Investigation of radiation damage in n+-in-n planar pixel sensors for future ATLAS pixel detector upgrades

The ATLAS detector is a multi-purpose detector within the large hadron collider at CERN in Geneva. Its inner-most sub detector is the pixel detector which is an important part of the tracker system. It is a hybrid detector where readout electronics and sensors are manufactured separately and connected subsequently through bump bonds. Due to the location next to the interaction point sensors have to withstand high radiation. Test sensors were irradiated with neutrons at the JSI in Ljubljana and with protons at the irradiation center Karlsruhe and at CERN-PS. The radiation hardness of planar silicon n-in-n sensors was demonstrated in this thesis up to a fluence of 2E16 n_eq/cm², which is the expected end of life fluence for the inner layer after the HL-LHC upgrade of ATLAS. More charge than calculated with a simple trapping model is collected, indicating that some sort of stable charge amplification is taking place. The measurements were done with a beta particle source and with high energy beams of electrons and pions at test beam sites. An excellent hit efficiency of 97% was achieved

A model-driven traceability framework for software product lines

International audienceSoftware product line (SPL) engineering is a recent approach to software development where a set of software products are derived for a well defined target application domain, from a common set of core assets using analogous means of production (for instance, through Model Driven Engineering). Therefore, such family of products are built from reuse, instead of developed individually from scratch. SPL promise to lower the costs of development, increase the quality of software, give clients more flexibility and reduce time to market. These benefits come with a set of new problems and turn some older problems possibly more complex. One of these problems is traceability management. In the Europe an AMPLE project we are creating a common traceability framework across the various activities of the SPL development. We identified four orthogonal traceability dimensions in SPL development, one of which is an extension of what is often considered as "traceability of variability". This constitutes one of the two contributions of this paper. The second contribution is the specification of a metamodel for a repository of traceability links in the context of SPL and the implementation of a respective traceability framework. This framework enables fundamental traceability management operations, such as trace import and export, modification, query and visualization. The power of our framework is highlighted with an example scenari

Radiation hard 3D silicon pixel sensors for use in the ATLAS detector at the HL-LHC

The High Luminosity LHC (HL-LHC) upgrade requires the planned Inner Tracker (ITk) of the ATLAS detector to tolerate extremely high radiation doses. Specifically, the innermost parts of the pixel system will have to withstand radiation fluences above 1 × 1016 neqcm-2. Novel 3D silicon pixel sensors offer a superior radiation tolerance compared to conventional planar pixel sensors, and are thus excellent candidates for the innermost parts of the ITk. This paper presents studies of 3D pixel sensors with pixel size 50 × 50 μm2 mounted on the RD53A prototype readout chip. Following a description of the design and fabrication steps, Test Beam results are presented for unirradiated as well as heavily irradiated sensors. For particles passing at perpendicular incidence, it is shown that average efficiencies above 96% are reached for sensors exposed to fluences of 1 × 1016 neqcm-2 when biased to 80 V.publishedVersio

Understanding ATLAS infrastructure behaviour with an Expert System

The ATLAS detector requires a huge infrastructure consisting of numerous interconnected systems forming a complex mesh which undergoes constant maintenance and upgrades. The ATLAS Technical Coordination Expert System provides, by the means of a user interface, a quick and deep understanding of the infrastructure, which helps to plan interventions by foreseeing unexpected consequences, and to understand complex events when time is crucial in the ATLAS control room. It is an object-oriented expert system based on the knowledge composed of inference rules and information from diverse domains such as detector control and safety systems, gas, water, cooling, ventilation, cryogenics, and electricity distribution. This paper discusses the latest developments in the inference engine and the implementation of the most probable cause algorithm based on them. One example from the annual maintenance of the 15°C water circuit chillers is discussed

ATLAS Technical Coordination Expert System

When planning an intervention on a complex experiment like ATLAS, the detailed knowledge of the system under intervention and of the interconnection with all the other systems is mandatory. In order to improve the understanding of the parties involved in an intervention, a rule-based expert system has been developed. On the one hand this helps to recognise dependencies that are not always evident and on the other hand it facilitates communication between experts with different backgrounds by translating between vocabularies of specific domains. To simulate an event this tool combines information from different areas such as detector control (DCS) and safety (DSS) systems, gas, cooling, ventilation, and electricity distribution. The inference engine provides a list of the systems impacted by an intervention even if they are connected at a very low level and belong to different domains. It also predicts the probability of failure for each of the components affected by an intervention. Risk assessment models considered are fault tree analysis and principal component analysis. The user interface is a web-based application that uses graphics and text to provide different views of the detector system adapted to the different user needs and to interpret the dat

Beam tests of silicon pixel 3D-sensors developed at SINTEF

For the purpose of withstanding very high radiation doses, silicon pixel sensors with a ‘3D’ electrode geometry are being developed. Detectors of this kind are highly interesting for harch radiation environments such as expected in the High Luminosity LHC, but also for space physics and medical applications. In this paper, prototype sensors developed at SINTEF are presented and results from tests in a pion beam at CERN are given. These tests show that these 3D sensors perform as expected with full efficiency at bias voltages between 5 and 15VBeam tests of silicon pixel 3D-sensors developed at SINTEFacceptedVersionpublishedVersio

Graph-based algorithm for the understanding of failures in the ATLAS infrastructure

The ATLAS Technical Coordination Expert System is a knowledge-based application which describes and simulates the ATLAS experiment based on its components and their relationships with differing levels of granularity but with an emphasis on general infrastructure. It facilitates the sharing of knowledge and improves the communication among experts with different backgrounds and domains of expertise. The developed software has become essential for the planning of interventions as it gives easily insight into their consequences. Furthermore, it has also proven to be useful for exploring the most effective ways to improve the ATLAS operation and reliability by identifying points of failure with significant impact. The underlying database describes more than 13,000 elements with 89,000 relationships among them. It combines information from diverse domains such as detector control and safety systems, gas and water supplies, cooling, ventilation, cryogenics, and electricity distribution. As the most recent addition, a tool to identify the most probable cause of a failure state has been developed. This paper discusses the graph-based algorithm currently implemented by that tool and shows its behaviour based on the parameters entered by the user. An example in form of a real failure event is given which demonstrates the potential of the Expert System for understanding major failures faster in urgent situations

Scalable manufacturing of fibrous nanocomposites for multifunctional liquid sensing

Cellulose-based paper electronics is an attractive technology to meet the growing demands for naturally abundant, biocompatible, biodegradable, flexible, inexpensive, lightweight and highly miniaturizable sensory materials. The price reduction of industrial carbon nanotube (CNT) grades offers opportunities to manufacture electrically conductive papers whose resistivity is responsive to environmental stimuli, such as the presence of water or organic solvents. Here, a highly sensitive paper nanocomposite is developed by integrating CNTs into a hierarchical network of pulp fibers and nanofibrillated cellulose. The aqueous-phase dynamic web forming process enables the scalable production of sensory paper nanocomposites with minimal nanoparticle loss due to the tailored interfacial bonding between CNT and cellulose components. The resulting materials are applied as multifunctional liquid sensors, such as leak detection and wave monitoring. The sensitivity to liquid water spans an outstanding four orders of magnitude even after 30 cycles and 6-month natural aging, due to the hydroexpansion of the hierarchical cellulose network, which alters the intertube distance between neighboring CNTs. The re-organization of percolated CNTs modifies the electron transport in wet areas of the sheet, which can be predicted by an equivalent circuit of resistors for the rapid detection and quantification of various liquids over large surfaces

Radiation hard 3D silicon pixel sensors for use in the ATLAS detector at the HL-LHC

The High Luminosity LHC (HL-LHC) upgrade requires the planned Inner Tracker (ITk) of the ATLAS detector to tolerate extremely high radiation doses. Specifically, the innermost parts of the pixel system will have to withstand radiation fluences above 1 × 1016 neqcm-2. Novel 3D silicon pixel sensors offer a superior radiation tolerance compared to conventional planar pixel sensors, and are thus excellent candidates for the innermost parts of the ITk. This paper presents studies of 3D pixel sensors with pixel size 50 × 50 μm2 mounted on the RD53A prototype readout chip. Following a description of the design and fabrication steps, Test Beam results are presented for unirradiated as well as heavily irradiated sensors. For particles passing at perpendicular incidence, it is shown that average efficiencies above 96% are reached for sensors exposed to fluences of 1 × 1016 neqcm-2 when biased to 80 V.publishedVersio