Showing papers by "Richard French published in 2016"

Charge collection and field profile studies of heavily irradiated strip sensors for the ATLAS inner tracker upgrade

Abstract: The ATLAS group has evaluated the charge collection in silicon microstrip sensors irradiated up to a fluence of 1×1016 neq/cm2, exceeding the maximum of 1.6×1015 neq/cm2 expected for the strip tracker during the high luminosity LHC (HL-LHC) period including a safety factor of 2. The ATLAS12, n+-on-p type sensor, which is fabricated by Hamamatsu Photonics (HPK) on float zone (FZ) substrates, is the latest barrel sensor prototype. The charge collection from the irradiated 1×1 cm2 barrel test sensors has been evaluated systematically using penetrating β-rays and an Alibava readout system. The data obtained at different measurement sites are compared with each other and with the results obtained from the previous ATLAS07 design. The results are very consistent, in particular, when the deposit charge is normalized by the sensor's active thickness derived from the edge transient current technique (edge-TCT) measurements. The measurements obtained using β-rays are verified to be consistent with the measurements using an electron beam. The edge-TCT is also effective for evaluating the field profiles across the depth. The differences between the irradiated ATLAS07 and ATLAS12 samples have been examined along with the differences among the samples irradiated with different radiation sources: neutrons, protons, and pions. The studies of the bulk properties of the devices show that the devices can yield a sufficiently large signal for the expected fluence range in the HL-LHC, thereby acting as precision tracking sensors.

Detailed studies of full-size ATLAS12 sensors

Abstract: The “ATLAS ITk Strip Sensor Collaboration” R&D group has developed a second iteration of single-sided n+-in-p type micro-strip sensors for use in the tracker upgrade of the ATLAS experiment at the High-Luminosity (HL) LHC. The full size sensors measure approximately 97×97mm2 and are designed for tolerance against the 1.1×1015neq/cm2 fluence expected at the HL-LHC. Each sensor has 4 columns of 1280 individual 23.9mm long channels, arranged at 74.5μm pitch. Four batches comprising 120 sensors produced by Hamamatsu Photonics were evaluated for their mechanical, and electrical bulk and strip characteristics. Optical microscopy measurements were performed to obtain the sensor surface profile. Leakage current and bulk capacitance properties were measured for each individual sensor. For sample strips across the sensor batches, the inter-strip capacitance and resistance as well as properties of the punch-through protection structure were measured. A multi-channel probecard was used to measure leakage current, coupling capacitance and bias resistance for each individual channel of 100 sensors in three batches. The compiled results for 120 unirradiated sensors are presented in this paper, including summary results for almost 500,000 strips probed. Results on the reverse bias voltage dependence of various parameters and frequency dependence of tested capacitances are included for validation of the experimental methods used. Comparing results with specified values, almost all sensors fall well within specification.

Study of surface properties of ATLAS12 strip sensors and their radiation resistance

Abstract: A radiation hard n + -in- p micro-strip sensor for the use in the Upgrade of the strip tracker of the ATLAS experiment at the High Luminosity Large Hadron Collider (HL-LHC) has been developed by the “ATLAS ITk Strip Sensor collaboration” and produced by Hamamatsu Photonics. Surface properties of different types of end-cap and barrel miniature sensors of the latest sensor design ATLAS12 have been studied before and after irradiation. The tested barrel sensors vary in “punch-through protection” (PTP) structure, and the end-cap sensors, whose stereo-strips differ in fan geometry, in strip pitch and in edge strip ganging options. Sensors have been irradiated with proton fluences of up to 1×10 16 n eq /cm 2 , by reactor neutron fluence of 1×10 15 n eq /cm 2 and by gamma rays from 60 Co up to dose of 1 MGy. The main goal of the present study is to characterize the leakage current for micro-discharge breakdown voltage estimation, the inter-strip resistance and capacitance, the bias resistance and the effectiveness of PTP structures as a function of bias voltage and fluence. It has been verified that the ATLAS12 sensors have high breakdown voltage well above the operational voltage which implies that different geometries of sensors do not influence their stability. The inter-strip isolation is a strong function of irradiation fluence, however the sensor performance is acceptable in the expected range for HL-LHC. New gated PTP structure exhibits low PTP onset voltage and sharp cut-off of effective resistance even at the highest tested radiation fluence. The inter-strip capacitance complies with the technical specification required before irradiation and no radiation-induced degradation was observed. A summary of ATLAS12 sensors tests is presented including a comparison of results from different irradiation sites. The measured characteristics are compared with the previous prototype of the sensor design, ATLAS07.

Evaluation of the performance of irradiated silicon strip sensors for the forward detector of the ATLAS Inner Tracker Upgrade

Abstract: The upgrade to the High-Luminosity LHC foreseen in about ten years represents a great challenge for the ATLAS inner tracker and the silicon strip sensors in the forward region. Several strip sensor designs were developed by the ATLAS collaboration and fabricated by Hamamatsu in order to maintain enough performance in terms of charge collection efficiency and its uniformity throughout the active region. Of particular attention, in the case of a stereo-strip sensor, is the area near the sensor edge where shorter strips were ganged to the complete ones. In this work the electrical and charge collection test results on irradiated miniature sensors with forward geometry are presented. Results from charge collection efficiency measurements show that at the maximum expected fluence, the collected charge is roughly halved with respect to the one obtained prior to irradiation. Laser measurements show a good signal uniformity over the sensor. Ganged strips have a similar efficiency as standard strips.

Embedded pitch adapters: A high-yield interconnection solution for strip sensors

Abstract: A proposal to fabricate large area strip sensors with integrated, or embedded, pitch adapters is presented for the End-cap part of the Inner Tracker in the ATLAS experiment. To implement the embedded pitch adapters, a second metal layer is used in the sensor fabrication, for signal routing to the ASICs. Sensors with different embedded pitch adapters have been fabricated in order to optimize the design and technology. Inter-strip capacitance, noise, pick-up, cross-talk, signal efficiency, and fabrication yield have been taken into account in their design and fabrication. Inter-strip capacitance tests taking into account all channel neighbors reveal the important differences between the various designs considered. These tests have been correlated with noise figures obtained in full assembled modules, showing that the tests performed on the bare sensors are a valid tool to estimate the final noise in the full module. The full modules have been subjected to test beam experiments in order to evaluate the incidence of cross-talk, pick-up, and signal loss. The detailed analysis shows no indication of cross-talk or pick-up as no additional hits can be observed in any channel not being hit by the beam above 170 mV threshold, and the signal in those channels is always below 1% of the signal recorded in the channel being hit, above 100 mV threshold. First results on irradiated mini-sensors with embedded pitch adapters do not show any change in the interstrip capacitance measurements with only the first neighbors connected.

Usability study to qualify a dexterous robotic manipulator for high radiation environments

Abstract: Based at CERN, the European Organization for Nuclear Research, the Large Hadron Collider (LHC) is the world's largest and most powerful particle accelerator. From 2025, the LHC will be upgraded to allow it to achieve a factor of 10 higher luminosity, which increases the rate of collisions, essential for probing new physics phenomena in the future. The route to high luminosity LHC (HL-LHC) involves various detector upgrades and requires significant infrastructure changes. Recent measurements by CERN Radiation Protection, verifying previous calculations by The University of Sheffield (UoS), has raised awareness about the need to restrict human activity in the HL-LHC experimental, construction and maintenance areas due to exposure from high levels of radiation. Examining the case of the ATLAS detector upgrade, the collaborative partnership between UoS and UK industry is developing state-of-the-art robotic instrumentation, capable of tolerating high radiation levels. The main object of this research is a feasibility study with a TRL (technology readiness level) of three, to determine how materials and sub components of dexterous robotic systems behave after exposure to high levels of radiation. This is evaluation uses novel robotic irradiation equipment, techniques and test methods housed in the Birmingham University (UK) Irradiation Facility. One finger of an unmodified Shadow Robot Company “Hand”, a highly dexterous robotic manipulator, was exposed to specific doses of high radiation in a temperature controlled thermal chamber. Cooled by a liquid nitrogen evaporative system, the irradiation system moves samples continuously through a homogeneous proton beam. Movement is provided by a radiation hard pre-configured XY-Axis Cartesian Robot. The methods and techniques developed as a result of this TRL3 research will further aid the application and deployment of robotic and autonomous systems into highly radioactive environments. Based on preliminary findings it has been concluded that finger materials and basic electrical components can tolerate hazardous radiation environments, with careful selection and substitution of a minimal amount of materials, radiation hardness is also possible. Further work is scheduled for the irradiation of a fully instrumented and powered robotic hand to determine working hour tolerance.

Underpinning UK high-value manufacturing: Development of a robotic re-manufacturing system

Abstract: Impact and its measure of outcome is a given performance indicator within academia. Impact metrics and the associated understanding play a large part of how academic research is judged and ultimately funded. Natural progression of successful scientific research into industry is now an essential tool for academia. This paper describes what began over ten years ago as a concept to automate a bespoke welding system, highlighting its evolution from the research laboratories of The University of Sheffield to become a platform technology for aerospace re-manufacturing developed though industry-academia collaboration. The design process, funding mechanisms, research and development trials and interaction between robotic technology and experienced welding engineers has made possible the construction of a robotic aerospace turbofan jet engine blade re-manufacturing system. This is a joint collaborative research and development project carried out by VBC Instrument Engineering Limited (UK) and The University of Sheffield (UK) who are funded by the UK governments' innovation agency, Innovate-UK with the Aerospace Technology Institute, the Science and Facilities Technology Council (STFC) and the Engineering and Physical Sciences Research Council (EPSRC).

High Value Intelligent Aerospace Turbofan Jet Engine Blade Re-manufacturing System

Abstract: Development of any advanced, intelligent robotic welding system requires correct interrogation of welding parameters and output. Advanced programming of robots, data interpretation from associated sensory and feedback systems are required to mirror human input. Using process analysis to determine stimuli, replacement of human sensory receptors with electronic sensors, vision systems and high speed data acquisition and control systems allows for the intelligent fine tuning of multiple welding parameters at any one time. This paper demonstrates the design process, highlighting interaction between robotics and experienced welding engineers, towards construction of an autonomous aerospace turbofan jet engine blade re-manufacturing system. This is a joint collaborative research and development project carried out by VBC Instrument Engineering Ltd (UK) and The University of Sheffield (UK) who are funded by the UK governments’ innovation agency, Innovate-UK and the Aerospace Technology Institute (UK).