5,278 research outputs found
Extrinisic Calibration of a Camera-Arm System Through Rotation Identification
Determining extrinsic calibration parameters is a necessity in any robotic
system composed of actuators and cameras. Once a system is outside the lab
environment, parameters must be determined without relying on outside artifacts
such as calibration targets. We propose a method that relies on structured
motion of an observed arm to recover extrinsic calibration parameters. Our
method combines known arm kinematics with observations of conics in the image
plane to calculate maximum-likelihood estimates for calibration extrinsics.
This method is validated in simulation and tested against a real-world model,
yielding results consistent with ruler-based estimates. Our method shows
promise for estimating the pose of a camera relative to an articulated arm's
end effector without requiring tedious measurements or external artifacts.
Index Terms: robotics, hand-eye problem, self-calibration, structure from
motio
Position Resolution in LaBr3 and LaCl3 Scintillators Using Position-Sensitive Photomultiplier Tubes
Advanced scintillator materials such as LaBr3:Ce and LaCl3:Ce hold great promise for future hard X-ray and gamma-ray astrophysics missions due to their high density, high light output, good linearity, and fast decay times. Of particular importance for future space-based imaging instruments, such as coded-aperture telescopes, is the precise spatial location of individual gamma-ray interactions. We have investigated the position and energy resolution achievable within monolithic (5 cm × 5 cm × 1 cm) LaBr3:Ce and LaCl3:Ce crystals using position-sensitive light readout devices, including a position-sensitive photomultiplier tube and a multi-anode photomultiplier tube. We present the results of these tests and discuss the applicability of such advanced scintillators to future high-energy imaging astrophysics missions
Simulated Performance of 3-DTI Gamma-Ray Telescope Concepts
We present Monte Carlo simulations of two astronomical gamma-ray telescope concepts based on the ThreeDimensional Track Imager (3- DTI) detector. The 3-DTI consists of a time projection chamber with two-dimensional, crossedstrip micro-well detector readout. The full three- dimensional reconstruction of charged-particle tracks in the gas volume is obtained from transient digitizers, which record the time signature of the charge collected in the wells of each strip. Such detectors hold great promise for advanced Compton telescope (ACT) and advanced pair telescope (APT) concepts due to the very precise measurement of charged particle momenta that is possible (Compton recoil electrons and electron-positron pairs, respectively). We have investigated the performance of baseline ACT and APT designs based on the 3-DTI detector using simulation tools based on GEANT3 and GEANT4, respectively. We present the expected imaging, spectroscopy, polarimetry, and background performance of each design
Gas micro-well track imaging detectors for gamma-ray astronomy
We describe our program to develop gas micro-well detectors (MWDs) as three-dimensional charged particle trackers for use in advanced gamma-ray telescope concepts. A micro-well detector consists of an array of individual micro-patterned gas proportional counters opposite a planar drift electrode. The well anodes and cathodes may be connected in X and Y strips, respectively, to provide two-dimensional imaging. When combined with transient digitizer electronics, which record the time signature of the charge collected in the wells of each strip, full three-dimensional reconstruction of charged-particle tracks in large gas volumes is possible. Such detectors hold great promise for advanced Compton telescope (ACT) and advanced pair telescope (APT) concepts due to the very precise measurement of charged particle momenta that is possible (Compton recoil electrons and electron-positron pairs, respectively). We present preliminary lab results, including detector fabrication, prototype electronics, and initial detector testing. We also discuss applications to the ACT and APT mission concepts, based on GEANT3 and GEANT4 simulations
Module production of the one-arm AFP 3D pixel tracker
The ATLAS Forward Proton (AFP) detector is designed to identify events in
which one or two protons emerge intact from the LHC collisions. AFP will
consist of a tracking detector, to measure the momentum of the protons, and a
time of flight system to reduce the background from multiple proton-proton
interactions. Following an extensive qualification period, 3D silicon pixel
sensors were selected for the AFP tracker. The sensors were produced at CNM
(Barcelona) during 2014. The tracker module assembly and quality control was
performed at IFAE during 2015. The assembly of the first AFP arm and the
following installation in the LHC tunnel took place in February 2016. This
paper reviews the fabrication process of the AFP tracker focusing on the pixel
modules.Comment: PIXEL 2016 proceedings; Submitted to JINS
A Combined Compton and Coded-aperture Telescope for Medium-energy Gamma-ray Astrophysics
A future mission in medium-energy gamma-ray astrophysics would allow for many
scientific advancements, e.g. a possible explanation for the excess positron
emission from the Galactic Center, a better understanding of nucleosynthesis
and explosion mechanisms in Type Ia supernovae, and a look at the physical
forces at play in compact objects such as black holes and neutron stars.
Additionally, further observation in this energy regime would significantly
extend the search parameter space for low-mass dark matter. In order to achieve
these objectives, an instrument with good energy resolution, good angular
resolution, and high sensitivity is required. In this paper we present the
design and simulation of a Compton telescope consisting of cubic-centimeter
Cadmium Zinc Telluride (CdZnTe) detectors as absorbers behind a silicon tracker
with the addition of a passive coded mask. The goal of the design was to create
a very sensitive instrument that is capable of high angular resolution. The
simulated telescope showed achievable energy resolutions of 1.68 FWHM at
511 keV and 1.11 at 1809 keV, on-axis angular resolutions in Compton mode
of 2.63 FWHM at 511 keV and 1.30 FWHM at 1809 keV, and is
capable of resolving sources to at least 0.2 at lower energies with
the use of the coded mask. An initial assessment of the instrument in Compton
imaging mode yields an effective area of 183 cm at 511 keV and an
anticipated all-sky sensitivity of 3.6 x 10 photons cm s
for a broadened 511 keV source over a 2-year observation time. Additionally,
combining a coded mask with a Compton imager to improve point source
localization for positron detection has been demonstrated
Characterising encapsulated nuclear waste using cosmic-ray muon tomography
Tomographic imaging techniques using the Coulomb scattering of cosmic-ray
muons have been shown previously to successfully identify and characterise low-
and high-Z materials within an air matrix using a prototype scintillating-fibre
tracker system. Those studies were performed as the first in a series to assess
the feasibility of this technology and image reconstruction techniques in
characterising the potential high-Z contents of legacy nuclear waste containers
for the UK Nuclear Industry. The present work continues the feasibility study
and presents the first images reconstructed from experimental data collected
using this small-scale prototype system of low- and high-Z materials
encapsulated within a concrete-filled stainless-steel container. Clear
discrimination is observed between the thick steel casing, the concrete matrix
and the sample materials assayed. These reconstructed objects are presented and
discussed in detail alongside the implications for future industrial scenarios.Comment: 6 pages, 4 figure
Technical Proposal for FASER: ForwArd Search ExpeRiment at the LHC
FASER is a proposed small and inexpensive experiment designed to search for
light, weakly-interacting particles during Run 3 of the LHC from 2021-23. Such
particles may be produced in large numbers along the beam collision axis,
travel for hundreds of meters without interacting, and then decay to standard
model particles. To search for such events, FASER will be located 480 m
downstream of the ATLAS IP in the unused service tunnel TI12 and be sensitive
to particles that decay in a cylindrical volume with radius R=10 cm and length
L=1.5 m. FASER will complement the LHC's existing physics program, extending
its discovery potential to a host of new, light particles, with potentially
far-reaching implications for particle physics and cosmology.
This document describes the technical details of the FASER detector
components: the magnets, the tracker, the scintillator system, and the
calorimeter, as well as the trigger and readout system. The preparatory work
that is needed to install and operate the detector, including civil
engineering, transport, and integration with various services is also
presented. The information presented includes preliminary cost estimates for
the detector components and the infrastructure work, as well as a timeline for
the design, construction, and installation of the experiment.Comment: 82 pages, 62 figures; submitted to the CERN LHCC on 7 November 201
MScMS-II: an innovative IR-based indoor coordinate measuring system for large-scale metrology applications
According to the current great interest concerning large-scale metrology applications in many different fields of manufacturing industry, technologies and techniques for dimensional measurement have recently shown a substantial improvement. Ease-of-use, logistic and economic issues, as well as metrological performance are assuming a more and more important role among system requirements. This paper describes the architecture and the working principles of a novel infrared (IR) optical-based system, designed to perform low-cost and easy indoor coordinate measurements of large-size objects. The system consists of a distributed network-based layout, whose modularity allows fitting differently sized and shaped working volumes by adequately increasing the number of sensing units. Differently from existing spatially distributed metrological instruments, the remote sensor devices are intended to provide embedded data elaboration capabilities, in order to share the overall computational load. The overall system functionalities, including distributed layout configuration, network self-calibration, 3D point localization, and measurement data elaboration, are discussed. A preliminary metrological characterization of system performance, based on experimental testing, is also presente
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