La mise en œuvre de nouvelles formulations d’électrolytes adaptées à des électrodes positives à haut potentiel pour batterie lithium-ion est un défi majeur pour des systèmes à haute densité d’énergie. Afin d’obtenir une stabilité en oxydation supérieure à 5 V vs. Li+/Li, différents solvants (dinitriles, lactones, phosphates) ont été analysés. Nous avons montré par voltampérométrie cyclique que des électrolytes contenant du sébaconitrile sont stables jusqu’à 5,3 V vs. Li+/Li sur LiCoPO4. Toutefois, les résultats obtenus par impédance électrochimique et spectroscopie photoélectronique X ont révélé la présence d’une nouvelle interface à l’électrode positive issue de la dégradation de l’électrolyte. Bien que cette dégradation limite la cyclabilité, une optimisation de l’interface formée pourrait s’avérer un atout du point de vue de la sûreté du système grâce à une protection de l’électrode positive. / Implementation of new electrolyte formulations adapted to high potential positive electrodes for lithium-ion battery is a key challenge for high energy density systems. In order to obtain stability in oxidation greater than 5 V vs. Li+/Li, various solvents (dinitriles, lactones, phosphates) were analyzed. We have shown by cyclic voltammetry that electrolytes containing sebaconitrile are stable up to 5.3 V vs. Li+/Li on LiCoPO4. Nonetheless, the results obtained by electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy revealed the presence of a new interface onto the positive electrode due to electrolyte degradation. Even though this degradation limits the cycle ability, optimization of the formed interface could be an asset in view of the system safety through the protection of the positive electrode.

In this study, quantum chemical methods have been used to study two isomers of the proposed high energy density material N8. It has been suggested as a green substitute for conventional solid rocket fuel. Several techniques were used to study the barrier height towards decomposition along reaction path of four N8 isomers. The potential energy surfaces around the transition states of two of the isomers were further investigated. Results show that the bond length of the isomers may have been overestimated, and one of the isomers has a lower barrier and may have a more complicated reaction route. Furthermore, there is a rather large difference in barrier height between calculations at the CCSD and CCSD(T) levels of theory / I den här studien har kvantkemiska beräkningsmetoder använts för att studera två isomerer av N8. På grund av sitt höga energiinnehåll har N8 föreslagits som ett grönt alternativ till konventionellt fast racketbränsle. Flera tekniker har använts för att studera barriären för nedbrytning utefter reaktionskoordinaten för fyra N8-isomerer. Potentialytan runt aktiveringstillståndet för två av isomererna studerades närmare. Resultaten visar att bindningslängden hos isomererna kan ha överskattats och en av isomererna har en lägre barriär samt kan ha en mer komplicerad reaktionsväg. Vidare är det en tämligen stor skillnad i aktiveringsenergi mellan CCSD- och CCSD(T)- nivåerna.

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Laser-driven plasma accelerators can produce high-energy, high peak current ion beams by irradiating solid materials with ultra-intense laser pulses. This innovative concept attracts a lot of attention for various multidisciplinary applications as a compact and energy-efficient alternative to conventional accelerators. The maturation of plasma accelerators from complex physics experiments to turnkey particle sources for practical applications necessitates breakthroughs in the generated beam parameters, their robustness and scalability to higher repetition rates and efficiencies. This thesis investigates viable optimisation strategies for enhancing ion acceleration from thin foil targets in ultra-intense laser-plasma interactions. The influence of the detailed laser pulse parameters on plasma-based ion acceleration has been systematically investigated in a series of experiments carried out on two state-of-the-art high-power laser systems. A central aspect of this work is the establishment and integration of laser diagnostics and operational techniques to advance control of the interaction conditions for maximum acceleration performance. Meticulous efforts in continuously monitoring and enhancing the temporal intensity contrast of the laser system, enabled to optimise ion acceleration in two different regimes, each offering unique perspectives for applications. Using the widely established target-normal sheath acceleration (TNSA) scheme and adjusting the temporal shape of the laser pulse accordingly, proton energies up to 70 MeV were reliably obtained over many months of operation. Asymmetric laser pulses, deviating significantly from the standard conditions of an ideally compressed pulse, resulted in the highest particle numbers and an average energy gain ≥ 37 %. This beam quality enhancement is demonstrated across a broad range of parameters, including thickness and material of the target, laser energy and temporal intensity contrast. To overcome the energy scaling limitations of TNSA, the second part of the thesis focuses on an advanced acceleration scheme occurring in the relativistically induced transparency (RIT) regime. The combination of thin foil targets with precisely matched temporal contrast conditions of the laser enabled a transition of the initially opaque targets to transparency upon main pulse arrival. Laser-driven proton acceleration to a record energy of 150 MeV is experimentally demonstrated using only 22 J of laser energy on target. The low-divergent high-energy component of the accelerated beam is spatially and spectrally well separated from a lower energetic TNSA component. Start-to-end simulations validate these results and elucidate the role of preceding laser light in pre-expanding the target along with the detailed acceleration dynamics during the main pulse interaction. The ultrashort pulse duration of the laser facilitates a rapid succession of multiple known acceleration regimes to cascade efficiently at the onset of RIT, leading to the observed beam parameters and enabling ion acceleration to unprecedented energies. The discussed acceleration scheme was successfully replicated at two different laser facilities and for different temporal contrast levels. The results demonstrate the robustness of this scenario and that the optimum target thickness decreases with improved laser contrast due to reduced pre-expansion. Target transparency was found to identify the best-performance shots within the acquired data sets, making it a suitable feedback parameter for automated laser and target optimisation to enhance stability of plasma accelerators in the future. Overall, the obtained results and described optimisation strategies of this thesis may become the guiding step for the further development of laser-driven ion accelerators.:1 Introduction 1.1 Motivation 1.2 Thesis outline 2 Fundamentals of laser-matter interactions 2.1 Plasma 2.1.1 Plasma properties 2.1.2 Dispersion relation of a plasma 2.1.3 Laser propagation in a plasma 2.2 Laser-matter interactions 2.2.1 Ionisation processes 2.2.2 Electron dynamics in the laser field 2.2.3 Ponderomotive force 2.2.4 Plasma heating processes 2.3 Laser-driven ion acceleration mechanisms 2.3.1 Target normal sheath acceleration 2.3.2 Radiation pressure acceleration 2.3.3 Acceleration in the relativistically induced transparency regime 3 Methodology for high-power laser experiments 3.1 High-power lasers 3.1.1 High-power laser techniques 3.1.2 Temporal contrast of high-power laser systems 3.1.3 DRACO laser system 3.1.4 J-KAREN-P laser system 3.2 Experimental Area 3.2.1 Short-f chamber at HZDR 3.2.2 Short-f chamber at KPSI 3.3 Targets 3.4 Optical diagnostic 3.4.1 Transmitted and reflected laser light 3.4.2 Spectral phase measurements 3.5 Particle diagnostic 3.5.1 Thomson parabola spectrometer 3.5.2 Time of flight measurements 3.5.3 Spatial proton beam profiler 3.5.4 Radiochromic films 3.5.5 Nuclear activation measurements 4 Optimisation of sheath acceleration for high-quality proton beams 4.1 Introduction 4.2 Temporal contrast at experimental environment 4.3 Plasma mirror 4.3.1 Plasma mirror implementation at DRACO-PW 4.3.2 Plasma mirror characterisation at DRACO-PW 4.4 Temporal pulse shaping by spectral phase modification 4.4.1 Theory on temporal pulse shaping 4.4.2 Experimental realisation and results 4.5 Proton acceleration under optimised temporal contrast conditions 4.6 Experimental results 4.7 Discussion on numerical simulations 4.8 Conclusions 5 Enhanced ion acceleration in the relativistic transparency regime 5.1 Introduction 5.2 Experimental setup using the J-KAREN-P laser 5.3 Experimental results 5.4 Laser-induced breakdown and target pre-expansion 5.5 Elucidating ion acceleration in the relativistically induced transparency regime 5.5.1 Details on simulation methodology 5.5.2 Simulation results 5.6 Acceleration in the RIT regime for modified temporal contrast 5.6.1 Experimental setup using the DRACO-PW laser 5.6.2 Experimental results using the DRACO-PW laser 5.6.3 Simulation results for modified temporal contrast 5.7 Conclusions 6 Ion acceleration beyond the 100 MeV frontier from cascading acceleration schemes 6.1 Introduction 6.2 Experimental setup 6.3 Experimental results 6.3.1 Analysis of acceleration performance 6.3.2 Spatial proton beam profile 6.3.3 Nuclear activation measurement 6.3.4 Scaling of maximum proton energy 6.4 Numerical simulations 6.4.1 Simulation setup 6.4.2 Simulation results & discussion 6.5 Conclusions 7 Summary and outlook Appendix References

Extremely high currents can be generated in relativistic short pulse laser interactions with matter. This raises the question if return currents can be used to drive a conventional fast Z-pinch process to produce high energy density (HED) matter. At the HZDR Draco Laser facility, cryogenic hydrogen jet targets are investigated for laser acceleration of protons, and Z-pinch phenomena may have been observed. This thesis addresses this possibility with a multi-timescale theoretical treatment of relativistic laser interactions with cylindrical hydrogen jets and metallic wire targets. To achieve this, the hydrodynamic ray-tracing (HD-RT) method is invented to determine the plasma temperature invhydrogen jets irradiated at laser intensity of 𝑎0 ≈ 1. The HD-RT fit reveals bulk-electron temperatures of 250 eV to 300 eV in experiments but the electron thermal temperature are overestimated invthe Particle-in-cell (PIC) simulations. The HD-RT method now provides a testbed platform which can be used to benchmark the PIC method. At higher laser intensity of 𝑎0 ≈ 15, the HD-RT method resolved the different temperature distributions within the hydrogen jets. The surface plasma exhibits a significantly higher temperature (∼ 300 eV), and bulk has a lower temperature ≲ 100 eV. Additionally, a jump in the shadow diameter of the expanding hydrogen jet plasma is observed with optical probing at 30 ps to 40 ps. These indicate that the surface return current is heating the target surface and induces a cylindrical shock. Two-dimensional and three-dimensional PIC simulations are conducted to study the generation mechanisms of the return current. The simulations reveal that the return current, concentrated in the ∼ 0.1 µm skin depth layer on the wire, has a duration of 100 femtosecond (fs) scale, and propagates along the wire due to surface wave propagation, for the 30 fs duration laser pulse. Based on those findings, the theory of generating convergent shock waves on wire targets initiated by the short pulse surface return current is developed. It is found that the compression shock wave arises from a prompt magnetic pressure, during the current pulse, plus a longer duration ablation pressure due to the surface heating. The corresponding simulations are consistent with the measured hydrogen jet shadow diameter, whose jump behavior is identified as evidence of the rebound shock, after the convergence of the initial shock to the axis. A return current scaling law is then developed to predict this behavior in targets of arbitrary atomic number (Z) and radii (≥ 1 µm). The relative magnitude of the magnetic and ablative pressures vary with target radius and atomic number. An experiment conducted at the HED-HiBEF Instrument of the European XFEL shows direct observation of the convergent shock wave on a 25 µm diameter copper wire, with peak pressure reaching ∼ 100 TPa at convergence. The rebound shock is also directly imaged. The scaling theory is validated with this experiment and exhibits good consistency. These experiments provide clear evidence that the short-pulse return current does not drive a conventional Z-pinch process, but a transient surface heating of the target instead, which causes the ablative pressure shock compression. Furthermore, the mechanisms causing the instabilities are studied under the assumptions of shortpulse and long-pulse return current. The results demonstrate that the filament structures observed in the hydrogen jets, and at late times in wires, can result from the thermal expansion of initial density perturbations caused by the transient hot electron dynamics, and from Weibel instabilities arising from the increasing plasma scale length. This conclusion further supports the theory of short pulse return current. The results of this thesis open a new regime to achieve extreme high pressure conditions (∼ 100 TPa) by using a J-level short pulse laser, and have established a robust theoretical framework for future applications of utilizing laser-driven return currents in the field of HED physics.:Contents 1 Introduction 1 2 Return current generation and propagation in high-intensity laser-solid interactions 6 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 Return current in 3D PIC simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.3 Return current in 2D PIC simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.4 Surface return current propagation in infinite plasma wire . . . . . . . . . . . . . . . . 14 2.4.1 Surface wave generation mechanism . . . . . . . . . . . . . . . . . . . . . . . . 14 2.4.2 Model description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.4.3 Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.5 Bulk return current generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3 Bulk return current heating and bulk plasma temperature benchmark with the experiment 24 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.2 Testbed platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.2.1 Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.2.2 HD-RT fit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.2.2.1 Hydrodynamics simulation - HD . . . . . . . . . . . . . . . . . . . . . 27 3.2.2.2 Ray-tracing simulation - RT . . . . . . . . . . . . . . . . . . . . . . . 28 3.2.2.3 𝜒2 fit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.3 PIC simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 3.5 Future prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 4 Surface return current heating and convergent shock compression driven by the surface return current 35 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 4.2 Dynamic shock compression initiated by the surface return current . . . . . . . . . . . 36 4.2.1 The Z-pinch effect induced by the strong transient magnetic field . . . . . . . . 36 4.2.2 Heating mechanism of surface return current . . . . . . . . . . . . . . . . . . . 37 4.2.3 Hydrodynamic time scale of the convergent compression in hydrogen jets initi- ated by the Z-pinch and surface ablation . . . . . . . . . . . . . . . . . . . . . . 39 4.2.4 Scaling law of return current compression to high Z and large radius solid target 40 4.3 Convergent shock compression in hydrogen jets and probed with optical laser . . . . . 43 4.4 Convergent shock compression in copper wires and probed by X-ray free electron lasers (XFEL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 4.4.1 Experiment setup and results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 4.4.2 PIC simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 4.4.3 Hydrodynamic simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.4.4 Phase contrast image simulation . . . . . . . . . . . . . . . . . . . . . . . . . . 53 4.4.5 High-pressure physics experiment designation based on the return current heating 55 4.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 5 Plasma instabilities in high-intensity laser solid interactions 57 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 5.2 Thermal expansion dominated plasma instabilities . . . . . . . . . . . . . . . . . . . . 58 5.2.1 Obtained the plasma initial condition after laser irradiation . . . . . . . . . . . 58 5.2.2 Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 5.3 MRT instabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 5.3.1 Initial conditions of the MRT instabilities . . . . . . . . . . . . . . . . . . . . . 60 5.3.2 Simulation data processing with FFT method . . . . . . . . . . . . . . . . . . . 62 5.3.3 Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 5.4 Kinetic instabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 5.4.1 Weibel instabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 5.4.2 Biermann battery mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 5.4.3 Determination of the hydrogen plasma conditions . . . . . . . . . . . . . . . . . 65 5.4.4 Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 5.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 6 Summary and outlook 71 7 Appendix 73 7.1 Single electron dynamics in a laser field . . . . . . . . . . . . . . . . . . . . . . . . . . 73 7.2 Pondermotive force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 7.3 Hot electron temperature scaling in laser-plasma interactions . . . . . . . . . . . . . . 77 7.4 X-ray transmission propagation simulations . . . . . . . . . . . . . . . . . . . . . . . . 77 7.5 FDTD method to solve the equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 7.6 Experimental details of the optical microscope . . . . . . . . . . . . . . . . . . . . . . 80 7.7 Measurement of the variation of the initial target diameter . . . . . . . . . . . . . . . 80 7.8 Discussion of the HD-RT fit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 7.9 Equation of state of hydrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 7.10 Ionization state of the target . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 7.11 Radiative cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 7.12 2D3V-PIC simulation versus 3D-PIC Simulation . . . . . . . . . . . . . . . . . . . . . 85 7.13 Low-temperature-collision correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 7.14 Effect of the Coulomb logarithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 7.15 Lateral heat transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 7.15.1 Hot-electron-pressure gradient in transverse direction . . . . . . . . . . . . . . . 89 7.15.2 Lateral heat transfer by diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . 91 7.16 Bulk electron temperature along the longitudinal direction of the wire . . . . . . . . . 91

Ce travail de thèse suit l'apparition récente de ces nouvelles sources intenses et courtes de rayonnement dans la gamme X/XUV que sont les lasers X/XUV à électrons libres (XFEL). Contrairement aux sources optiques qui déposent principalement leur énergie via les électrons libres, les photons X/XUV déposent leur énergie dans la matière par la photoionisation de couches internes avec éjection de photo-électrons, suivie par l'éjection d'électrons Auger et d'électrons de recombinaison à trois corps dans la distribution d'électrons libres. Le chauffage se fait donc par l'intermédiaire de la structure atomique. La forte intensité des XFELs permet de faire jusqu'à un trou par atome dans un solide produisant ainsi, sur une échelle femtoseconde, un état exotique fortement hors-équilibre appelé solide creux. Cet état exotique instable se désexcite via un ensemble de processus atomiques élémentaires. Nous nous sommes intéressés dans cette thèse au développement d'outils permettant de calculer la cinétique des populations atomiques, couplée à la cinétique des électrons libres, pendant la transition à densité ionique constante, de solide à plasma dense en passant par l'état de solide creux, induit par le rayonnement XFEL irradiant une cible solide. Tout le défi ici a été de calculer cette cinétique couplée hors-équilibre entre ces états de la matière de nature très différente. Pour répondre a ce défi nous avons développé deux modèles cinétiques d'interaction XFELsolide, pour lesquels la description d'un solide comme un plasma froid dégénéré nous a permis d'utiliser une même approche plasma pendant l'ensemble de la transition du solide au plasma. L'ensemble de la physique atomique HETL d'intérêt ayant lieu à densité du solide, bien avant la détente de la matière, nous avons développé deux codes associés à ces modèles pour une utilisation à densité ionique constante. Pour aborder l'étude nous nous sommes d'abord concentrés sur la cinétique des électrons liés en supposant une distribution d'électrons libres à l'équilibre (ce qui suppose une thermalisation instantanée des électrons libres). Dans le cadre de l'approche de plasma dense étendue jusqu'au solide, nous avons développé un modèle collisionnel-radiatif généralisé. Cette généralisation passe par l'identification d'un lien entre état solide et plasma au niveau des processus atomiques élémentaires. Le code développé à partir de ce modèle nous a permis d'étudier des résultats expérimentaux et ainsi d'améliorer notre description des effets de densités dans les plasmas denses. Dans une seconde partie nous avons ajouté à l'étude la cinétique des électrons libres en considérant une distribution d'électrons libres hors-équilibre. Le code associé, basé sur la discrétisation de cette distribution et son couplage avec les états liés, nous a permis d'étudier le rôle des processus atomiques élémentaires dans la thermalisation de la distribution d'électrons libres. / This work follows the recent development of the free electron lasers in the X-ray and XUV-ray range (XFEL). Unlike optical sources that deposit their energy via the free electrons, the X/XUV photons deposit their energy directly via photoionization of inner shell electrons with the ejection of photo-electrons, followed by the ejection of Auger electrons and three body recombination electrons in the free electron distribution. The matter is thus heated via the atomic structure. The high XFEL intensity allows one to make up to one hole per atom in a solid, thus producing, on a femtosecond time scale, an exotic state, highly out of equilibrium, called hollow cristal. This unstable exotic state deexcite via a set of elementary atomic processes. In this work we were interested in the development of tools to calculate the atomic population kinetics, coupled to the free electron kinetics, during the transition at constant ionic density, from solid to dense plasma, induced by an XFEL irradiating a solid target. The goal here was to calculate this out of equilibrium coupled kinetics between states of matter having a very different nature. To address this problem we have developed two kinetics models of XFEL interaction with solids. In both these models the description of the solid as a cold degenerated plasma allowed us to use the same plasma approach during all the solid-plasma transition. Considering the fact that all the atomic physics takes place at solid density, way before the matter relaxation, we have developed two codes, associated with these two models, for a use at constant ionic density. To approach this study, we first focused on the bound electron kinetics assuming a free electron distribution at equilibrium (i.e. hypothesis of instantaneous thermalization of the free electrons). In the framework of the dense plasma approach extended up to the solid state, we have developed a generalized collisional radiative model. This generalization goes through the identification of a link between the solid state and the plasma state for the elementary atomic processes. The code associated with this model allowed us to study experimental results and to improve our description of the density effects in dense plasmas. In a second part the free electron kinetics is included in the model with a free electron distribution out of thermodynamic equilibrium. The associated code, based on the discretization of this distribution and its coupling with bound atomic states allowed us to study the role of the atomic elementary processes in the free electron distribution thermalization.

To enable future environmentally friendly access to space by means of solid rocket propulsion a viable replacement to the hazardous ammonium perchlorate oxidizer is needed. Ammonium dinitramide (ADN) is one of few such compounds currently known. Unfortunately compatibility issues with many polymer binder systems and unexplained solid-state behavior have thus far hampered the development of ADN-based propellants. Chapters one, two and three offer a general introduction to the thesis, and into relevant aspects of quantum chemistry and polymer chemistry. Chapter four of this thesis presents extensive quantum chemical and spectroscopic studies that explain much of ADN’s anomalous reactivity, solid-state behavior and thermal stability. Polarization of surface dinitramide anions has been identified as the main reason for the decreased stability of solid ADN, and theoretical models have been developed to explain and predict the solid-state stability of general dinitramide salts. Experimental decomposition characteristics for ADN, such as activation energy and decomposition products, have been explained for different physical conditions. The reactivity of ADN towards many chemical groups is explained by ammonium-mediated conjugate addition reactions. It is predicted that ADN can be stabilized by changing the surface chemistry with additives, for example by using hydrogen bond donors, and by trapping radical intermediates using suitable amine-functionalities. Chapter five presents several conceptual green energetic materials (GEMs), including different pentazolate derivatives, which have been subjected to thorough theoretical studies. One of these, trinitramide (TNA), has been synthesized and characterized by vibrational and nuclear magnetic resonance spectroscopy. Finally, chapter six covers the synthesis of several polymeric materials based on polyoxetanes, which have been tested for compatibility with ADN. Successful formation of polymer matrices based on the ADN-compatible polyglycidyl azide polymer (GAP) has been demonstrated using a novel type of macromolecular curing agent. In light of these results further work towards ADN-propellants is strongly encouraged. / QC 20101103

Diagnosing the temperatures and densities of plasmas is critical to the understanding of a wide variety of phenomena. Everything from equations of state for warm dense matter (WDM) found in Jovian planets and inertial confinement fusion (ICF) to turbulent and dissipative processes in laser-produced plasmas, rely on accurate and precise measurements of temperature and density. This work presents improvements on two distinct techniques for measuring temperatures and densities in plasmas: x-ray Thomson scattering (XRTS), and Langmuir probes (LPs). At the OMEGA laser facility, experiments on warm dense matter were performed by firing lasers at an ablator foil and driving a planar shock into cryogenically cooled liquid deuterium. XRTS in the collective scattering regime was implemented to probe the matter, measuring densities of n_e ~ 4.3 x 10²³ cm^-3, temperatures of T_e ~ 12 eV and ionizations of Z ~ 1.0. Through an extension to XRTS theory for inhomogeneous systems, it was possible to extract an additional parameter, the length scale of the shock, whose value of ? ~ 1.33 nm was consistent with the predicted mean free path, and therefore the thickness of the shock. A unique triple Langmuir probe prototype was designed and tested at the Gregori group's lab at the University of Oxford. This probe was designed for a high temporal resolution of ~ 200 MHz for probing laser-produced shocks. The probes were used to measure the shock formed from ablating carbon rods in an argon gas fill. The probe yielded plasma parameters of n_e ~ 1.0 x 10¹⁷ cm^-3 , and T^e ~ 1.5 eV, consistent with measurements from interferometry and emission spectroscopy.

The recent development of free-electron lasers operating at XUV and X-ray wavelengths are proving vital for the exploration of matter in extreme conditions. The ultra-short pulse length and high peak brightness these light sources provide, combined with a tunable X-ray wavelength range, makes them ideally suited both for creating high energy density samples and for their subsequent study. In this thesis I describe the work done on the XUV free-electron laser FLASH in Hamburg, aimed at creating homogeneous samples of warm dense matter through the process of volumetric XUV photo-absorption, and the theoretical work undertaken to understand the process of high-intensity laser-matter interactions. As a first step, we have successfully demonstrated intensities above 10¹⁷ Wcm-2 at a wavelength of 13.5 nm, by focusing the FEL beam to micron and sub-micron spot sizes by means of a multilayer-coated off-axis parabolic mirror. Using these record high intensities, we have demonstrated for the first time saturable absorption in the XUV. The effect was observed in aluminium and magnesium samples and is due to the bleaching of a core-state absorption channel by the intense radiation field. This result has major implications for the creation of homogeneous high energy density systems, as a saturable absorption channel allows for a more homogeneous heating mechanism than previously thought possible. Further, we have conducted soft X-ray emission spectroscopy measurements which have delivered a wealth of information on the highly photo-excited system under irradiation, immediately after the excitation pulse, yet before the system evolves into the warm dense matter state. Such strongly photo-excited samples have also been studied theoretically, by means of density functional theory coupled to molecular dynamics calculations, yielding detailed electronic structure information. The use of emission spectroscopy as a probe for solid-density and finite-temperature systems is discussed in light of these results. Theoretical efforts have further been made in the study of the free-free absorption of aluminium as the system evolves from the solid state to warm dense matter. We predict an absorption peak in temperature as the system heats and forms a dense plasma. The physical significance of this effect is discussed in terms of intense light-matter interactions on both femtosecond and picosecond time-scales.

In der vorliegenden Arbeit wird die Darstellung neuer organischer Polyazide dokumentiert, die durch einfache nucleophile Substitution mittels NaN3 dargestellt werden können. Organische Azide mit der Formel RN3 können sich unter Stickstoff-Abspaltung in exothermen, teilweise explosionsartigen Reaktionen zersetzen. Sie sind daher prinzipiell als energiereiche Materialien (HEDM) für entsprechende Anwendungen geeignet. Die als Treibladungsmaterialien potentiell geeignetsten, handhabungssicheren, dendritischen Polyazide werden unter anderem mittels Thermogravimetrie und Differenzkalorimetrie analysiert. In einer neuen Synthesemethode können die wenig bekannten Heteroazidomethane aus Tris(azidomethyl)amin erzeugt werden. Von besonderem Interesse ist dabei die Synthese neuartiger Azidohalogenmethane. Diese können durch analytische Gas-Chromatographie charakterisiert und mittels präparativer Gas-Chromatographie isoliert werden. Durch die 1,3-dipolare Cycloaddition mit Cyclooctin konnten einige Heteroazidomethane zu Triazolen abgefangen und so einer Einkristall-Röntgen-Strukturanalyse zugeführt werden. Als letztes in der homologen Reihe der Azidomethane noch fehlendes Azid konnte Tetraazidomethan synthetisiert werden. Das Perazidomethan besitzt mit 93.3% den für organische Azide höchstmöglichen Stickstoffgehalt. Seine Existenz wurde bislang lediglich durch molekültheoretische Berechnungen nahegelegt. Die Synthese dieses homoleptischen Kohlenstoffazides gelang durch die Behandlung von Trichloracetonitril mit Natriumazid. Es ließ sich durch präparative GC als extrem explosive, farblose Flüssigkeit isolieren. Mit Hilfe der analytischen GC konnten sowohl der Siedepunkt als auch die Polarität von C(N3)4 abgeschätzt werden. C(N3)4 wird desweiteren durch IR, MS, 13C-NMR und 15N-NMR-Spektroskopie sowie durch Einkristall-Röntgen-Strukturanalysen seiner Abfangprodukte mit Cyclooctin charakterisiert. Mit Wasser zeigt C(N3)4 eine quantitative Hydrolyse unter Bildung von Carbonyldiazid. Durch Austauschprozesse mit Na15N3 konnte die mögliche Dissoziation von C(N3)4 nachgewiesen werden. Reaktionen von C(N3)4 mit Phosphinen führen zu Cyanamidderivaten, mit Norbornen sowie Norbornadien wurden über vielstufige Reaktionsmechanismen Aminotetraazole erhalten.