337 research outputs found

    First Results from Nb3Sn Coatings of 2.6 GHz Nb SRF Cavities Using DC Cylindrical Magnetron Sputtering System

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    A DC cylindrical magnetron sputtering system has been commissioned and operated to deposit Nb3Sn onto 2.6 GHz Nb SRF cavities. After optimizing the deposition conditions in a mock-up cavity, Nb-Sn films are deposited first on flat samples by multilayer sequential sputtering of Nb and Sn, and later annealed at 950 {\deg}C for 3 hours. X-ray diffraction of the films showed multiple peaks for the Nb3Sn phase and Nb (substrate). No peaks from any Nb3Sn compound other than Nb3Sn were detected. Later three 2.6 GHz Nb SRF cavities are coated with ~1 μ\mum thick Nb3Sn. The first Nb3Sn coated cavity reached close to Eacc = 8 MV/m, demonstrating a quality factor Q0 of 3.2 x 108 at Tbath = 4.4 K and Eacc = 5 MV/m, about a factor of three higher than that of Nb at this temperature. Q0 was close to 1.1 x 109, dominated by the residual resistance, at 2 K and Eacc = 5 MV/m. The Nb3Sn coated cavities demonstrated Tc in the range of 17.9 - 18 K. Here we present the commissioning experience, system optimization, and the first results from the Nb3Sn fabrication on flat samples and SRF cavities.Comment: 21st Intl Conf Radio Frequency Superconductivity (SRF 2023

    Sweet-Tasting Natural Proteins Brazzein and Monellin: Safe Sugar Substitutes for the Food Industry

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    This article presents the results of a comprehensive toxicity assessment of brazzein and monellin, yeast-produced recombinant sweet-tasting proteins. Excessive sugar consumption is one of the leading dietary and nutritional problems in the world, resulting in health complications such as obesity, high blood pressure, and cardiovascular disease. Although artificial small-molecule sweeteners widely replace sugar in food, their safety and long-term health effects remain debatable. Many sweet-tasting proteins, including thaumatin, miraculin, pentadin, curculin, mabinlin, brazzein, and monellin have been found in tropical plants. These proteins, such as brazzein and monellin, are thousands-fold sweeter than sucrose. Multiple reports have presented preparations of recombinant sweet-tasting proteins. A thorough and comprehensive assessment of their toxicity and safety is necessary to introduce and apply sweet-tasting proteins in the food industry. We experimentally assessed acute, subchronic, and chronic toxicity effects, as well as allergenic and mutagenic properties of recombinant brazzein and monellin. Our study was performed on three mammalian species (mice, rats, and guinea pigs). Assessment of animals’ physiological, biochemical, hematological, morphological, and behavioral indices allows us to assert that monellin and brazzein are safe and nontoxic for the mammalian organism, which opens vast opportunities for their application in the food industry as sugar alternatives

    Collins and Sivers transverse-spin asymmetries in inclusive muoproduction of ρ0\rho^0 mesons

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    The production of vector mesons in deep inelastic scattering is an interesting yet scarsely explored channel to study the transverse spin structure of the nucleon and the related phenomena. The COMPASS collaboration has performed the first measurement of the Collins and Sivers asymmetries for inclusively produced ρ0\rho^0 mesons. The analysis is based on the data set collected in deep inelastic scattering in 20102010 using a 160GeV/c160\,\,\rm{GeV}/c μ+\mu^+ beam impinging on a transversely polarized NH3\rm{NH}_3 target. The ρ0\rho^{0} mesons are selected from oppositely charged hadron pairs, and the asymmetries are extracted as a function of the Bjorken-xx variable, the transverse momentum of the pair and the fraction of the energy zz carried by the pair. Indications for positive Collins and Sivers asymmetries are observed

    Insight into the electronic structure of the centrosymmetric skyrmion magnet GdRu2_2Si2_2

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    The discovery of a square magnetic-skyrmion lattice in GdRu2_2Si2_2, with the smallest so far found skyrmion diameter and without a geometrically frustrated lattice, has attracted significant attention, particularly for potential applications in memory devices and quantum computing. In this work, we present a comprehensive study of surface and bulk electronic structures of GdRu2_2Si2_2 by utilizing momentum-resolved photoemission (ARPES) measurements and first-principles calculations. We show how the electronic structure evolves during the antiferromagnetic transition when a peculiar helical order of 4ff magnetic moments within the Gd layers sets in. A nice agreement of the ARPES-derived electronic structure with the calculated one has allowed us to characterize the features of the Fermi surface (FS), unveil the nested region along the kzk_z at the corner of the 3D FS, and reveal their orbital compositions. Our findings suggest that the Ruderman-Kittel-Kasuya-Yosida interaction plays a decisive role in stabilizing the spiral-like order of Gd 4ff moments responsible for the skyrmion physics in GdRu2_2Si2_2. Our results provide a deeper understanding of electronic and magnetic properties of this material, which is crucial for predicting and developing novel skyrmion-based devices.Comment: 13 pages, 8 figure

    Preservation of the High Quality Factor and Accelerating Gradient of Nb3Sn-coated Cavity During Pair Assembly

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    Two CEBAF 5-cell accelerator cavities have been coated with Nb3Sn film using the vapor diffusion technique. One cavity was coated in the Jefferson Lab Nb3Sn cavity coating system, and the other in the Fermilab Nb3Sn coating system. Both cavities were measured at 4 K and 2 K in the vertical dewar test in each lab and then assembled into a cavity pair at Jefferson Lab. Previous attempts to assemble Nb3Sn cavities into a cavity pair degraded the superconducting properties of Nb3Sn-coated cavities. This contribution discusses the efforts to identify and mitigate the pair assembly challenges and will present the results of the vertical tests before and after pair assembly. Notably, one of the cavities reached the highest gradient above 80 mT in the vertical test after the pair assembly.Comment: 21st Intl Conf Radio Frequency Superconductivity (SRF 2023

    Flux Expulsion and Material Properties of Niobium Explored in 644-650 MHz Cavities

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    Upcoming projects requiring high-Q ~650 MHz medium-to-high-β{\beta} elliptical cavities drive a need to understand magnetic RF loss mechanisms and mitigations in greater detail. High-temperature annealing and fast-cooldowns have proven effective techniques for promoting magnetic flux expulsion in cavities, however the extent of their effectiveness has been observed to vary between niobium material lot and vendor. We explore the fast-cooldown method, and high-temperature annealing (900{\deg}C) in 644-650 MHz cavities fabricated from two different niobium vendors: Tokyo-Denkai, and Ningxia. which promote flux-expulsion efficiency. Using EBSD and PPMS methods, we aim to trace cavity flux expulsion efficiency to specific, measurable properties of the bulk niobium material, which, if identified, can lead to methods by which the flux expulsion properties of Nb material can be predicted prior to cavity fabrication, and can enable fine-tuning of cavity temperature treatments

    Advanced surface treatments for medium-velocity superconducting RF cavities for high accelerating gradient continuous-wave operation

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    Nitrogen-doping and furnace-baking are advanced high-Q0 recipes developed for 1.3 GHz TESLA-type cavities. These treatments will significantly benefit the high-Q0 linear accelerator community if they can be successfully adapted to different cavity styles and frequencies. Strong frequency- and geometry- dependence of these recipes makes the technology transfer amongst different cavity styles and frequencies far from straightforward, and requires rigorous study. Upcoming high-Q0 continuous-wave linear accelerator projects, such as the proposed Michigan State University Facility for Rare Isotope Beam Energy Upgrade, and the underway Fermilab's Proton Improvement Plan-II, could benefit enormously from adapting these techniques to their beta_opt = 0.6 ~650 MHz 5-cell elliptical superconducting rf cavities, operating at an accelerating gradient of around ~17 MV/m. This is the first investigation of the adaptation of nitrogen doping and medium temperature furnace baking to prototype 644 MHz beta_opt = 0.65 cavities, with the aim of demonstrating the high-Q0 potential of these recipes in these novel cavities for future optimization as part of the FRIB400 project R&D. We find that nitrogen-doping delivers superior Q0, despite the sub-GHz operating frequency of these cavities, but is sensitive to the post-doping electropolishing removal step and experiences elevated residual resistance. Medium temperature furnace baking delivers reasonable performance with decreased residual resistance compared to the nitrogen doped cavity, but may require further recipe refinement. The gradient requirement for the FRIB400 upgrade project is comfortably achieved by both recipes.Comment: 16 pages, 5 figure

    Spin Density Matrix Elements in Exclusive ρ0\rho ^0 Meson Muoproduction

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    We report on a measurement of Spin Density Matrix Elements (SDMEs) in hard exclusive ρ0\rho ^0 meson muoproduction at COMPASS using 160~GeV/cc polarised μ+ \mu ^{+} and μ \mu ^{-} beams impinging on a liquid hydrogen target. The measurement covers the kinematic range 5.0~GeV/c2c^2 <W<< W < 17.0~GeV/c2c^2, 1.0 (GeV/cc)2^2 <Q2<< Q^2 < 10.0 (GeV/cc)2^2 and 0.01 (GeV/cc)2^2 <pT2<< p_{\rm{T}}^2 < 0.5 (GeV/cc)2^2. Here, WW denotes the mass of the final hadronic system, Q2Q^2 the virtuality of the exchanged photon, and pTp_{\rm{T}} the transverse momentum of the ρ0\rho ^0 meson with respect to the virtual-photon direction. The measured non-zero SDMEs for the transitions of transversely polarised virtual photons to longitudinally polarised vector mesons (γTVL\gamma^*_T \to V^{ }_L) indicate a violation of ss-channel helicity conservation. Additionally, we observe a dominant contribution of natural-parity-exchange transitions and a very small contribution of unnatural-parity-exchange transitions, which is compatible with zero within experimental uncertainties. The results provide important input for modelling Generalised Parton Distributions (GPDs). In particular, they may allow one to evaluate in a model-dependent way the role of parton helicity-flip GPDs in exclusive ρ0\rho ^0 production

    Morphological features of skin changes in the undetermined clinical picture of psoriasis and atopic dermatitis in children

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    The purpose of work was to compare pathomorphological changes in biopsy specimens of plaque skin elements in children with undetermined clinical picture of the disease with changes in typical forms of psoriasis and atopic dermatitis.Цель работы – сравнить патоморфологические изменения в биоптатах бляшечных элементов кожи при неопределенной клинической картине заболевания у детей с изменениями при типичных формах псориаза и атопического дерматита

    An observation of the f0(1710)f_0(1710) meson in the ωϕ\omega\phi system in the Pion-BeBe Interaction at Momentum of 29 GeV

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    The charge-exchange reaction πpnω(783)ϕ(1020)\pi^-p \rightarrow n\,\omega(783)\phi(1020), ωπ+ππ0\omega \rightarrow \pi^+\pi^-\pi^0, ϕK+K\phi \rightarrow K^+K^- is studied with the upgraded VES facility (U-70, Protvino) in the interaction of a 29 GeV pion beam with a beryllium target. The distribution over the invariant mass of the system MωϕM_{\omega\phi} shows a near-threshold signal. A partial wave analysis reveals that the scalar state (JPC=0++J^{PC}=0^{++}) dominates in this mass region. The observed signal can be described with a contribution of the known resonance f0(1710)f_0(1710). Using OPE approximation for the reaction πpnf0(1710)\pi^-p \rightarrow n\, f_0(1710) the product of branching fractions is found to be: Br(f0(1710)ππ)Br(f0(1710)ωϕ)=(4.8±1.2)103Br(f_0(1710)\rightarrow \pi\pi)\cdot Br(f_0(1710)\rightarrow \omega\phi) = (4.8 \pm 1.2) \cdot 10^{-3}
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