72023452
Preliminary timing measurements on a data acquisition chain for a SiPM-based detector for prostate imaging
Prostate cancer (PC) is one of the most common diseases in western countries and a leading cause of cancer death. A variety of treatment options are available but a precise disease characterization is needed: evaluation of cancer location, size, and extent and an indication of tumor aggressiveness. The current standard for diagnosing PC is transrectal ultrasound guided sextant biopsy. A novel multidisciplinary approach is required. Imaging may play a key role provided that dedicated prostate imagers and procedures are available: considerable improvements have been achieved in diagnosis with the Magnetic Resonance Imaging (MRI) and nuclear medicine (Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT)) techniques. Nevertheless, due to sub-optimal prostate imaging geometries with these generic large instruments preventing separation of the signal from surrounding organs, the sensitivity, spatial resolution and lesion contrast detected are lower compared to what can be potentially achievable with optimized dedicated prostate imagers and procedures. Fully exploiting the Time Of Flight (TOF) capability would allow not only to increase the Signal-to-Noise ratio (SNR) / Noise Equivalent Count Rate (NECR) but also to get rid of the huge background coming from neighboring organs i.e. the bladder. Recently a new research project was initiated by a large INFN collaboration, and a “TOF-PET and MRI for prostate cancer diagnosis and follow up experiment” (TOPEM) was financed as a 3-year experiment by the Italian “INFN Commissione Scientifica Nazionale V” with the goal of designing, building and testing in phantom tests an endorectal PET-TOF probe compatible with MRI.
46500747
Implementation of a bidimensional compressor for a high-energy physics experiment
CARLOSv3 is the third version of a chip that plays a significant role in the data acquisition chain of the A Large Ion Collider Experiment (ALICE) silicon drift detector (SDD). ALICE is one of the foremost high-energy physics experiments (HEPE) conducted within the Large Hadron Collider at CERN, the European Organization for Nuclear Research in Geneva. CARLOSv3 was principally designed and built for the on-line compression of the input dataset originating from a physical bidimensional silicon sensor. To compress a bidimensional dataset, a bidimensional data compressor was required. The compressor was designed for the ALICE SDD Experiment but could be applied to all experiments in which an incoming stream dataset originates from a bidimensional sensor.
109308730
Heavy-Ions induced SEE effects measurements for the STRURED ASIC
With the aim of developing a radiation-tolerant circuit, a digital test microelectronic device has been designed and fabricated by using a standard-cell library of a 130-nm CMOS technology, including three different architectures to correct circuit malfunctions induced by the occurrence of Single-Event Effects (SEEʼs). SEEʼs are one of the main reasons of failures affecting electronic circuits operating in harsh radiation environments, such as in experiments performed at High Energy Physics (HEP) colliders or in apparatus to be operated in Space. On the same digital circuit specifically designed, three redundant architectures added to a basic scheme have been implemented in order to evaluate their effectiveness to prevent SEE. This may give an indication on their usage in future digital circuits specifically designed for the above mentioned applications. We present the results of SEE cross section measurements performed on a test digital device exposed to a high energy heavy ion beam at the SIRAD irradiation facility of the INFN National Laboratories of Legnaro (Padova Italy).
56367755
Design of an integrated particle detector-cell based on latchup effect
The paper describes an innovative idea for a silicon pixel detector. The principle is based on latchup effect that is common in to-date CMOS technologies working in a radiation environment. A prototype was constructed in the past with commercial components and here is described in detail an integrated version of the design. In principle the detector has low triggering and dead time, can operate at room temperature, does not require a high voltage power supply and is intrinsically tolerant to radiation. As a latchup-based detector can be constructed using state-of-the-art CMOS technologies, here it is presented a design of a prototype that will be implemented on a commercial 0.35 μm Bi-CMOS technology and tested at Electronics Department of Torino Politecnico.
123625473
Architecture of a general purpose embedded Slow-Control Adapter ASIC for future high-energy physics experiments
Abstract This work is aimed at defining the architecture of a new digital ASIC, namely Slow-Control Adapter (SCA), which will be designed in a commercial 130-nm CMOS technology. This chip will be embedded within a high-speed data acquisition optical link (GBT) to control and monitor the front-end electronics in future high-energy physics experiments. The GBT link provides a transparent transport layer between the SCA and control electronics in the counting room. The proposed SCA supports a variety of common bus protocols to interface with end-user general-purpose electronics. Between the GBT and the SCA a standard 100 Mb/s IEEE-802.3 compatible protocol will be implemented. This standard protocol allows off-line tests of the prototypes using commercial components that support the same standard. The project is justified because embedded applications in modern large HEP experiments require particular care to assure the lowest possible power consumption, still offering the highest reliability demanded by very large particle detectors.
109494522
Design, realization and test of a rad-hard 2D-compressor and packing chip for high energy physics experiments
CARLOSv3 is a third version of a chip that plays a significant role in the data acquisition chain of the A Large Ion Collider Experiment Inner Tracking System experiment. It has been designed and realized with a 0.25 μm CMOS 3-metal rad-hard digital library. The chip elaborates and compresses, by means of a bi-dimensional compressor, data belonging to a so-called event. The compressor looks for cross-shaped clusters within the whole data set coming from the silicon detector. To test the chip a specific PCB has been designed; it contains the connectors for probing the ASIC with a pattern generator and a logic state analyzer. The chip is inserted on the PCB using a ZIF socket. This allows to test the 35 packaged samples out of the total amount of bare chips we have from the foundry. The test phase has shown that 32 out of 35 chips under test work well. It is planned to redesign a new version of the chip by adding extra features and to submit the final version of CARLOS upon the final DAQ chain will be totally tested both in Bologna and at CERN.
14253637
Finite size effects on the galaxy number counts: Evidence for fractal behavior up to the deepest scale
We introduce and study two new concepts which are essential for the quantitative analysis of the statistical quality of the available galaxy samples. These are the dilution effect and the small scale fluctuations. We show that the various data that are considered as pointing to a homogenous distribution are all affected by these spurious effects and their interpretation should be completely changed. In particular, we show that finite size effects strongly affect the determination of the galaxy number counts, namely the number versus magnitude relation (N (< m)) as computed from the origin. When one computes N (< m) averaged over all the points of a redshift survey, one observes an exponent α = D/5 ≈ 0.4 compatible with the fractal dimension D ≈ 2 derived from the full correlation analysis. Instead the observation of an exponent α ≈ 0.6 at relatively small scales, where the distribution is certainly not homogeneous, is shown to be related to finite size effects. We conclude therefore that the observed counts correspond to a fractal distribution with dimension D ≈ 2 in the entire range 12 ⪅ m ⪅ 28, that is to say the largest scales ever probed for luminous matter. In addition our results permit to clarify various problems of the angular catalogs, and to show their compatibility with the fractal behaviour. We consider also the distribution of Radio-galaxies, Quasars and γ-ray bursts, and we show their compatibility with a fractal structure with D ≈ 1.6–1.8. Finally we have established a quantitative criterion that allows us to define and predict the statistical validity of a galaxy catalog (angular or three-dimensional).
33686678
Force distribution in a randomly perturbed lattice of identical particles with 1/r2 pair interaction.
We study the statistics of the force felt by a particle in the class of a spatially correlated distribution of identical pointlike particles, interacting via a 1/r2 pair force (i.e., gravitational or Coulomb), and obtained by randomly perturbing an infinite perfect lattice. We specify the conditions under which the force on a particle is a well-defined stochastic quantity. We then study the small displacements approximation, giving both the limitations of its validity and, when it is valid, an expression for the force variance. The method introduced by Chandrasekhar to find the force probability density function for the homogeneous Poisson particle distribution is extended to shuffled lattices of particles. In this way, we can derive an approximate expression for the probability distribution of the force over the full range of perturbations of the lattice, i.e., from very small (compared to the lattice spacing) to very large where the Poisson limit is recovered. We show in particular the qualitative change in the large-force tail of the force distribution between these two limits. Excellent accuracy of our analytic results is found on detailed comparison with results from numerical simulations. These results provide basic statistical information about the fluctuations of the interactions (i) of the masses in self-gravitating systems like those encountered in the context of cosmological N -body simulations, and (ii) of the charges in the ordered phase of the one-component plasma, the so-called Coulomb or Wigner crystal.
14845268
Real Space Statistical Properties of Standard Cosmological Models
After reviewing some basic relevant properties of stationary stochastic processes (SSP), we discuss the properties of the so‐called Harrison‐Zeldovich like spectra of mass density perturbations. These correlations are a fundamental feature of all current standard cosmological models. Examining them in real space we note they imply a sub‐poissonian normalized variance in spheres σM2(R) ∼ R−4 lnR. In particular this latter behavior is at the limit of the most rapid decay (∼ R−4) of this quantity possible for any stochastic distribution (continuous or discrete). In a simple classification of all SSP into three categories, we highlight with the name “super‐homogeneous” the properties of the class to which models like this, with P(0) = 0, belong. In statistical physics language they are well described as lattice or glass‐like. We illustrate their properties through two simple examples: (i) the “shuffled” lattice and the One Component Plasma at thermal equilibrium.
14466810
Basic properties of galaxy clustering in the light of recent results from the Sloan Digital Sky Survey
We discuss some of the basic implications of recent results on galaxy correlations published by the SDSS collaboration. In particular we focus on the evidence which has been recently presented for the scale and nature of the transition to homogeneity in the galaxy distribution, and results which describe the dependence of clustering on luminosity. The two questions are in fact strictly entangled, as the stability of the measure of the amplitude of the correlation function depends on the scale at which the mean density becomes well defined. We note that the recent results which indicate the convergence to well defined homogeneity in a volume equivalent to that of a sphere of radius 70 Mpc/h, place in doubt previous detections of luminosity bias from measures of the amplitude of the correlation function. We emphasize that the way to resolve these issues is to first use, in volume limited samples corresponding to different ranges of luminosity, the unnormalized two point statistics to establish the scale (and value) at which the mean density becomes well defined. We note also that the recent SDSS results for these statistics are in good agreement with those obtained by us through analyses of many previous samples, confirming in particular that the galaxy distribution is well described by a fractal dimension D 2 up to a scale of at least 20 Mpc/h. We discuss critically the agreement of this new data with current theoretical models.
6446445
Generation of primordial cosmological perturbations from statistical mechanical models
The initial conditions describing seed fluctuations for the formation of structure in standard cosmological models, i.e. the Harrison-Zeldovich distribution, have very characteristic ‘‘super-homogeneous’’ properties: they are statistically translation invariant and isotropic, and the variance of the mass fluctuations in a region of volume V grows more slowly than V. We discuss the geometrical construction of distributions of points in R 3 with similar properties encountered in tiling and in statistical physics, e.g. the Gibbs distribution of a onecomponent system of charged particles in a uniform background @one-component plasma ~OCP!#. Modifications of the OCP can produce equilibrium correlations of the kind assumed in the cosmological context. We then describe how such systems can be used for the generation of initial conditions in gravitational N-body simulations.