Evaluation of fine-pitch hybrid silicon pixel detector prototypes for the CLIC vertex detector in laboratory and test-beam measurements

The Compact Linear Collider (CLIC) is a concept for a high-energy, high-luminosity e+ e− linear collider for precision measurements of Standard Model processes and to search for new phenomena, proposed to be built after the lifetime of the upgraded Large Hadron Collider. The beam conditions expected at CLIC impose strict requirements on the CLIC detector design in order for the physics programme to be achieved. In the vertex detector subsystem, the pixelated detectors are required to achieve a spatial resolution of approximately 3μm, a hit detection efficiency ≥99.7%, a timing resolution of ≤5ns, and a material budget per layer of 0.2% of a radiation length. Currently, no pixel detector technology can achieve these requirements simultaneously, therefore prototype pixel detectors with novel designs are being developed and tested within the CLIC detector and physics collaboration. The CLICpix2 hybrid readout ASIC aims to fulfil the CLIC vertex detector requirements. It has been designed using a 65nm CMOS process with a fine pixel pitch of 25×25μm^2, simultaneous per-pixel charge and time measurements, and power-pulsing capabilities. Within this thesis, the performance of CLICpix2 ASICs bump-bonded to active-edge planar silicon sensors is evaluated using laboratory and test-beam measurements. The detectors were hybridised using a novel single-chip bonding process, and the interconnect quality is quantified using a data-driven pixel categorisation scheme. High interconnect qualities are achieved for a small number of assemblies, with yields up to 99.6%. The formulated categorisation method successfully identifies unexpected behaviour of the devices, which were used as feedback to the manufacturer to optimise the solder bump-bonding process. Calibration measurements are also performed to convert the threshold and charge measurements of the assemblies into physical units. The performance of the two highest quality assemblies is evaluated and compared to the CLIC vertex detector requirements. Test-beam data recorded at the CERN and DESY test-beam facilities with CLICpix2 planar sensor assemblies is reconstructed using the Corryvreckan software framework, significantly contributed to as part of this study. Similar results are recorded for both assemblies, despite the large differences in test-beam telescope set-ups and data reconstruction processes used for each. The intrinsic spatial resolution of CLICpix2 assemblies with 130 μm planar sensors is determined to be <3μm. CLICpix2 planar sensor assemblies are calculated to have hit detection efficiencies of above 99.95% at the optimal operating conditions, and an intrinsic timing resolution of ≤5 ns is achieved after a time-walk correction is applied to the pixel data. The CLICpix2 detectors meet the hit detection efficiency, spatial resolution, and timing resolution requirements of the CLIC vertex detector with planar silicon sensors of thickness 130μm. To achieve these requirements with the target sensor thickness of 50μm, a silicon sensor with enhanced charge sharing or a smaller pixel pitch would be required

User Manual for the Corryvreckan Test Beam Data Reconstruction Framework, Version 1.0

Test beam data reconstruction is a task that requires a large amount of flexibility due to the heterogeneous data acquisition environments found in these experiments. Often, detectors with different readout schemes such as triggered, frame-based or data driven approaches are combined in a single setup. In order to correlate these data and to reconstruct particle tracks, a versatile event building algorithm and analysis framework is required. Corryvreckan is a flexible, fast and lightweight test beam data reconstruction framework based on a modular concept of the reconstruction chain. It is written in modern C++, requires a minimum of external dependencies and is designed to be fully configurable by the user without the need to alter code. This document presents the user manual of the software as of release version 1.0.Test beam data reconstruction is a task that requires a large amount of flexibility due to the heterogeneous data acquisition environments found in these experiments. Often, detectors with different readout schemes such as triggered, frame-based or data driven approaches are combined in a single setup. In order to correlate these data and to reconstruct particle tracks, a versatile event building algorithm and analysis framework is required. Corryvreckan is a flexible, fast and lightweight test beam data reconstruction framework based on a modular concept of the reconstruction chain. It is written in modern C++ , requires a minimum of external dependencies and is designed to be fully configurable by the user without the need to alter code. This document presents the user manual of the software as of release version 1.0

Development of novel single-die hybridisation processes for small-pitch pixel detectors

Hybrid pixel detectors require a reliable and cost-effective interconnect technology adapted to the pitch and die sizes of the respective applications. During the ASIC and sensor R&D phase, especially for small-scale applications, such interconnect technologies need to be suitable for the assembly of single dies, typically available from Multi-Project-Wafer submissions. Within the CERN EP R&D programme and the AIDAinnova collaboration, innovative hybridisation concepts targeting vertex-detector applications at future colliders are under development. Recent results of two novel interconnect methods for pixel pitches of 25 µm and 55 µm are presented in this contribution – an industrial fine-pitch SnAg solder bump-bonding process adapted to single-die processing using support wafers, as well as a newly developed in-house single-die interconnection process based on Anisotropic Conductive Film (ACF). The fine-pitch bump-bonding process is qualified with hybrid assemblies from a recent bonding campaign at Frauenhofer IZM. Individual CLICpix2 ASICs with 25 µm pixel pitch were bump-bonded to active-edge silicon sensors with thicknesses ranging from 50 µm to 130 µm. The device characterisation was conducted in the laboratory as well as during a beam test campaign at the CERN SPS beam-line, demonstrating an interconnect yield of about 99.7%.Hybrid pixel detectors require a reliable and cost-effective interconnect technology adapted to the pitch and die sizes of the respective applications. During the ASIC and sensor R&D phase, especially for small-scale applications, such interconnect technologies need to be suitable for the assembly of single dies, typically available from Multi-Project-Wafer submissions. Within the CERN EP R&D programme and the AIDAinnova collaboration, innovative hybridisation concepts targeting vertex-detector applications at future colliders are under development. Recent results of two novel interconnect methods for pixel pitches of 25 µm and 55 µm are presented in this contribution — an industrial fine-pitch SnAg solder bump-bonding process adapted to single-die processing using support wafers, as well as a newly developed in-house single-die interconnection process based on Anisotropic Conductive Film (ACF). The fine-pitch bump-bonding process is qualified with hybrid assemblies from a recent bonding campaign at Frauenhofer IZM. Individual CLICpix2 ASICs with 25 µm pixel pitch were bump-bonded to active-edge silicon sensors with thicknesses ranging from 50 µm to 130 µm. The device characterisation was conducted in the laboratory as well as during a beam test campaign at the CERN SPS beam-line, demonstrating an interconnect yield of about 99.7%. The ACF interconnect technology replaces the solder bumps by conductive micro-particles embedded in an epoxy film. The electro-mechanical connection between the sensor and ASIC is achieved via thermocompression of the ACF using a flip-chip device bonder. The required pixel pad topology is achieved with an in-house Electroless Nickel Immersion Gold (ENIG) plating process. This newly developed ACF hybridisation process is first qualified with the Timepix3 ASICs and sensors with 55 µm pixel pitch. The technology can be also used for ASIC-PCB/FPC integration, replacing wire bonding or large-pitch solder bumping techniques. This contribution introduces the two interconnect processes and presents preliminary hybridisation results with CLICpix2 and Timepix3 sensors and ASICs.Hybrid pixel detectors require a reliable and cost-effective interconnect technology adapted to the pitch and die sizes of the respective applications. During the ASIC and sensor R&D phase, especially for small-scale applications, such interconnect technologies need to be suitable for the assembly of single dies, typically available from Multi-Project-Wafer submissions. Within the CERN EP R&D programme and the AIDAinnova collaboration, innovative hybridisation concepts targeting vertex-detector applications at future colliders are under development. Recent results of two novel interconnect methods for pixel pitches of 25um and 55um are presented in this contribution -- an industrial fine-pitch SnAg solder bump-bonding process adapted to single-die processing using support wafers, as well as a newly developed in-house single-die interconnection process based on ACF. The fine-pitch bump-bonding process is qualified with hybrid assemblies from a recent bonding campaign at Frauenhofer IZM. Individual CLICpix2 ASICs with 25um pixel pitch were bump-bonded to active-edge silicon sensors with thicknesses ranging from 50um to 130um. The device characterisation was conducted in the laboratory as well as during a beam test campaign at the CERN SPS beam-line, demonstrating an interconnect yield of about 99.7%. The ACF interconnect technology replaces the solder bumps by conductive micro-particles embedded in an epoxy film. The electro-mechanical connection between the sensor and ASIC is achieved via thermocompression of the ACF using a flip-chip device bonder. The required pixel pad topology is achieved with an in-house ENIG plating process. This newly developed ACF hybridisation process is first qualified with the Timepix3 ASICs and sensors with 55um pixel pitch. The technology can be also used for ASIC-PCB/FPC integration, replacing wire bonding or large-pitch solder bumping techniques

Time and Energy Calibration of Timepix3 Assemblies with Thin Silicon Sensors

The Timepix3 ASIC is a multi-purpose readout chip for hybrid pixel detectors. It can measure time and energy simultaneously by employing time-of-arrival (ToA) and time-over-threshold (ToT) techniques. In the presented work, a time efficient method for pixel-by-pixel calibration of both ToA and ToT is investigated. Five assemblies of Timepix3 ASICs bump bonded to silicon pixel sensors of different thicknesses between 50 μm and 150 μm are calibrated with electrical test pulses, x-ray fluorescence and beams of minimum ionising particles in a reference telescope. After calibration, the energy resolution at 6.40 keV is 9.3 %. For 120 GeV/c pions, time resolutions down to 0.72 ns are achieved

Strategic R&D Programme on Technologies for Future Experiments - Annual Report 2020

This report summarises the activities and achievements of the strategic R&D programme on technologies for future experiments in the year 2020

Annual Report 2023 and Phase-I Closeout

This report summarises the activities of the CERN strategic R&D programme on technologies for future experiments during the year 2023, and highlights the achievements of the programme during its first phase 2020-2023

The surgical safety checklist and patient outcomes after surgery: a prospective observational cohort study, systematic review and meta-analysis

© 2017 British Journal of Anaesthesia Background: The surgical safety checklist is widely used to improve the quality of perioperative care. However, clinicians continue to debate the clinical effectiveness of this tool. Methods: Prospective analysis of data from the International Surgical Outcomes Study (ISOS), an international observational study of elective in-patient surgery, accompanied by a systematic review and meta-analysis of published literature. The exposure was surgical safety checklist use. The primary outcome was in-hospital mortality and the secondary outcome was postoperative complications. In the ISOS cohort, a multivariable multi-level generalized linear model was used to test associations. To further contextualise these findings, we included the results from the ISOS cohort in a meta-analysis. Results are reported as odds ratios (OR) with 95% confidence intervals. Results: We included 44 814 patients from 497 hospitals in 27 countries in the ISOS analysis. There were 40 245 (89.8%) patients exposed to the checklist, whilst 7508 (16.8%) sustained ≥1 postoperative complications and 207 (0.5%) died before hospital discharge. Checklist exposure was associated with reduced mortality [odds ratio (OR) 0.49 (0.32–0.77); P\u3c0.01], but no difference in complication rates [OR 1.02 (0.88–1.19); P=0.75]. In a systematic review, we screened 3732 records and identified 11 eligible studies of 453 292 patients including the ISOS cohort. Checklist exposure was associated with both reduced postoperative mortality [OR 0.75 (0.62–0.92); P\u3c0.01; I2=87%] and reduced complication rates [OR 0.73 (0.61–0.88); P\u3c0.01; I2=89%). Conclusions: Patients exposed to a surgical safety checklist experience better postoperative outcomes, but this could simply reflect wider quality of care in hospitals where checklist use is routine

Prospective observational cohort study on grading the severity of postoperative complications in global surgery research

Background The Clavien–Dindo classification is perhaps the most widely used approach for reporting postoperative complications in clinical trials. This system classifies complication severity by the treatment provided. However, it is unclear whether the Clavien–Dindo system can be used internationally in studies across differing healthcare systems in high- (HICs) and low- and middle-income countries (LMICs). Methods This was a secondary analysis of the International Surgical Outcomes Study (ISOS), a prospective observational cohort study of elective surgery in adults. Data collection occurred over a 7-day period. Severity of complications was graded using Clavien–Dindo and the simpler ISOS grading (mild, moderate or severe, based on guided investigator judgement). Severity grading was compared using the intraclass correlation coefficient (ICC). Data are presented as frequencies and ICC values (with 95 per cent c.i.). The analysis was stratified by income status of the country, comparing HICs with LMICs. Results A total of 44 814 patients were recruited from 474 hospitals in 27 countries (19 HICs and 8 LMICs). Some 7508 patients (16·8 per cent) experienced at least one postoperative complication, equivalent to 11 664 complications in total. Using the ISOS classification, 5504 of 11 664 complications (47·2 per cent) were graded as mild, 4244 (36·4 per cent) as moderate and 1916 (16·4 per cent) as severe. Using Clavien–Dindo, 6781 of 11 664 complications (58·1 per cent) were graded as I or II, 1740 (14·9 per cent) as III, 2408 (20·6 per cent) as IV and 735 (6·3 per cent) as V. Agreement between classification systems was poor overall (ICC 0·41, 95 per cent c.i. 0·20 to 0·55), and in LMICs (ICC 0·23, 0·05 to 0·38) and HICs (ICC 0·46, 0·25 to 0·59). Conclusion Caution is recommended when using a treatment approach to grade complications in global surgery studies, as this may introduce bias unintentionally

Critical care admission following elective surgery was not associated with survival benefit: prospective analysis of data from 27 countries

This was an investigator initiated study funded by Nestle Health Sciences through an unrestricted research grant, and by a National Institute for Health Research (UK) Professorship held by RP. The study was sponsored by Queen Mary University of London