Showing papers by "Vladimír Linhart published in 2007"

The silicon microstrip sensors of the ATLAS semiconductor tracker

Abstract: This paper describes the AC-coupled, single-sided, p-in-n silicon microstrip sensors used in the Semiconductor Tracker (SCT) of the ATLAS experiment at the CERN Large Hadron Collider (LHC). The sensor requirements, specifications and designs are discussed, together with the qualification and quality assurance procedures adopted for their production. The measured sensor performance is presented, both initially and after irradiation to the fluence anticipated after 10 years of LHC operation. The sensors are now successfully assembled within the detecting modules of the SCT, and the SCT tracker is completed and integrated within the ATLAS Inner Detector. Hamamatsu Photonics Ltd. supplied 92.2% of the 15,392 installed sensors, with the remainder supplied by CiS.

Characterization of 3D thermal neutron semiconductor detectors

Abstract: Neutron semiconductor detectors for neutron counting and neutron radiography have an increasing importance. Simple silicon neutron detectors are combination of a planar diode with a layer of an app ...

Role of electrode metallization in performance of semi-insulating GaAs radiation detectors

Abstract: In the present work, a comparative study of semi-insulating (SI) GaAs radiation detectors with different blocking (Schottky) and ohmic contact metallization is presented. The detectors fabricated from “detector-grade” bulk SI GaAs are characterized by current–voltage measurements and their detection performance is evaluated from pulse-height spectra of 241 Am and 57 Co γ-sources. Observed results are evaluated and discussed. Importance of the optimized electrodes technology of SI GaAs detector with good performance is demonstrated.

Composite polycrystalline boron nitride for alpha and neutron detectors

Abstract: Hexagonal Boron Nitride polycrystalline material can act as semiconductor neutron detector which converts neutrons to alpha particles as a result of the neutron reaction with 10 B. Therefore by testing for the response to alpha radiation BN or any other similar compounds, which have a relative large cross section to absorb neutrons; one can obtain a preliminary indication on its ability to detect neutrons. Among the successful compounds we studied and reported here is composite BN. The polycrystalline studied BN were bound as planar detectors with different binders, such as Polystyrene or Nylon-6, and coated with different metal electrodes such as ITO, Aquadag, Al and Cu. The planar BN detector plates which contained initially only the natural amount of the active 10 B of 20% were further diluted by the binder to only 10% of 10 B. Despite the low content of neutron active conversion isotope and very low signal to noise (S/N) ratio of about 2, the neutron caused events could be counted by subtracting the noise from the signal. In addition, the BN was also irradiated on an intensive neutron beam and the results will be shown.

Modified Hecht model qualifying radiation damage in standard and oxygenated silicon detectors from 10 MeV protons

Abstract: The Hecht model describes the charge collection efficiency of semiconductor detectors using the mean free path of the charge carriers. While the fits to data are very good for non-irradiated detectors, modifications to the model are necessary to take into account the structural changes in the detectors induced by their exposure to high particle fluences. A modified model is presented. In this model, the mean free path depends on the shape of the electric field and on the charge carrier lifetimes. The lifetimes were measured experimentally from the front- and back-illuminations of the detectors by 660 nm laser light and by α particles from an 241 Am source. This new Hecht model was successfully fitted to alpha and beta charge collection efficiencies of standard and oxygenated silicon detectors after their irradiation by 10 MeV protons with fluences varying from 10 11 to 3×10 14 p/cm 2 .