100,413 research outputs found
A 8-channels low-noise CMOS readout circuit for silicon detectors with on-chip front-end JFET
No full textWe propose a CMOS circuit designed to be used with silicon drift detectors (SDDs) coupled to scintillators for /spl gamma/-ray imaging applications. The circuit is composed by 8 analog channels, each including a low-noise preamplifier, a 6th order semiGaussian shaping amplifier with four selectable peaking times from 1.8 /spl mu/s up to 6 /spl mu/s, a peak stretcher and a baseline holder. The integrated time constant used for the shaping are implemented by means of a recently proposed 'RC' cell. This cell is based on the de-magnification of the current flowing in a resistor R by means of the use of current mirrors. The 8 analog channels of the chip are multiplexed to a single analog output. A suitable digital section provides self-resetting of the channels, trigger output and the programming of independent threshold on the analog channels by means of a programmable serial register and 3-bit DACs. In this work, the main features of the circuit are first presented. The experimental results obtained in the characterization of the prototype are then reported and discussed. The energy resolution measured using a single channel of the chip with a silicon drift detector droplet (SDD/sup 3/) is of 128 eV at 6 keV with the detector cooled at -20/spl deg/C
An 8-channel DRAGO readout circuit for silicon detectors with integrated front-end JFET
No full textWe have developed a CMOS circuit to be used with Silicon Drift Detectors (SDDs) for X-ray spectroscopy and γ-ray imaging applications. The circuit operates with the input transistor integrated directly on the detector wafer. The circuit is composed of 8 analog channels, each including a low-noise voltage preamplifier, a 6th order semi-Gaussian shaping amplifier, with four selectable peaking times from 1.8 μs up to 6 μs, and a peak stretcher. The integrated time constant used for the shaping are implemented by means of a recently proposed 'RC' cell. This cell is based on the de-magnification of the current flowing in a resistor R thanks to the use of current mirrors. The 8 analog channels of the chip are multiplexed to a single analog output. A digital section provides self-resetting of the channels, trigger output and the external programming of independent threshold on the analog channels by means of a 3 bit DAC and a programmable serial register. In this work, the main features of the circuit are described. The measurement results obtained in the characterization of the prototype are then reported and discussed. The energy resolution measured using a single channel of the chip with a Silicon Drift Detector Droplet (SDD 3) is of 128 eV at 6 keV with the detector cooled at -20°C. Spectroscopy measurements using a multi-element SDD are also shown. © 2006 IEEE
Early copper metallurgy in Central Italy: Issues of production and social consumption
No full textThe Later Neolithic (c. 4500 to 3600 BC) and the Copper Age (c. 3600 to 2200 BC) in centrai Italy witness the first introduction and diffusion of copper-based artefacts. Metal finds are very limited during thc Neolithic, though their number increases remarkably in the Copper Age, up to almost 400 items. Interestingly, it is observed that the scarce Neolithic metal artefacts are evenly distributed within settlement and burial sites, whcreas the vast majority of the Copper Age finds are
located in funerary contexts, It appears that metallurgy played a marginal role within the Neolithic communities, and it progressively became an important element within prehistoric society during the 4th and the 3rd millennia BC. There is also little doubt that burial played a key role as a social
arena for metal to bc fully incorporated into prehistoric society.
However, it is not yct clear how far metal objects wcrc used in the Copper Age bcfore being deposited in graves, and whether some artcfacts were used at all. Prior to entering the grave copper axes, daggers and awls may have been used within different sphcres of action and for different purposes. In order to understand how a major technological innovation such as metallurgy was integratcd into Copper Age society, metal objects need to be investigated to assess their potential
both as tools and as symbols. The Copper Age in Centrai Italy, being coincident with the first massive diffusion of copper-based metallurgy in the arca, seems to be an appropriate example to
investigate in detail the parallcl devclopmcnt of metallurgieal techniques and their impact on society.
Reprcsentative copper objects from funerary sitcs havc been carefully selected on thc basis of context, chronology, typology, and geographical distribution. The objects are being investigated by a range of analytical techniques (X-ray fluorescence, optical metallography, mass spectrometry,
scanning clectron microscopy, X-ray diffraction) in order to assess: (I) their physico-chcmical properties and how far they could have bccn used as practical tools; (2) thc provenance and
diffusion of thc metal; (3) thc rclationship bctwcen chemical composition, manufacturing process, and typology. The functionality of thesc objccts, based on experimental paramctcrs, allows a better understanding of their practical and symbolic role within prehistoric society in Central Italy
Detection and study of a palimpsest: macro-X-ray fluorescence scanning in the Loggia Room of Galatea
No full textWithin the frame of a collaboration among the Accademia Nazionale dei Lincei, XGLab-Bruker and ENEA, some of the Renaissance wall paintings decorating Villa Farnesina interiors have been investigated by macro-X-ray fluorescence (MAXRF). In this paper is presented and discussed a case study concerning some sketches discovered about 50 years ago during the detachment of painted curtains. Results have brought to light a palimpsest whose discussion calls into question the attribution proposed when it has been discovered
A CMOS circuit for high-stability X-ray Spectroscopy with Silicon Drift Detectors with on-chip JFET
No full textWe propose a CMOS circuit designed to be used with silicon drift detectors (SDDs) for high-resolution and high peak stability X-ray spectroscopy. The circuit is developed in the framework of a project for researches on 'exotic atoms' (e.g. kaonic hydrogen) at e/sup -//e/sup +/ colliders. The circuit is composed by a low-noise charge preamplifier and by a 6th order semiGaussian shaping amplifier with four selectable peaking times from 0.7 /spl mu/s up to 3 /spl mu/s. The preamplifier operates with the input JFET directly integrated on the detector itself. A low-frequency current-mode feedback loop allows to stabilize the operating point of the input JFET with respect to background and leakage current variations. The feedback capacitor is integrated on the detector and its value is not known precisely in advance. The preamplifier is designed with the possibility to adjust externally its decay time to match the fixed time constant of the pole/zero network. A baseline holder senses the baseline voltage shifts at the output of the circuits due to the DC changes of the drain voltage of the input JFET in correspondence of background variations and provides a feedback loop back to the preamplifier to stabilize the output baseline. A bipolar shaping provides a timing signal required by the experiment. A first prototype has been realized in the 0.35 /spl mu/m AMS technology. The energy resolution measured using the chip with a SDD of 5 mm/sup 2/ is of 137 eV at 6 keV (ENC = 8e/sup -/ rms)
A CMOS readout circuit for silicon drift detectors with on-clip JFET and feedback capacitors
No full textWe propose a CMOS circuit designed to be used with silicon drift detectors (SDDs) for high-resolution and high peak stability X-ray spectroscopy. The circuit is developed in the framework of a project for researches on exotic atoms (e.g., kaonic hydrogen) at e-/e+ colliders. The circuit is composed by a low-noise charge preamplifier, by a sixth-order semi-Gaussian shaping amplifier with four selectable peaking times from 0.7 mus up to 3 mus, and by a bipolar shaping amplifier to provide a timing signal required by the experiment. The preamplifier operates with the input JFET directly integrated on the detector itself. A low-frequency current-mode feedback loop allows to stabilize the operating point of the input JFET with respect to background and leakage current variations. The feedback capacitor is also integrated on the detector. Because its value is not known precisely a priori, the preamplifier is designed with the possibility to adjust externally its decay time to match the fixed time constant of the pole/zero network. A baseline holder senses the baseline voltage shifts at the output of the circuits due to the dc changes of the drain voltage of the input JFET in correspondence of background variations and provides a feedback loop back to the preamplifier to stabilize the output baseline. A first prototype has been realized in the 0.35-mum AMS technology. The energy resolution measured using the chip with a SDD of 5 mm2 is of 137 eV at 6 keV (ENC=8 e-rms
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
From noise to information. Analysing macro-XRF mapping of strontium impurities in Raphael's Baglioni Entombment in the Galleria Borghese, Rome
No full textIn the paintings of the Old Masters, strontium is present only as an impurity of the materials, that is the gypsum used for the preparation of the panels, and for this reason its presence is generally considered – at best – accidental information. However, an in-depth study of the distribution of strontium beneath the surface of Raphael's Entombment in the Borghese Gallery in Rome by means of MA-XRF provided detailed information regarding a reapplication of the preparatory gypsum ground layers on an area probably damaged before the painter began the execution of the painting. Furthermore, the comparison of MA-XRF distribution maps for lead and strontium with radiographic images, aimed to establish at what point the painter decided to eliminate a female figure in the centre of the painting, and the state of completion of the figure when this occurred
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