Detection of ionising radiation using single photon avalanche diodes

Single photon avalanche diodes (SPADs) are highly sensitive solid-state photon detectors, and since their inception in 2003 into complementary metal oxide semiconductor (CMOS) technologies, have provided a platform of highly integrated and low-cost mass manufacture detectors, capable of rapid detection of single photons. The consequent commercial potential has led to the development and availability of a range of CMOS SPAD sensors and arrays. As a consequence of their mature development in advanced processes, detection sensitivity and timing capabilities, CMOS SPADs have found their way into multiple applications, most notably biomedical fluorescence lifetime imaging microscopy (FLIM), Light Detection and Ranging (LiDAR), Time-of-Flight (ToF) imaging, Single Photon Counting (SPC), high speed imaging, biological particle tracking and more recently visible light communications. Although, all current applications are constrained to the visible and near infrared spectrums. The advances and broad applications of CMOS SPADs has led to increased development towards further miniaturisation, performance improvements and developing highly integrated intelligent sensors. Therefore, the investigation of the application of SPADs in the detection of ionising radiation has significant commercial potential as an alternative technology to current detectors. The goal of this research is to explore the direct detection of ionising radiation with CMOS SPADs. The fundamental mechanism for detection is a depleted junction operated in Geiger mode, with an induced electric field that allows sensitive detection of generated electron-hole pairs as a result of incident radiation. Therefore, based on this principle it was hypothesised that SPADs can be applied beyond current photon specific detection applications into the detection of ionising radiation. Furthermore, high energy physics is transitioning towards CMOS processes with all the unprecedented advantages it provides. Therefore, it is believed that with SPAD advancement and maturity in CMOS technology, this parallel and continually developing technology may lend itself favourably towards progress and application in the detection of ionising radiation. This work reports on a 3D-stacked backside illuminated (BSI) CMOS SPAD image sensor for the detection of accelerated electrons, pions and X-rays, utilising a scanning electron microscope, synchrotron particle accelerators and X-ray tube sources respectively. For accelerated electron detection, electron energies from 5 to 30 keV were detected, and statistical significance was found that both SPAD excess bias voltage and/or incident accelerated electron energy result in a distinct output. Furthermore, the SPAD image sensor was able to achieve time-resolved imaging of the electron beam raster scan pattern. For X-ray detection, X-rays with peak photon energies from 30 to 160 keV were detectable using an X-ray tube, and it was found that an increase in either SPAD bias voltage, output beam voltage or beam intensity results in higher relative average counts per pixel, therefore demonstrating the potential application of SPAD image sensors in X-ray imaging. These results are the first demonstration and application of a CMOS SPAD in the detection of accelerated electrons and X-rays. Further investigation revealed that the attenuation of lower energy photons from an X-ray tube spectrum results in approximately 200 % increase in relative average counts. Furthermore, The BSI CMOS SPAD image sensor was irradiated with a high energy pion beam at 120 GeV, using the Super Proton Synchrotron (SPS) at CERN, and high energy electrons at 2.5 GeV, using an electron accelerator at ELSA. For the pion irradiation, pions were conclusively detected, and it was found that an increase in SPAD bias voltage results in higher relative average counts per pixel. No conclusive detection of higher energy electrons was observed as a result of low beam intensity. After the pion irradiation, radiation damage to the SPAD image sensor was observed. These results are the first demonstration and application of a CMOS SPAD in the detection of high energy charged particles

Improved light extraction efficiency of complementary metal-oxide semiconductor hot carrier lights sources with the use of improved back-end-of-line light directing structures

Previous research has shown that the use of back-end-of-line (BEOL) light directing structures with silicon hot carrier light sources in a complementary metal-oxide semiconductor results in improved light extraction efficiency. This work focuses on the design of an improved back-end-of-line structure for improving light extraction efficiency when using substrate-based silicon light emitters. With the use of FRED optical engineering ray-tracing software, it was found that a significant amount of generated light is lost at the material interfaces of the optical structure, including losses due to significant internal reflections. Therefore, an optimized optical structure was designed to reduce internal reflections at the base of the structure. Simulation results show a 33.6% improvement in light extraction efficiency over the previously designed parabolic optical structure, over the visible spectrum. The light sources were tested using a parameter analyzer, radiometer, spectrometer, and goniometer. It was calculated that the luminance exiting the optimized optical structure had a 55.66-factor improvement over the control structure and a 1.35-factor improvement over the parabolic structure. Furthermore, the optimized structure had a 1.38-factor improvement in light extraction efficiency over the parabolic structure. Overall, the improved designed pipe-like BEOL light directing structure helped to improve the device luminescence and light emission direction from the light source, which invariably increased the light extraction efficiency.INSiAVA (Pty) Ltd.http://spie.org/publications/journals/optical-engineeringpm2020Electrical, Electronic and Computer Engineerin

Ionizing Radiation Effects in Silicon Photonics Modulators

Silicon photonics (SiPh) shows considerable potential as a radiation-hard technology for building the optical data transmission links for future high-energy physics (HEP) experiments at CERN. Optical modulators are a key component of optical links, which will need to withstand radiation doses in excess of 10 MGy. The geometrical parameters and doping concentrations of two popular types of SiPh modulators, Mach–Zehnder and ring modulators (RMs), have been varied in order to study their impact on the device radiation tolerance. They were exposed to an X-ray beam to test their resistance to ionizing radiation. The RM with the highest doping concentration is shown to be the most tolerant, showing no degradation in performance up to the highest dose of 11 MGy. Moreover, we report first evidence of the dependence of the radiation tolerance on the RM operating temperature.Silicon photonics (SiPh) shows considerable potential as a radiation-hard technology for building the optical data transmission links for future high-energy physics (HEP) experiments at CERN. Optical modulators are a key component of optical links, which will need to withstand radiation doses in excess of 10 MGy. The geometrical parameters and doping concentrations of two popular types of SiPh modulators, Mach–Zehnder and ring modulators (RMs), have been varied in order to study their impact on the device radiation tolerance. They were exposed to an X-ray beam to test their resistance to ionizing radiation. The RM with the highest doping concentration is shown to be the most tolerant, showing no degradation in performance up to the highest dose of 11 MGy. Moreover, we report first evidence of the dependence of the radiation tolerance on the RM operating temperature

Semi-supervised near-miss fall detection for ironworkers with a wearable inertial measurement unit

Accidental falls (slips, trips, and falls from height) are the leading cause of occupational death and injury in construction. As a proactive accident prevention measure, near miss can provide valuable data about the causes of accidents, but collecting near-miss information is challenging because current data collection systems can largely be affected by retrospective and qualitative decisions of individual workers. In this context, this study aims to develop a method that can automatically detect and document near-miss falls based upon a worker's kinematic data captured from wearable inertial measurement units (WIMUs). A semi-supervised learning algorithm (i.e., one-class support vector machine) was implemented for detecting the near-miss falls in this study. Two experiments were conducted for collecting the near-miss falls of ironworkers, and these data were used to test developed near-miss fall detection approach. This WIMU-based approach will help identify ironworker near-miss falls without disrupting jobsite work and can help prevent fall accidents.Y

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

Strategic R&D Programme on Technologies for Future Experiments - Annual Report 2021

This report summarises the activities and main achievements of the CERN strategic R&D programme on technologies for future experiments during the year 2021

Extension of the R&D Programme on Technologies for Future Experiments

we have conceived an extension of the R&D programme covering the period 2024 to 2028, i.e. again a 5-year period, however with 2024 as overlap year. This step was encouraged by the success of the current programme but also by the Europe-wide efforts to launch new Detector R&D collaborations in the framework of the ECFA Detector R&D Roadmap. We propose to continue our R&D programme with the main activities in essentially the same areas. All activities are fully aligned with the ECFA Roadmap and in most cases will be carried out under the umbrella of one of the new DRD collaborations. The program is a mix of natural continuations of the current activities and a couple of very innovative new developments, such as a radiation hard embedded FPGA implemented in an ASIC based on System-on-Chip technology. A special and urgent topic is the fabrication of Al-reinforced super-conducting cables. Such cables are a core ingredient of any new superconducting magnet such as BabyIAXO, PANDA, EIC, ALICE-3 etc. Production volumes are small and demands come in irregular intervals. Industry (world-wide) is no longer able and willing to fabricate such cables. The most effective approach (technically and financially) may be to re-invent the process at CERN, together with interested partners, and offer this service to the community

Annual Report 2022

This report summarises the activities and main achievements of the CERN strategic R&D programme on technologies for future experiments during the year 202

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