Search results for "beam [charged particle]"
showing 10 items of 686 documents
Effect of Penetrating Irradiation on Polarization Reversal in PZT Thin Films
2006
Spatially non-uniform imprint behavior induced by X-ray synchrotron, electron, and neutron irradiation has been investigated in Pb(Zr,Ti)O3 thin films. The obtained effects have been explained as a result of acceleration of the bulk screening process induced by irradiation. It has been shown that the spatial distribution of the internal bias field is determined by the domain pattern existing during irradiation. The microstructural changes in the structural characteristics during fatigue cycling have been revealed by high resolution synchrotron X-ray diffraction experiments. Their correlation with the evolution of the switching characteristics has been revealed and discussed.
Artificially inscribed defects in opal photonic crystals
2005
Opals are three-dimensional photonic crystals, self-assembled from dielectric spherical beads into a face-centered cubic lattice. By introducing intentional defects in the crystal lattice, one modifies features such as spontaneous emission and the directionality of diffracted light. We here present a method for the artificial introduction of a lattice of such intentional defects in self-assembled poly(methyl methacrylate) (PMMA) photonic crystals by means of electron beam lithography. The inscribed defects are of the size of an individual bead, providing a broad spectral range between adjacent resonance peaks. This opens for devices with single line transmission in the photonic band gap, as…
Visible light apparatus for preliminary tests of x-ray optics
2006
We report a useful visible light testing procedure for a first analysis of soft X-ray grazing incidence optics (0.1-2 keV). Although diffraction is a limit in the application of this method, great advantages are obtained by running the tests in air with direct access to modify the geometrical mounting of the individual mirror shells. We present the experimental apparatus and show the first results of the investigation of light weight optics based on plastic foil material and comparison with results obtained with an X-ray beam.
Preparation of superconducting thin films of UNiAl
2005
Abstract Epitaxial thin films of the unconventional heavy fermion superconductor UNi 2 Al 3 we prepared by coevaporation of the elementary components in a molecular beam epitaxy system (MBE). The phase purity and structural quality of the films deposited on (0 1 0)- or (1 1 2)-oriented YAlO 3 substrates were studied by X-ray diffraction and RHEED. The observed R ( T ) behavior is consistent with data obtained from bulk samples and proves the purity of the films. Superconductivity was found with transition temperature T c =0.97 K.
Isotropic compensation of diffraction-driven angular dispersion
2007
We report on an optical arrangement capable of compensating angular dispersion of paraxial wave fields developed by diffractive optical elements (DOEs). Schematically, the system is a beam expander in which two phase-only zone plates have been inserted, remaining afocal the coupled system. The DOE, which induces a continuous set of dispersive tilted plane waves, is placed at a specific position within the proposed setup providing an output spectrum with achromatic angular deviation. A directional matching between phase fronts and pulse fronts of output wave packets is demonstrated.
Characterization of a cryogenic ion guide at IGISOL
2012
A small volume cryogenic ion guide has been characterized at the IGISOL facility, Jyvaskyla, as a prototype to verify whether there are any major obstacles to the use of high-density cryogenic helium gas for the stopping and extraction of high-energy ions from a large volume cryogenic ion catcher. The expected temperature scaling of the mass flow through the ion guide has been confirmed, showing that for the same helium density, the differential pumping requirements are less stringent for cryogenic operation. At 90 K a clear reduction in the mass-analyzed impurities is achieved, although lower temperatures are required to freeze out oxygen and nitrogen. This is supported by the reduction in…
Accuracy assessment of cone beam computed tomography-derived laboratory-based surgical templates on partially edentulous patients
2011
Objectives: The aim of the present prospective clinical study was to evaluate the match between the positions and axes of the virtually planned and the placed implants using laboratory-based surgical guides generated from cone beam computed tomography (CBCT). Materials and methods: A total of 132 implants were placed with the aid of 3D-based transfer templates in 52 consecutive partially edentulous patients between April 2008 and March 2010. After individual adaptation of the scan templates and CBCT scanning, the acquired data for virtual implant planning and simulation were processed using the med3D software program. After finalizing the virtual placement of the implants the radiographic t…
Elastic Recoil Detection Analysis
2008
In 1976, a Canadian group described in detail for the first time a new ion beam analytical method based on the elastic recoil of target nuclei collided with high-energy heavy incident ions. In this case, 25–40-MeV 35Cl impinged on a multilayer C or Cu (backing)/LiF or LiOH/Cu (30–150 nm)/LiF or LiOH and H, Li, O, and F recoiled atoms were detected. These exemplified the main characteristics of elastic recoil detection analysis (ERDA): its sensitivity to depth distribution and its ability to detect light elements in heavy substrates. In 1979, the use of megaelectronvolt energy 4He beams permitted the use of ERDA to be extended to depth profiling of hydrogen isotopes in the near-surface regio…
Measurement of the n-TOF beam profile with a micromegas detector
2004
A Micromegas detector was used in the neutron Time-Of-Flight (n_TOF) facility at CERN to evaluate the spatial distribution of the neutron beam as a function of its kinetic energy. This was achieved over a large range of neutron energies by using two complementary processes: at low energy by capture of a neutron via the 6Li(n,[alpha])t reaction, and at high energy by elastic scattering of neutrons on gas nuclei (argon+isobutane or helium+isobutane). Data are compared to Monte Carlo simulations and an analytic function fitting the beam profile has been calculated with a sufficient precision to use in neutron capture experiments at the n_TOF facility. http://www.sciencedirect.com/science/artic…
Compensation of missing wedge effects with sequential statistical reconstruction in electron tomography.
2014
Electron tomography (ET) of biological samples is used to study the organization and the structure of the whole cell and subcellular complexes in great detail. However, projections cannot be acquired over full tilt angle range with biological samples in electron microscopy. ET image reconstruction can be considered an ill-posed problem because of this missing information. This results in artifacts, seen as the loss of three-dimensional (3D) resolution in the reconstructed images. The goal of this study was to achieve isotropic resolution with a statistical reconstruction method, sequential maximum a posteriori expectation maximization (sMAP-EM), using no prior morphological knowledge about …