1,720,967 research outputs found
Studies of scintillator efficiency in the Hall-A high resolution spectrometers at Jefferson Lab.
No full textApplications of Silicon Photomultipliers in Personal Radiation Detection and Nuclear Imaging
No full textA Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Master of Science in Physics, University of Regina. xi, 139p.Originally developed as the readout for calorimeters in high-energy physics experiments, the
silicon photomultiplier (SiPM) has found use in a wide range of fields requiring the detection
of low-intensity light. This thesis discusses work on two such applications: in the development
of a prototype personal radiation detector (PRD), and in the imaging of a radioactive
source.
The ability to detect above-background levels of radiation has received increased attention
in recent years, not least from the perspective of national security agencies in, for example,
tracking the movement of illicit radioactive materials, or in dealing with potential
fall-out from nuclear accidents. In such potentially hazardous environments, there has been
an increased demand for improved PRDs for use by emergency workers and first-responders.
Motivated by an NSERC-funded partnership with Environmental Instruments Canada Inc.
(EIC), the first part of this thesis focuses on a project to develop a small, low-cost, easy-to-use
prototype gross-counting gamma-radiation detector based upon SiPM technology. Limited
by size and cost requirements, measurements suggested the Hamamatsu S12572-050C model
(3 3 mm2) as the preferred choice of SiPM, and subsequent work tested several SiPM/lightproducing
medium combinations. A PTFE (teflon)-wrapped common plastic scintillator (BC-416), coupled to the SiPM, was identified as the medium providing the most significant
sensitivity enhancement with respect to EIC’s existing detection device (incorporating
a Geiger-Müller tube as its photosensor), while minimising cost and maintaining the overall
physical size of EIC’s detector. An additional project positively assessed the suitability of
SiPMs for thermal neutron detection using scintillating fibres coated in successive layers of
zinc sulphide and boron carbide.
The second part of this thesis (funded through the Sylvia Fedoruk Centre for Nuclear
Innovation) presents a preliminary characterisation of two SensL MatrixSM-9 SiPM array
modules, in preparation for their use in a “PhytoPET” plant-imaging system to be built at the
University of Regina. Such arrays of SiPMs are now available commercially as part of modular,
turnkey readout systems designed specifically for use in high-resolution, state-of-the-art
medical-imaging applications. However, PET systems designed to image plants – such as
the (operational) PhytoPET system based at Duke University – typically utilise multi-anode
photomultiplier tubes. Singles measurements are reported for each SiPM array, coupled in
turn to a PTFE-wrapped BC-416 plastic scintillator in several configurations. Pixelated images
of noise and various laboratory sources are reconstructed from output data files using
dedicated codes, and the array-trigger error of each module is mapped over a wide-range of
adjustable array and pixel thresholds.Studentye
Heavy Gas Cherenkov Detector Construction for Hall C at Thomas Jefferson National Accelerator Facility
No full textA Thesis Submitted to the Faculty of Graduate Studies and Research in Partial Fulfillment of the Requirements for the Degree of Master of Science in Physics, University of Regina. ix, 104 p.The Thomas Jefferson National Accelerator Facility (JLab) has undertaken the 12 GeV Upgrade to double the accelerating energy of its electron beam. This attracts many interesting proposals to probe the quark-gluon nature of nuclear matter at higher energy, therefore a new set of equipment is required. Experimental Hall C of JLab has planned to construct a new Super High Momentum Spectrometer (SHMS) to replace the existing Short Orbit Spectrometer (SOS). The University of Regina is assigned to construct the Heavy Gas Cˇ erenkov (HGC) Detector as part of the SHMS focal plane detectors. This detector will be used as critical component to provide reliable π/K
separation between 3-11 GeV/c central momenta in the SHMS experimental program. In this thesis, we will report the design, quality control studies and simulated expected performances of the HGC detector.Studentye
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Large Area MultiPixel Photon Counters on the Search for Exotic Hybrid Mesons at GlueX
No full textA Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Master of Science in Physics, University of Regina. xii, 98 l.The GlueX project aims to elucidate the confinement property of quantum chromodynamics. Silicon PhotoMultipliers (SiPMs) will be the readout for the GlueX
Barrel Calorimeter (BCAL), a key subsystem of the detector designed for the GlueX
project. The important and most desired characteristic of SiPMs is their immunity
to magnetic fields, since the BCAL is placed immediately in a 2:2 T solenoid. Other
advantages compared to conventional PMTs is that they operate using low bias voltage (< 100 V ), have higher photon detection efficiency, lower cost, and are more
compact and robust. SiPMs offer much promise to revolutionize light detection in
particle, but also medical and space physics, among other.
Hamamatsu, a Japanese photonics company, will manufacture the SiPMs for the
BCAL. These photosensors are arrays of 16 - 3 x 3 mm2 SiPMs. In this thesis,
discusses the test carried out for one 2010 Hamamatsu unit and ten 2011 (years of
manufacture) first article Hamamatsu SiPM units. The tests are the first fiber-based
tests for the SiPMs. The two major tests are the photon detection efficiency (PDE)
and the gain uniformity of their cells and sub-cells. Depending on the method of
measurement, the extracted PDE fell in the range of 15-30%, while the cells exhibited
gain uniformity mostly within 10%. The result of this thesis will be directly used
by the GlueX collaboration towards quality control of the 4000 units ordered for the
BCAL.Studentye
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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