Search results for "beam"
showing 10 items of 2126 documents
Structural modifications induced by electron irradiation in SiO2 glass: Local densification measurements
2009
We report a study on the structural modifications induced in amorphous silicon dioxide (a-SiO2) by electron irradiation in the dose range from 1.2?103 to 5?106?kGy. This study has been performed by investigating the properties of the 29Si hyperfine structure of the E '? center by electron paramagnetic resonance (EPR) spectroscopy. Our data suggest that the structural modifications induced by irradiation take place through the nucleation of confined high-defective and densified regions statistically dispersed into the whole volume of the material. In addition, we have estimated that in the high dose limit (D?105?kGy) the degree of densification associated to the local (within the defective r…
Phonon Cooling of Nanomechanical Beams with Tunnel Junctions
2009
We demonstrate electronic cooling of 1D phonon modes in suspended nanowires for the first time, using normal-metal-insulator-superconductor (N-I-S) tunnel junctions. Simultaneous cooling of both electrons and phonons to a common temperature was achieved. In comparison with nonsuspended devices, better cooling performance is achieved in the whole operating range of bath temperatures between 0.1-0.7 K. The observed low-temperature thermal transport characteristics are consistent with scattering of ballistic phonons at the nanowire-bulk contact as being the mechanism limiting thermal transport. At the lowest bath temperature of the experiment approximately 100 mK, both phonons and electrons in…
Investigation of heavy ion produced defect structures in insulators by small angle scattering
1985
Fast heavy ions produce stable defects in most dielectrica. As examples mica, Polyethylenterephtalat and Polystyrol were irradiated with Ar, Ni, Kr, Xe and U ions in an energy range from 0.5 up to 20 MeV/u. The resulting defects were investigated by neutron and x-ray small-angle scattering. The ion beam supplied by the UNILAC accelerator at GSI Darmstadt is characterized by its small emittance, the well defined mass, charge and energy of the ions and their stochastical distribution in the phase space. In scattering experiments the system of scattering centers created by these ions causes a scattered intensity distribution which strongly depends on the orientation of the sample with respect …
Color centers and structural damage in LiF induced by 150 MeV Kr ions
2012
Color centers and evolution of structure defects were investigated in LiF crystals irradiated at room temperature with 150 MeV 84Kr ions with a beam current of 10nA/cm2 in the fluence range 1011 - 1014 ions/cm2 at the cyclotron accelerator DC-60 (Astana, Kazakhstan). At the fluence of 1011 ions/cm2, SEM imaging revealed mainly formation of etchable ion tracks. Above this fluence, severe structural modifications in the irradiated layer were observed which include the ion-induced formation of dislocations and grains with nano-scale dimensions. The role of fluence in the concentration of electronic color centers and structural modifications is discussed.
Study of intrinsic energy dependence of α-alanine and dose intercomparison with ESR and ISE techniques
1993
Abstract The intrinsic energy behavior of the radiation chemical yields G(R·) and G(NH3) which determine the dose response for the alanine/ESR and alanine/Ion-Selective Electrode (ISE) system, is an important characteristic for the consistent use in different radiation environments. Therefore, the response of ISS and Gent α-alanine dosimeters in the dose range 0.1 to 700 kGy was examined with 60Co, bremsstrahlung and electron beam radiation. Bremsstrahlung beams with end point energy between 5 and 12 MeV and electron beams with mean energy at the effective point of measurement between 4 and 25 MeV were used. Analysis of the 60Co calibration results shows that there are no significant differ…
Stable and long-time operation of a soft x-ray laser for user applications experiments
2011
LASERIX is a high-power laser facility leading to High-repetition-rate XUV laser pumped by Titanium:Sapphire laser. The aim of this laser facility is to offer Soft XRLs in the 30-7 nm range and auxiliary IR beam that could also be used to produce synchronized XUV sources. This experimental configuration highly enhances the scientific opportunities of the facility, giving thus the opportunity to realize both X-ray laser experiments and more generally pump/probe experiments, mixing IR and XUV sources. In this contribution, the main results concerning both the development of XUV sources(X-Ray lasers and HHG sources) and their use for applications are presented.
Microanalytical methods for in-situ high-resolution analysis of rock varnish at the micrometer to nanometer scale
2015
Abstract A wide range of analytical techniques were used to investigate rock varnish from different locations (Negev, Israel; Knersvlakte, South Africa; Death Valley and Mojave Desert, California): a 200 nm-femtosecond laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS), an electron probe microanalyzer (EPMA), focused ion beam (FIB) slicing, and scanning transmission X-ray microscopy–near edge X-ray absorption fine structure spectroscopy (STXM–NEXAFS). This combination enables comprehensive high-spatial-resolution analysis of rock varnish. Femtosecond LA-ICP-MS and EPMA were used for quantitative determination of element concentrations. In-situ measurements were conducte…
Preparation and structural analysis of Fe2+xTi1−x thin films in the C14 Laves phase stability range
2002
Abstract We report the epitaxial growth of single phase (0 0 1)-oriented thin films of Fe2+xTi1−x in the C14 Laves phase stability range using molecular beam epitaxy (MBE). The growth was studied by reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD). The onset temperature for epitaxial growth and the temperature range for improved crystalline coherence were identified. From X-ray reflectometry analysis the rms roughness was estimated to 0.5 nm for typical film thicknesses of 22 nm. As revealed by scanning tunneling microscopy (STM), this roughness is discrete and due to step edges corresponding to the full c-axis length of Fe2Ti. The epitaxial growth implies an …
<title>Measurement methods of laser beam parameters</title>
2007
A wide range of measurements have been used during time in order to define the characteristics of laser beam, therefore it is useful to analyze and re-establish the role of each type of measurement. The scope of these measurements is to increase the precision and reproducibility with which beams propagate, interact and can be focused on a target (part) in an industrial process.
Three-Dimensional Superconducting Nanohelices Grown by He+-Focused-Ion-Beam Direct Writing
2019
Novel schemes based on the design of complex three-dimensional (3D) nanoscale architectures are required for the development of the next generation of advanced electronic components. He+ focused-ion-beam (FIB) microscopy in combination with a precursor gas allows one to fabricate 3D nanostructures with an extreme resolution and a considerably higher aspect ratio than FIB-based methods, such as Ga+ FIB-induced deposition, or other additive manufacturing technologies. In this work, we report the fabrication of 3D tungsten carbide nanohelices with on-demand geometries via controlling key deposition parameters. Our results show the smallest and highest-densely packed nanohelix ever fabricated s…