88 research outputs found
EBSD investigation of SiC for HTR fuel particles
Xavier Bourrat : Present Address ISTO - CNRS-Université d'OrléansInternational audienceElectron back-scattering diffraction (EBSD) can be successfully performed on SiC coatings for HTR fuel particles. EBSD grain maps obtained from thick and thin unirradiated samples are presented, along with pole figures showing textures and a chart showing the distribution of grain aspect ratios. This information is of great interest, and contributes to improving the process parameters and ensuring the reproducibility of coating
Hadron Energy Reconstruction for the ATLAS Calorimetry in the Framework of the Non-parametrical Method
This paper discusses hadron energy reconstruction for the ATLAS barrel
prototype combined calorimeter (consisting of a lead-liquid argon
electromagnetic part and an iron-scintillator hadronic part) in the framework
of the non-parametrical method. The non-parametrical method utilizes only the
known ratios and the electron calibration constants and does not require
the determination of any parameters by a minimization technique. Thus, this
technique lends itself to an easy use in a first level trigger. The
reconstructed mean values of the hadron energies are within of the
true values and the fractional energy resolution is . The value of the ratio
obtained for the electromagnetic compartment of the combined calorimeter is
and agrees with the prediction that for this
electromagnetic calorimeter. Results of a study of the longitudinal hadronic
shower development are also presented. The data have been taken in the H8 beam
line of the CERN SPS using pions of energies from 10 to 300 GeV.Comment: 33 pages, 13 figures, Will be published in NIM
Evaluation of Fermi Read-out of the ATLAS Tilecal Prototype
Prototypes of the \fermi{} system have been used to read out a prototype of the \atlas{} hadron calorimeter in a beam test at the CERN SPS. The \fermi{} read-out system, using a compressor and a 40 MHz sampling ADC, is compared to a standard charge integrating read-out by measuring the energy resolution of the calorimeter separately with the two systems on the same events. Signal processing techniques have been designed to optimize the treatment of \fermi{} data. The resulting energy resolution is better than the one obtained with the standard read-out
Response of the ATLAS tile calorimeter prototype to muons
A study of high energy muons traversing the ATLAS hadron Tile calorimeter in the barrel region in the energy range between 10 and 300~GeV is presented. Both test beam experimental data and Monte Carlo simulations are given and show good agreement. The Tile calorimeter capability of detecting isolated muons over the above energy range is demonstrated. A signal to background ratio of about 10 is expected for the nominal LHC luminosity (). The photoelectron statistics effect in the muon shape response is shown. The e/mip ratio is found to be ; the e/ ratio is in the range 0.91 - 0.97. The energy loss of a muon in the calorimeter, dominated by the energy lost in the absorber, can be correlated to the energy loss in the active material. This correlation allows one to correct on an event by event basis the muon energy loss in the calorimeter and therefore reduce the low energy tails in the muon momentum distribution
A measurement of the energy loss spectrum of 150 GeV muons in iron
The energy loss spectrum of 150 GeV muons has been measured with a prototype of the ATLAS hadron calorimeter in the H8 beam of the CERN SPS.\\ The differential probability per radiation length of a fractional energy loss has been measured in the range ; it is then compared with the theoretical predictions for energy losses due to bremsstrahlung and production of electron-positron pairs or of energetic knock-on electrons.\\ The integrated probability is in agreement with the theoretical predictions of and . %7.8.96 - start Agreement with theory is also found in two intervals of where production of electron-positron pairs and knock-on electrons dominates. In the region of bremsstrahlung dominance () the measured integrated probability is in agreement with the theoretical value of , obtained using Petrukhin and Shestakov's \cite{PS} description of the bremsstrahlung process. The same result is about 3.6 standard deviations (defined as the quadratic sum of statistical and systematic errors) lower than the theoretical prediction of , obtained using Tsai's \cite{TS} description of bremsstrahlung
A cyclic universe with colour fields
The topology of the universe is discussed in relation to the singularity
problem. We explore the possibility that the initial state of the universe
might have had a structure with 3-Klein bottle topology, which would lead to a
model of a nonsingular oscillating (cyclic) universe with a well-defined
boundary condition. The same topology is assumed to be intrinsic to the nature
of the hypothetical primitive constituents of matter (usually called preons)
giving rise to the observed variety of elementary particles. Some
phenomenological implications of this approach are also discussed.Comment: 21 pages, 9 figures; v.4: final versio
Results from a combined test of an electromagnetic liquid argon calorimeter with a hadronic scintillating-tile calorimeter
The first combined test of an electromagnetic liquid argon accordion calorimeter and a hadronic scintillating-tile calorimeter was carried out at the CERN SPS. These devices are prototypes of the barrel calorimeter of the future ATLAS experiment at the LHC. The energy resolution of pions in the energy range from 20 to 300~GeV at an incident angle of about 11 is well-described by the expression \sigma/E = ((46.5 \pm 6.0)\%/\sqrt{E} +(1.2 \pm 0.3)\%) \oplus (3.2 \pm 0.4)~\mbox{GeV}/E. Shower profiles, shower leakage, and the angular resolution of hadronic showers were also studied
Advanced characterization techniques for SiC and PyC coatings on high-temperature reactor fuel particles
International audienceEnhancing the safety of high-temperature reactors (HTRs) is based on the quality of the fuel particles, requiring good knowledge of the microstructure of the four-layer particles designed to retain the fission products during irradiation and under accidental conditions. This paper focuses on the intensive research work performed to characterize the micro- and nanostructure of each unirradiated layer (silicon carbide and pyrocarbon coatings). The analytic expertise developed in the 1970s has been recovered and innovative advanced characterization methods have been developed to improve the process parameters and to ensure the production reproducibility of coatings
Optimization and monitoring of the production of thermal barriers coatings
The production of thermal barriers using High Power Plasma Spraying (HPPS) requires both optimal spraying conditions and control over the stability of the manufacturing process. One way in which to reach these two goals is to undertake a métallographie inspection of a polished section of the pieces which are manufactured. This entails systematic, reproducible appraisals so as to follow the evolution of the measured magnitudes. The present article shows the approach adopted to optimize a metallographie inspection station. The goal is to use it as a rapid and economical line control tool based on the principal of a quality control approach
XRD and SEM/EDS Study of the Phase Distribution in the UO2 and Carbon Reactional System at High Temperature
International audienceSeveral fissile kernels are considered for the TRISO particles of (Very) – High Temperature Reactors (V)-HTR. Considering uranium as the fissile nucleus, the basic chemical composition of the TRISO fuel is always made of UO2 which can be added by some UC2 carbide. The high level operating temperature of this fuel implies to determine the products formed by the interactions between these two previous compounds. Some UO2 kernels embedded in black carbon were heated in the 1250–1400°C temperature range in order to determine the kinetics of gaseous species formation [1] and the relative stability of the oxide and carbide phases. After High Temperature Mass Spectrometry (HTMS) experiments, the products formed during the interaction between uranium oxide (UO2) and carbon powders were characterized by various global and punctual analysis methods. The XRD diagram showed the presence of UO2 and UC phases. The contrasts of density observed by SEM in the Quadrant Back-Scattering Detector (QBSD) mode also allowed to highlight both oxide and carbide phase distributions within the TRISO kernels. During SEM observations, some particles showed particular profiles resulting from “non-uniform” reactional mechanisms as already described by Lindemer [2]. In other singular cases, the interaction between UO2 and carbon led to the formation of the UC phase in the middle of the kernel, the UO2 phase remaining at the outside part. Complementary EDS analyses confirmed the results on both oxide and carbide phases. By considering the interference energies between the K-ray of carbon and the N-ray of uranium, the study of the ray intensities consolidated the contrast distributions observed in SEM. Thanks to these results, some assumptions are also advanced concerning the dissolution of oxygen in the UC crystalline structure
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