A. Stefanini

The CDF Central and Endwall Hadron Calorimeter

Abstract The CDF central and endwall hadron calorimeter covers the polar region between 30° and 150° and a full 2π in azimuth. It consists of 48 steel-scintillator central modules with 2.5 cm sampling and 48 steel-scintillator endwall modules with 5.0 cm sampling. A general description of the detector is given. Calibration techniques and performance are discussed. Some results of the test beam studies are shown.

EVALUATION OF ELEMENTAL AND COMPOUND SEMICONDUCTORS FOR X-RAY DIGITAL RADIOGRAPHY

Abstract We present a comparative study of the performance of elemental and compound solid state crystals of possible use in X-raY digital radiography. The general purpose EGS4 code was used to simulate photon-electron transport in the energy range 20 to 60 keV. The efficiency and the energy resolution, as a function of X-ray energy, are calculated and correlated to the different physical characteristics of the crystals considered.

Design and Construction of the CDF Central Tracking Chamber

Abstract We describe the design and construction of a large drift chamber of a novel design well adapted for operation in high magnetic fields and in the high track density environment of hadron colliders.

Design and construction of new central and forward muon counters for CDF II

New scintillation counters have been designed and constructed for the upgradation of the CDF detector at the Fermilab Tevatron in order to complete the muon coverage of the central detector and to extend it to a larger pseudorapidity interval. A novel light collection technique using wavelength shifting fibers, together with high-quality polystyrene-based scintillator resulted in compact counters with good and stable light collection efficiency over lengths extending up to 320 cm. Their design and construction is described and results of their initial performance are reported.

Use of silicon and GaAs pixel detectors for digital autoradiography

Solid state detectors made of Si (4.8/spl times/8 mm/sup 2/) and GaAs (6.4/spl times/8 mm/sup 2/) pixel matrices bump-bonded to the Omega2 and Omega3 electronic read-out systems, developed at CERN for H.E.P. experiments, have been used to obtain autoradiographic images of clusters of human epithelial cells and DNA fragments separated via electrophoresis, both labeled with /sup 32/P. The system has shown a good minimum detectable activity per unit area of 2.10/sup -4/ cps mm/sup -2/, and has proved linear for a count rate in the range 0.2-20 cpa, typical of autoradiography. The pixel dimensions are 75/spl times/500 /spl mu/m/sup 2/ (Si-Omega2) and 50/spl times/500 /spl mu/m/sup 2/ (GaAs-Omega3), respectively. We are able to clearly localize clusters of cells which have incorporated the radioactive tracer and DNA fragments on an electrophoretic gel on paper (blots).

GaAs pixel radiation detector as an autoradiography tool for genetic studies

Abstract We present an autoradiography tool to be used mainly for genetic studies. It performs a quantitative analysis of radioactivity and can follow a dynamic process. We designed several applications, in particular one aimed at detecting hybridization of radio-labeled DNA fragments with known DNA-probes deposited on a micro-array. The technique is based on GaAs pixel array detector and low threshold, large dynamic range and good sensitivity integrated electronics developed for medical applications, suitable to detect markers (gamma or beta) such as 14C, 35S, 33P, 32P, 125I, even at very low activities. A Monte Carlo simulation of β− detection in GaAs is presented here in order to study the spatial resolution characteristics of such a system. For several biological applications, the electronics is required to perform at high temperatures (from 37° to 68°): we present here studies of noise and minimum threshold as a function of the temperature.

Gallium arsenide pixel detectors for medical imaging

Gallium arsenide pixel detectors processed on a 200 μm Semi-Insulating (SI) Hitachi substrate were bump-bonded to the Omega3 electronics developed at CERN for high energy physics [1]. The pixel dimensions are 50 μm × 500 μm for a total of 2048 cells and an active area of ∼0.5 cm2. Our aim is to use this system for medical imaging. We report the results obtained after irradiation of the detector with different X-ray sources on phantoms with different contrasts. The system showed good sensitivity to X-rays from 241Am (60 keV) and 109Cd (22.1 keV). It is also sensitive to β− particles from 90Sr as well as from 32P which is used as a tracer for autoradiography applications. The inherent high absorption efficiency of GaAs associated with the self-triggering capabilities of the pixel readout system reduced considerably the acquisition time compared with traditional systems based on silicon or emulsions. The present configuration is not optimised for X-ray imaging. The reduction of the pixel dimensions to 200 μm × 200 μm together with the integration of a counter in the pixel electronics would make the detector competitive for applications like mammography or dental radiology. For certain applications in biochemistry, such as DNA sequencing, where good spatial resolution is required only in one direction, the present setup should allow the best spatial resolution available up to now with respect to other digital autoradiographic systems. DNA sequencing tests are now under way.

AUTORADIOGRAPHY WITH SILICON STRIP DETECTORS

A digital autoradiography system based on double sided silicon strip detectors (1.6 × 1.6 mm2 active surface with 100 μm pitch) has been developed and successfully tested with beta-emitting tracers. It is shown here that the system is able to perform imaging of organic material with specific sensitivity as small as 0.002 nCi/mm2, and to record activity measurements with good linearity in the range 0.002–20 nCi/mm2. Autoradiographic images of clusters of mammary cells marked with ortho-(32P)phosphate, obtained with an exposure time of about 10 min are presented.

Measurements of shadowing in low |Q2| electroproduction on nuclei

Measurements of inelastic electron scattering have been made in the range 2.2 < ν < 3.8 GeV and 0.1 < |Q2| < 0.3 (GeV/c)2, on a selection of nuclei ranging from hydrogen and deuterium to uranium, by measuring the scattered electron only. Detailed calculations have been made of the contribution of radiative tails to the measured yield. The results show a small ‘shadowing’ consistent with other electroproduction experiments, and also with photoproduction experiments in this ν range, but the shadowing decreases rapidly as |Q2| increases.

Phase contrast imaging simulation and measurements using polychromatic sources with small source-object distances

Phase contrast imaging is a technique widely used in synchrotron facilities for nondestructive analysis. Such technique can also be implemented through microfocus x-ray tube systems. Recently, a relatively new type of compact, quasimonochromatic x-ray sources based on Compton backscattering has been proposed for phase contrast imaging applications. In order to plan a phase contrast imaging system setup, to evaluate the system performance and to choose the experimental parameters that optimize the image quality, it is important to have reliable software for phase contrast imaging simulation. Several software tools have been developed and tested against experimental measurements at synchrotron facilities devoted to phase contrast imaging. However, many approximations that are valid in such conditions (e.g., large source-object distance, small transverse size of the object, plane wave approximation, monochromatic beam, and Gaussian-shaped source focal spot) are not generally suitable for x-ray tubes and othe...