The goal of the DIRAC experiment at CERN (PS212) is to measure the π+π− atom lifetime with 10% precision. Such a measurement would yield a precision of 5% on the value of the S-wave ππ scattering ...lengths combination |a0−a2|. Based on part of the collected data we present a first result on the lifetime, τ=2.91−0.62+0.49×10−15 s, and discuss the major systematic errors. This lifetime corresponds to |a0−a2|=0.264−0.020+0.033mπ−1.
A hodoscope system constructed with a scintillating fiber array and a multianode photomultiplier is described. The results of laboratory and beam tests on the hodoscope response, efficiency and ...spatial resolution are discussed.
Experimental results obtained with commercially available PSPMs coupled to 0.5-mm diameter scintillating fiber arrays show space resolution of < 200 μm and time resolution better than 1 ns with a ...detection efficiency of about 90%. In addition, the preliminary studies indicate the feasibility of separating double-tracks with a minimum distance of 3 mm using this technology.
In the last decade a new radiographic technique has been establishing itself which makes the most of technological progress in the fields of laser optics, of materials and of computer science and ...integrates conventional techniques introducing the digital image also into radiographic diagnosis. The authors, who have gained a wide experience in both the theory and the applications of Computed Radiography (CR), carefully reviewed Italian literature and found no review article on technical theoretical principles, while many such papers are found in international literature. Therefore, they took the lead for a review paper on this subject. For easier reading, the paper was divided into three parts: the first one is the necessary introduction to the physical parameters to understand radiographic images, i.e., the signal-to-noise ratio, the modulation transfer function, the Wiener spectrum and the detective quantum efficiency. The second part deals with the physical features of the formation of conventional radiographic images: the latest notions about the conversion of X-ray energy into light photons by intensifying screen phosphors are here reported. Finally, radiographic image readability is related to the characteristics of the screen-film system. The third part of the paper deals with CR, in particular with the problems related to image acquisition through the screens called imaging plates, to the laser reading technique and to image reconstruction. Finally, the different physical phenomena leading to radiant image degradation are examined sequentially, bearing in mind that the diagnostic yield of CR images can be improved with image processing, to obtain images which can be compared to conventional ones.
Metabolic bone disorders are extremely interesting from an epidemiological, clinical and social point of view. In particular, some of them are important for they are typical of elderly people--i.e., ...the portion of population which is on the increase due to the lengthening of the average life. On the other hand, thanks to the current intervention techniques, the number of chronic nephropathics (in whom metabolic bone conditions may develop) has markedly increased. Therefore, sufficiently reliable methods are needed to allow the thorough evaluation of bone mineral components. Unfortunately, these methods are only of quantitative value because they are unable to discriminate the statuses of the two essential bone components--i.e., cortex and spongiosa--; we all know that bone mineral loss can currently be quantified only when amounting to < 20% of the total value, due to the addition of the mineral contents of the two components. In this paper the authors briefly report on the noninvasive techniques currently in use for the measurement of bone mineral components, especially relative to their physical bases, the knowledge of which is essential for a correct evaluation. The authors accurately reviewed the literature data relative to the various techniques and compared the results obtained by the different authors. Thus, no personal experience is reported, since this paper is aimed at being considered as a reference mark for the reader to be helped in the choice of the equipment suiting him most. However, as to preventing metabolic osteopathies, quantitative methods cannot yield absolute data, which addresses the current research to densitometry by means of the Compton method. The latter may finally lead to the development of operative equipment allowing not only the separate measurement of cortical and spongiose values, but also the qualitative evaluation of bone status--i.e., not limited to mineral loss but including also the determination of the protein, fat and water components.
Scintillating fibre technology has made substantial progress, and has demonstrated great potential for fast tracking and triggering at high luminosity experiments in Particle Physics. This talk ...presents some recent issues of the RD-17 project at CERN for fast and precise readout of scintillating fibre arrays, as well as for upgrade of position-sensitive photomultipliers. Excellent matching of scintillating fibre and position-sensitive photomultiplier, in particular in time characteristics, allowed to realise high detector performances, typically represented by spatial resolution of ∼ 125 μm as well as time resolution better than 1 ns with detection efficiency greater than 95 %.
The authors show the results of an experimental study on the light conversion efficiency of the absorbed energy from an incident X-ray beam by different kinds of intensifying screens. They stress ...that the absolute speed curves drawn for each intensifying screen, express (in the energy range 10 to 100 keV) the light output for an incident X-ray of a certain energy value. In this way, the knowledge of the X-ray tube emission spectra for a fixed kVp allows to forecast with good accuracy, the light output and the emerging spectra from an intensifying screen. They emphasize the importance of the K-edge (K shell electrons binding energy) as a factor affecting the phosphors behaviour both for what concerns the radiation filtration and the light conversion efficiency of the absorbed radiation.
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