Search results for "electromagnetic [current]"
showing 10 items of 1008 documents
Oxygen-excess-related point defects in glassy/amorphous SiO2 and related materials
2012
Abstract An insight is given into recent experimental advances in the spectroscopic studies of oxygen-excess intrinsic defects, in glassy SiO 2 and α-quartz. By controlling excess oxygen in a-SiO 2 , and the conditions of F 2 -laser irradiation, SiO 2 glass samples can be obtained with optical absorption almost exclusively dominated by single defect, oxygen dangling bonds (“non-bridging oxygen hole centers” or NBOHCs), without the presence of complementary Si dangling bonds (generic “E′-centers”). This allows for a more accurate determination of the spectral shape of NBOHC optical absorption in UV and vacuum UV spectral regions. The temperature dependence of NBOHC electron paramagnetic reso…
Theoretical and experimental study of primary radiation defects in KNbO3 perovskite crystals
2000
Abstract The results of large-scale computer simulations of point defects – F-type electron centers and hole polarons bound to a potassium vacancy – in perovskite KNbO3 crystals are presented. One-site polarons and two-site (molecular) polarons are expected to coexist, both are characterized by close absorption energies around 1 eV. The transient absorption spectra and decay kinetics observed after ns-pulsed electron beam irradiation have been measured for different KNbO3 crystals. The relaxation kinetics of the optical density vary considerably for different impurity concentrations and sample stoichiometries. Experimental data are discussed in the light of the presented calculations.
Quantitative analysis of rhenium in irradiated tungsten
2021
Abstract Pure tungsten (W), irradiated to 3.5 dpa in a target of the Swiss neutron spallation source (SINQ), was characterized using high-sensitivity HPGe gamma ray spectroscopy to identify the present radionuclides. Synchrotron X-ray absorption spectroscopy was used to quantify the amount of Re produced in the irradiated W. An atomic concentration of 0.61% Re in the irradiated W was determined from the height of the L3-edge X-ray absorption edge jump. Analysis of the local atomic structure from the extended X-ray absorption fine structure (EXAFS) spectra indicates that rhenium (Re) produced in the system is mainly coordinated by W atoms and partly coordinated by void defects. First-princip…
Recent developments in the evaluation of Mössbauer line intensities
1985
The angular dependence of the intensities of pure or mixed multipole transitions is formulated in a new fashion, which takes into account arbitrary texture of the Mossbauer absorber ranging from complete orientation (single crystals) over preferred orientation to random powders and an anisotropic absorption fraction of the nuclei. The application of the theory is demonstrated by means of typical examples from the literature.
Combined High Dose and Temperature Radiation Effects on Multimode Silica-Based Optical Fibers
2013
International audience; We investigate the response of Ge-doped, P-doped, pure-silica, or Fluorine-doped fibers to extreme environments combining doses up to MGy(SiO $_{{{2}}}$) level of 10 keV X-rays and temperatures between 25 C and 300 C . First, we evaluate their potential to serve either as parts of radiation tolerant optical or optoelectronic systems or at the opposite, for the most sensitive ones, as punctual or distributed dosimeters. Second, we improve our knowledge on combined ionizing radiations and temperature (R&T) effects on radiation-induced attenuation (RIA) by measuring the RIA spectra in the ultraviolet and visible domains varying the R&T conditions. Our results reveal the…
Steady-State X-Ray Radiation-Induced Attenuation in Canonical Optical Fibers
2020
The so-called canonical optical fibers (OFs) are samples especially designed to highlight the impact of some manufacturing process parameters on the radiation responses. Thanks to the results obtained on these samples, it is thus possible to define new procedures to better control the behaviors of OFs in radiation environments. In this article, we characterized the responses, under steady-state X-rays, of canonical samples representative of the most common fiber types differing by their core-dopants: pure silica, Ge, Al, and P. Their radiation-induced attenuation (RIA) spectra were measured online at both room temperature (RT) and liquid nitrogen temperature (LNT), in the energy range [~0.6…
Radiation effects on silica-based preforms and optical fibers-I: Experimental study with canonical samples
2008
International audience; Prototype samples of preforms and associated fibers have been designed and fabricated through MCVD process to investigate the role of fluorine (F) and germanium (Ge) doping elements on the radiation sensitivity of silica-based glasses. We characterized the behaviors of these canonical samples before, during and after 10 keV X-ray irradiation through several spectroscopic techniques, to obtain global information (in situ absorption measurements, electron paramagnetic resonance) or spatially-resolved information (confocal microscopy, absorption and luminescence on preform). These tests showed that, for the Ge-doped fiber and in the 300–900 nm range, the radiation-induc…
Prompt Photon Identification in the ALICE Experiment: The Isolation Cut Method
2007
Submitted for publication in NIM; The ALICE experiment at LHC will detect and identify prompt photons and light neutral mesons with the PHOS and EMCal detectors. Charged particles will be detected and identified by the central tracking system. In this paper, a method to identify prompt photons and to separate them from the background of hadrons and decay photons in PHOS with the help of isolation cuts is presented.
Identification of photon-tagged jets in the ALICE experiment
2007
30 pp.-- PACS numbers: 25.75.Nq, 24.10.Lx, 25.75.-q, 29.40.Vj.-- Published in: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. Volume 585, Issues 1-2, 21 January 2008, Pages 28-39.-- Final full-text version of the paper available at: http://dx.doi.org/10.1016/j.nima.2007.10.050.
The nature of the 4.8 eV optical absorption band induced by vacuum-ultraviolet irradiation of glassy SiO2
2000
Abstract The controversial optical absorption band centered at 4.8 eV, which is present in nearly all irradiated silicas, was investigated. It is caused by at least two different defects: non-bridging oxygen hole center (NBOHC) and interstitial ozone (O3). Both species have absorption bands at 4.8 eV, the O3-related band is identified by its susceptibility to bleaching by 4 to 5 eV photons, by a smaller halfwidth and by its independence from the NBOHC-associated 1.9 eV photoluminescence (PL) band. The contribution of NBOHC to the 4.8 eV band is dominant in most cases, while O3 is important in F2 excimer laser-irradiated samples of oxygen-rich glassy SiO2.