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Assessment of Orientation Dependence of Deformation Structures in Cold Rolled Duplex Steel: A Study Combining Ebsd and Generalized Pole Figures
No full textThe development of advanced materials with optimum structural and mechanical propertiesrequires a detailed control of their microstructures, textures and crystalline defects. Differenttechniques can be used for the characterization of those microstructures and defects, but it istheir combination that could result in an exhaustive understanding of the microstructural andorientational developments on these materials.X-Ray Diffraction (XRD) can be employed to obtain a “global” characterization ofmicrostructure and texture, since the presence of defects in the sample produces shift andbroadening of diffraction peaks. Different models have been developed to quantify thesedefects, some of which require fitting the complete diffraction pattern while others justindividual peaks. These techniques can be extended to texture measurements, oftenrepresented through pole figures (PFs), wherein diffraction patterns are obtained for differentsample orientations. This allows the determination of defect density in function of orientationsand their representation in Generalized Pole Figures (GPFs).On the other hand, for a more “local” characterization, Electron Backscatter Diffraction(EBSD) has proven to be extremely useful for microstructural and orientational analysis,allowing to assess defect accumulation in individual grains and orientations.This preprint research paper has not been peer reviewed. Electronic copy available at: https://ssrn.com/abstract=5172488Preprint not peer reviewed1In this work, a set of 32205 duplex steel samples cold-rolled up to 79% reduction (in stepsof approximately 20%) are studied, aiming to investigate the evolution of defect storage withdeformation in different orientations and texture components. For this purpose, Lauediffraction patterns have been obtained for these samples in P07 beamline in Petra III station(DESY), from which PFs and GPFs were obtained. This information is complemented withEBSD results, where dislocation arrays and grain and subgrain structures for particularorientations are studied. The combination of both techniques allowed for an exhaustiveanalysis of defect storage and microstructural orientations developed with increasingdeformation
Differentiable Models for Control of Complex Physical Systems: A Case Study in Laser Pulse Shaping
No full textPrecise control of the temporal profile of laser pulses is critical for many scientific and industrial applications. Achieving this via spectral shaping is particularly challenging in complex systems due to nonlinear effects, input fluctuations, and hardware imperfections. Conventional approaches - such as manual iterative tuning, precomputed spectral settings, or evolutionary optimization - are often insufficient or scale poorly with system complexity. We introduce a differentiable physics-based framework for spectral pulse shaping that embeds a physical model of the laser within a gradient-based optimization loop. This approach enables rapid system identification and control, accurately capturing complex laser dynamics while optimizing control inputs to achieve target temporal pulse shapes. We demonstrate the method by shaping near-infrared pulses as a proof of concept for photoinjector laser systems, highlighting its generality and potential for high-dimensional control of complex physical systems
TelePix - A fast region of interest trigger and timing layer for the EUDET Telescopes
No full textTest beam facilities are essential to study the response of novel detectors to particles. At the DESY II Test Beam facility, users can test their detectors with an electron beam with a momentum from 1–6 GeV. To track the beam particles, EUDET-style telescopes are provided in each beam area. They provide excellent spatial resolution, but the time resolution is limited by the rolling shutter architecture to a precision of approximately 230 μs. Since the demand on particle rates – and hence track multiplicities – is increasing timing is becoming more relevant. DESY foresees several upgrades of the telescopes. TelePix is an upgrade project to provide track timestamping with a precision of better than 5 ns and a configurable region of interest to trigger the telescope readout. Small scale prototypes have been characterized in laboratory and test beam measurements. Laboratory tests with an injection corresponding to 2300 electrons show a S/N of above 20. Test beam characterization shows efficiencies of above 99% over a threshold range of more than 100 mV and time resolutions of 2.4 ns at low noise rates
Convergent-beam attosecond x-ray crystallography
No full textSub-ångström spatial resolution of electron density coupled with sub-femtosecond temporal resolution is required to directly observe the dynamics of the electronic structure of a molecule after photoinitiation or some other ultrafast perturbation. Meeting this challenge, pushing the field of quantum crystallography to attosecond timescales, would bring insights into how the electronic and nuclear degrees of freedom couple, enable the study of quantum coherences involved in molecular dynamics, and ultimately enable these dynamics to be controlled. Here we propose to reach this realm by employing convergent-beam X-ray crystallography with high- power attosecond pulses from a hard-X-ray free-electron laser. We show that with dispersive optics, such as multilayer Laue lenses of high numerical aperture, it becomes possible to encode time into the resulting diffraction pattern with deep sub-femtosecond precision. Each snapshot diffraction pattern consists of Bragg streaks that can be mapped back to arrival times and positions of X-rays on the face of a crystal. This can span tens of femtoseconds, and can be finely sampled as we demonstrate experimentally. The approach brings several other advantages, such as an increase of the number of observable reflections in a snapshot diffraction pattern, all fully integrated, to improve the speed and accuracy of serial crystallography—especially for crystals of small molecules
Sub-2W tunable laser based on silicon photonics power amplifier
No full textHigh-power tunable lasers are intensely pursued due to their vast application potential such as in telecom, ranging and molecular sensing. Integrated photonics, however, is usually considered not suitable for high-power applications mainly due to its small size which limits the energy storage capacity and therefore the output power. In the late 90s, to improve the beam quality and increase the stored energy, large-mode-area (LMA) fibers were introduced in which the optical mode area is substantially large. Such LMA fibers have transformed the high-power capability of fiber systems ever since. Introducing such an LMA technology at the chip-scale can play an equally disruptive role with high power signal generation from an integrated photonics system. To this end, in this work we demonstrate such a technology, and show a very high-power tunable laser with the help of a silicon photonics based LMA power amplifier. We show output power reaching 1.8 W over a tunability range of 60 nm, spanning from 1.83 µm to 1.89 µm, limited only by the seed laser. Such an integrated LMA device can be used to substantially increase the power of the existing integrated tunable lasers currently limited to a few tens of milliwatts. The power levels demonstrated here reach and surpass that of many benchtop systems which truly makes the silicon photonics based integrated LMA device poised towards mass deployment for high power applications without relying on benchtop systems
Grain alignment in hexaferrite permanent magnets by compaction at room and elevated temperatures
No full textShape-controlled precursors enable grain alignment without using an applied magnetic field in the permanent magnet material strontium hexaferrite. The effect is investigated by conducting four series of experiments using different compaction methods: two cold and two hot compactions. The hypothesis is that magnetic short-circuiting will diminish the grain alignment (texture) in cold compacted samples. The two cold compactions were performed below the Curie temperature, one being a simple cold-pressing (CP) and the other being a cold-pressing followed by sintering (CPS). The CP samples showed a relatively weak texture and low remanent magnetisation, while the CPS method yielded a slightly sharpened texture and improved remanent magnetisation compared with CP. In the two hot compactions, the pressing was done above the Curie temperature, using spark plasma sintering (SPS) and induction pressing (IP). SPS and IP samples both showed remarkably sharper textures than the cold-pressed pellets, with roughly doubled texture strength, and consequently better remanent magnetisation. The bulk density of the hot compacted samples increased almost twofold compared with that of the cold compactions. Hot compaction outperforms cold compaction with regard to density, sharpness of texture and remanent magnetisation. This is explained by inter-particle magnetic short-circuiting during cold pressing, which hinders the alignment process and reduces the bulk density
Measurement of asymmetries in decays at Belle II
No full textWe report measurements of time-dependent asymmetries in decays based on a data sample of events collected at the resonance with the Belle II detector. The Belle II experiment operates at the SuperKEKB asymmetric-energy collider. We measure decay-time distributions to determine -violating parameters and . We determine these parameters for two ranges of invariant mass: , which is dominated by decays, and a complementary region . Our results have improved precision as compared to previous measurements and are consistent with theory predictions
Measurement of multidifferential cross sections for dijet production in proton–proton collisions at
No full textA measurement of the dijet production cross section is reported based on proton–proton collision data collected in 2016 at by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of up to 36.3. Jets are reconstructed with the anti- algorithm for distance parameters of and 0.8. Cross sections are measured double-differentially (2D) as a function of the largest absolute rapidity of the two jets with the highest transverse momenta and their invariant mass , and triple-differentially (3D) as a function of the rapidity separation , the total boost , and either or the average of the two jets. The cross sections are unfolded to correct for detector effects and are compared with fixed-order calculations derived at next-to-next-to-leading order in perturbative quantum chromodynamics. The impact of the measurements on the parton distribution functions and the strong coupling constant at the mass of the boson is investigated, yielding a value of
Search for a heavy pseudoscalar Higgs boson decaying to a 125 GeV Higgs boson and a Z boson in final states with two tau and two light leptons in proton-proton collisions at = 13 TeV
No full textA search for a heavy pseudoscalar Higgs boson, A, decaying to a 125 GeV Higgs boson h and a Z boson is presented. The h boson is identified via its decay to a pair of tau leptons, while the Z boson is identified via its decay to a pair of electrons or muons. The search targets the production of the A boson via the gluon-gluon fusion process, gg A, and in association with bottom quarks, A. The analysis uses a data sample corresponding to an integrated luminosity of 138 fb collected with the CMS detector at the CERN LHC in proton-proton collisions at a centre-of-mass energy of = 13 TeV. Constraints are set on the product of the cross sections of the A production mechanisms and the A Zh decay branching fraction. The observed (expected) upper limit at 95% confidence level ranges from 0.049 (0.060) pb to 1.02 (0.79) pb for the gg A process and from 0.053 (0.059) pb to 0.79 (0.61) pb for the A process in the probed range of the A boson mass, , from 225 GeV to 1 TeV. The results of the search are used to constrain parameters within the benchmark scenario of the minimal supersymmetric extension of the standard model. Values of below 2.2 are excluded in this scenario at 95% confidence level for all values in the range from 225 to 350 GeV
The optical properties of 3 + 3 macrocyclic Schiff base thin material obtained by the Molecular Beam Epitaxy method
No full text3 + 3 optically active macrocyclic Schiff bases were synthesized in the reaction between 4-tert-butyl-2,6-diformylphenol with (1R,2R)-(+)-1,2-diphenylethylenediamine (S1) or (1S,2S)-(−)-1,2-diphenylethylenediamine (S1a). The new compounds were spectroscopically characterised by NMR, IR, X-ray (S1a), UV–Vis and fluorescence spectroscopy. The S1a molecule creates channels with distances between oxygen atoms ranging from 5.8-6.3 Å and sufficiently large to host acetonitrile molecule. Both compounds exhibit green-yellow emission in solution and solid state. Thin layers of the S1 compound obtained via Molecular Beam Epitaxy (MBE) were characterised by scanning electron microscopy with energy-dispersive X-ray spectroscopy SEM/EDS and atomic force microscopy (AFM). The optical properties of the S1/Si thin material were analysed using spectroscopic ellipsometry (SE), fluorescence spectroscopy and synchrotron radiation (SR). The time constant for the decay investigated under SR, denoted by τ1, was determined to be approximately 1.02 ns, suggesting a fast deactivation process of the excited electronic state in the S1/Si material. The ellipsometric analysis of the S1/Si layer showed semiconducting behaviour with pronounced absorption features in the UV range, attributed to π → π* and n → π* transitions, characteristic of Schiff bases. The band-gap energy, determined using the Tauc method, is 3.46 ± 0.01 eV. These analyses highlight the material’s potential in applications requiring precise control of optical properties. In the emission spectrum of S1a, a significant emission peak of approximately 561 nm indicates the presence of a prominent emissive process within this wavelength. The S1a compound is emissive in the yellow-green region of the spectrum and has a longer decay time, which suggests that it can be used in sensing optical technologie