106 research outputs found
Programmable active pixel sensor to investigate neural interactions within the retina
No full textDetection of the visual scene by the eye and the resultant neural interactions of the retina-brain system give us our perception of sight. We have developed an Active Pixel Sensor (APS) to be used as a tool for both furthering understanding of these interactions via experimentation with the retina and to make developments towards a realisable retinal prosthesis. The sensor consists of 469 pixels in a hexagonal array. The pixels are interconnected by a programmable neural network to mimic lateral interactions between retinal cells. Outputs from the sensor are in the form of biphasic current pulse trains suitable to stimulate retinal cells via a biocompatible array. The APS will be described with initial characterisation and test results
Charge sharing in silicon pixel detectors
No full textWe used a pixellated hybrid silicon X-ray detector to study the effect of the sharing of generated charge between neighbouring pixels over a range of incident X-ray energies, 13-36 keV. The system is a room temperature, energy resolving detector with a Gaussian FWHM of 265 eV at 5.9 keV. Each pixel is 300 mu m square, 300 mu m deep and is bump bonded to matching read out electronics. The modelling packages MEDICI and MCNP were used to model the complete X-ray interaction and the subsequent charge transport. Using this software a model is developed which reproduces well the experimental results. The simulations are then altered to explore smaller pixel sizes and different X-ray energies. Charge sharing was observed experimentally to be 2% at 13 keV rising to 4.5% at 36 keV, for an energy threshold of 4 keV. The models predict that up to 50% of charge may be lost to the neighbouring pixels, for an X-ray energy of 36 keV, when the pixel size is reduced to 55 mu m
Fast pipelined trigger processors for the forward muon chambers of the H1 experiment on the Hadron Electron Ring Accelerator (HERA) at DESY, Hamburg
No full textCharacterization of the CBC2 readout ASIC for the CMS strip-tracker high-luminosity upgrade
No full textThe CMS Binary Chip 2 (CBC2) is a full-scale prototype ASIC developed for the front-end readout of the high-luminosity upgrade of the CMS silicon strip tracker. The 254-channel, 130 nm CMOS ASIC is designed for the binary readout of double-layer modules, and features cluster-width discrimination and coincidence logic for detecting high-PT track candidates. The chip was delivered in January 2013 and has since been bump-bonded to a dual-chip hybrid and extensively tested. The CBC2 is fully functional and working to specification: we present the result of electrical characterization of the chip, including gain, noise, threshold scan and power consumption, together with the performance of the stub finding logic. Finally we will outline the plan for future developments towards the production version
Development of a thinned back-illuminated CMOS active pixel sensor for extreme ultraviolet spectroscopy and imaging in space science
No full textThe mercury imaging X-ray spectrometer (MIXS) on bepicolombo
No full textThe Mercury Imaging X-ray Spectrometer (MIXS) on the BepiColombo Mercury Planetary Orbiter (MPO) will measure fluorescent X-ray emission from the surface of Mercury in the energy range 0.5–7.5 keV, which is induced by incident solar X-rays and solar wind electrons and protons. These X-rays will reveal the elemental composition of the surface of Mercury and aid the determination of the planet's evolution.
MIXS is a two component instrument. A collimated channel (MIXS-C) provides measurements on scales of 70–270 km, sufficient to separate the major Mercurian terrains. A second channel (MIXS-T) is the first imaging X-ray telescope for planetary remote sensing and will make measurements on spatial scales of less than 10 km for major elements during solar flares, sufficient to isolate surface landforms, such as craters and their internal structures. The spatial resolution achieved by MIXS-T is made possible by novel, low mass microchannel plate X-ray optics, in a Wolter type I optical geometry.
MIXS measurements of surface elemental composition will help determine rock types, the evolution of the surface and ultimately a probable formation process for the planet. In this paper we present MIXS and its predicted performance at Mercury as well as discussing the role that MIXS measurements will play in answering the major questions about Mercury
A pair of custom ASICs for bias generation and clock buffering in space-based CCD camera systems
No full textDevelopment of flexible arrays for in vivo neuronal recording and stimulation
No full textRecent developments in low-power electronics and semiconductor fabrication techniques have found many applications in the life sciences. High-density electrode arrays are becoming well established as tools for the measurement of neuronal signals. The fabrication of arrays on flexible materials allows for 2Dposition sensitive recording of cellular activity in vivo and for the possibility of direct in vivo stimulus. Using flexible polymer materials, compliant with semiconductor fabrication techniques, we demonstrate a process allowing the fabrication of flexible multi-site microelectrode neuronal recording and stimulating arrays. We describe the development of both 8 and 61 electrode arrays on polyimide substrates with 50 and 5 mm minimum linewidths respectively. Further studies have realised 8-electrode arrays using gold on Polydimethylsiloxane (PDMS), an alternative biocompatible material, with linewidths of 14 mm: Implementing low noise amplification, 2.6 mV rms (bandpass typically 80–2000 Hz), the polyimide 8-electrode arrays have been used to record electroretinogram and ganglion cell action potentials in situ from the frog retina (Rana temporaria). Such arrays coupled to pixellated CMOS sensors, incorporating on-board neural networking should allow for the recovery of basic functionality in the human retina. More specifically, where retinal degeneration has affected only the photosensitive elements of the eye we can utilise the remaining neuronal pathways. Initial stimulation studies for electro-deposited platinum electrodes of 4 nA/mm2 indicate upper breakdown limits for charge density approaching 40 mC m2: Investigations of lifetime stimulation of a 50 mm diameter electrode, of typical impedance less than 20 kO at 1 kHz, suggest operational limits over lifetime in the order of 10 mC m2: These charge densities are adequate for neuronal cell stimulation
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