100 research outputs found
Self-calibration technique for characterization of integrated THz waveguides
Emerging high-frequency accelerator technology in the terahertz regime is
promising for the development of compact high-brightness accelerators and high
resolution-power beam diagnostics. One resounding challenge when scaling to
higher frequencies and to smaller structures is the proportional scaling of
tolerances which can hinder the overall performance of the structure.
Consequently, characterizing these structures is essential for nominal
operation. Here, we present a novel and simple self-calibration technique to
characterize the dispersion relation of integrated hollow THz-waveguides. The
developed model is verified in simulation by extracting dispersion
characteristics of a standard waveguide a priori known by theory. The extracted
phase velocity does not deviate from the true value by more than . In experiments the method demonstrates its ability to measure
dispersion characteristics of non-standard waveguides embedded with their
couplers with an accuracy below and precision of . Equipped with dielectric lining the metallic waveguides act as slow
wave structures, and the dispersion curves are compared without and with
dielectric. A phase synchronous mode, suitable for transverse deflection, is
found at .Comment: to be submitted to $\textit{Physical Review Accelerators and Beams}
On the Short-Time Compositional Stability of Periodic Multilayers
The short-time stability of concentration profiles in coherent periodic
multilayers consisting of two components with large miscibility gap is
investigated by analysing stationary solutions of the Cahn-Hilliard diffusion
equation. The limits of the existence and stability of periodic concentration
profiles are discussed as a function of the average composition for given
multilayer period length. The minimal average composition and the corresponding
layer thickness below which artificially prepared layers dissolve at elevated
temperatures are calculated as a function of the multilayer period length for a
special model of the composition dependence of the Gibbs free energy. For
period lengths exceeding a critical value, layered structures can exist as
metastable states in a certain region of the average composition. The phase
composition in very thin individual layers, comparable with the interphase
boundary width, deviates from that of the corresponding bulk phase.Comment: 29 pages including 7 figures, to be published in Thin Solid Film
Dissecting the Shared Genetic Architecture of Suicide Attempt, Psychiatric Disorders, and Known Risk Factors
Background Suicide is a leading cause of death worldwide, and nonfatal suicide attempts, which occur far more frequently, are a major source of disability and social and economic burden. Both have substantial genetic etiology, which is partially shared and partially distinct from that of related psychiatric disorders. Methods We conducted a genome-wide association study (GWAS) of 29,782 suicide attempt (SA) cases and 519,961 controls in the International Suicide Genetics Consortium (ISGC). The GWAS of SA was conditioned on psychiatric disorders using GWAS summary statistics via multitrait-based conditional and joint analysis, to remove genetic effects on SA mediated by psychiatric disorders. We investigated the shared and divergent genetic architectures of SA, psychiatric disorders, and other known risk factors. Results Two loci reached genome-wide significance for SA: the major histocompatibility complex and an intergenic locus on chromosome 7, the latter of which remained associated with SA after conditioning on psychiatric disorders and replicated in an independent cohort from the Million Veteran Program. This locus has been implicated in risk-taking behavior, smoking, and insomnia. SA showed strong genetic correlation with psychiatric disorders, particularly major depression, and also with smoking, pain, risk-taking behavior, sleep disturbances, lower educational attainment, reproductive traits, lower socioeconomic status, and poorer general health. After conditioning on psychiatric disorders, the genetic correlations between SA and psychiatric disorders decreased, whereas those with nonpsychiatric traits remained largely unchanged. Conclusions Our results identify a risk locus that contributes more strongly to SA than other phenotypes and suggest a shared underlying biology between SA and known risk factors that is not mediated by psychiatric disorders.Peer reviewe
Low Gain FEL Oscillator Option for PETRA IV
Next generation synchrotron storage rings will have electron beam density approaching that necessary for driving an XFEL. It falls short of the quality required for the high-gainx-ray regime above 1 keV, mainly due to the large energy spread and small peak current, but is sufficient to reach low gain regime. Here we show that integration of an XFELO insertion is feasible within the PETRA IV upgrade projec
Low Gain FEL Oscillator Option for PETRA IV
Next generation synchrotron storage rings will have electron beam density approaching that necessary for driving an XFEL. It falls short of the quality required for the high-gainx-ray regime above 1 keV, mainly due to the large energy spread and small peak current, but is sufficient to reach low gain regime. Here we show that integration of an XFELO insertion is feasible within the PETRA IV upgrade project
Commissioning of a Calibration Device for Second Sound Quench Detection
An important part of research and development in the field of superconducting radio frequency technology is the quench detection since these breakdowns of superconductivity often limit the cavity performance. Although the second sound based quench detection is widely used, only few studies dealing with its systematic uncertainties exist. Hence, the vertical test stands at the cavity test facility of DESY were extended by calibration device prototypes in order to estimate the accuracy of this method. For the first time at DESY, artificial signals have been generated and reconstructed by heating power film resistors. These second sound signals are determined using noise canceling algorithms and the existing reconstruction software. To evaluate the reconstructed positions, the absolute distance between reconstructed and true coordinates is calculated. Thus, a first uncertainty map of the cavity surface is created to quantify the reconstruction results of actual cavity quenches including systematic effects of the quench positioning like the varying sensor coverage around the cavity
Commissioning of a Calibration Device for Second Sound Quench Detection
An important part of research and development in the field of superconducting radio frequency technology is the quench detection since these breakdowns of superconductivity often limit the cavity performance. Although the second sound based quench detection is widely used, only few studies dealing with its systematic uncertainties exist. Hence, the vertical test stands at the cavity test facility of DESY were extended by calibration device prototypes in order to estimate the accuracy of this method. For the first time at DESY, artificial signals have been generated and reconstructed by heating power film resistors. These second sound signals are determined using noise canceling algorithms and the existing reconstruction software. To evaluate the reconstructed positions, the absolute distance between reconstructed and true coordinates is calculated. Thus, a first uncertainty map of the cavity surface is created to quantify the reconstruction results of actual cavity quenches including systematic effects of the quench positioning like the varying sensor coverage around the cavity
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