre. Während die räumlich-zeitliche Kopplung von Laserpuls und Targetparametern transiente Phänomene auf Femtosekunden- und Nanometerskalen erzeugt, die für den Beschleunigungsprozess entscheidend sind, waren diese Skalen der experimentellen Beobachtung bisher weitgehend unzugänglich. Computersimulationen von lasergetriebenen Plasmen liefern dabei wertvolle Einblicke in die zugrunde liegende Physik. Dennoch mangelt es noch an Vorhersagemöglichkeiten aufgrund des massiven Rechenaufwands, um Parameterstudien in 3D mit hoher Auflösung für längere Simulationszeiten durchzuführen. In dieser Arbeit wird die optimale Beschleunigung von Protonen aus ultradünnen Folien nach der Wechselwirkung mit einem ultrakurzen Ultrahochintensitäts-Laserpuls unter Einbeziehung realistischer Kontrastbedingungen bis zu einer Pikosekunde vor dem Hauptpuls untersucht. Hierbei ermöglichen neu implementierte fortschrittliche Ionisierungsmethoden für den hoch skalierbaren, quelloffenen Partikel-in-Zelle-Code PIConGPU von nun an Studien dieser Art. Bei der Unterstützung zweier Experimentalkampagnen führten diese Methoden zu einem tieferen Verständnis der Laser-Wake eld-Beschleunigung bzw. des Schmelzens kolloidaler Kristalle, da nun experimentelle Beobachtungen mit simulierter Ionisations- und Plasmadynamik erklärt werden konnten. Im Anschluss werden explorative 3D3V Simulationen verbesserter Laser-Ionen-Beschleunigung vorgestellt, die auf dem Schweizer Supercomputer Piz Daint durchgeführt wurden. Dabei veränderte die Einbeziehung realistischer Laserkontrastbedingungen die Intrapulsdynamik des Beschleunigungsprozesses signifikant. Im Gegensatz zu einem perfekten Gauß-Puls erlaubte eine bessere räumlich-zeitliche Überlappung der Protonen mit dem Ursprung der Elektronenwolke die volle Ausnutzung des Beschleunigungspotentials, was zu höheren maximalen Energien führte. Die Adaptation bekannter analytischer Modelle erlaubte es, die Ergebnisse qualitativ und in ausgewählten Fällen auch quantitativ zu bestätigen. Trotz der in den 1D-Modellen nicht abgebildeten komplexen 3D-Plasmadynamik zeigt die Vorhersage erstaunlich gut das obere Limit der erreichbaren Ionen-Energien im TNSA Szenario. Strahlungssignaturen, die aus synthethischen Diagnostiken von Elektronen, Protonen und Bremsstrahlungsphotonen gewonnen wurden, zeigen, dass der Target-Zustand bei maximaler Laserintensität einkodiert ist, was einen Ausblick darauf gibt, wie Experimente Einblicke in dieses bisher unbeobachtbare Zeitfenster gewinnen können. Mit neuen Freie-Elektronen-Röntgenlasern sind Beobachtungen auf Femtosekunden-Nanometerskalen endlich zugänglich geworden. Damit liegt ein Benchmarking der physikalischen Modelle für Plasmasimulationen bei Festkörperdichte nun in Reichweite, aber Experimente sind immer noch selten, komplex, und schwer zu interpretieren. Zuletzt werden daher in dieser Arbeit die ersten Start-zu-End-Simulationen der Pump-Probe Wechselwirkungen von optischem sowie Röntgenlaser mit Festkörpern mittels des Photonenstreu-Codes ParaTAXIS vorgestellt. Darüber hinaus dienten die zugehörigen PIC-Simulationen als Grundlage für die Planung und Durchführung eines LCLS-Experiments zur erstmaligen Beobachtung einer durch nah-relativistische Kurzpuls-Laserpulse getriebenen Festkörper-Plasma-Dichte, dessen Auflösungsbereich gleichzeitig bis auf Femtosekunden und Nanometer vordrang

Comparing field ionization models in simulations of laser-matter interaction

Field ionization plays an important role in modeling the interaction of high-power, ultra-short laser pulses with matter. Many field ionization models exist that have predictive capability at non-relativistic laser intensities and for laser pulse durations much longer than the atomic time scales. Most existing models take a quasi-static approach to the laser field on atomic dimensions and time scales. Yet, with pulses as short as a few ~10 to ~100 as and intensities of 1021 W/cm2 the feasibility of these approximations becomes questionable. Still, the exploration of plasma effects in relativistic laser matter interaction requires to test the boundaries of validity for these models. This thesis will take a step to point out the difficulties to be considered when existing ionization models are applied to such extreme cases

Spectral Control via Multi-Species Effects in PW-Class Laser-Ion Acceleration

Laser-ion acceleration with ultra-short pulse, PW-class lasers is dominated by non-thermal, intra-pulse plasma dynamics. The presence of multiple ion species or multiple charge states in targets leads to characteristic modulations and even mono-energetic features, depending on the choice of target material. As spectral signatures of generated ion beams are frequently used to characterize underlying acceleration mechanisms, thermal, multi-fluid descriptions require a revision for predictive capabilities and control in next-generation particle beam sources. We present an analytical model with explicit inter-species interactions, supported by extensive ab initio simulations. This enables us to derive important ensemble properties from the spectral distribution resulting from those multi-species effects for arbitrary mixtures. We further propose a potential experimental implementation with a novel cryogenic target, delivering jets with variable mixtures of hydrogen and deuterium. Free from contaminants and without strong influence of hardly controllable processes such as ionization dynamics, this would allow a systematic realization of our predictions for the multi-species effect.Comment: 4 pages plus appendix, 11 figures, paper submitted to a journal of the American Physical Societ

Deliverable D4.4 Simulated coherent scattering data from plasma and non–plasma samples

Deliverable D4.4 of work package 4 (SIMEX) in EUCALL

Exercise Intolerance in Patients With Heart Failure

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A Laser-Plasma Ion Beam Booster Based on Hollow-Channel Magnetic Vortex Acceleration

Laser-driven ion acceleration can provide ultra-short, high-charge, low-emittance beams. Although undergoing extensive research, demonstrated maximum energies for laser-ion sources are non-relativistic, complicating injection into high-$\beta$ accelerator elements and stopping short of desirable energies for pivotal applications, such as proton tumor therapy. In this work, we decouple the efforts towards relativistic beam energies from a single laser-plasma source via a proof-of-principle concept, boosting the beam into this regime through only a few plasma stages. We employ full 3D particle-in-cell simulations to demonstrate the capability for capture of high-charge beams as produced by laser-driven sources, where both source and booster stages utilize readily available laser pulse parameters.Comment: 4 pages, 4 figures, submitted for peer revie

Laser-plasma ion beam booster based on hollow-channel magnetic vortex acceleration

Laser-driven ion acceleration provides ultrashort, high-charge, low-emittance beams, which are desirable for a wide range of high-impact applications. Yet after decades of research, a significant increase in maximum ion energy is still needed. This paper introduces a quality-preserving staging concept for ultraintense ion bunches that is seamlessly applicable from the nonrelativistic plasma source to the relativistic regime. Full three-dimensional particle-in-cell simulations prove robustness and capture of a high-charge proton bunch, suitable for readily available and near-term laser facilities. Published by the American Physical Society 202

Exascale and ML Models for Accelerator Simulations

Computational modeling is essential to the exploration and design of advanced particle accelerators. The modeling of laser-plasma acceleration and interaction can achieve predictive quality for experiments if adequate resolution, full geometry and physical effects are included. Here, we report on the significant evolution in fully relativistic full-3D modeling of conventional and advanced accelerators in the WarpX and ImpactX codes with the introduction of Exascale supercomputing and AI/ML models. We will cover the first PIC simulations on an Exascale machine, the need for and evolution of open standards, and based on our fully open community codes, the connection of time and space scales from plasma to conventional beamlines with data-driven machine-learning models