Abstract In light of our recent research, we discussed the possibility of observing quasimonochromatic Cherenkov Radiation (ChR) spectral lines from a dispersive medium (thin quartz radiator). Such ...experimental results were verified on the Mainz Microtron MAMI, Germany 1, while both the polarization currents analytical model 2 and Geant4 3 simulations were used to analyze the results. To describe the Cherenkov radiation process, the Geant4 toolkit uses only the approximation obtainable for an infinitely thick emitter (cos θ = 1 / βn ( λ ), where θ is Cherenkov’s angle of emission, β is reduced velocity, and n ( λ ) is a refractive index as a function of emitted radiation’s wavelength λ ) and doesn’t consider its actual dimensions. Tamm’s theory 4 predicts some broadening of the ChR angular distribution with a radiator thinning. Consequently, Geant4 gave inadequate results for the pencil-like electron beams compared to the polarization currents model and the experiment. However, unlike in the analytical calculations, we needed to consider more realistic Gaussian electron beams to obtain better results with Geant4. Therefore, obtained results primarily manifest beam characteristics rather than the ChR itself, i.e., its intrinsic characteristics are masked. Now, the idea is to present additional simulation results with further variations of the quartz’s thickness (in preparation for future experiments), confirming the last conclusion without any doubt.
—An analytical approach based on the polarization currents method is used to calculate the effect of the detector angular aperture on the vacuum Vavilov–Cherenkov radiation (VChR) polarization for an ...inclined dielectric plate. The simulation results show that an increase in the azimuthal detector aperture increases the VChR detection efficiency without average polarization degradation.
The radiation losses of a relativistic charge moving in vacuum near a dielectric radiator in which Vavilov – Cherenkov radiation is generated are estimated. For a charge moving near the flat surface ...of an infinite radiator (along the charge path), the radiation losses are calculated based on the existing theory. For a finite radiator of length L along the charge trajectory (that is, for the radiator with input and output planar faces perpendicular to the charge propagation path that give rise the edge effects), we have developed a model for calculating the radiation characteristics by the polarization current method. For this model, the radiation losses are calculated, and it is shown that with allowance for the edge effects, the losses in the finite radiator on Vavilov–Cherenkov radiation are higher by 2–3 orders of magnitude compared to the losses of the infinite radiator.
For over half a century, Vavilov–Cherenkov radiation (VCR) has been used for detecting elementary particles. Lately, some authors have proposed using the coherent VCR emitted by a short particle ...bunch for measuring its length. Towards this, they envisage using dielectric targets of conical (or more complex) shapes whereby the radiation is transported to a vacuum with minimum losses for multiple reflections. Unfortunately, analytical methods for deriving the VCR spectral and angular characteristics are restricted to targets with simplest geometries even for noncoherent radiation. In this paper, the characteristics of Vavilov–Cherenkov radiation emitted by an inclined dielectric plate are analytically derived using the imaging and polarization-current approaches. Our calculations adequately reproduce the results of a recent experiment. We demonstrate that not only the bunch length, but also its transverse profile can be probed using its VCR.
In this work, the micro-arc oxidation method is used to fabricate surface-modified complex-structured titanium implant coatings to improve biocompatibility. Depending on the utilized electrolyte ...solution and micro-arc oxidation process parameters, three different types of coatings (one of them-oxide, another two-calcium phosphates) were obtained, differing in their coating thickness, crystallite phase composition and, thus, with a significantly different biocompatibility. An analytical approach based on X-ray computed tomography utilizing software-aided coating recognition is employed in this work to reveal their structural uniformity. Electrochemical studies prove that the coatings exhibit varying levels of corrosion protection.
and
experiments of the three different micro-arc oxidation coatings prove high biocompatibility towards adult stem cells (investigation of cell adhesion, proliferation and osteogenic differentiation), as well as
biocompatibility (including histological analysis). These results demonstrate superior biological properties compared to unmodified titanium surfaces. The ratio of calcium and phosphorus in coatings, as well as their phase composition, have a great influence on the biological response of the coatings.
Modern accelerator technologies may provide electron beams consisting of ultrashort bunches with transverse sizes, which are much larger than longitudinal sizes. The spectral-angular characteristics ...of coherent Cherenkov radiation (CChR) produced by such bunches have thus been considered. We simulated the characteristics of CChR and those from a single charge on the basis of the polarization current model, which allowed us to consider finite sizes for the Cherenkov radiator. We calculated the angular distribution of the CChR from a bunch tilted by angle ψ, with respect to the velocity direction, with the assumption of a 3-D Gaussian charge distribution in the bunch. Contrary to the azimuthally symmetrical distribution of conventional ChR, a strong azimuthal asymmetry was observed in the CChR from the tilted bunch. The maximal yield of the CChR may be achieved if the tilt angle ψ coincides with the Cherenkov angle Θch=arccos(1/nβ), βc is the charge velocity and n is the refraction index.
•The coherent Cherenkov radiation from tilted electron bunches has been investigated.•The coherent Cherenkov radiation produced from such a bunch possesses the strong azimuthal asymmetry.•The direction of the maximal radiation yield is defined by the plane containing a bunch axes and its velocity.
In this paper we discuss the possibility of proof-of-principle experiment to observe backward transition radiation in EUV region as a first step for beam diagnostics. We have carried out simulations ...of backward transition radiation angular distributions in the EUV region for molybdenum target for different geometries. The simulation results are promising for beam diagnostics purposes.
Abstract
The micro-arc oxidation method was applied to modify the surface of 3D printed titanium implants with a complex internal structure. Two different electrolyte solutions were used for ...thesurface modification, for which the respective working parameters of the micro-arc oxidation process were developed. Surface coatings formed with these parameters on the 3D implants have the same chemical composition and have the same surface morphology as surface coatings on 2D substrates. The measurement of the coating thickness using the X-ray microtomography demonstrates that this method is a useful tool for the thickness control of porous surface coatings at the inside and outside of the 3D titanium implants.
PDF
