Analytical treatment of the wakefields driven by transversely shaped beams in a planar slow-wave structure

The suppression of transverse wakefield effects using transversely elliptical drive beams in a planar structure is studied with a simple analytical model that unveils the geometric nature of this phenomenon. By analyzing the suggested model we derive scaling laws for the amplitude of the longitudinal and transverse wake potentials as a function of the Gaussian beam ellipticity - $\sigma_x/a$. We explicitly show that in a wakefield accelerator application it is beneficial to use highly elliptical beams for mitigating transverse forces while maintaining the accelerating field. We consider two scaling strategies: 1) aperture scaling, where we keep a constant charge to have the same accelerating gradient as in a cylindrical structure and 2) charge scaling, where aperture is the same as in the cylindrical structure and charge is increased to match the gradient.Comment: 10 pages, 6 figure

Structure and properties of nanostructured ZrN coatings obtained by vacuum-arc evaporation using RF discharge

Nanostructured films of zirconium nitride have been synthesized using an ion plasma vacuum-arc deposition technique in combination with a high-frequency (RF) discharge on AISI 430 stainless steel at 150 °C. Structural examination using X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM) with microanalysis (EDX), transmission electron microscopy (TEM), and nanoidentation was undertaken to reveal phase and chemical composition, surface morphology, microstructure and nanohardness of the coatings. The developed technology provided low-temperature film synthesis, minimized discharge breakdown decreasing formation of macroparticles (MPs) and allowed to deposit ZrN coatings with hardness variation 26.6–31.5 GPa and enhanced corrosion resistance characteristics. It was revealed that ZrN single-phase coatings of cubic modification with fine-crystalline grains of 20 nm in size were formed. The corrosion resistance of coatings has been tested in 0.9% quasiphysiological NaCl solution

Structure and properties of nanostructured ZrN coatings obtained by vacuum-arc evaporation using RF discharge

Nanostructured films of zirconium nitride have been synthesized using an ion plasma vacuum-arc deposition technique in combination with a high-frequency (RF) discharge on AISI 430 stainless steel at 150 °C. Structural examination using X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM) with microanalysis (EDX), transmission electron microscopy (TEM), and nanoidentation was undertaken to reveal phase and chemical composition, surface morphology, microstructure and nanohardness of the coatings. The developed technology provided low-temperature film synthesis, minimized discharge breakdown decreasing formation of macroparticles (MPs) and allowed to deposit ZrN coatings with hardness variation 26.6–31.5 GPa and enhanced corrosion resistance characteristics. It was revealed that ZrN single-phase coatings of cubic modification with fine-crystalline grains of 20 nm in size were formed. The corrosion resistance of coatings has been tested in 0.9% quasiphysiological NaCl solution

Nanostructured ZrO₂ ceramic PVD coatings on Nd-Fe-B permanent magnets

The results of vacuum-arc deposition (PVD) of thin ZrO2 coatings to protect the surface of Nd-Fe-B permanent magnets used as repelling devices in orthodontics are presented. Magnetic devices are offered as an optimum and biologically safe forcegenerating system for orthodontic tooth movement. The structure, phase composition and mechanical properties of zirconium oxide films have been investigated by means of SEM, XRD, EDX, XRF and nanoindentation methods. The coatings are formed of polycrystalline ZrO2 films of monoclinic modification with average grain size 25 nm. The influence of the ZrO2 coating in terms of its barrier properties for corrosion in quasiphysiological 0.9% NaCl solution has been studied. Electrochemical measurements indicated good barrier properties of the coating on specimens in the physiological solution environment

Field induced evolution of regular and random 2D domain structures and shape of isolated domains in LiNbO₃ and LiTaO₃

The shapes of isolated domains produced by application of the uniform external electric field in different experimental conditions were investigated experimentally in single crystalline lithium niobate LiNbO3 and lithium tantalate LiTaO3. The study of the domain kinetics by computer simulation and experimentally by polarization reversal of the model structure using two-dimensional regular electrode pattern confirms applicability of the kinetic approach to explanation of the experimentally observed evolution of the domain shape and geometry of the domain structure. It has been shown that the fast domain walls strictly oriented along X directions appear after domain merging

Time-dependent conduction current in lithium niobate crystals with charged domain walls

We present the experimental study of the increase and decrease of the abnormal conduction current appeared during polarization reversal at elevated temperatures (120-250 °C) in stoichiometric and MgO doped lithium niobate single crystals. It is shown that the conduction current is caused by existence of the through charged domain walls. The time dependence of the conduction current has been measured in low electric field immediately after partial switching. The maximal value of the conduction current in crystal with through charged domain walls is of 4-5 orders of magnitude higher than in initial single domain state. The activation energy is 1.1 eV. © 2013 AIP Publishing LLC

Anti-corrosion ceramic coatings on the surface of Nd-Fe-B repelling magnets

The results of vacuum-arc deposition of thin ZrO₂coatings to protect the surface of Nd-Fe-B permanent magnets used as repelling devices in orthodontics are presented. The structure, phase composition and mechanical properties of zirconium dioxide films have been investigated by means of SEM, XRD, EDX, XRF and nanoindentation method. It was revealed the formation of polycrystalline ZrO₂ films of monoclinic modification with average grain size 25 nm. The influence of the ZrO₂ coating in terms of its barrier properties for corrosion in quasi-physiological 0.9 NaCl solution has been studied. Electrochemical measurements indicated good barrier properties of the coating on specimens in the physiological solution environment

A Precision Measurement of Nuclear Muon Capture on 3He

The muon capture rate in the reaction mu- 3He -> nu + 3H has been measured at PSI using a modular high pressure ionization chamber. The rate corresponding to statistical hyperfine population of the mu-3He atom is (1496.0 +- 4.0) s^-1. This result confirms the PCAC prediction for the pseudoscalar form factors of the 3He-3H system and the nucleon.Comment: 13 pages, 6 PostScript figure