[en] Silicon detectors in particle physics experiments at the CERN Large Hadron Collider (LHC) will be exposed to high levels of damaging radiation. The resulting changes in detector doping concentration (N_eff) have been identified as the principal obstacle to long-term operation in the LHC environment. We have previously proposed a model whereby the transfer of charge between closely spaced defects in the terminal clusters formed during heavy particle irradiation is responsible for a significant fraction of these changes in N_eff. The defects involved, the divacancy (V₂) and two unidentified intrinsic defects known as E70 and E170, are postulated to exchange charge via a manifestly non-Shockley-Read-Hall mechanism. Although the model has been remarkably successful in describing experimental measurements at room temperature, direct observations of the charge exchange process have not been forthcoming, not least because of the complexity of the spectroscopic techniques required. We present a comparison between cryogenic measurements of N_eff and the predictions of the model in order to test further the validity of our work to date

[en] In this work, the application of numerical device simulation to the analysis of high resistivity silicon microstrip detectors is illustrated. The analysis Of DC, AC and transient responses of a single-sided, DC-coupled detector has been carried out, providing results in good agreement with experimental data. In particular, transient-mode simulation has been exploited to investigate the collection of charges generated by ionizing particles. To this purpose, an additional generation term has been incorporated into the transport equations; the motion of impact-generated carriers under the combined action of ohmic and diffusive forces is hence accounted for. Application to radiation tolerance studies is also introduced

[en] Radiation hardness is a critical design constraint for current and future generation silicon detectors, which are foreseen to undergo radiation fluences higher than 1x10¹⁴ cm^-2 1-MeV neutron equivalent. Recently, low-temperature operating conditions have been suggested as an effective means to recover the negative effects of radiation damage on silicon detector collection properties. In order to investigate such an effect, simulations have been carried out using the ISE-TCAD DESSIS device simulator. The simulated results are compared with charge collection spectra obtained with 1064 nm laser pulses on devices irradiated with 23 GeV protons as a function of detector bias voltage. Thousands of simulation results have been cross-checked with the experimental data. The results obtained so far indicate that the 'three-level model' can be successfully extended to predict irradiated detector behavior at least down to a temperature of 190 K

[en] The accuracy on the measurments of the Z⁰ width foreseen at LEP/SLC will be limited by the error on the normalization from the small angle luminosity monitors at the level of a few per cent. We show how the measurement of large angle e⁺e^- events produced near to the Z⁰ pole will enable a much more accurate measurement of Γ_z or Γ_ee/Γ_z to be made, as soon as the integrated luminosity is larger than ≅ 1 pb^-1. This measurement is free from most systematic errors affecting the other proposed techniques. Using this method, the expected ultimate relative accuracy on Γ_ee/Γ_z is ≅ 1.10^-3 (1.5.10^-2 neutrino families) after ≅ 10⁷ Z⁰. (orig.)

[en] In this paper we discuss an enhanced approach to the analysis of radiation-damaged silicon devices, with reference to numerical modelling implemented in a general-purpose device simulator. In particular, the emission and capture mechanism of deep levels are accounted for by means of Shockley-Read-Hall theory and shallow-level sensitivity to radiation is considered by means of a donor removal model. The effects produced by regions containing very high defect concentrations (referred to as 'clusters') are considered by calculating the direct charge exchange between two deep levels. The resulting analysis technique has been validated and calibrated by means of comparison with experimental measurements carried out on irradiated samples. The model is shown to provide comprehensive and accurate results for several radiation damage phenomena

[en] An approach to the numerical simulation of silicon microstrip detectors is discussed, with particular emphasis on the modeling of radiation damage consequences. Within the framework of a general-purpose device simulator, extension have been made aimed at describing both the transduction mechanism exploited by such devices and at providing a physically grounded account of structural modification induced by continuing exposure to radiation. In particular, influence of deep-level traps is discussed, and some limitations of simpler models are pointed out

[en] The application of a general-purpose device-simulator to the analysis of silicon microstrip radiation detector is described. Physical models include charge-collection dynamics, as well as radiation-induced deep-level recombination centers. Realistic description of multiple-strip devices can be accounted for. To allow for validation of the analysis tool, actual detectors have been measured, before and after being irradiated with neutrons. Simulation predictions agree well with experiments. Limitations of the adopted model are discussed, with reference to simulation-based comparison with higher-order models

[en] Octave is one of the most widely used open source tools for numerical analysis and liner algebra. Our project aims to improve Octave by introducing support for GPU computing in order to speed up some linear algebra operations. The core of our work is a C library that executes some BLAS operations concerning vector- vector, vector matrix and matrix-matrix functions on the GPU. OpenCL functions are used to program GPU kernels, which are bound within the GNU/octave framework. We report the project implementation design and some preliminary results about performance.

[en] In this work, the application of the general-purpose device simulator HFIELDS to the analysis of silicon microstrip detectors is presented. In the framework of CMS collaboration, a comprehensive device characterization has been performed by means of steady-state (DC) and small-signal (AC) numerical analyses. The study of charge collection dynamics has been carried out as well, by means of transient analysis. Simulation results exhibit a good agreement with literature data, and allow for detailed insights of device behavior. This makes it possible to investigate device-performance sensitivity to fabrication and environmental parameters and highlights potential applications of numerical analysis as a device design and optimization aid. (orig.)

[en] The techniques used in the construction of the double-sided ladders for the L3 Silicon Microvertex Detector (SMD) are presented. The detector consists of two cylindrical layers, each of 12 ladders, with double-sided silicon detectors which provide r-phi and z coordinates measurements. This description includes ladder mechanical design and the assembly. A novel solution to readout the z-coordinates is presented. It optimizes very effectively the removal of heat generated by the readout electronics and minimizes the radiation length in the central region. Some results from the survey of the individual ladders are also discussed. (orig.)