Search results for " beam"
showing 10 items of 1274 documents
Irradiation-induced damage in porous low-k materials during low-energy heavy-ion elastic recoil detection analysis
2006
Abstract With the implementation of time-of-flight elastic recoil detection (ToF-ERD) for the analysis of thin films with high depth resolution using a standard ‘low-energy’ accelerator, routine application of ERD in semiconductor technology becomes possible. In case of irradiation-sensitive materials, like organosilicate low- k films, the energetic incident beam damages the sample during the measurement, resulting in loss of the lighter elements and, as a consequence, altering the sample composition. The ion beam induced damage is investigated for 19 F, 35 Cl, 63 Cu, 79 Br and 127 I beams at energies of 6–16 MeV and typical fluences for ERD analysis. By means of Fourier transform infrared …
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 …
Dissimilar joining of copper to stainless steel and TA6V to stainless steel by high power beams : understanding and modeling of physicochemical pheno…
2010
The present study is dedicated to the comprehension of the mechanism of materials mixing during dissimilar welding by high power beam sources. We have been interested in joining of two couples of metallic materials which present different metallurgical problems: •copper- stainless steel (miscibility gap, important difference in physical properties);•TA6V- stainless steel (oxidation on air, formation of intermetallic phases which made the joint brittle).For the first couple of materials, continuous laser Nd:YAG welding and electron beam welding have been applied. The experimental study of morphology evolution, composition, microstructure and mechanical properties has allowed establishing the…
First attempt of the measurement of the beam polarization at an accelerator with the optical electron polarimeter POLO
2005
The conventional methods for measuring the polarization of electron beams are either time consuming, invasive or accurate only to a few percent. We developped a method to measure electron beam polarization by observing the light emitted by argon atoms following their excitation by the impact of polarized electrons. The degree of circular polarization of the emitted fluorescence is directly related to the electron polarization. We tested the polarimeter on a test GaAs source available at the MAMI electron accelerator in Mainz, Germany. The polarimeter determines the polarization of a 50 keV electron beam decelerated to a few eV and interacting with an effusive argon gas jet. The resulting de…
Beam test results of IHEP-NDL Low Gain Avalanche Detectors(LGAD)
2020
A High-Granularity Timing Detector (HGTD) is proposed based on the Low-Gain Avalanche Detector (LGAD) for the ATLAS experiment to satisfy the time resolution requirement for the up-coming High Luminosity at LHC (HL-LHC). We report on beam test results for two proto-types LGADs (BV60 and BV170) developed for the HGTD. Such modules were manufactured by the Institute of High Energy Physics (IHEP) of Chinese Academy of Sciences (CAS) collaborated with Novel Device Laboratory (NDL) of the Beijing Normal University. The beam tests were performed with 5 GeV electron beam at DESY. The timing performance of the LGADs was compared to a trigger counter consisting of a quartz bar coupled to a SiPM read…
Preliminary application of thermoluminescence and single aliquot regeneration method for dose reconstruction in soda lime glass
2013
The research described in this paper shows that the use of the single aliquot regeneration (SAR) method for thermoluminescence (TL) measurements applied to soda lime glasses allows to carry out a retrospective dose evaluation. We have followed a fast and efficient sample preparation procedure which permits measurements without powdering and sieving processes. We have analyzed the TL signal of commercial soda lime watch glass irradiated with 6 Mega Volts (MV) LINAC photons, 10 MeV LINAC electrons and 62 MeV protons. After the initial exposure and following TL reading, the samples are successively irradiated with increasing doses of photons. Therefore, for each sample its calibration curve is…
Si Donor Incorporation in GaN Nanowires
2015
With increasing interest in GaN based devices, the control and evaluation of doping are becoming more and more important. We have studied the structural and electrical properties of a series of Si-doped GaN nanowires (NWs) grown by molecular beam epitaxy (MBE) with a typical dimension of 2-3 μm in length and 20-200 nm in radius. In particular, high resolution energy dispersive X-ray spectroscopy (EDX) has illustrated a higher Si incorporation in NWs than that in two-dimensional (2D) layers and Si segregation at the edge of the NW with the highest doping. Moreover, direct transport measurements on single NWs have shown a controlled doping with resistivity from 10(2) to 10(-3) Ω·cm, and a car…
PLZT laser beam modulator
1992
Abstract Laser beam modulator on transparent electrooptic PLZT ceramics are developed for the use in teaching process in schools and universities. Characteristics of the modulator and its electronic control unit are given.