Advanced pixel architectures for scientific image sensors

We present recent developments from two projects targeting advanced pixel architectures for scientific applications. Results are reported from FORTIS, a sensor demonstrating variants on a 4T pixel architecture. The variants include differences in pixel and diode size, the in-pixel source follower transistor size and the capacitance of the readout node to optimise for low noise and sensitivity to small amounts of charge. Results are also reported from TPAC, a complex pixel architecture with ~160 transistors per pixel. Both sensors were manufactured in the 0.18μm INMAPS process, which includes a special deep p-well layer and fabrication on a high resistivity epitaxial layer for improved charge collection efficiency

CMOS Monolithic Active Pixel Sensors (MAPS) for future vertex detectors

This paper reviews the development of CMOS Monolithic Active Pixel Sensors (MAPS) for future vertex detectors. MAPS are developed in a standard CMOS technology. In the imaging field, where the technology found its first applications, they are also known as CMOS Image Sensors. The use of MAPS as a detector for particle physics was first proposed at the end of 1999. Since then, their good performance in terms of spatial resolution, efficiency, radiation hardness have been demonstrated and work is now well under way to deliver the first MAPS-based vertex detectors.Comment: Invited talk at International Symposium on the Development of Detectors for Particle, AstroParticle and Synchrtron Radiation Experiments, Stanford Ca (SNIC06) 4 pages, pdf, 2 TIFF figures, PSN000

High resolution pixel detectors for e+e- linear colliders

The physics goals at the future e+e- linear collider require high performance vertexing and impact parameter resolution. Two possible technologies for the vertex detector of an experimental apparatus are outlined in the paper: an evolution of the Hybrid Pixel Sensors already used in high energy physics experiments and a new detector concept based on the monolithic CMOS sensors.Comment: 8 pages, to appear on the Proceedings of the International Workshop on Linear Colliders LCWS99, Sitges (Spain), April 28 - May 5, 199

The Highly Miniaturised Radiation Monitor

We present the design and preliminary calibration results of a novel highly miniaturised particle radiation monitor (HMRM) for spacecraft use. The HMRM device comprises a telescopic configuration of active pixel sensors enclosed in a titanium shield, with an estimated total mass of 52 g and volume of 15 cm$^3$. The monitor is intended to provide real-time dosimetry and identification of energetic charged particles in fluxes of up to 10$^8$ cm$^{-2}$ s$^{-1}$ (omnidirectional). Achieving this capability with such a small instrument could open new prospects for radiation detection in space.Comment: 17 pages, 15 figure

RIFT process analysis for the production of green composites in flax fibers and bio-based epoxy resin

In this work, a dual objective is carried out on composite materials in flax fiber and bio-based epoxy resin: to determine the process parameters and to develop a numerical model for highlighting the potential of and the limits in the production of “green” laminates through a RIFT process (Resin Infusion under Flexible Tool). For these reasons, compressibility tests were performed in order to evaluate the behavior of commercial flax woven under the vacuum bag. Subsequently, permeability tests were performed in order to evaluate the permeability curves necessary for the numerical study of the infusion process. For the numerical analyses, the commercial software PAM-RTM was adopted and validated. In this work, vaseline oil was used as the injected resin for the validation, and a bio-based epoxy commercial system was used for the study of the infusion process in a simple case study. The results were compared with a petroleum-based epoxy system typically used for infusion processes, showing the potentiality and the critical use of bio-based resins for infusion processes

Performance of a novel wafer scale CMOS active pixel sensor for bio-medical imaging

Recently CMOS Active Pixels Sensors (APSs) have become a valuable alternative to amorphous Silicon and Selenium Flat Panel Imagers (FPIs) in bio-medical imaging applications. CMOS APSs can now be scaled up to the standard 20 cm diameter wafer size by means of a reticle stitching block process. However despite wafer scale CMOS APS being monolithic, sources of non-uniformity of response and regional variations can persist representing a significant challenge for wafer scale sensor response. Non-uniformity of stitched sensors can arise from a number of factors related to the manufacturing process, including variation of amplification, variation between readout components, wafer defects and process variations across the wafer due to manufacturing processes. This paper reports on an investigation into the spatial non-uniformity and regional variations of a wafer scale stitched CMOS APS. For the first time a per-pixel analysis of the electro-optical performance of a wafer CMOS APS is presented, to address inhomogeneity issues arising from the stitching techniques used to manufacture wafer scale sensors. A complete model of the signal generation in the pixel array has been provided and proved capable of accounting for noise and gain variations across the pixel array. This novel analysis leads to readout noise and conversion gain being evaluated at pixel level, stitching block level and in regions of interest, resulting in a coefficient of variation ≤ 1.9%. The uniformity of the image quality performance has been further investigated in a typical X-ray application, i.e. mammography, showing a uniformity in terms of CNR among the highest when compared with mammography detectors commonly used in clinical practise. Finally, in order to compare the detection capability of this novel APS with the currently used technology (i.e. FPIs), theoretical evaluation of the Detection Quantum Efficiency (DQE) at zero-frequency has been performed, resulting in a higher DQE for this detector compared to FPIs. Optical characterization, X-ray contrast measurements and theoretical DQE evaluation suggest that a trade off can be found between the need of a large imaging area and the requirement of a uniform imaging performance, making the DynAMITe large area CMOS APS suitable for a range of bio-medical applications

Hyperacusis in children with attention deficit hyperactivity disorder: a preliminary study

The association between hyperacusis and developmental disorders such as autism spectrum disorders has been extensively reported in the literature; however, the specific prevalence of hyperacusis in attention deficit hyperactivity disorder (ADHD) has never been investigated. In this preliminary study, we evaluated the presence of hyperacusis in a small sample of children affected by ADHD compared to a control group of healthy children. Thirty normal hearing children with a diagnosis of ADHD and 30 children matched for sex and age were enrolled in the study. All children underwent audiological and multidisciplinary neuropsychiatric evaluation. Hearing was assessed using pure tone audiometry and immittance test; ADHD was diagnosed following the Diagnostic and Statistical Manual of Mental Disorder criteria. Hyperacusis was assessed through the administration of a questionnaire to parents and an interview with children. Hyperacusis was diagnosed in 11 children (36.7%) in the study group and in four children (13.3%) in the control group; this difference was statistically significant (p = 0.03). The preliminary results of this study suggest a higher presence of hyperacusis in children with attention deficit hyperactivity disorder compared to control children. More studies on larger samples are necessary to confirm these results