M. Paganoni

Solid state photodetectors like silicon photomultipliers (SiPMs) are playing an important role in several fields of medical imaging, life sciences and high energy physics. They are able to sense optical photons with a single photon detection time precision below 100 ps, making them ideal candidates to read the photons generated by fast scintillators in time of flight positron emission tomography (TOF-PET). By implementing novel high-frequency readout electronics, it is possible to perform a completely new evaluation of the best timing performance achievable with state-of-the-art analog-SiPMs and scintillation materials. The intrinsic SiPM single photon time resolution (SPTR) was measured with Ketek, HPK, FBK, SensL and Broadcom devices. Also, the best achieved coincidence time resolution (CTR) for these devices was measured with LSO:Ce:Ca of [Formula: see text] mm3 and [Formula: see text] mm3 size crystals. The intrinsic SPTR for all devices ranges between 70 ps and 135 ps FWHM when illuminating the entire [Formula: see text] mm2 or [Formula: see text] mm2 area. The obtained CTR with LSO:Ce:Ca of [Formula: see text] mm3 size ranges between 58 ps and 76 ps FWHM for the SiPMs evaluated. Bismuth Germanate (BGO), read out with state of-the-art NUV-HD SiPMs from FBK, achieved a CTR of 158 [Formula: see text] ps and 277 [Formula: see text] ps FWHM for [Formula: see text] mm3 and [Formula: see text] mm3 crystals, respectively. Other BGO geometries yielded 167 [Formula: see text] 3 ps FWHM for [Formula: see text] mm3 and 235 [Formula: see text] 5 ps FWHM for [Formula: see text] mm3 also coupled with Meltmount (n = 1.582) and wrapped in Teflon. Additionally, the average number of Cherenkov photons produced by BGO in each 511 keV event was measured to be 17 [Formula: see text] 3 photons. Based on this measurement, we predict the limits of BGO for ultrafast timing in TOF-PET with Monte Carlo simulations. Plastic scintillators (BC422, BC418), BaF2, GAGG:Ce codoped with Mg and CsI:undoped were also tested for TOF performance. Indeed, BC422 can achieve a CTR of 35 [Formula: see text] 2 ps FWHM using only Compton interactions in the detector with a maximum deposited energy of 340 keV. BaF2 with its fast cross-luminescence enables a CTR of 51 [Formula: see text] 5 ps FWHM when coupled to VUV-HD SiPMs from FBK, with only ∼22% photon detection efficiency (PDE). We summarize the measured CTR of the various scintillators and discuss their intrinsic timing performance.

Scintillator based radiation detectors readout by SiPMs successively break records in their reached time resolution. Nevertheless, new challenges in time of flight positron emission tomography (TOF-PET) and high energy physics are setting unmatched goals in the 10 ps range. Recently it was shown that high frequency (HF) readout of SiPMs significantly improves the measured single photon time resolution (SPTR), allowing to evaluate the intrinsic performance of large area devices; e.g. FBK NUV-HD SiPMs of [Formula: see text] mm2 area and 40 [Formula: see text]m single photon avalanche diode (SPAD) size achieve 90 ps FWHM. In TOF-PET such readout allows to lower the leading edge detection threshold, so that the fastest photons produced in the crystal can be utilized. This is of utmost importance if a high SPTR and prompt Cherenkov light generated by the hot-recoil electron upon 511 keV photo-absorption should improve timing. This paper shows that high-frequency bipolar transistor readout of state-of-the-art SiPMs coupled to high-performance scintillators can substantially improve the best achievable coincidence time resolution (CTR) in TOF-PET. In this context a CTR of 158 [Formula: see text] 3 ps FWHM with [Formula: see text] mm3 BGO crystals coupled to FBK SiPMs is achieved. This faint Cherenkov signal is as well present in standard LSO scintillators, which together with low SPTR values (<90 ps FWHM) improves the CTR of [Formula: see text] mm3 LSO:Ce:Ca coupled to FBK NUV-HD [Formula: see text] mm2 with 25 [Formula: see text]m SPAD size to 61 [Formula: see text] 2 ps FWHM using HF-electronics, as compared to 73 [Formula: see text] 2 ps when readout by the NINO front-end ASIC. When coupling the LSO:Ce:Ca crystals to FBK NUV-HD SiPMs of [Formula: see text] mm2 and 40 [Formula: see text]m SPAD size, using HF-electronics, a CTR of even 58 [Formula: see text] 3 ps for [Formula: see text] mm3 and 98 [Formula: see text] 3 ps for [Formula: see text] mm3 is achieved. This new experimental data will allow to further discuss the timing limits in scintillator-based detectors.

The performance of a light sharing and recirculation mechanism that allows the extraction of depth of interaction (DOI) are investigated in this paper, with a particular focus on timing. In parallel, a method to optimize the coincidence time resolution (CTR) of PET detectors by use of the DOI information is proposed and tested. For these purposes, a dedicated 64-channels readout setup has been developed with intrinsic timing resolution of 16 ps FWHM. Several PET modules have been produced, based on LYSO:Ce scintillators and commercial silicon photomultiplier (SiPM) arrays, with [Formula: see text] mm2 individual SiPM size. The results show the possibility to achieve a timing resolution of 157 ps FWHM, combined with the already demonstrated spatial resolution of 1.5 mm FWHM, DOI resolution of 3 mm FWHM, and energy resolution of 9% FWHM at 511 keV, with 15 mm long crystals of section [Formula: see text] mm2 and [Formula: see text] mm2. At the same time, the extraction of the DOI coordinate has been demonstrated not to deteriorate the timing performance of the PET module.

Objective.Time-of-flight-positron emission tomography would highly benefit from a coincidence time resolution (CTR) below 100 ps: improvement in image quality and patient workflow, and reduction of delivered dose are among them. This achievement proved to be quite challenging, and many approaches have been proposed and are being investigated for this scope. One of the most recent consists in combining different materials with complementary properties (e.g. high stopping power for 511 keVγ-ray and fast timing) in a so-calledheterostructure,metascintillatorormetapixel. By exploiting a mechanism of energy sharing between the two materials, it is possible to obtain a fraction of fast events which significantly improves the overall time resolution of the system.Approach.In this work, we present the progress on this innovative technology. After a simulation study using the Geant4 toolkit, aimed at understanding the optimal configuration in terms of energy sharing, we assembled four heterostructures with alternating plates of BGO and EJ232 plastic scintillator. We fabricated heterostructures of two different sizes (3 × 3 × 3 mm3and 3 × 3 × 15 mm3), each made up of plates with two different thicknesses of plastic plates. We compared the timing of these pixels with a standard bulk BGO crystal and a structure made of only BGO plates (layeredBGO).Main results.CTR values of 239 ± 12 ps and 197 ± 10 ps FWHM were obtained for the 15 mm long heterostructures with 100µm and 200µm thick EJ232 plates (both with 100µm thick BGO plates), compared to 271 ± 14 ps and 303 ± 15 ps CTR for bulk and layered BGO, respectively.Significance.Significant improvements in timing compared to standard bulk BGO were obtained for all the configurations tested. Moreover, for the long pixels, depth of interaction (DOI) collimated measurements were also performed, allowing to validate a simple model describing light transport inside the heterostructure.

A new method for obtaining depth of interaction (DOI) information in PET detectors is presented in this study, based on sharing and redirection of scintillation light among multiple detectors, together with attenuation of light over the length of the crystals. The aim is to obtain continuous DOI encoding with single side readout, and at the same time without the need for one-to-one coupling between scintillators and detectors, allowing the development of a PET scanner with good spatial, energy and timing resolutions while keeping the complexity of the system low. A prototype module has been produced and characterized to test the proposed method, coupling a LYSO scintillator matrix to a commercial SiPMs array. Excellent crystal separation is obtained for all the scintillators in the array, light loss due to depolishing is found to be negligible, energy resolution is shown to be on average 12.7% FWHM. The mean DOI resolution achieved is 4.1 mm FWHM on a 15 mm long crystal and preliminary coincidence time resolution was estimated in 353 ps FWHM.

The double-differential production cross-section of positive pions, $d^2\sigma^{\pi^{+}}/dpd\Omega$, measured in the HARP experiment is presented. The incident particles are 8.9 GeV/c protons directed onto a beryllium target with a nominal thickness of 5% of a nuclear interaction length. The measured cross-section has a direct impact on the prediction of neutrino fluxes for the MiniBooNE and SciBooNE experiments at Fermilab. After cuts, 13 million protons on target produced about 96,000 reconstructed secondary tracks which were used in this analysis. Cross-section results are presented in the kinematic range 0.75 GeV/c < $p_{\pi}$ < 6.5 GeV/c and 30 mrad < $\theta_{\pi}$ < 210 mrad in the laboratory frame.

A precision measurement of the double-differential production cross-section, d2σπ+/dpdΩ, for pions of positive charge, performed in the HARP experiment is presented. The incident particles are protons of 12.9 GeV/c momentum impinging on an aluminium target of 5% nuclear interaction length. The measurement of this cross-section has a direct application to the calculation of the neutrino flux of the K2K experiment. After cuts, 210 000 secondary tracks reconstructed in the forward spectrometer were used in this analysis. The results are given for secondaries within a momentum range from 0.75 to 6.5 GeV/c, and within an angular range from 30 mrad to 210 mrad. The absolute normalization was performed using prescaled beam triggers counting protons on target. The overall scale of the cross-section is known to better than 6%, while the average point-to-point error is 8.2%.

Over the last years, interest in using time-of-flightbased Positron Emission Tomography (TOF-PET) systems has significantly increased.High time resolution in such PET systems is a powerful tool to improve signal to noise ratio and therefore to allow smaller exposure rates for patients as well as faster image acquisition.Improvement in coincidence time resolution (CTR) in PET systems to the level of 200 ps FWHM requires the optimization of all parameters in the photon detection chain influencing the time resolution: crystal, photodetector and readout electronics.After reviewing the factors affecting the time resolution of scintillators, we will present in this paper the light yield and CTR obtained for different scintillator types (LSO:Ce, LYSO:Ce, LGSO:Ce, LSO:Ce:0.4Ca,LuAG:Ce, LuAG:Pr) with different cross-sections, lengths and reflectors.Whereas light yield measurements were made with a classical PMT, all CTR tests were performed with Hamamatsu-MPPCs S10931-050P.The CTR measurements were based on the time-over-threshold method in a coincidence setup using the ultra fast amplifier-discriminator chip NINO and a fast oscilloscope.Strong correlations between light yield and CTR were found.Excellent results have been obtained for LYSO crystals of 2 2 10 mm and LYSO pixels of 0.75 0.75 10 mm with a CTR of 175 ps and 188 ps FWHM, respectively.Index Terms-Lutetium-aluminum garnets, lutetium-oxy-orthosilicate (LSO), multi-pixel photon counters (MPPCs), silicon photomultipliers (SiPM), time-based readout, time-over-threshold discrimination. I. INTRODUCTIONT IME of flight in PET has become, as a result of the emer- gence of fast silicon photomultipliers (SiPMs), an increasingly attractive instrument to enhance the quality of medical imaging with far reaching impacts on patient care and hospital expenditures.Furthermore, certain diagnostic methods such as novel endoscopic interventions employing PET in addition to

Metasurfaces and, in particular, metalenses have attracted large interest and enabled various applications in the near-infrared and THz regions of the spectrum. However, the metalens design in the visible range stays quite challenging due to the smaller nanostructuring scale and the limited choice of lossless CMOS-compatible materials. We develop a simple yet efficient design of a polarization-independent, broadband metalens suitable for many CMOS-compatible fabrication techniques and materials and implement it for the visible spectral range using niobium pentoxide (Nb2O5). The produced metalens demonstrates high transmittance and focusing ability as well as a large depth of focus, which makes it a promising solution for a new generation of silicon photomultiplier photodetectors with reduced fill factor impact on the performance and reduced electron–hole generation regions, which altogether potentially leads to improved photodetection efficiency and other characteristics.

The determination of the intrinsic light yield (LY <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">int</sub> ) of scintillating crystals, i.e. number of optical photons created per amount of energy deposited, constitutes a key factor in order to characterize and optimize their energy and time resolution. However, until now measurements of this quantity are affected by large uncertainties and often rely on corrections for bulk absorption and surface/edge state. The novel idea presented in this contribution is based on the confinement of the scintillation emission in the central upper part of a 10 mm cubic crystal using a 1.5 MeV electron beam with diameter of 1 mm. A black non-reflective pinhole aligned with the excitation point is used to fix the light extraction solid angle (narrower than total reflection angle), which then sets a light cone travel path through the crystal. The final number of photoelectrons detected using a Hamamatsu R2059 photomultiplier tube (PMT) was corrected for the extraction solid angle, the Fresnel reflection coefficient and quantum efficiency (QE) of the PMT. The total number of optical photons produced per energy deposited was found to be 40000 ph/MeV ± 9% (syst) ±3% (stat) for LYSO. Simulations using Geant4 were successfully compared to light output measurements of 2 × 2 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> section crystals with lengths of 5-30 mm, in order to validate the light transport model and set a limit on Light Transfer Efficiency estimations.

We present the results of the first exposure of a Liquid Argon TPC to a multi-GeV neutrino beam.The data have been collected with a 50 liters ICARUS-like chamber located between the CHORUS and NOMAD experiments at the CERN West Area Neutrino Facility (WANF).We discuss both the instrumental performance of the detector and its capability to identify and reconstruct low-multiplicity neutrino interactions.

In the last 10 years, a new way of doing science is spreading in the world thank to the development of virtual research communities across many geographic and administrative boundaries. A virtual research community is a widely dispersed group of researchers and associated scientific instruments working together in a common virtual environment. This new kind of scientific environment, usually addressed as a “collaboratory”, is based on the availability of high-speed networks and broadband access, advanced virtual tools and Grid-middleware technologies which, altogether, are the elements of the e-Infrastructures. The European Commission has heavily invested in promoting this new way of collaboration among scientists funding several international projects with the aim of creating e-Infrastructures to enable the European Research Area and connect the European researchers with their colleagues based in Africa, Asia and Latin America. In this paper we describe the actual status of these e-Infrastructures and present a complete picture of the virtual research communities currently using them. Information on the scientific domains and on the applications supported are provided together with their geographic distribution.

The EndoTOFPET-US project aims to develop a multimodal detector to foster the development of new biomarkers for prostate and pancreatic tumors. The detector will consist of two main components: an external plate, and a PET extension to an endoscopic ultrasound probe. The external plate is an array of LYSO crystals read out by silicon photomultipliers (SiPM) coupled to an Application Specific Integrated Circuit (ASIC). The internal probe will be an highly integrated and miniaturized detector made of LYSO crystals read out by a fully digital SiPM featuring photosensor elements and digital readout in the same chip. The position and orientation of the two detectors will be tracked with respect to the patient to allow the fusion of the metabolic image from the PET and the anatomic image from the ultrasound probe in the time frame of the medical procedure. The fused information can guide further interventions of the organ, such as biopsy or in vivo confocal microscopy.

The construction and performance of a large area scintillator-based time-of-flight detector for the HARP experiment at CERN are reported. An intrinsic counter time resolution of ∼160 ps was achieved. The precision on the time calibration and monitoring of the detector was maintained at better than 100 ps by using dedicated cosmic rays runs, a fast laser-based system and calibrations with beam particles. The detector was operated on the T9 PS beamline during 2001 and 2002. A time-of-flight resolution of ∼200 ps was obtained, providing π/p discrimination at more than 3σ up to 4.0 GeV/c momentum.

A measurement of the double-differential cross-section for the production of charged pions in proton--tantalum collisions emitted at large angles from the incoming beam direction is presented. The data were taken in 2002 with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 \GeVc to 12 \GeVc hitting a tantalum target with a thickness of 5% of a nuclear interaction length. The angular and momentum range covered by the experiment ($100 \MeVc \le p < 800 \MeVc$ and $0.35 \rad \le \theta <2.15 \rad$) is of particular importance for the design of a neutrino factory. The produced particles were detected using a small-radius cylindrical time projection chamber (TPC) placed in a solenoidal magnet. Track recognition, momentum determination and particle identification were all performed based on the measurements made with the TPC. An elaborate system of detectors in the beam line ensured the identification of the incident particles. Results are shown for the double-differential cross-sections ${{\mathrm{d}^2 \sigma}} / {{\mathrm{d}p\mathrm{d}\theta}}$ at four incident proton beam momenta (3 \GeVc, 5 \GeVc, 8 \GeVc and 12 \GeVc). In addition, the pion yields within the acceptance of typical neutrino factory designs are shown as a function of beam momentum. The measurement of these yields within a single experiment eliminates most systematic errors in the comparison between rates at different beam momenta and between positive and negative pion production.

The breakneck evolution of modern programming languages aggravates the development of deductive verification tools, which struggle to timely and fully support all new language features. To address this challenge, we present ByteBack: a verification technique that works on Java bytecode. Compared to high-level languages, intermediate representations such as bytecode offer a much more limited and stable set of features; hence, they may help decouple the verification process from changes in the source-level language. ByteBack offers a library to specify functional correctness properties at the level of the source code, so that the bytecode is only used as an intermediate representation that the end user does not need to work with. Then, ByteBack reconstructs some of the information about types and expressions that is erased during compilation into bytecode but is necessary to correctly perform verification. Our experiments with an implementation of ByteBack demonstrate that it can successfully verify bytecode compiled from different versions of Java, and including several modern language features that even state-of-the-art Java verifiers (such as KeY and OpenJML) do not directly support—thus revealing how ByteBack 's approach can help keep up verification technology with language evolution.

A method to determine the running of alpha from a measurement of small-angle Bhabha scattering is proposed and worked out. The method is suited to high statistics experiments at e+e- colliders, which are equipped with luminometers in the appropriate angular region. A new simulation code predicting small-angle Bhabha scattering is also presented

A measurement of the double-differential π± production cross-section in proton–carbon, proton–copper and proton–tin collisions in the range of pion momentum 100 MeV/c≤p<800 MeV/c and angle 0.35 rad≤θ<2.15 rad is presented. The data were taken with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 GeV/c to 12 GeV/c hitting a target with a thickness of 5% of a nuclear interaction length. The tracking and identification of the produced particles was done using a small-radius cylindrical time projection chamber (TPC) placed in a solenoidal magnet. An elaborate system of detectors in the beam line ensured the identification of the incident particles. Results are shown for the double-differential cross-sections d2σ/dpdθ at four incident proton beam momenta (3 GeV/c, 5 GeV/c, 8 GeV/c and 12 GeV/c).

We have developed a Time-of-flight high resolution and commercially viable detector module for the application in small PET scanners. A new approach to depth of interaction (DOI) encoding with low complexity for a pixelated crystal array using a single side readout and 4-to-1 coupling between scintillators and photodetectors was investigated. In this method the DOI information is estimated using the light sharing technique. The detector module is a 1.53×1.53×15 mm3 matrix of 8×8 LYSO scintillator with lateral surfaces optically depolished separated by reflective foils. The crystal array is optically coupled to 4×4 silicon photomultipliers (SiPM) array and readout by a high performance front-end ASIC with TDC capability (50 ps time binning). The results show an excellent crystal identification for all the scintillators in the matrix, a timing resolution of 530 ps, an average DOI resolution of 5.17 mm FWHM and an average energy resolution of 18.29% FWHM.

The digital silicon photomultiplier (SiPM) has been commercialised by Philips as an innovative technology compared to analog silicon photomultiplier devices. The Philips digital SiPM, has a pair of time to digital converters (TDCs) connected to 12800 single photon avalanche diodes (SPADs). Detailed measurements were performed to understand the low photon time response of the Philips digital SiPM. The single photon time resolution (SPTR) of every single SPAD in a pixel consisting of 3200 SPADs was measured and an average value of 85 ps full width at half maximum (FWHM) was observed. Each SPAD sends the signal to the TDC with different signal propagation time, resulting in a so called trigger network skew. This distribution of the trigger network skew for a pixel (3200 SPADs) has been measured and a variation of 50 ps FWHM was extracted. The SPTR of the whole pixel is the combination of SPAD jitter, trigger network skew, and the SPAD non-uniformity. The SPTR of a complete pixel was 103 ps FWHM at 3.3 V above breakdown voltage. Further, the effect of the crosstalk at a low photon level has been studied, with the two photon time resolution degrading if the events are a combination of detected (true) photons and crosstalk events. Finally, the time response to multiple photons was investigated.

Parallax error is a common issue in high-resolution preclinical positron emission tomography (PET) scanners as well as in clinical scanners that have a long axial field of view (FOV), which increases estimation uncertainty of the annihilation position and therefore degrades the spatial resolution. A way to address this issue is depth-of-interaction (DOI) estimation. In this work we propose two machine learning-based algorithms, a dense and a convolutional neural network (NN), as well as a multiple linear regression (MLR)-based method to estimate DOI in depolished PET detector arrays with single-sided readout. The algorithms were tested on an 8× 8 array of 1.53× 1.53× 15 mm3 crystals and a 4× 4 array of 3.1× 3.1× 15 mm3 crystals, both made of Ce:LYSO scintillators and coupled to a 4× 4 array of 3× 3 mm3 silicon photomultipliers (SiPMs). Using the conventional linear DOI estimation method resulted in an average DOI resolution of 3.76 mm and 3.51 mm FWHM for the 8× 8 and the 4× 4 arrays, respectively. Application of MLR outperformed the conventional method with average DOI resolutions of 3.25 mm and 3.33 mm FWHM, respectively. Using the machine learning approaches further improved the DOI resolution, to an average DOI resolution of 2.99 mm and 3.14 mm FWHM, respectively, and additionally improved the uniformity of the DOI resolution in both arrays. Lastly, preliminary results obtained by using only a section of the crystal array for training showed that the NN-based methods could be used to reduce the number of calibration steps required for each detector array.

A cluster of multi-anode photomultiplier tubes (MaPMTs) equipped with focusing lenses in front of the tubes was tested in a prototype ring imaging Cherenkov (RICH) detector in a charged particle beam. The readout electronics were capable of capturing the data at 40 MHz. The effects due to charged particles and magnetic field on the MaPMT performance were also studied. The results are used to evaluate the MaPMT as a possible photodetector for the LHCb RICH detectors.

Silicon photomultipliers (SiPMs) and scintillators are often arranged in the shape of arrays in Positron Emission Tomography (PET) systems. Digital SiPMs provide signal readout in single photon avalanche diode (SPAD) level. From the photon count rate measurement of each SPAD cell of digital SiPM, we found that the output scintillating photons distribute in an area larger than the scintillator physical coupling area. Taking advantage of the possibility to enable/disable individual cells of the digital SiPM, a group of Lutetium-yttrium oxyorthosilicate (LYSO) crystals with different dimensions coupled to a digital SiPM was used to study the influence of using different SiPM active area on the number of photons detected, energy resolution and coincidence time resolution (CTR). For the same crystal coupled to the digital SiPM, the larger the active area of digital SiPM, the higher the number of photons detected. The larger active area of the digital SiPM also results in a better energy resolution after saturation correction. The best energy resolution full width half maximum (FWHM) obtained for the 2 × 2 × 5 mm3, 2 × 2 × 10 mm3, 2 × 2 × 15 mm3, 2 × 2 × 20 mm3 LYSO crystals was 10.7%, 11.6%, 12.1%, 12.5%, respectively. For crystals with different cross sections coupled to the digital SiPM, we found that the larger the cross section of coupling area, the more photons were detected and thus a better energy resolution was obtained. The CTR of crystals fully wrapped with Teflon or without wrapping was measured by positioning two identical crystals facing each other. A larger area of digital SiPM improves the CTR and the CTR reaches the plateau when the active area is larger than 2.2 × 2.2 mm2 with both two configurations of wrapping. The best CTR value for the 2 × 2 × 5 mm3, 2 × 2 × 10 mm3, 2 × 2 × 15 mm3, 2 × 2 × 20 mm3 LYSO crystals was 128.9 ps, 148.4 ps, 171.6 ps, 177.9 ps, respectively. The measurements performed lead us to conclude that optimising the coupling between crystal and SiPM to extract more scintillating photons can improve the energy resolution and CTR.

A precise calibration and monitoring system has been developed for the HARP experiment scintillator-based time of flight system. An Nd-YAG laser with passive Q-switch and active/passive mode-locking and a custom-made laser light injection system based on a bundle of IR monomode optical fibers were used. The laser pulse timing was provided by a novel ultrafast InGaAs MSM photodiode, with 30 ps risetime. Experience over a several month data taking period in 2001 and 2002 shows that drifts in timing down to about 70 ps can be traced.

In small animal and organ dedicated PET scanners, the knowledge of depth of interaction (DOI) of the gamma ray along the main axis of the scintillator is a fundamental information in order to avoid parallax error and to achieve high performances in terms of spatial resolution. Recently we developed a new method to obtain the DOI function for a single side readout PET module, recirculating the scintillation light in the matrix by means of a mirror placed on top of the module. In a complete PET scanner, periodical DOI calibrations have to be performed to prevent time dependent miscalibrations and performance degradations. The current DOI calibration relies on a coincidence system between the module and an external scintillator to provide a priori the DOI information and it is clearly not feasible in a real system without unpractical disassemblies of the scanner. In this paper we develop instead a fast and precise calibration method based on uniform irradiation of the scintillators. Three irradiation modalities are presented, in particular one where the source is placed on top of the module, one with the source placed on one side of the module and one that exploits the internal radioactivity of the scintillator. The three different procedures are evaluated and the calibration method is validated by comparing the information provided by the coincidence setup.

In the search for new materials and technologies to push the timing performances of TOF-PET detectors, it is important to have a model capable of predicting the coincidence time resolution (CTR) of the system to be implemented. While for bulk, standard scintillators a model that takes into account the intrinsic properties of the material (and the characteristics of the photodetector) is already well established, it has never been experimentally validated for composite structures. As heterostructured scintillators – i.e. the combination of two or more materials with complementary properties – are emerging as a possible solution to the conflict between fast timing and high detection efficiency for TOF-PET detectors, such validation becomes necessary. In this work, by using a time-correlated single photon counting (TCSPC) setup capable of simultaneously recording the TCSPC signal and the scintillation pulse on an event-by-event basis, we experimentally demonstrate that the scintillation kinetics of heterostructures can be modeled as a linear combination of the scintillation kinetics of the materials that constitute the heterostructure itself. Based on these results, we develop an extension of well-established CTR analytical model which can be applied to heterostructured scintillators.

The Small angle TIle Calorimeter (STIC) provides calorimetric coverage in the very forward region of the DELPHI experiment at the CERN LEP collider. The structure of the calorimeters, built with a so-called “shashlik” technique, gives a perfectly hermetic calorimeter and still allows for the insertion of tracking detectors within the sampling structure to measure the direction of the showering particle. A charged-particle veto system, composed of two scintillator layers, makes it possible to trigger on single photon events and provides e–γ separation. Results are presented from the extensive studies of these detectors in the CERN testbeams prior of installation and of the detector performance at LEP.

The particle identification (PID) methods used for the calculation of secondary pion yields with the HARP forward spectrometer are presented. Information from time of flight and Cherenkov detectors is combined using likelihood techniques. The efficiencies and purities associated with the different PID selection criteria are obtained from the data. For the proton–aluminium interactions at 12.9 GeV/c incident momentum, the PID efficiencies for positive pions are 86% in the momentum range below 2 GeV/c, 92% between 2 and 3 GeV/c and 98% in the momentum range above 3 GeV/c. The purity of the selection is better than 92% for all momenta. Special emphasis has been put on understanding the main error sources. The final PID uncertainty on the pion yield is 3.3%.

Pulsed Electric Fields (PEF) technology is a promising non-thermal processing method for inactivation of microorganisms. A small PEF bench system able to treat a 0.4 ml static liquid volume has been built and tested at the laboratories of the Università del Piemonte Orientale in Alessandria, Italy. The technique used to produce the required fields consists of charging high voltage cables of various lengths and subsequently discharge them on a cylindrical cell. The pulse intensity can be adjusted to reach a maximum electric field in the cell of about 35 kV/cm and the pulse frequency can reach 10 Hz. We describe the PEF system in some detail and, as a benchmark of its performances, we report preliminary results obtained on Escherichia coli (ATCC 25922) at 109 Cfu/ml concentration suspended in a McIlvaine buffer (pH 7.2).

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Positron Emission Tomography (PET) scanners require high performances in term of spatial resolution and sensitivity to allow early detection of cancer masses. In small animal and organ dedicated PET scanners the Depth of Interaction (DOI) information has to be obtained to avoid parallax errors and to reconstruct high resolution images. In the whole body PET, the DOI information can be useful to correct for the time jitter of the optical photons along the main axis of the scintillator, improving the time performances. In this work we present the development of PET module designed to reach high performance as compared to the current scanners while keeping the complexity of the system reasonably low. The module presented is based on a 64 LYSO (Lutetium-yttrium oxyorthosilicate) crystals matrix and on a 4×4 MPPC (Multi Pixels Photon Counter) array as detector in a 4 to 1 coupling between the crystals and the detector and a single side readout. The lateral surfaces of the crystals are optically treated to be unpolished. The DOI and the energy resolution of the PET module are presented and a fast method to obtain the DOI calibration is discussed.

The detection of cancer in its early stage is known to be of key importance to improve cancer treatment and thus reduces mortality and cost. As a consequence, this has led to a growing interest in developing high performance multimodal imaging devices capable of detecting smallest possible tumors. As part of this approach, the EndoTOFPET-US project, a European FP7 program, aims to develop new biomarkers for the pancreatic and prostatic cancers. Testing such markers requires improving the detection of smaller tumors and performing biopsies based on combined anatomic and functional image information. The detection of small tumors using PET detectors also entails high sensitivity and high spatial resolution. One particular objective of this project is to develop a prototype of a novel bi-modal, TOFPET and ultrasound, endoscope for the detection of early stage pancreatic or prostatic tumors. It consists of two separate PET detectors, one a 23×23cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> total area external plate (placed outside the body) with 256 arrays of 4×4 LYSO crystals of 3.1×3.1×15mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> size coupled to Hamamatsu MPPC monolithic arrays of 3×3mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> single sensors, and an internal (endoscopic) PET probe that consists of an array of 9×18 L YSO fibers with a size of 0.71×0.71×10mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> coupled to a fully digital SiPM [1,2]. This PET tip is attached to a conventional ultrasound endoscope. Electronic 'collimation' provided by time of flight measurements between the external PET plate and the internal PET probe allows the necessary sensitivity to efficiently reject background. This, however, requires a coincidence time resolution of 200ps FWHM. High spatial resolution of ≤ 1mm can be achieved due to the very high granularity of the endoscopic PET probe consisting of crystal pixel sizes of less than 800μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> section. In this paper we present the design and current development of the PET modules for the endoscopic probe as well as their performance in terms of light yield (LY) and coincidence time resolution (CTR) made with different prototypes.

The extraction of scintillation light from an inorganic scintillator is one of the major bottlenecks in time-of-flight positron emission tomography (ToF-PET) because it directly affects the energy and time resolution of the gamma detector. To increase the light extraction efficiency, we use photonic crystal slabs (PCS), defined as thin dielectric layers structured with a 2-D, or 3-D, periodic pattern. A higher light output, combined with a reduction of the average path length traversed by the photons in the crystal before extraction, leads to a more precise evaluation of the particle time detection. This also implies a better coincidence time resolution (CTR). These improvements translate to ToF-PET reconstructed images with a higher signal-to-noise ratio and lead to more accurate diagnoses, faster exams, and possibly a reduced patient radiation dose. In this paper, we present the results obtained using lutetium-yttrium oxyorthosilicate, Lu2(1-x)Y2xSiO5 samples patterned with nanoimprinted PCS. Comparative light yield (LY) measurements show an improvement of a factor 1.68 for a naked configuration, whereas CTR goes from 535 to 315 ps.

ClearPEM-Sonic is an innovative imaging device specifically developed for breast cancer. The possibility to work in PEM-Ultrasound multimodality allows to obtain metabolic and morphological information increasing the specificity of the exam. The ClearPEM detector is developed to maximize the sensitivity and the spatial resolution as compared to Whole-Body PET scanners. It is coupled with a 3D ultrasound system, the SuperSonic Imagine Aixplorer that improves the specificity of the exam by providing a tissue elasticity map. This work describes the ClearPEM-Sonic project focusing on the technological developments it has required, the technical merits (and limits) and the first multimodal images acquired on a dedicated phantom. It finally presents selected clinical case studies that confirm the value of PEM information.

This paper describes the characterization of crystal matrices and silicon photomultiplier arrays for a novel Positron Emission Tomography (PET) detector, namely the external plate of the EndoTOFPET-US system. The EndoTOFPET-US collaboration aims to integrate Time-Of-Flight PET with ultrasound endoscopy in a novel multimodal device, capable to support the development of new biomarkers for prostate and pancreatic tumors. The detector consists in two parts: a PET head mounted on an ultrasound probe and an external PET plate. The challenging goal of 1 mm spatial resolution for the PET image requires a detector with small crystal size, and therefore high channel density: 4096 LYSO crystals individually readout by Silicon Photomultipliers (SiPM) make up the external plate. The quality and properties of these components must be assessed before the assembly. The dark count rate, gain, breakdown voltage and correlated noise of the SiPMs are measured, while the LYSO crystals are evaluated in terms of light yield and energy resolution. In order to effectively reduce the noise in the PET image, high time resolution for the gamma detection is mandatory. The Coincidence Time Resolution (CTR) of all the SiPMs assembled with crystals is measured, and results show a value close to the demanding goal of 200 ps FWHM. The light output is evaluated for every channel for a preliminary detector calibration, showing an average of about 1800 pixels fired on the SiPM for a 511 keV interaction. Finally, the average energy resolution at 511 keV is about 13 %, enough for effective Compton rejection.

The demand for detectors with a time resolution below 100 ps is at the center of research in different fields, from high energy physics to medical imaging. In recent years, interest has grown in nanomaterials that, benefiting from quantum confinement effects, can feature ultra-fast scintillation kinetics and tunable emission. However, standard characterization methods for scintillation properties–relying on radiation sources with an energy range of several hundreds of keV–are not suitable for these materials due to their low stopping power, leading to a slowdown of this R&amp;amp;D line. We present a new method to characterize the time resolution and light output of scintillating materials, using a soft (0–40 keV energy) pulsed X-ray source and optimized high-frequency readout electronics. First, we validated the proposed method using standard scintillators. Then, we also demonstrated the feasibility to measure the time resolution and get an insight into the light output of nanomaterials (InGaN/GaN multi-quantum well and CsPbBr 3 perovskite). This technique is, therefore, proposed as a fundamental tool for characterization of nanomaterials and, more in general, of materials with low stopping power to better guide their development. Moreover, it opens the way to new applications where fast X-ray detectors are requested, such as time-of-flight X-ray imaging.

The CMS Electromagnetic crystal Calorimeter (ECAL) must be precisely inter-calibrated if its full potential performance is to be realized.In this note, a detailed Monte Carlo study of in-situ intercalibration of the ECAL crystals using isolated electrons is described.The achievable precision depends on the quality and number of available electrons per crystal.This in turn depends upon the position of the crystals and the corresponding thickness of material in front of the ECAL.

This paper presents the development of an Internet-of-Things (IoT) Cooperative System (IoT-CS) based on local Event-Driven response. After introducing IoT basic concepts and most common computational schemes (with particular attention on the differences between Cloud, Fog, and Cooperative computing paradigms), an innovative scheme for IoT will be presented. Thanks to the introduction and development of several intermediate layers between the sensor network and the Cloud, the hereby proposed system allows overcoming most of the problems of the state-of-the-art paradigms. In order to validate the proposed solution the most relevant aspects of this implementations will be presented.

For the physics program of the CMS experiment at the LHC to be carried out successfully, excellent electromagnetic calorimetry is required. Given the thermal properties of CMS ECAL, keeping the constant term of the energy resolution below 0.5% needs its temperature to be stabilized at 18/spl deg/C within 0.05/spl deg/C. A prototype module of ECAL with the final cooling system has been tested at CERN to check its integration with the read-out electronics and verify that it complies with the severe thermal requirements. The thermal performance of the cooling system is reported here.

The extensive use of scintillating crystals in medical imaging field is generating a growing interest in Monte Carlo simulation of light transportation and photon collection inside inorganic materials. The critical parameters under study which affect the performance of medical devices are the number of photons collected per unit of energy deposited (light yield), the energy resolution, the effect of dimensions and surface state and the time profiles of the scintillation process. Moreover, most of the crystals used in Positron Emission Tomography (PET) applications, such as lutetium orthosilicate (LSO), are anisotropic, potentially influencing the performances. In particular the recent development of time of flight PET scanners requires a detailed knowledge of timing profiles of the crystals in terms of time of arrival of single photons, scintillation rise and decay times. Furthermore the effort towards innovative endoscopic probe for PET examination requires an extensive analysis of the effect of the dimensions of small crystals on the parameters mentioned. Different simulation tools are employed nowadays for detailed studies of interaction of particles in inorganic materials and tracing of the scintillating photons produced. In particular our attention is focused on SLitrani and Geant4. SLitrani is a general purpose Monte-Carlo program simulating light propagation, developed for high energy experiments, in particular in the frame of the CMS experiment at LHC. Its most advanced characteristics is the ability to handle anisotropic materials, thus retaining a quite general application. Geant4 is a general purpose Monte Carlo toolkit widely used in high energy physics, astroparticle physics and nuclear physics, which includes an optical physics process category to simulate the production and propagation of light. In the frame of the Crystal Clear Collaboration, we have been developing and testing innovative scintillation technologies for medical applications, and with this respect Monte Carlo techniques are powerful tools for investigating the performances of our setups. In order to validate and accurately describe the inorganic crystals developed we have been comparing the performances of the SLitrani and Geant4 frameworks, and started a preliminary comparison with experimental results obtained in our laboratories.

We present the results obtained by exposing samples of silica aerogel of different thickness and optical properties to pion and proton beams with momenta between 6 and 10 GeV/c in the PS testbeam facility at CERN. Two large diameter pad hybrid photodiodes with 2048 channels, produced at CERN, have been used as photon detectors. Separate Cherenkov rings produced by the different particles were reconstructed obtaining pion/proton separation over the whole momentum range. The number of photoelectrons was measured as a function of aerogel thickness and was found to be in agreement with Monte Carlo expectations.

The aim of the EndoTOFPET-US collaboration is to develop a multi-modal imaging tool combining ultrasound with time-of-flight positron emission tomography into an endoscopic imaging device. One of the objectives of this scanner is to reach a coincidence time resolution of 200 ps full width at half maximum. The external detector is constructed with 256 matrices of 4×4 lutetium–yttrium oxyorthosilicate scintillating crystals, each with a size of 3.5×3.5×15mm3, coupled to 256 Hamamatsu TSV multi-pixel photon counter arrays (S12643-050CN). A full characterisation of these arrays has been performed in order to assure the quality of the arrays prior to the gluing to the crystal matrices. The breakdown voltage, dark count rate and single photon time resolution have been measured both at DESY and CERN. After this characterisation, the crystal matrices were glued to the multi-pixel photon counter arrays. The coincidence time resolution of each module has been measured at CERN using an ultra-fast amplifier-discriminator as the reference readout ASIC. Results of the characterisation of multi-pixel photon counter arrays and the crystal modules are presented here.

A prototype for the new DELPHI luminosity monitor has been built and tested. The scope of this prototype is to measure the response of the proposed calorimeter in the region which is most critical for the luminosity measurement, i.e., at the inner edge of the acceptance. The aim of the new luminosity monitor is to measure the LEP (Large Electron Position Collider) luminosity with per mill systematic uncertainty. This requires experimental biases at the level of 50 mu m or less in the definition of the fiducial volume. The technique used ensures good energy resolution and high spatial uniformity. With the prototype, better than 2% uniformity in response and an energy resolution of 3% at 45 GeV have been achieved.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The structure of a shashlik calorimeter allows the insertion of tracking detectors within the longitudinal sampling to improve the accuracy in the determination of the direction of the showering particle and the eπ separation ability. The new forward calorimeter of the DELPHI detector has been equipped with two planes of silicon pad detectors respectively after 4 and 7.4 radiation lengths. The novelty of these silicon detectors is that to cope with the shashlik readout fibers, they had to incorporate 1.4 mm holes every cm2. The detector consists of circular strips with a radial pitch of 1.7 mm and an angular granularity of 22.5°, read out by means of the MX4 preamplifier. The preamplifier is located at 35 cm from the silicon detector and the signal is carried by Kapton cables bonded to the detector. The matching to the MX4 input pitch of 44 μm was made by a specially developed fanin hybrid.

E-infrastructures are becoming in Europe and in other regions of the world standard platforms to support e-Science and foster virtual research communities. This chapter provides the reader with a comprehensive view of the developments of e-Infrastructures in China, India, Asia-Pacific, Mediterranean, Middle-East, Sub-Saharan Africa, South-East Europe and Latin America and with an outlook on the very important issue of their long term sustainability.

A program's exceptional behavior can substantially complicate its control flow, and hence accurately reasoning about the program's correctness. On the other hand, formally verifying realistic programs is likely to involve exceptions—a ubiquitous feature in modern programming languages. In this paper, we present a novel approach to verify the exceptional behavior of Java programs, which extends our previous work on ByteBack. ByteBack works on a program's bytecode, while providing means to specify the intended behavior at the source-code level; this approach sets ByteBack apart from most state-of-the-art verifiers that target source code. To explicitly model a program's exceptional behavior in a way that is amenable to formal reasoning, we introduce Vimp: a high-level bytecode representation that extends the Soot framework's Grimp with verification-oriented features, thus serving as an intermediate layer between bytecode and the Boogie intermediate verification language. Working on bytecode through this intermediate layer brings flexibility and adaptability to new language versions and variants: as our experiments demonstrate, ByteBack can verify programs involving exceptional behavior in all versions of Java, as well as in Scala and Kotlin (two other popular JVM languages).

Heterostructured scintillators are gaining ground as a possible solution to the trade-off between the high sensitivity and fast timing of detectors for time-of-flight positron emission tomography (TOF-PET). They consist of stacks of alternating layers of two materials with complementary properties: high stopping power and ultrafast timing. The fast emitter improves the timing performance of the detector. However, layering is a limiting factor for the best achievable time resolution, as it worsens light transport. This effect can be mitigated by increasing light collection and retrieving the depth-of-interaction (DOI) information. The double-sided readout can meet both requirements.In this work, we use high-frequency electronics in a double-sided readout configuration with a 3x3x20mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> BGO&EJ232 heterostructure. By selecting the photopeak events, we were able to achieve a DOI resolution of 6.4±0.5mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The improvement in coincidence time resolution (CTR), compared to the single-sided readout, is 18% for all photopeak events (from 256±8 to 211±6ps) and 36% when considering only photopeak events that share the energy between the two materials (from 200±6 to 128±4ps).

This paper presents the complete design, the hardware implementation, and the experimental validation of a distributed intelligence Internet-of-Things (IoT) system, based on Heterogeneous Event-Driven Edge Mesh Architecture (HED-EMA). The latter differentiates from most common computational schemes (i.e. Cloud computing) since it distributes intelligence at local level. The proposed IoT system has a bottom-up structure composed by three main layers: Sensing/Actuation, Edge, and Cloud. It exploits commercial devices, specifically programmed and configured in order to operate within the IoT paradigm. Aiming to validate the proposed system, experimental data coming from two specific setups (home-setup and automotive-setup) will be presented and discussed. Data are extracted by a distributed sensors network, real-time collected, and processed. The lower response time compared to standard Cloud architectures and the whole system power consumption reduction are then demonstrated.

Modern PET detectors rely on fast and accurate timing performances in order to provide improved lesion detectability and reduced patient scan times. Optimizing the coincidence timing resolution (CTR) is an important facet that helps achieve high PET detector performance. On the way of improving the CTR to sub-100 ps, and ultimately to 10 ps, research on all detector components is necessary, including the scintillator, photodetector and electronic readout. The digital SiPM, where each single photon avalanche diode (SPAD) is connected to its own readout, has gained a lot of attention as the ultimate photodetector. However, extended power consumption and the enormous number of channels makes the realization challenging. Hence, in this contribution we investigate a semidigital approach, realized with the pixelation of an analog SiPM. We tested a single SiPM from HPK (S13360-6075V) compared to a 2x2 SiPM array (S13361-3075N-02) and a 3x3 SiPM array (S13361-2075N-03) with a 6x6x3 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> crystal and a 6x6x20 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> crystal, readout by our in-house developed acquisition system employing NINO as front-end ASIC. Preliminary results show that the single SiPM array routinely performed better than the pixelated arrays while reading each of the individual SiPMs independently, correcting for time walk and properly combining the time-stamps. A minimum CTR value of 117 ± 53ps wascrystal achieved using the single SiPM array with the 6x6x3 mm for the NINO electronics readout. Using a HF bipolar transistor readout, a similar trend was observed, with a minimum CTR of 116 ± 5 ps for the single array and the 6x6x3 mm3crystal. A-priori this result is surprising because, due to the lower capacitance of the smaller SiPMs, electronic noise should be reduced leading to better timing. The most probable explanation for this counter-intuitive result is the 4 or 9 times lower number of scintillation photons generating each SiPM signal, which together with correlated noise sources (optical cross-talk) leads to excess noise, especially in the applied leading edge time discrimination.

A novel technique for longitudinal segmentation of shashlik calorimeters has been tested in the CERN West Area beam facility. A 25 tower very fine samplings e.m. calorimeter has been built with vacuum photodiodes inserted in the first 8 radiation lengths to sample the initial development of the shower. Results concerning energy resolution, impact point reconstruction and electron/pion separation are reported.

We present the results obtained by testing in a beam sample of silica aerogel which is foreseen as one of the radiators for the Ring Imaging Cherenkov counter of LHCb. Pion and proton beams with momenta ranging from 6 to 10 GeV/c traversed different thickness of aerogel. Two large diameter (12 cm) Hybrid Photodiodes with 2048 channels, produced at CERN, were used as photodetectors. The number of photoelectrons and the radius of the Cherenkov rings allowed pion–proton separation over the whole considered momentum range.

Two techniques for longitudinal segmentation of shashlik calorimeters are proposed. Results concerning energy resolution and e/π separation are reported.

A calibration and monitoring system for the Harp experiment scintillator-based time of flight system has been developed, by using an Nd-YAG laser with passive Q-switch and active/passive mode-locking and a custom made laser light injection system based on it bundle of IR monomode optical fibers. For the laser pulse timing a novel ultrafast InGaAs MSM photodiode, with 30 ps risetime, has been used. Experience over a several months data taking period in 2001 and 2002 shows that drifts in timing down to about 70 ps can be traced.

E-infrastructures are becoming in Europe and in other regions of the world standard platforms to support e-Science and foster virtual research communities. This chapter provides the reader with a comprehensive view of the developments of e-Infrastructures in China, India, Asia-Pacific, Mediterranean, Middle-East, Sub-Saharan Africa, South-East Europe and Latin America and with an outlook on the very important issue of their long term sustainability.

This paper describes the characterization of crystal matrices and silicon photomultiplier arrays for a novel Positron Emission Tomography (PET) detector, namely the external plate of the EndoTOFPET-US system. The EndoTOFPET-US collaboration aims to integrate Time-Of-Flight PET with ultrasound endoscopy in a novel multimodal device, capable to support the development of new biomarkers for prostate and pancreatic tumors. The detector consists in two parts: a PET head mounted on an ultrasound probe and an external PET plate. The challenging goal of 1 mm spatial resolution for the PET image requires a detector with small crystal size, and therefore high channel density: 4096 LYSO crystals individually readout by Silicon Photomultipliers (SiPM) make up the external plate. The quality and properties of these components must be assessed before the assembly. The dark count rate, gain, breakdown voltage and correlated noise of the SiPMs are measured, while the LYSO crystals are evaluated in terms of light yield and energy resolution. In order to effectively reduce the noise in the PET image, high time resolution for the gamma detection is mandatory. The Coincidence Time Resolution (CTR) of all the SiPMs assembled with crystals is measured, and results show a value close to the demanding goal of 200 ps FWHM. The light output is evaluated for every channel for a preliminary detector calibration, showing an average of about 1800 pixels fired on the SiPM for a 511 keV interaction. Finally, the average energy resolution at 511 keV is about 13 %, enough for effective Compton rejection.

The CMS electromagnetic calorimeter is a very challenging detector which aims at providing high precision calorimetry in the Large Hadron Collider (LHC) environment. It consists of about 75,000 PbWO4 crystals that have to operate reliably for at least 10 years, in a high radiation environment. The readout electronics must sustain high data rates. In the last year new radiation hard readout electronics and a new cooling system were adopted and successfully tested. A large effort was also devoted to test the first modules performance in an electron beam, to validate the monitoring system and the calibration strategy. With more than one-third of the barrel modules produced, the calorimeter is well into its construction phase. An overview of the calorimeter design and of its construction status will be given, as well as the predicted performance at the LHC.

A preliminary analysis of the data collected in 2000 with the DELPHI detector at e + e collision energy above 200 GeV was performed in order to extract the hadronic and leptonic cross-sections, the leptonic forward-backward asymmetries and the polarization of -leptons. Various interpretations of the results including possible physics beyond the Standard Model, are presented. In particular, the data are used to investigate potential contact interactions and for Z 0 bosons, and for the eects of gravity in large extra dimensions.

The calibration and monitoring system constructed for the HARP experiment scintillator-based time of flight system is described. It is based on a Nd-Yag laser with passive Q-switch and active/passive mode-locking, with a custom made laser light injection system based on a bundle of IR monomode optical fibers. A novel ultrafast InGaAs MSM photodiode, with 30 ps risetime, has been used for the laser pulse timing . The first results from the 2001–2002 data taking are presented, showing that drifts in timing down to about 70 ps can be traced.

This paper describes the characterization of crystal matrices and silicon photomultiplier arrays for a novel Positron Emission Tomography (PET) detector, namely the external plate of the EndoTOFPET-US system. The EndoTOFPET-US collaboration aims to integrate Time-Of-Flight PET with ultrasound endoscopy in a novel multimodal device, capable to support the development of new biomarkers for prostate and pancreatic tumors. The detector consists in two parts: a PET head mounted on an ultrasound probe and an external PET plate. The challenging goal of 1 mm spatial resolution for the PET image requires a detector with small crystal size, and therefore high channel density: 4096 LYSO crystals individually readout by Silicon Photomultipliers (SiPM) make up the external plate. The quality and properties of these components must be assessed before the assembly. The dark count rate, gain, breakdown voltage and correlated noise of the SiPMs are measured, while the LYSO crystals are evaluated in terms of light yield and energy resolution. In order to effectively reduce the noise in the PET image, high time resolution for the gamma detection is mandatory. The Coincidence Time Resolution (CTR) of all the SiPMs assembled with crystals is measured, and results show a value close to the demanding goal of 200 ps FWHM. The light output is evaluated for every channel for a preliminary detector calibration, showing an average of about 1800 pixels fired on the SiPM for a 511 keV interaction. Finally, the average energy resolution at 511 keV is about 13 %, enough for effective Compton rejection.

Introduction: ClearPEM is a positron emission mammography (PEM) prototype scanner developed within the framework of the Crystal Clear Collaboration. It consists of two planar detector heads (16 × 18 cm2) mounted on a dedicated gantry that can rotate to perform breast tomographic acquisition; head distance can be adjusted to fit patient's breast that hangs out of a circular aperture in the scanner bed. Moreover, gantry can rotate to 90° in order to perform planar axillary lymph node examinations. It is equipped with 6144 LYSO:Ce crystal of 2 × 2 × 20 mm3; each side of a 32 crystal matrix is optically coupled to a 32-pixel Hamamatsu S8550 Avalanche Photo-Diode array (APDs), allowing the estimation of the Depth of Interaction information. A MLEM list-mode reconstruction algorithm is implemented.

The ClearPEM-Sonic is a multimodal system dedicated to mammography, capable of providing co-registered metabolic, anatomical and structural information through combination of positron emission tomography with ultrasound elastographic imaging. The project is aimed to improve early stage detection of breast cancer through the high-resolution and high-sensitivity metabolic information provided by PEM, and the high-resolution anatomic information from US. Further improvements in the specificity of the system is provided by the ability to rule out non-cancerous findings from PEM, taking advantage of elastography imaging information. The ClearPEM-Sonic has been developed by the Crystal Clear Collaboration and is currently installed at Hopital Nord, Marseille, in the frame of CERIMED, the European Centre for Research in Medical Imaging. The detector is based on LYSO:Ce crystals, each of 2x2x20 mm3, grouped in 192 matrices of 8x4 crys- tals. BaSO4 is used as coating material and reflector. Read out is performed individually on both 2x2 mm2 faces of each crystal, using avalanche photodiodes (APDs). The detector performance has been thoroughly tested during the commissioning phase, confirming a spatial resolution of 1.5 mm, and a DOI precision of 2 mm. The co-registration software developed has proved to accurately superimpose images coming from the different modalities with a precision better than 2 mm. The clinical trial (phase 1) is being carried out on 20 patients with a known breast lesion who have been injected with FDG for a whole-body PET/CT as part of their diagnostic process. Results are compared to conventional imaging and MRI, with biopsy as a golden standard, to validate the use of ClearPEM-Sonic as a clinical imaging instrument for early detection of breast cancer.

In the frame of research and development for electromagnetic calorimetry at future e/sup +/e/sup -/ linear colliders, different techniques have been studied to implement longitudinal segmentation in Shashlik calorimeters. Two prototypes with 5/spl times/5 cm/sup 2/ lead/scintillator towers and readout by means of wavelength-shifting fibers have been built. The longitudinal segmentation of the shower is achieved by modifying the front part of the detector. In the first prototype, vacuum photodiodes have been inserted laterally for the first eight X/sub 0/, while in the second prototype a slow scintillator has been used in the first five X/sub 0/. Both of the prototypes have been exposed to beam at CERN. The performance in term of energy resolution, spatial resolution, and e//spl pi/ separation are described.

A Consortium between four LHC Computing Centers (Bari, Milano, Pisa and Trieste) has been formed in 2010 to prototype Analysis-oriented facilities for CMS data analysis, profiting from a grant from the Italian Ministry of Research. The Consortium aims to realize an ad-hoc infrastructure to ease the analysis activities on the huge data set collected at the LHC Collider. While Tier2 Computing Centres, specialized in organized processing tasks like Monte Carlo simulation, are nowadays a well established concept, with years of running experience, site specialized towards end user chaotic analysis activities do not yet have a defacto standard implementation. In our effort, we focus on all the aspects that can make the analysis tasks easier for a physics user not expert in computing. On the storage side, we are experimenting on storage techniques allowing for remote data access and on storage optimization on the typical analysis access patterns. On the networking side, we are studying the differences between flat and tiered LAN architecture, also using virtual partitioning of the same physical networking for the different use patterns. Finally, on the user side, we are developing tools and instruments to allow for an exhaustive monitoring of their processes at the site, and for an efficient support system in case of problems. We will report about the results of the test executed on different subsystem and give a description of the layout of the infrastructure in place at the site participating to the consortium.

The new Small Angle TIIe Calorimeter (STIC) covers the forward regions in DELPHI. The main motivation for its construction was to achieve a systematic error of 0.1% on the luminosity determination. This detector consists of a “shashlik” type calorimeter, equipped with two planes of silicon pad detectors placed respectively after 4 and 7.4 radiation lengths. A veto counter, composed of two scintillator planes, covers the front of the calorimeter to allow ϱ − γ separation and to provide a neutral energy trigger. The physics motivations for this project, results from extensive testbeam measurements and the performance during the 1994 LEP run are reported here.

A large, worldwide distributed, scientific community is running intensively physics analyses on the first data collected at LHC. In order to prepare for this unprecedented computing challenge, the four LHC experiments have developed distributed computing models capable of serving, processing and archiving the large number of events produced by data taking, amounting to about 15 petabytes per year. The experiments workflows for event reconstruction from raw data, production of simulated events and physics analysis on skimmed data generate hundreds of thousands of jobs per day, running on a complex distributed computing fabric. All this is possible thanks to reliable Grid services, which have been developed, deployed at the needed scale and thouroughly tested by the WLCG Collaboration during the last ten years. In order to provide a concrete example, this paper concentrates on CMS computing model and CMS experience with the first data at LHC.

The offline and computing activities in preparation to the CMS data taking are reviewed. The readiness of the computing fabric and the status of the Grid services employed by CMS are presented. The strategy towards the full commissioning of the computing and offline systems is discussed.

The LHC experiments have thousands of collaborators distributed worldwide who expect to run their physics analyses on the collected data. Each of the four experiments will run hundreds of thousands of jobs per day, including event reconstruction from raw data, analysis on skimmed data, and production of simulated events. At the same time tens of petabytes of data will have to be easily available on a complex distributed computing fabric for a period of at least ten years. These challenging goals have prompted the development and deployment of reliable Grid services, which have been thouroughly tested and put at the needed scale over the last years. This paper concentrates on CMS computing needs for data taking at LHC and highlights the INFN-Grid contribution to the effort.

The CMS electromagnetic calorimeter aims at providing high precision calorimetry at the large madron collider (LHC). It consists of about 75.000 lead tungstate (PbWO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) crystals that have to operate reliably for at least 10 years, in a high radiation environment. In order to profit fully from the very good intrinsic energy resolution of the crystals, severe requirements on their temperature stability must be satisfied. Another challenge is given by the high data rates to be sustained by the readout electronics. With more than a half of the barrel modules produced, the calorimeter is well into its production phase. A large effort was devoted to optimize the integration between mechanics, cooling and readout electronics. The performance of the first modules has been tested in an electron beam, to validate the monitoring system and the calibration strategy. Very satisfactory results were achieved, in complete agreement with the goals of ECAL. An overview of the calorimeter design and of its construction status will be given, as well as the results from the testbeam measurements and the predicted performance at the LHC.

The DELPHI STIC detector is a lead-scintillator sampling calorimeter with wavelength shifting optical fibers used for light collection. The main goal of the calorimeter at LEP100 is to measure the luminosity with an accuracy better than 0.1%. The detector has been in operation since the 1994 LEP run. Presented here is the performance measured during the 1994-1995 LEP runs, with the emphasis on the achieved energy and space resolution, the long-term stability and the efficiency of the detector. The new bunch-trains mode of LEP requires a rather sophisticated trigger and timing scheme which is also presented. To control the trigger efficiency and stability of the calorimeter channels, a LED-based monitoring system has been developed.

The new luminosity monitor of the DELPHI detector, STIC (Small angle TIle Calorimeter), was built using a Shashlik technique. This technique does not provide longitudinal sampling of the showers, which limits the measurement of the direction of the incident particles and the e — π separation. For these reasons STIC was equipped with a Silicon Pad Shower Maximum Detector (SPSMD). In order to match the silicon detectors to the Shashlik read out by wavelength shifter (WLS) fibers, the silicon wafers had to be drilled with a precision better than 10 μm without damaging the active area of the detectors. This paper describes the SPSMD with emphasis on the fabrication techniques and on the components used. Some preliminary results of the detector performance from data taken with a 45 GeV electron beam at CERN are presented.

The CMS electromagnetic calorimeter is a very challenging detector which aims at providing high precision calorimetry in the Large Hadron Collider (LHC) environment. It consists of about 75,000 PbWO4 crystals that have to operate reliably for at least 10 years, in a high radiation environment. The readout electronics must sustain high data rates. In the last year new radiation hard readout electronics and a new cooling system were adopted and successfully tested. A large effort was also devoted to test the first modules performance in an electron beam, to validate the monitoring system and the calibration strategy. With more than one-third of the barrel modules produced, the calorimeter is well into its construction phase. An overview of the calorimeter design and of its construction status will be given, as well as the predicted performance at the LHC.

The possibility to improve depth of interaction (DOI) resolution and coincidence time resolution (CTR) of a pixellated PET module by enabling light re-circulation inside it with a light guide is well known. Typically the light guide consists of a non-scintillating material of about 1 mm thickness. In this work, we propose to further extend the concept by replacing the passive light guide with a fast scintillating material, in order to combine the benefits of light re-circulation with a fraction of very fast events, where the DOI is precisely known.Several configurations with such an active layer are proposed and studied in this work by means of Monte Carlo simulations with experimental verification. First, the possibility of replacing the glass light guide with a layer of LYSO is investigated. This configuration allows to reach DOI resolutions beyond the possibilities of a simple glass guide, while retaining comparable performances in terms of energy and timing resolutions. Then, the performance of two fast scintillators (BaF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and BC422) used as light guides, in combinations with crystal arrays made of both LYSO and BGO, is investigated. The fraction of shared events (i.e. those events where the 511 keV gamma ray scatters in the light guide and deposits the rest of its energy in the crystal array) in a 3 mm light guide is found to be around 1% for BC422, and 12.1% for BaF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> . Therefore, the configuration using the latter material is investigated in depth, and two alternative readout schemes are proposed, to maximize the collection of light produced by BaF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> . The results show that ∼ 100 ps FWHM CTR can be reached for shared events using a BaF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> light guide. Finally, the possibility to use such a detector design as a Compton camera is discussed.

A high-density calorimeter, consisting of magnetised iron planes interleaved by RPCs, as tracking and timing devices, is a good candidate for a next generation experiment on atmospheric neutrinos. With 34 kt of mass and in four years of data taking, this experiment will be sensitive to vμ → vχ oscillation with Δm2 > 6 × 10−5 and mixing near to maximal and fuly cover the region of oscillation parameters suggested by Super-Kamiokande results. Moreover, the experimental method will enable to measure the oscillation parameters from the modulation of the LE spectrum (vμ disappearance). For Δm2 > 3 × 10−3 eV2, this experiment can also establish whether the oscillation occurs into a tau or a sterile neutrino, by looking for an excess of muon-less events at high energies produced by upward-going tau neutrinos (vτ appearance).

The forward-backward asymmetries of the processes [Formula: see text] and [Formula: see text] were measured from a sample of hadronic Z decays collected by the DELPHI experiment between 1993 and 1995. Enriched samples of [Formula: see text] and [Formula: see text] events were obtained using lifetime information. The tagging of b and c quarks in these samples was based on the semileptonic decay channels b/c → X + μ and b/c → X + e combined with the charge flow information in the hemisphere opposite to the lepton. Averaging the results presented in this paper with those already published with 1991 and 1992 DELPHI data sample, the following pole asymmetries were obtained: [Formula: see text]

Two techniques for longitudinal segmentation of shashlik calorimeters are proposed. Results concerning energy resolution, impact point reconstruction and e//spl pi/ separation are reported.