Showing papers by "Wladyslaw Dabrowski published in 2003"

What does the eye tell the brain?: Development of a system for the large-scale recording of retinal output activity

Abstract: A multielectrode array system has been developed to study how the retina processes and encodes visual images. This system can simultaneously record the extracellular electrical activity from hundreds of retinal output neurons as a dynamic visual image is focused on the input neurons. The retinal output signals detected can be correlated with the visual input to study the neural code used by the eye to send information about the visual world to the brain. The system consists of the following components: (1) a 32 /spl times/ 16 rectangular array of 512 planar microelectrodes with a sensitive area of 1.7 square mm. The electrode spacing is 60 microns and the electrode diameter is 5 microns. (Hexagonal arrays with 519 electrodes are under development); (2) eight 64-channel custom-designed integrated circuits to platinize the electrodes and AC couple the signals; (3) eight 64-channel integrated circuits to amplify, band-pass filter and analog multiplex the signals; (4) a data acquisition system; and (5) data processing software. This paper will describe the design of the system, the experimental and data analysis techniques, and some first results with live retina. The system is based on techniques and expertise acquired in the development of silicon microstrip detectors for high energy physics experiments.

The development of diamond tracking detectors for the LHC

Abstract: Chemical vapor deposition diamond has been discussed extensively as an alternate sensor material for use very close to the interaction region of the LHC where extreme radiation conditions exist. During the last few years diamond devices have been manufactured and tested with LHC electronics with the goal of creating a detector usable by all LHC experiment. Extensive progress on diamond quality, on the development of diamond trackers and on radiation hardness studies has been made. Transforming the technology to the LHC specific requirements is now underway. In this paper we present the recent progress achieved.

Large-scale imaging of retinal output activity

Abstract: A system is being developed to study how the retina processes, encodes and communicates information about the visual world to the brain. It will image the activity of retinal output neurons over a region of live retina approaching that used for significant neural computation in the visual cortex. A prototype system consisting of 61 microelectrodes, covering an area of 0.17 mm 2 , is described, including some first results with monkey retina. The plans and status for a system with 512 microelectrodes, covering an area of 1.7 mm 2 , are also given.

Status of the R&D activity on diamond particle detectors

Abstract: Chemical Vapor Deposited (CVD) polycrystalline diamond has been proposed as a radiation-hard alternative to silicon in the extreme radiation levels occurring close to the interaction region of the Large Hadron Collider. Due to an intense research effort, reliable high-quality polycrystalline CVD diamond detectors, with up to 270 μm charge collection distance and good spatial uniformity, are now available. The most recent progress on the diamond quality, on the development of diamond trackers and on radiation hardness studies are presented and discussed.

Readout of silicon strip detectors

Abstract: Various architectural and technological options of readout electronics for silicon strip detectors in vertex and tracking applications are discussed briefly. The ABCD3T ASIC for the readout of silicon strip detectors in the ATLAS semiconductor tracker is presented. The architecture of the chip, some design issues and radiation effects are discussed.

Development of integrated circuits for readout of microelectrode arrays to image neuronal activity in live retinal tissue

Abstract: Two multichannel Application Specific Integrated Circuits (ASICs) for extracellular recording of neuronal signals from live retinal tissues using microelectrode arrays have been developed. In this paper we discuss the requirements concerning the IC parameters and characteristics as well as present the designs and the test results. The required electronic functionality has been divided into two ASICs: PLAT-64 and NEURO-64 realized in a 0.7 /spl mu/m CMOS process. The PLAT-64 chip comprises 64 capacitors of 150 pF each, and 64 addressable and controlled DC current sources for platinization of electrodes. The NEURO-64 chip comprises 64 channels of low noise amplifiers and bandpass filters and an analog multiplexer. The low noise performance of the preamplifier has been achieved by careful selection of a CMOS process and by proper sizing and biasing of the input devices. The required lower cut-off frequency of 20 Hz has been obtained by employing a novel RC filter structure.

Energy resolution of a silicon detector with the RX64 ASIC designed for X-ray imaging

Abstract: Results from a silicon microstrip detector coupled to the RX64 ASIC are presented. The system is capable of single photon counting in digital X-ray imaging, with foreseen applications to dual energy mammography and angiography. The main features of the detecting system are low noise (operation with threshold as low as E4 keV is possible), good spatial resolution (a pixel of 100 mm � 300 mm when oriented edge-on) and good counting rate capability (up to one million counts per channel with a maximum rate of about 200 kHz per channel). The energy resolution of the system, as obtained with several fluorescence X-ray lines, is described. r 2003 Elsevier B.V. All rights reserved. PACS: 87.57.� s; 07.50.Qx; 29.40.Gx; 29.30.Kv

New results on diamond pixel sensors using ATLAS frontend electronics

Abstract: Diamond is a promising sensor material for future collider experiments due to its radiation hardness. Diamond pixel sensors have been bump bonded to an ATLAS pixel readout chip using PbSn solder bumps. Single chip devices have been characterised by lab measurements and in a high-energy pion beam at CERN. Results on charge collection, spatial resolution, efficiency and the charge carrier lifetime are presented.

A silicon strip detector coupled to the RX64 ASIC for X-ray diagnostic imaging

Abstract: First results from a silicon microstrip detector with 100 mm pitch coupled to the RX64 ASIC are presented. The system is capable of single photon counting in digital X-ray imaging, with possible applications to dual energy mammography and angiography. The main features of the detecting system are low noise, good spatial resolution and high counting rate capability. The energy resolution and the conversion efficiency of the system are discussed, based on results obtained with fluorescence X-ray sources and quasi-monochromatic X-ray beams in the 8–36 keV energy range, with strips being either orthogonal or parallel to the incoming X-rays. We present also preliminary imaging results obtained with a plexiglass phantom with tiny cylindrical cavities filled with iodate solution, simulating patient vessels; in this case the X-ray beam has two components, respectively below and above the iodine Kedge at 33:17 keV:

Results about imaging with silicon strips for Angiography and Mammography

Abstract: We present results obtained with a single photon counting system consisting of 384 silicon microstrips of 100 micron pitch equipped with 6 RX64 ASICs. The ASIC includes a charge preamplifier, a shaper, a discriminator and a 20‐bit counter for each of its 64 channels. The energy resolution of the system has been measured in the range from 8 keV to 32 keV using fluorescence X‐ray lines from several targets, using either an Am‐241 source or an X‐ray tube. Then, the efficiency of the system has been determined using the specially developed quasi‐monochromatic X‐ray beams in the energy range 18–36 KeV. Good efficiency has been obtained in the edge‐on configuration, which is more suitable for the intended applications. The spatial resolution of the system has been verified using a special microfocus X‐ray tube equipped with capillaries. Finally, images of angiographic and mammographic test objects have been obtained with dual energy X‐ray beams and have then been processed with the dual energy subtraction technique. In particular, the contrast for the angiographic test object has been evaluated for different concentrations of an iodate solution injected into 1 mm and 2 mm diameter vessels. Further developments, including a double threshold version of the ASIC, are also discussed.

X-ray imaging with a silicon microstrip detector coupled to the RX64 ASIC

Abstract: A single photon counting X-ray imaging system, with possible applications to dual energy mammography and angiography, is presented. A silicon microstrip detector with 100 mm pitch strips is coupled to RX64 ASICs, each of them including 64 channels of preamplifier, shaper, discriminator and scaler. The system has low noise, good spatial resolution and high counting rate capability. Results on energy resolution have been obtained with a fluorescence source and quasi-monochromatic X-rays beams. Preliminary images obtained with an angiographic phantom are presented.

Monte Carlo Simulation of a Silicon Strip Detector Response For Angiography Applications. First approach

Abstract: We present First results of Monte Carlo simulation by the general purpose MCNP‐4C transport code of an experimental facility at Bologna S. Orsola hospital for studying the possible application of a X‐Ray detection system based on a silicon strip detector on a dual energy angiography. The quasi‐monochromatic X‐ray beam with the detector in the edge‐on configuration has been used to acquire images of a test object at two different energies (namely 31 and 35 keV) suitable for the K‐edge subtraction angiography application. As a test object a Plexiglas step wedge phantom with four cylindrical cavities, having 1 mm diameter was used. The cavities have been drilled and filled, with iodated contrast medium, whose concentration varied from 370 mg/ml to 92 mg/ml. Both the profiles obtained from measurements and the generated images where reproduced by computer simulation on a first approach to use this technique as an evaluation tool for future developments on the experimental setup.

Silicon strip detectors for two-dimensional soft X-ray imaging at normal incidence

Abstract: A simple prototype system for static two-dimensional soft X-ray imaging using silicon microstrip detectors irradiated at normal incidence is presented. Radiation sensors consist of single-sided silicon detectors made from 300 μm thick wafers, read by RX64 ASICs. Data acquisition and control is performed by a Windows PC workstation running dedicated LabVIEW routines, connected to the sensors through a PCI-DIO-96 interface. Two-dimensional images are obtained by scanning a lead collimator with a thin slit perpendicular to the strip axis, along the whole detector size; the several strip profiles (slices) taken at each position are then put together to form a planar image. Preliminary results are presented, illustrating the high-resolution imaging capabilities of the system with soft X-rays.

Performance of a radiation hard 128 channel analogue front-end chip for the readout of a silicon-based hybrid photon detector

Abstract: The performance is described of a front-end chip, the SCT128A-LC chip, originally developed for the readout of a silicon based Hybrid Photon Detector (HPD), which is part of an RICH detector to be run in an LHC experimental environment. The relatively low signal charge from single photoelectrons, impinging on the silicon pad sensor, put very stringent requirements on the noise performance of the front-end chip. An absolute noise calibration using X-ray sources and a 241 Am γ source was performed. It is demonstrated that sufficiently good signal over noise ratio can be obtained to use this chip for the read-out of an HPD in LHC experiments.

The silicon Multiplicity Detector for the NA50 experiment

Abstract: The operation and performance of the silicon strip Multiplicity Detector in the heavy-ion experiment NA50 at CERN are presented together with a selection of physics results. The main features of the detector are high speed (50 MHz sampling frequency), high granularity (more than 13,000 strips), and good radiation resistance. The detector provided a measurement of event centrality in Pb–Pb collisions, as well as target identification and the measurement of charged particle pseudorapidity distributions as a function of centrality.