Search results for "Physics::Accelerator Physics"
showing 10 items of 1235 documents
Highly localized accelerating beams using nano-scale metallic gratings
2015
Spatially accelerating beams are non-diffracting beams whose intensity is localized along curvilinear trajectories, also incomplete circular trajectories, before diffraction broadening governs their propagation. In this paper we report on numerical simulations showing the conversion of a high-numerical-aperture focused beam into a nonparaxial shape-preserving accelerating beam having a beam-width near the diffraction limit. Beam shaping is induced near the focal region by a diffractive optical element that consists of a non-planar subwavelength grating enabling a Bessel signature. This research was funded by the Spanish Ministry of Economy and Competitiveness under the project TEC2011-29120…
Achromatic Fresnel diffraction patterns
1993
Abstract A novel method for obtaining a single, but arbitrary, achromatic Fresnel diffraction pattern of any pupil with broadband parallel illumination is presented. The optical device simply consists of an achromatic objective and an on-axis zone plate. A criterion for selecting the system parameters in order to minimize the residual chromatic aberrations is given. The recording of the selected diffraction field is obtained with low chromatic aberrations even for white-light illumination. An experimental verification is shown to illustrate this approach.
White-light Fourier transformer with low chromatic aberration.
1992
A simple Fourier transformation system working with broadband parallel illumination is presented. The proposed setup, consisting of two on-axis zone plates and an achromatic objective, allows us to obtain the achromatic Fourier transform representation of the input at a finite distance with a low chromatic aberration. The discussion of the system, using the Fresnel diffraction theory, leads to an analytical expression to evaluate the transversal and longitudinal chromatic aberrations. It is shown that the resulting chromatic aberrations for typical values of the involved parameters are less than 1% over the entire visible spectrum.
Nonparaxial shape-preserving Airy beams with Bessel signature
2014
Spatially accelerating beams that are solutions to Maxwell equations may propagate along incomplete circular trajectories. Taking these truncated Bessel fields to the paraxial limit, some authors have sustained that it has recovered the known Airy beams (AiBs). Based on the angular spectrum representation of optical fields, we demonstrated that the paraxial approximation rigorously leads to off-axis focused beams instead of finite-energy AiBs. The latter will arise under the umbrella of a nonparaxial approach following elliptical trajectories in place of parabolas. The analytical expression of such a shape-preserving wave field under Gaussian apodization is disclosed by using third-order no…
Electromagnetic scattering by a strip grating with nonplanar illumination
1993
An angular-spectrum method combined with the Galerkin procedure has been used to evaluate the electromagnetic scattering of a beam radiated by an aperture antenna after being incident obliquely upon a strip grating. Integral expressions for the transmitted and reflected fields are obtained. The incident beam radiated by the antenna is diffracted in several beams corresponding to the propagative Floquet harmonics. An angular shift of the transmitted and reflected fundamental harmonic beams has been shown. Comparison between numerical and experimental results validates this method. © 1993 John Wiley & Sons, Inc.
Generation of accelerating beams using nano-scale metallic circular gratings
2014
Spatially accelerating beams that are solutions to the Maxwell equations may propagate along incomplete circular trajectories, after which diffraction broadening takes over and the beams spread out. In this paper we report on numerical simulations that show the conversion of a high-numerical-aperture focused beam into a nonparaxial shape-preserving accelerating beam having a beam-width near the diffraction limit. Beam shaping is induced by a diffractive optical element that consists of a non-planar sub-wavelength grating enabling a Bessel signature.
Characterization of Hong-Ou-Mandel bunched states by quantum homodyne tomography
2014
We experimentally demonstrate quantum homodyne tomography of Hong-Ou-Mandel bunched states, which are created by dynamically adjusting emission timings of two heralded single photons using coupled cavities.
Extension of Electron Monte Carlo Dose Calculation in Eclipse to Siemens Linear Accelerators
2009
Initially, the implementation of the macro Monte Carlo (MC) method into Eclipse (Varian Medical Systems), named eMC, was carried out for Varian accelerators only. In this work eMC algorithm has been modified to allow also accurate dose calculations for electron beams for Siemens accelerators.
The influence of Fermi motion on the comparison of the polarization transfer to a proton in elastic e→p and quasi-elastic e→A scattering
2019
Abstract A comparison between polarization-transfer to a bound proton in quasi-free kinematics by the A ( e → , e ′ p → ) knockout reaction and that in elastic scattering off a free proton can provide information on the characteristics of the bound proton. In the past the reported measurements have been compared to those of a free proton with zero initial momentum. We introduce, for the first time, expressions for the polarization-transfer components when the proton is initially in motion and compare them to the 2H data measured at the Mainz Microtron (MAMI). We show the ratios of the transverse ( P x ) and longitudinal ( P z ) components of the polarization transfer in H 2 ( e → , e ′ p → …
Measurements of the antiproton-proton elastic cross section in the beam momentum range between 180 and 600 MeV/c
1991
The differential cross section for antiproton-proton elastic scattering has been measured for the beam momenta between 180 and 600 MeV/c. The real-to-imaginary ratio of the forward elastic scattering amplitude is derived from the Coulomb-nuclear interference. The ratio is found to be close to zero between 180 and 500 MeV/c with a minimum ofρ=−0.14 at 260 MeV/c. This result is contrary to model predictions. The phase shifts for thes-,p- andd-waves are extracted. The partial wave compositions of the elastic and inelastic cross sections have been determined. A large contribution of thep-wave is identified in the antiproton-proton interactions at small momenta.