Radiation Damage Effects and Performance of Silicon Strip Detectors using LHC Readout Electronics

Future high energy physics experiments as the ATLAS experiment at CERN, will use silicon strip detectors for fast and high precision tracking information. The high hadron fluences in these experiments cause permanent damage in the silicon.Additional energy levels are introduced in the bandgap thus changing the electrical properties such as leakage current and full depletion voltage V_fd .Very high leakage currents are observed after irradiation and lead to higher electronic noise and thus decrease the spatial resolution.V_fd increases to a few hundred volts after irradiation and eventually beyond the point of stable operating voltages. Prototype detectors with either p-implanted strips (p-in-n) and n-implanted strip detectors (n-in-n) were irradiated to the maximum expected fluence in ATLAS.The irradiation and the following study of the current and V_fd were carried out under ATLAS operational conditions.The evolution of V_fd after irradiation is compared to models based on diode irradiations.The qualitative behaviour of V_fd as a func- tion of time is well described by these models although quantitative differences are observed between the different detectors.For the first time an annealing study is carried out on full size detectors showing that compared to diodes additional effects have to be taken into account.These properties include surface effects,geometric effects and process parameters. Measurements of V_fd on irradiated detectors show a temperature and frequency dependence indicating an influence of deep radiation induced damage levels.The obtained value of V_fd after irradiation can no longer be regarded as an absolute value due to the temperature and frequency dependence. The leakage current after irradiation is dominated by bulk effects.Although currents from the edge regions are much smaller than from the active area,guard rings are necessary to allow stable operation at high voltages after irradiation. It is shown that full size detectors with optimised guard ring design allow stable operation up to more than 400 V after irradiation.Parameters influencing the guard ring performance before irradiation are illustrated on prototype detectors. In general no systematic difference between p-in-n and n-in-n detectors in leak- age current,stability and the time dependence of V_fd is observed during this study. These results and the results from a testbeam with these detectors led to the change of the ATLAS detector baseline from n-in-n to p-in-n detectors. Non-irradiated and irradiated prototype detectors connected to fast analogue frontend electronics designed for LHC are tested with beta-sources and in a pion- testbeam.They show full functionality even after irradiation to the maximum expected fluence in ATLAS.At V_fd the observed signal to noise ratio (S/N) has not saturated which is attributed to the ballistic deficit caused by charge collection times in the order of the shaping time of the read out electronics.A calculation of the S/N increase after depletion as a function of charge collection time is in good agreement with the data.Between irradiated and non-irradiated detectors a decrease in S/N is observed.At sufficiently high voltages above V_fd the difference is explained by a noise increase due to higher leakage current while just above V_fd less signal is registered.The results presented illustrate that even after the maximum expected fluence ATLAS prototype detectors can be operated efficiently with LHC readout electronics

Lifetime evaluation of hot forged aerospace components by linking microstructural evolution and fatigue behaviour

AbstractThe present work aims at linking the local distribution of fatigue strength in a forged part to its manufacturing process. To this purpose, a predictive fatigue strength model for Inconel 718, also including the operating temperature, is derived from a reduced set of numerous microstructural parameters. The model is implemented, along with a microstructural evolution model from earlier work , into a finite element code in order to predict the local fatigue strength distribution in a component after being subjected to an arbitrary forging process

The ALICE Silicon Pixel Detector Control system and online calibration tools

The ALICE Silicon Pixel Detector (SPD) contains nearly 107 hybrid pixel cells. The operation of the SPD requires online control and monitoring of some 2000 parameters and » 50000DACs. Information for each channel is stored in a configuration database. Timing and data management (» 6GB of raw data each calibration) are critical issues. An overview of the SPD electronics read out chain and of the detector control system is given with a detailed description of the front-end controls and the calibration strategy. The status of commissioning and a preliminary evaluation of detector performance are presented

COPERNICUS KNOWLEDGE and INNOVATION HUBS

Copernicus, the European Space program ensures free data availability and the organisational and financial framework to provide standardized information products in its service domains atmosphere, marine, land monitoring, climate change, emergency management and human security. A key to success to the market uptake process is knowledge exchange among all actors from the various sectors involved, notably research and educational institutions, industry, and the public sector. As a successful instrument to foster and stimulate this exchange, maximize the impact and additionally boost related capacity building and training activities, the Copernicus Academy has been anchored in the European Space Strategy. The present paper highlights some key activities to leverage the potential of this dynamically growing network of experts from universities and research institutions, public and private organizations, companies, stakeholders, and increase the benefit to its members. The vision of establishing both physical implementations of regional Copernicus hubs and virtual Copernicus hubs, built on key elements of the European Innovation strategy, is discussed. Regional hubs, attached e.g. to centres of excellence, are essential to meet local needs for exchange and training to boost the user uptake. The increasing importance of virtual hubs is becoming evident as a critical means to maximise synergies among actors in the rapidly advancing technological areas. Proposed technical elements demonstrate innovative solutions to visualize and facilitate easy harvesting of the Copernicus Academy membeŕs expertise for different stakeholder and the public, and show cast possibilities of active involvement and exchange within the network

Detection of antihydrogen annihilations with a Si-micro-strip and pure CsI detector

In 2002, the ATHENA collaboration reported the creation and detection of cold (~15 K) antihydrogen atoms [1]. The observation was based on the complete reconstruction of antihydrogen annihilations, simultaneous and spatially correlated annihilations of an antiproton and a positron. Annihilation byproducts are measured with a cylindrically symmetric detector system consisting of two layers of double sided Si-micro-strip modules that are surrounded by 16 rows of 12 pure CsI crystals (13 x 17.5 x 17 mm^3). This paper gives a brief overview of the experiment, the detector system, and event reconstruction. Reference 1. M. Amoretti et al., Nature 419, 456 (2002).Comment: 7 pages, 5 figures; Proceedings for the 8th ICATPP Conference on Astroparticle, Particle, Space Physics, Detectors and Medical Physics Applications (Como, Italy October 2003) to be published by World Scientific (style file included

Z_2-Regge versus Standard Regge Calculus in two dimensions

We consider two versions of quantum Regge calculus. The Standard Regge Calculus where the quadratic link lengths of the simplicial manifold vary continuously and the Z_2-Regge Model where they are restricted to two possible values. The goal is to determine whether the computationally more easily accessible Z_2 model still retains the universal characteristics of standard Regge theory in two dimensions. In order to compare observables such as average curvature or Liouville field susceptibility, we use in both models the same functional integration measure, which is chosen to render the Z_2-Regge Model particularly simple. Expectation values are computed numerically and agree qualitatively for positive bare couplings. The phase transition within the Z_2-Regge Model is analyzed by mean-field theory.Comment: 21 pages, 16 ps-figures, to be published in Phys. Rev.