HZB Repository

    Surface Resistance Characterization of Nb3Sn using the HZB Quadrupole Resonator

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    Nb3Sn is a very promising candidate material for future SRF cavities. With a critical temperature more than twice as the one of bulk niobium, higher operational temperatures with still lower surface resistance are theoretically possible. The RF properties of a sample prepared by Cornell University were characterized using the HZB Quadrupole Resonator. In comparison to a coated cavity this device enables SRF measurements over an extended parameter space frequency, temperature and RF field and easy access to physical quantities such as critical field and penetration depth. In this contribution we present surface resistance and RF critical field measurements

    Gas assisted silver deposition with a focused electron beam

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    Focused electron beam induced deposition FEBID is a flexible direct write method to obtain defined structures with a high lateral resolution. In order to use this technique in application fields like plasmonics, suitable precursors which allow the deposition of desired materials have to be identified. Well known for its plasmonic properties, silver represents an interesting candidate for FEBID. For this purpose the carboxylate complex silver I pentafluoropropionate AgO2CC2F5 was used for the first time in FEBID and resulted in deposits with high silver contents up to 76 at. . As verified by TEM investigations, the deposited material is composed of pure silver crystallites in a carbon matrix. It showed good electrical properties and a strong Raman signal enhancement. Interestingly, silver crystal growth presents a strong dependency on electron dose and precursor refreshment

    Flash Infrared Annealing for Antisolvent Free Highly Efficient Perovskite Solar Cells

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    Organic inorganic perovskites have demonstrated an impressive potential for the design of the next generation of solar cells. Perovskite solar cells PSCs are currently considered for scaling up and commercialisation. Many of the lab scale preparation methods are however challenging to scale up or are environmentally unfriendly. The highest efficient PSCs are currently prepared using the antisolvent process, which utilises a significant amount of an organic solvent to induce perovskite crystallisation in a thin film. An antisolvent free method is developed in this work using flash infrared annealing FIRA to prepare methylammonium lead iodide MAPbI3 PSCs with a record stabilised power conversion efficiency of 18.3 . With an irradiation time of fewer than 2 s, FIRA enables the coating of glass and plastic substrates with pinhole free perovskite films that exhibit micrometre size crystalline domains. This work discusses the FIRA induced crystallisation mechanism and unveils the main parameters controlling the film morphology. The replacement of the antisolvent method and the larger crystalline domains resulting from flash annealing make FIRA a highly promising approach for the scale up of PSC manufactur

    Eigenmode computation of cavities with perturbed geometry using matrix perturbation methods applied on generalized eigenvalue problems

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    Generalized eigenvalue problems are standard problems in computational sciences. They may arise in electromagnetic fields from the discretization of the Helmholtz equation by for example the finite element method FEM . Geometrical perturbations of the structure under concern lead to a new generalized eigenvalue problems with different system matrices. Geometrical perturbations may arise by manufacturing tolerances, harsh operating conditions or during shape optimization. Directly solving the eigenvalue problem for each perturbation is computationally costly. The perturbed eigenpairs can be approximated using eigenpair derivatives. Two common approaches for the calculation of eigenpair derivatives, namely modal superposition method and direct algebraic methods, are discussed in this paper. Based on the direct algebraic methods an iterative algorithm is developed for efficiently calculating the eigenvalues and eigenvectors of the perturbed geometry from the eigenvalues and eigenvectors of the unperturbed geometr
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