Search results for "Axia"
showing 10 items of 638 documents
The AX-PET demonstrator—Design, construction and characterization
2011
Abstract Axial PET is a novel geometrical concept for Positron Emission Tomography (PET), based on layers of long scintillating crystals axially aligned with the bore axis. The axial coordinate is obtained from arrays of wavelength shifting (WLS) plastic strips placed orthogonally to the crystals. This article describes the design, construction and performance evaluation of a demonstrator set-up which consists of two identical detector modules, used in coincidence. Each module comprises 48 LYSO crystals of 100 mm length and 156 WLS strips. Crystals and strips are readout by Geiger-mode Avalanche Photo Diodes (G-APDs). The signals from the two modules are processed by fully analog front-end …
Proton spin and the cheshire cat principle
1991
Abstract We discuss the proton matrix element of the flavor-singlet axial current (FSAC), often referred to as proton spin, in terms of the chiral bag model with due account of the axial anomaly and quantum number fractionation. We conclude that the contribution due to gluons is significant for large bag radii and that it is crucial in order to establish the Cheshire cat principle.
Digital pulse-shape analysis with a TRACE early silicon prototype
2014
[EN] A highly segmented silicon-pad detector prototype has been tested to explore the performance of the digital pulse shape analysis in the discrimination of the particles reaching the silicon detector. For the first time a 200 tun thin silicon detector, grown using an ordinary floating zone technique, has been shown to exhibit a level discrimination thanks to the fine segmentation. Light-charged particles down to few MeV have been separated, including their punch-through. A coaxial HPGe detector in time coincidence has further confirmed the quality of the particle discrimination. K.; 2014 Elsevier B.V. All rights reserved
Characterisation of a symmetric AGATA detector using the imaging scanning technique
2013
Abstract The imaging scanning technique for the characterisation of large volume, highly segmented, HPGe detectors is demonstrated by comparing the measured spatial response of a symmetric AGATA crystal versus the theoretical calculations obtained with the Multi-Geometry Simulation (MGS) code. The signal rise-times measured as a function of the gamma-ray interaction positions, in both coaxial and planar regions of the detection volume, are presented and confronted with the expected behaviour obtained via MGS. The transition in charge carrier transport behaviour as a function of the depth is studied for the region of the complex electric field. In general, a fairly good agreement between the…
Spontaneous fission lifetimes from the minimization of self-consistent collective action
2013
The spontaneous fission lifetime of 264Fm has been studied within nuclear density functional theory by minimizing the collective action integral for fission in a two-dimensional quadrupole collective space representing elongation and triaxiality. The collective potential and inertia tensor are obtained self-consistently using the Skyrme energy density functional and density-dependent pairing interaction. The resulting spontaneous fission lifetimes are compared with the static result obtained with the minimum-energy pathway. We show that fission pathways strongly depend on assumptions underlying collective inertia. With the non-perturbative mass parameters, the dynamic fission pathway become…
Multipole modes in deformed nuclei within the finite amplitude method
2015
Background: To access selected excited states of nuclei, within the framework of nuclear density functional theory, the quasiparticle random phase approximation (QRPA) is commonly used. Purpose: We present a computationally efficient, fully self-consistent framework to compute the QRPA transition strength function of an arbitrary multipole operator in axially-deformed superfluid nuclei. Methods: The method is based on the finite amplitude method (FAM) QRPA, allowing fast iterative solution of QRPA equations. A numerical implementation of the FAM-QRPA solver module has been carried out for deformed nuclei. Results: The practical feasibility of the deformed FAM module has been demonstrated. I…
Annular binary filters for controlling the axial behaviour of optical systems
1998
The one-dimensional (1D) version of the iterative Fourier transform algorithm (IFTA) and a modified error diffusion algorithm are proposed for binarizing rotationally symmetric pupil filters designed to shape the axial impulse response of optical system. The resulting binary masks consist of a set of transparent and opaque annular zones of equal area or equal width. A numerical experiment in which we examine the performance of the binarization methods is carried out. In this experiment the resemblance between the axial diffractive behaviour of the binary version of an axially superresolving pupil filter, and that of the original continuous-tone filter is evaluated. It is shown that the perf…
A decade of SN 1993J : discovery of radio wavelength effects in the expansion rate
2009
We studied the growth of the shell-like radio structure of supernova SN 1993J in M 81 from September 1993 to October 2003 with very-long-baseline interferometry (VLBI) observations at the wavelengths of 3.6, 6, and 18 cm. We developed a method to accurately determine the outer radius (R) of any circularly symmetric compact radio structure such as SN 1993J. The source structure of SN 1993J remains circularly symmetric (with deviations from circularity under 2%) over almost 4000 days. We characterize the decelerated expansion of SN 1993J until approximately day 1500 after explosion with an expansion parameter m = 0.845 ± 0.005 (R ∝ tm). However, from that day onwards the expansion differs whe…
Anisotropic elasto-optic effect in optical fibers under axial strain: a perturbative approach
2016
We present a perturbative approximation to calculate the relative shift of the WGM resonances in a conventional optical fibers when an axial strain is applied. We consider the anisotropic character of the elasto-optic effect.
Influence of possible reflections on the operation of European ITER gyrotrons
2010
The theory describing the influence of reflection s on operation of gyrotrons with radial output is used for evaluating the effect of reflections on the operation of the ITER 170 GHz 2 MW coaxial cavity gyrotron, which is under development, and the 170 GHz 1 MW cylindrical cavity gyrotron as a fall back solution.