Showing papers by "Vladimír Linhart published in 2008"

Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics

Abstract: A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN.

Radiation hardness properties of full-3D active edge silicon sensors

Abstract: Full-three-dimensional (3D) pixel sensors, with electrodes penetrating through the entire silicon wafer, were fabricated at the Stanford Nanofabrication Facility, Stanford, California, USA. They have 71-mu m-inter-electrode spacing, active edges and a compatible geometry to the ATLAS pixel detector readout electronics. Several samples were irradiated with neutrons to different doses up to an equivalent fluence of 8.6 x 10(15) n(1MeVeq) cm(-2). This corresponds to the integrated fluence expected after similar to 5 years at the Large Hadron Collider (LHC) with a luminosity of 10(35) cm(-2) s(-1) at 4 cm from the interaction point, where the ATLAS B-Layer is placed. Before and after irradiation, signals were generated by a 1060 nm infrared laser calibrated to inject a charge of 14 fC. This corresponds to similar to 3.5 minimum ionizing particles and should not perturb the charge status of the radiation-induced defects. After 8.6 x 10(15) n(1MeVeq) cm(-2) the signal collected was similar to 38% and corresponded to similar to 7200e(-) for a substrate thickness of 235 pm. Signal efficiency, radiation-induced leakage current and related damage parameters are discussed here and compared with simulations. Full-3D silicon detectors with active edges are being considered for forward proton tagging at the LHC, for the ATLAS pixel B-layer replacement and for the ATLAS pixel upgrade. (C) 2007 Elsevier B.V. All rights reserved

The integration and engineering of the ATLAS SemiConductor Tracker Barrel

Abstract: The ATLAS SemiConductor Tracker (SCT) was built in three sections: a barrel and two end-caps. This paper describes the design, construction and final integration of the barrel section. The barrel is constructed around four nested cylinders that provide a stable and accurate support structure for the 2112 silicon modules and their associated services. The emphasis of this paper is directed at the aspects of engineering design that turned a concept into a fully-functioning detector, as well as the integration and testing of large sub-sections of the final SCT barrel detector. The paper follows the chronology of the construction. The main steps of the assembly are described with the results of intermediate tests. The barrel service components were developed and fabricated in parallel so that a flow of detector modules, cooling loops, opto-harnesses and Frequency-Scanning-Interferometry (FSI) alignment structures could be assembled onto the four cylinders. Once finished, each cylinder was conveyed to the next site for the mounting of modules to form a complete single barrel. Extensive electrical and thermal function tests were carried out on the completed single barrels. In the next stage, the four single barrels and thermal enclosures were combined into the complete SCT barrel detector so that it could be integrated with the Transition Radiation Tracker (TRT) barrel to form the central part of the ATLAS inner detector. Finally, the completed SCT barrel was tested together with the TRT barrel in noise tests and using cosmic rays.

X-ray fluorescence imaging with pixel detectors

Abstract: The main goal of this work is to determine the capabilities of the Medipix2 and Timepix devices for imaging in X-ray fluorescence (XRF) analysis. The energy resolution of these devices is not sufficient for identification of characteristic radiation in each pixel. The proposed method of per pixel spectra decomposition overcomes this disadvantage. The method splits into two phases: In the first (calibration) phase the spectroscopic responses of each pixel to the characteristic radiation of the individual elements are measured. In this way, a set of spectra (base vectors) is acquired for each pixel. In the second phase a complex spectrum of unknown sample is measured and then decomposed to spectra of individual elements. If the global elemental composition of the specimen is qualitatively known (or can be estimated) then elements with atomic number difference of 1 can be resolved. The spatial resolution is limited by the diameter of the pinhole aperture.

Engineering for the ATLAS SemiConductor Tracker (SCT) end-cap

Abstract: The ATLAS SemiConductor Tracker (SCT) is a silicon-strip tracking detector which forms part of the ATLAS inner detector. The SCT is designed to track charged particles produced in proton-proton collisions at the Large Hadron Collider (LHC) at CERN at an energy of 14 TeV. The tracker is made up of a central barrel and two identical end-caps. The barrel contains 2112 silicon modules, while each end-cap contains 988 modules. The overall tracking performance depends not only on the intrinsic measurement precision of the modules but also on the characteristics of the whole assembly, in particular, the stability and the total material budget. This paper describes the engineering design and construction of the SCT end-caps, which are required to support mechanically the silicon modules, supply services to them and provide a suitable environment within the inner detector. Critical engineering choices are highlighted and innovative solutions are presented – these will be of interest to other builders of large-scale tracking detectors. The SCT end-caps will be fully connected at the start of 2008. Further commissioning will continue, to be ready for proton-proton collision data in 2008.

Low-energy nuclear transitions in subrelativistic laser-generated plasmas

Abstract: The aim of the reported research is to contribute to investigation of new processes and methods interlinking nuclear and laser-plasma physics. With respect to requirements of nuclear experiments at medium-size high-power lasers, the selection of proper candidates for studying the excitation and decay of low-lying nuclear states is reviewed. An experimental approach to the identification of low-energy nuclear transitions is discussed, simple estimates of the 181Ta excitation yield in the laser-generated plasma provide a theoretical basis for planning future work. First tests and results of the experiments at the laser facility PALS are presented.

Correlation of electrical and optical properties with charge collection efficiency of In-doped and In + Si co-doped CdTe

Abstract: The effect of Si co-doping on electrical, optical and spectroscopic properties of In-doped CdTe was investigated. The concentration of Si atoms in the charge was 1×10 17 cm −3 . All Si co-doped samples were n-types, with the resistivity higher than 1×10 9 Ω cm. The dominant deep level E D =0.67 eV was determined by temperature dependence of the Hall effect measurement and compared with the low-temperature photoluminescence. Cd-rich or Te-rich annealing was used to eliminate this deep level, which strongly affects the charge collection efficiency of samples. The deep level together with a poor charge collection efficiency were found in both as-grown or annealed Si co-doped samples contrary to samples with only In doping, where the detector quality improvement was observed after Te-rich annealing.