The accelerator and particle physics communities are considering a lepton Linear Collider LC as the most appropriate machine to carry out high precision particle physics research in the TeV energy regime. The Compact Linear Collider CLIC and the International Linear Collider ILC are the two proposals for the future e+e- LC. Both designs achieve a luminosity L above 10^(34) cm-2 s-1 at the interaction point IP, satisfying the particle physics requirements. The LC consists of different systems, being the Final Focus System FFS the last one before colliding the beam at the IP. It is responsible to focus the beams at sizes in the range of nanometres by means of the Final Doublet FD. The FFS designs of the CLIC and ILC projects are based on a new local chromaticity correction scheme which has never been experimentally tested before. The Accelerator Test Facility ATF2 at KEK (Japan) aims to experimentally verify the feasibility of the FFS based on this novel scheme. The present thesis is devoted to the design and higher order optimisation of FFS for linear colliders based on the local chromaticity correction scheme. The CLIC design luminosity L0 is 5.9·10^(34) cm-2 s-1 assuming head-on collisions. However the beams cross each other at the IP forming an angle of 20 mrad. Due to this crossing scheme the luminosity would be reduced by 90%. Crab cavities are dedicated to tilt the bunches in order to provide head-on like collisions preserving the design L0. In this thesis different solutions that recover the design luminosity for the CLIC FFS are proposed. The designs of a new ATF2 Nominal and Ultra-low beta* lattices, to test the feasibility of the ILC and CLIC FFS respectively, are presented in this thesis. The expected IP vertical beam sizes sy* for these lattices are 38 and 23 nm respectively, at this beam size regime the magnetic field quality of the FFS magnets is a concern. Indeed, the evaluated sy* with the measured multipole components is 100% for the Nominal lattice and 400% for the Ultra-low beta* lattice. The study of the higher order aberrations performed in this thesis is crucial for identifying possible cures that minimise the observed beam size growth. Different solutions have been studied: (i) replacing the FD by better field quality magnets, (ii) swapping the ATF2 quadrupole magnets according to their skew sextupole component and (iii) modifying the lattice optics. The new lattice designs ATF2 Bx2.5By1.0 and ATF2 Ultra-low betay* are based on the prosposed solutions. The impact of the multipoles components is effectively minimsed for both new designs, achieving a sy* equal to 38 and 27 nm ,respectively. The tuning study of the FFS determines its feasibility under realistic error conditions. 100 machines with different initial error configurations are used to address this problem. The tuning simulation study for the alternative CLIC FFS design takes into account BPM resolution, the effect of synchrotron radiation and the misalignment errors of the magnets, being the later a critical parameter on the tuning performance of the system. The motion of the magnetic centre when shunting the quadrupole magnet might represent a limiting factor for further improvement of its alignment. Dedicated measurements at ATF2 have shown a motion of the magnetic centre below 1 micrometre for a shunting variation of 20%. Under this alignment condition the tuning study of the CLIC FFS shows that 80% of the machines reach a L equal or above than L0. The errors included in the tuning study of the ATF2 lattices are misalignments, tilts and miss-powering of the ATF2 FFS magnets. The simulated tuning results show that 80% of the machines reach a final sy* that does not exceed in more than 11% and 35% the design sy* for the ATF2 Bx2.5By1.0 and Ultra-low beta_y* lattices respectively. These results demonstrate the theoretical feasebility of FFS based on the novel chromaticity correction scheme.

The method evolved from an Investigation of transmission line methods of measuring the absorption of electromagnetic radiations in liquids. An equation was derived relating the phase angle of the voltage reflection coefficient to the length of the liquid filled line beyond a short circuit. The experimental results show that this equation describes exactly the behaviour of the phase angle as the depth of liquid filling the transmission line is varied. The equation has been shown to be true for a wide range of liquids (a) Non-absorbing liquids, i.e. Benzole. (b) Liquids with a low absorption, i.e. Chlorobenzene and Cyclohexanol. (c) Dilute solutions of polar substances in non-polar solvents, i.e. Chlorobenzene in Benzole. (d) Liquids with high absorptions, i.e. Water and Alcohol. (e) Electrolytic solutions, i.e. Sodium Chloride in water. Values of the phase constants and attenuation coefficients for these liquids have been deduced from the graphs showing phase angle plotted against liquid depth, with an accuracy that compares favourably with other established methods. The method has been applied to an investigation of the absorption of microwaves (lambda = 9.1 sms) by ox blood and serum at room temperature and the inner body temperature of 37°C, and these results have been compared with those obtained for distilled water at these two temperatures. The variation of the phase constant and attenuation coefficient of sodium chloride solutions with concentration has also been investigated, from 0.15N (physiological saline) up to 2N. This method, which depends upon measurement of phase shift alone for the determination of alpha and beta, requires a very much simpler form of apparatus than other methods. The method is best suited to liquids with low values of alpha and high values of beta, and a modification to the apparatus and experimental method has been suggested which should enable values to be obtained more rapidly. This modification has not so far been made, since the accuracy obtainable with this phase shift method is inferior to that of the null techniques recently introduced into dielectric measurements.

No description available.

In the past decades correlated-electron physics due to strong Coulomb interactions and topological physics caused by band inversion often induced by strong spin-orbit coupling have been the workhorses of solid state research. While commonly considered as disparate phenomena, it was realized in the early 2010s that the interplay between the comparably strong Coulomb and spin-orbit interactions in the $5d$ transition metal oxides may result in hitherto unforeseen properties. The layered perovskite Sr$\textsubscript{2}$IrO$\textsubscript{4}$ has attracted special attention due to the observation of an unconventional Mott-insulating phase and predictions of exotic superconductivity. Less is known about its three-dimensional counterpart SrIrO$\textsubscript{3}$, since rather than the cubic perovskite structure it adopts the thermodynamically stable hexagonal polymorph thereof. This thesis therefore sets out to establish the synthesis of epitaxially stabilized perovskite SrIrO$\textsubscript{3}$ by pulsed laser deposition and to investigate its electronic and magnetic structure by state-of-the-art x-ray spectroscopy techniques. In this endeavor the appropriate thermodynamic conditions for the growth of high-quality SrIrO$\textsubscript{3}$ are identified with a focus on the prevention of cation off-stoichiometry and the sustainment of layer-by-layer growth. In the thus-optimized films the cubic perovskite symmetry is broken by a tetragonal distortion due to epitaxial strain and additional cooperative rotations of the IrO$\textsubscript{6}$ octahedra. As a consequence of the thermodynamic instability of the IrO$\textsubscript{2}$ surface layer, the films unexpectedly undergo a conversion to a SrO termination during growth. In an attempt to disentangle the interplay between spin-orbit and Coulomb interaction the three-dimensional electronic structure of perovskite SrIrO$\textsubscript{3}$ is investigated in a combined experimental and theoretical approach using soft x-ray angle-resolved photoelectron spectroscopy and \textit{ab initio} density functional theory calculations. The experimentally found metallic ground state hosts coherent quasiparticle peaks with a well-defined Fermi surface and is theoretically described by a single half-filled band with effective total angular momentum $J_\text{eff} = 1/2$ only upon incorporation of a sizeable local Coulomb repulsion and -- to a lesser extent -- the broken cubic crystal symmetry in the film. Upon reduction of the SrIrO$\textsubscript{3}$ thickness below a threshold of four unit cells the scales are tipped in favor of a Mott-insulating phase as the on-site Coulomb repulsion surmounts the diminishing kinetic energy upon transition into the two-dimensional regime. Concomitantly, a structural transition occurs because the corner-shared octahedral network between substrate and film imposes constraints upon the IrO$\textsubscript{6}$ octahedral rotations in the thin-film limit. The striking similarity between the quasi-two-dimensional spin-orbit-induced Mott insulator Sr$\textsubscript{2}$IrO$\textsubscript{4}$ and SrO-terminated SrIrO$\textsubscript{3}$ in the monolayer limit underlines the importance of dimensionality for the metal-insulator transition and possibly opens a new avenue towards the realization of exotic superconductivity in iridate compounds. Whether the analogy between SrIrO$\textsubscript{3}$ in the two-dimensional limit and its Ruddlesden-Popper bulk counterparts extends to their complex magnetic properties ultimately remains an open question, although no indications for a remanent (anti)ferromagnetic order were found. The unprecedented observation of an x-ray magnetic circular dichroism at the O~$K$-absorption edge of iridium oxides in an external magnetic field promises deeper insights into the intricate connection between the $J_\text{eff} = 1/2$ pseudospin state, its hybridization with the oxygen ligand states and the magnetic order found in the Ruddlesden-Popper iridates. / In den vergangenen Jahrzehnten waren die Physik korrelierter Elektronen aufgrund starker Coulomb- sowie topologische Physik aufgrund durch Spin-Bahn-Wechselwirkung induzierter Bandinversion die Zugpferde der Festkörperforschung. Während diese zuvor gemeinhin als disjunkt wahrgenommen wurden, setzte sich Anfang der 2010er Jahre die Einsicht durch, dass das Zusammenspiel der ähnlich starken Coulomb- und Spin-Bahn-Wechselwirkung in $5d$ Übergangsmetalloxiden zu unvorhergesehenen Eigenschaften führen kann. Bedingt durch die Entdeckung einer unkonventionellen Mott-isolierenden Phase sowie Vorhersagen exotischer Supraleitung wurde dem geschichteten Perowskit Sr$\textsubscript{2}$IrO$\textsubscript{4}$ besondere Aufmerksamkeit zuteil. Über dessen dreidimensionales Pendant SrIrO$\textsubscript{3}$ ist weniger bekannt, da es anstelle der kubischen Perowskitstruktur eine thermodynamisch stabilere polymorphe Gitterstruktur annimmt. Ziel dieser Thesis ist daher die Synthese von epitaktisch stabilisiertem Perowskit-SrIrO$\textsubscript{3}$ mittels gepulster Laserablation sowie die Untersuchung dessen elektronischer und magnetischer Struktur mit modernsten Röntgenspektroskopiemethoden. In diesem Bestreben werden zunächst die thermodynamischen Bedingungen für das Wachstum von qualitativ hochwertigem SrIrO$\textsubscript{3}$ mit dem Fokus auf der kationischen Stöchiometrie sowie dem Erreichen lagenweisen Schichtwachstums identifiziert. In derart optimierten Filmen wird die kubische Symmetrie von einer tetragonalen Verzerrung aufgrund epitaktischer Verspannung sowie von kooperativen Verdrehungen der IrO$\textsubscript{6}$ Oktaeder gebrochen. Während des Wachstums findet infolge der thermodynamischen Instabilität der obersten IrO$\textsubscript{2}$ Lage eine Umwandlung zu einer SrO-Terminierung der Oberfläche statt. Mit dem Ziel das Zusammenspiel von Spin-Bahn- und Coulomb-Wechselwirkung in SrIrO$\textsubscript{3}$ zu entwirren wird dessen dreidimensionale elektronische Struktur in Kombination von winkelaufgelöster Photoelektronenspektroskopie im weichen Röntgenbereich und \textit{ab initio} Dichtefunktionaltheorie untersucht. Der experimentell beobachtete metallische Grundzustand weist kohärente Quasiteilchenzustände mit wohldefinierter Fermifläche auf und wird theoretisch durch ein halbgefülltes Band mit effektivem Gesamtdrehmoment $J_\text{eff} =1/2$ beschrieben, sofern eine substanzielle lokale Coulombabstoßung sowie - in geringerem Maße - die gebrochene kubische Symmetrie berücksichtigt werden. Bei Schichtdicken unterhalb von vier Einheitszellen neigt sich das Gleichgewicht zugunsten einer Mott-isolierenden Phase, da die lokale Coulombabstoßung die im Zweidimensionalen reduzierte kinetische Energie zunehmend überwiegt. Gleichzeitig findet ein struktureller Übergang statt, da das Netzwerk aus Sauerstoffoktaedern deren Rotationen in dünnen Filmen Randbedingungen auferlegt. Die verblüffende Ähnlichkeit zwischen dem quasi-zweidimensionalen Mott-Isolator Sr$\textsubscript{2}$IrO$\textsubscript{4}$ und SrO-terminiertem Monolagen-SrIrO$\textsubscript{3}$ unterstreicht die Bedeutung der Dimensionalität für den Metall-Isolator-Übergang und eröffnet neue Möglichkeiten zur Realisierung exotischer Supraleitung in Iridaten. Die Frage, ob sich die Analogie zwischen SrIrO$\textsubscript{3}$ im zweidimensionalen Limes und den quasi-zweidimensionalen Ruddlesden-Popper-Iridaten auf deren komplexe magnetische Eigenschaften erstreckt, bleibt schlussendlich offen, gleichwohl keine Hinweise auf eine remanente (anti-)ferromagnetische Ordnung hindeuten. Die bisher erste Beobachtung eines magnetischen Zirkulardichroismus an der O~$K$-Absorptionskante eines Iridiumoxids in einem externen Magnetfeld verspricht tiefere Einsichten in den komplexen Zusammenhang zwischen dem $J_\text{eff} = 1/2$ Pseudospin-Zustand, dessen Hybridisierung mit den Valenzzuständen der Sauerstoffliganden sowie der magnetischen Ordnung in Iridatverbindungen.

Outstanding scientific results and statistical overview of the Institute of Ion Beam Physics and Materials Research in 2008

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The Rossendorf Beamline (ROBL) - located at BM20 of the European Synchrotron Radiation Facility (ESRF) in Grenoble, France - is in operation since 1998. This 6th report covers the period from January 2007 to December 2008. In these two years, 50 peerreviewed papers have been published based on experiments done at the beamline. The average citation index, which increased constantly over the years, has now reached 3.5 (RCH) and 3.0 (MRH), indicating that papers are predominately published in journals with high impact factors. Six exemplary highlight reports on the following pages should demonstrate the scientific strength and diversity of the experiments performed on the two end-stations of the beamline, dedicated to Radiochemistry (RCH) and Materials Research (MRH). Demand for beamtime remains very high as in the previous years, with an average oversubscription rate of 1.8 for ESRF experiments. The attractiveness of our beamline is based upon the high specialization of its two end-stations. RCH is one of only two stations in Europe dedicated to x-ray absorption spectroscopy of actinides and other radionuclides. The INE beamline at ANKA provides superior experimental flexibility and extends to lower energies, including important elements like P and S. In contrast, ROBL-RCH provides a much higher photon flux, hence lower detection limits crucial for environmental samples, and a higher energy range extending to elements like Sb and I. Therefore, both beamlines are highly complementary, covering different aspects of radiochemistry research. Once the MARS beamline at SOLEIL is ready to run radionuclides (>2010), it will cover a third niche (Materials Science of actinides, including irradiated fuel) not accessible for the two other beamlines. The Materials Research Hutch MRH has realized an increasing number of in-situ investigations in the last years. On the one hand thin film systems were characterized during magnetron sputtering. On the other hand diffraction experiments under controlled atmosphere were performed. A high variety of experimental parameters was covered by varying pressure, temperature and atmospheric compositions including highly reactive gases. Furthermore structural investigations were combined with electrical conductivity measurements. These kind of in-situ experiments are the key to monitor and understand reaction mechanism or the influence of process parameters, which are again the basis to tailor materials properties on demand. The core competences of MRH are these experimental possibilities, which make it unique among other diffraction beamlines. In fall 2007, ROBL was reviewed by an international panel on behalf of the ESRF. The very positive panel report recommended a renewal of the contract between ESRF and FZD for the next five years, and a major upgrade of critical optical components of the beamline to keep ROBL competitive for the next decade. The FZD will provide 2 Mio € from 2009 to 2011 for this upgrade, which will be performed in parallel to the major upgrade of the ESRF to minimize the downtime. According to the current plans of the ESRF, our users have to expect that ROBL will have only limited or no operation for several months from August 2011 on. Since July 2004 the beamline is a member of the pooled facilities of ACTINET – European Network of Excellence. In the reported period, RCH has provided 27 % of its inhouse beamtime to perform 11 ACTINET experiments. The success of ACTINET within FP-6 has now led to a renewal of ACTINET within FP-7, running until end of 2011.

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