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Corrections of high order nonlinearities in the LHC and High Luminosity LHC beam optics
No full textThe impact of high order nonlinear magnetic field errors on the performance of the Large Hadron Collider LHC and its planned High Luminosity upgrade, the HL LHC, has been extensively studied. Particularly, the presence of such errors in the Insertion Regions IR has shown significant repercussions due to the high beta functions and feed down to lower orders caused by crossing schemes. This thesis aims to explore different methods for effectively addressing these high order errors, with the ultimate goal of identifying and correcting them to optimize beam optics and enhance machine performance. Simulation studies are employed, using a novel and flexible correction algorithm developed during the course of this PhD research. Various strategies are investigated to improve corrections by targeting Resonance Driving Terms RDTs associated with diverse error sources. Notably, the algorithm accounts for the feed down effects and avoids symmetry assumptions between the counter circulating particle beams. Special attention is devoted to decapole and dodecapole errors, which have demonstrated detrimental effects on amplitude detuning due to feed down based on previous measurements in the LHC. The anticipated increase in optics sensitivity to errors in the IRs of the HL LHC further underscores the importance of addressing these errors. The thesis also investigates the influence of misalignments within the IRs housing the detector experiments of both, LHC and HL LHC, machine configurations, in particular in the final focusing triplets and the nonlinear corrector packages. Correction options are evaluated, focusing on the utilization of the nonlinear corrector packages to address errors in the new separation and recombination dipoles in the HL LHC, where increased decapole errors had been expected. Experimental studies are conducted to validate the findings. These studies involve replicating the nonlinear errors anticipated in the HL LHC by powering the correctors in the LHC. Additionally, significant efforts are dedicated to mitigating the feed down effects arising from decapole and dodecapole field errors in order to minimize amplitude detuning, which plays a crucial role in maintaining optimal beam stability and performance. To address this challenge, novel corrections involving the operational implementation of dodecapole correctors in the IRs have been introduced for the first time. These corrections have demonstrated their efficacy in successfully reducing the undesired feed down effects. The results of these experiments provide valuable insights into the mitigation of high order errors and contribute to the overall understanding of beam dynamics in advanced particle accelerator
THz EPR based Magneto Structural Correlations for Cobalt II Single Ion Magnets with Bis Chelate Coordination
Get PDFNew cobalt II based complexes with [N2O2] coordination formed by two bis chelate ligands were synthesized and characterized by a multi technique approach. The complexes possess an easy axis anisotropy D lt; 0 and magnetic measurements show a field induced slow relaxation of magnetization. The spin reversal barriers, i.e., the splitting of the two lowest Kramers doublets UZFS , have been measured by THz EPR spectroscopy, which allows to distinguish the two crystallographically independent species present in one of the complexes. Based on these experimental UZFS energies together with those for related complexes reported in literature, it was possible to establish magneto structural correlations. UZFS linearly depends on the elongation parameter amp; 949;T of the pseudo tetrahedral coordination, which is given by the ratio between the average obtuse and acute angles at the cobalt II ion, while UZFS was found to be virtually independent of the twist angle of the chelate planes. With increasing deviation from the orthogonality of the latter, the rhombicity E D increase
Structural characterization of two prototypical repressors of SorC family reveals tetrameric assemblies on DNA and mechanism of function
No full textThe SorC family of transcriptional regulators plays a crucial role in controlling the carbohydrate metabolism and quorum sensing. We employed an integrative approach combining X ray crystallography and cryo electron microscopy to investigate architecture and functional mechanism of two prototypical representatives of two sub classes of the SorC family DeoR and CggR from Bacillus subtilis. Despite possessing distinct DNA binding domains, both proteins form similar tetrameric assemblies when bound to their respective DNA operators. Structural analysis elucidates the process by which the CggR regulated gapA operon is derepressed through the action of two effectors fructose 1,6 bisphosphate and newly confirmed dihydroxyacetone phosphate. Our findings provide the first comprehensive understanding of the DNA binding mechanism of the SorC family proteins, shedding new light on their functional characteristic
Correlative in situ Spectro microscopy of Supported Single CuO Nanoparticles Unveiling the Relationships between Morphology and Chemical State during Thermal Reduction
No full textThe activity, selectivity, and lifetime of nanocatalysts critically depend on parameters such as their morphology, support, chemical composition, and oxidation state. Thus, correlating these parameters with their final catalytic properties is essential. However, heterogeneity across nanoparticles NPs is generally expected. Moreover, their nature can also change during catalytic reactions. Therefore, investigating these catalysts in situ at the single particle level provides insights into how these tunable parameters affect their efficiency. To unravel this question, we applied spectro microscopy to investigate the thermal reduction of SiO2 supported copper oxide NPs in ultrahigh vacuum. Copper was selected since its oxidation state and morphological transformations strongly impact the product selectivity of many catalytic reactions. Here, the evolution of the NPs chemical state was monitored in situ during annealing and correlated with their morphology in situ. A reaction front was observed during the reduction of CuO to Cu2O. From the temperature dependence of this front, the activation energy was extracted. Two parameters were found to strongly influence the NP reduction the initial nanoparticle size and the chemical state of the SiO2. substrate. The CuOx reduction was found to be completed first on smaller NPs and was also favored over partially reduced SiOx regions that resulted from X ray beam irradiation. This methodology with single particle level spectro microscopy resolution provides a way of isolating the influence of diverse morphologic, electronic, and chemical influences on a chemical reaction. The knowledge gained is crucial for the future design of more complex multimetallic catalytic system
Transformation induced plasticity in zirconia during tensile loading A combined microscopy and synchrotron X ray refraction study
No full textThe stress induced tetragonal to monoclinic t m zirconia phase transformation can provide a certain degree of plasticity to Ceria stabilized Ce TZP zirconia based composites. Characterizing and monitoring this phase transition on a millimeter size range, within the bulk and in situ remains a challenge. In this work, the mechanical behavior of Ce TZP based composite was studied in tension, combining microscopy and synchrotron X ray refraction techniques. In contrast with microscopy methods, which only provide surface information, X ray refraction radiography SXRR allowed the visualization of all the transformation bands, over the entire length and thickness of tested specimens, opening up new avenues for in situ stress induced t m transformation studie
Unravelling quantum dynamics using flow equations
Get PDFThe study of many body quantum dynamics in strongly correlated systems is extremely challenging. To date, few numerical methods exist that are capable of simulating the non equilibrium dynamics of two dimensional quantum systems, which is partly due to complexity theoretic obstructions. In this work, we present a technique able to overcome this obstacle, by combining continuous unitary flow techniques with the newly developed method of scrambling transforms. We overcome the assumption that approximately diagonalizing the Hamiltonian cannot lead to reliable predictions for relatively long times. Rather, we show that the method achieves good accuracy in both localized and delocalized phases and makes reliable predictions for a number of quantities including infinite temperature autocorrelation functions. We complement our findings with rigorous incremental bounds on the truncation error. Our approach shows that, in practice, the exploration of intermediate scale time evolution may be more feasible than is commonly assumed, challenging near term quantum simulator
Antiferromagnetic order in the layered magnetic topological insulator MnBi2Se4 probed by resonant soft x ray scattering
No full textThe quasi two dimensional magnetic topological insulator MnBi2 amp; 8290;Se4, stabilized via nonequilibrium molecular beam epitaxy, is investigated by resonant soft x ray scattering. Kiessig fringes are observed, confirming a high sample quality and a thin film thickness of 10 septuple layers amp; 8764;13 nm . An antiferromagnetic Bragg peak is observed at the structurally forbidden reflection, whose magnetic nature is validated by studying its temperature, energy, and polarization dependence. Through a detailed analysis, an A type antiferromagetic order with in plane moments is implied. This alternative spin structure in MnBi2 amp; 8290;Se4, in contrast to the Ising antiferromagnetic states in other magnetic topological insulators, might be relevant for hosting new topological state
Analysis of the Effect of Operating Conditions on the Performance of a Direct Ammonia Fuel Cell Using Multiphysics Modelling
Get PDFUnderstanding the physical and chemical basis of device operation is important for their development. While hydrogen fuel cells are a widely studied topic, direct ammonia fuel cells DAFCs are a smaller field with fewer studies. Although the theoretical voltage of a DAFC is approximately equal to that of a hydrogen fuel cell, the slow kinetics of the ammonia oxidation reaction hamper cell performance. Therefore, development of anode catalysts is especially needed for practical viability of the DAFCs. To study DAFC operation, specifically interactions between reaction kinetics and different transport phenomena, we developed a one dimensional model of a DAFC and performed a sensitivity analysis for several parameters related to the cell operating conditions e.g., temperature, relative humidity and properties e.g., catalyst loading . As expected, temperature and relative humidity were very important for cell power. However, while faster reaction kinetics improved the cell performance, simply increasing the catalyst loading did not always produce a comparable enhancement. These and other observations about the relative importance of the operating parameters should help to prioritize and guide future development of and research on DAFCs. Further studies are needed to understand and optimize e.g. humidity management in different scenario
In Situ Analysis of Stress and Microstructure Evolution during Welding of High Alloy Steels Using Energy Dispersive X Ray Diffraction
Get PDFConstrained thermal expansion and contraction during welding cause a compression tension cycle and plastic deformation in the heat affected zone, leading to work hardening. The nature of this hardening effect isotropic or kinematic determines the final local yield stress and thus affects the residual stress state. Therefore, mechanical hardening must be modeled correctly in welding simulations for accurately predicting welding residual stresses. Previous studies, relying on comparisons with experimental ex situ results, led to different recommendations regarding the choice of the hardening model and thus require clarification. In this work, the stress evolution in the heat affected zone of a tungsten inert gas weld is studied in situ using energy dispersive x ray diffraction and a novel method of stress analysis based on crystallite anisotropy. Additionally, microstructural information is gathered through line profile analysis. Results are shown for both austenitic and ferritic high alloy steels and compared to ex situ results including a validation of the new method of stress analysis. Finally, conclusions on the nature of work hardening are draw
Hyping direct seawater electrolysis hinders electrolyzer development
Get PDFTo limit global warming to less than 1.5 C, global greenhouse gas emissions must be reduced by 45 by 2030 and reach net zero by 205