1,721,002 research outputs found
Internal polarized gas targets: systematic studies on intensity and correlated effects
No full textThe work carried out during the PhD was dedicated to the study of high-density polarized
gas targets used in high-energy physics. The thesis is related to the PAX experiment,
which aims to produce a beam of polarized anti-protons, by means of spin-filtering with a
polarized atomic target. In order to obtain the densities required by high-energy particle
physic, gaseous targets are a combination of an Atomic Beam Source and a storage cell.
The possibility to improve the various components of the ABS and the storage cell has been
evaluated, through dedicated systematic studies, using the facilities available in “Spinlab”
of Universit´a di Ferrara.
The attenuation of a collimated beam passing through the rest gas of a vacuum system
has been studied; different nozzle geometries have been tested (comparing the measured
data with the data calculated by simulation programs); design and tests of an new kind
of injection tube with internal fins (with the aim of decreasing the conductance of the
storage cell without diminishing the acceptance and thus to increase the integrated target
thickness).
Estimation of the attenuation coefficients and total cross sections have been derived from
the measurements of the attenuation of a hydrogen or deuterium beam. This quantities
are important for projecting new ABS and to improve the existing ones. A favorable
nozzle geometry (called “trumpet”) that increases the beam intensity has been derived
from simulations and experimental tests. Tests on the injection tubes with fins did not
give positive results when applied to the PAX storage cell geometry; however a azimuthal
motion of the atoms of a focused beam emerged from the measurements, a motion that
until now has been completely neglected
A magnetic system for the CLAS12 proposal
No full textThe conceptual design of a magnetic system for an experiment to measure the transverse spin effects in SIDIS at 11 GeV with a transversely polarized target using the CLAS12 detector at Jefferson Lab is presented. A proposal has been submitted to study spin azimuthal asymmetries in semi-inclusive Deep Inelastic Scattering (SIDIS) using an 11 GeV polarized electron beam from the upgraded CEBAF facility and the CLAS12 detector equipped with a transversely polarized target. The main focus of the experiment will be the measurement of transverse target single and double spin asymmetries (TTSA) in the reaction epa ̈ ehX, where e is an electron, pa is transversely polarized proton, h is a meson (e.g. a pion or a kaon) and X is the undetected final state. The details of the conceptual design of the shielding magnetic system and transverse dipole are reported
Test Bench Studies and Simulations of Atomic Beam Sources
No full textTwo new test bench studies have deepened the understanding of polarized gas targets and the atomic beam sources (ABS) that fill them. The attenuation coefficient for beam loss due to rest gas scattering has been measured over a range of beam velocities. The total scattering cross sections can be extracted from these measurements for the first time.
Low conductance injection tubes have the potential to increase the thickness of storage cell targets. Injection tubes with internal fins were characterized, and the beam loss at the tube exit was larger than expected. Beam simulations agree with the measured intensity loss only when the atoms’ trajectories have a non‐zero azimuthal velocity component
Tesori ritrovati: Strumenti storici per Farmacia, Chimica, Botanica della Collezione Instrumentaria delle Scienze Fisiche dell’Università di Ferrara
No full textThe collection of historical physics instruments (Collezione Instrumentaria delle Scienze Fisiche) comprehends scientific instruments which are the remaining of the Ferrara University Physics Cabinet (1782-1950 ca.). On the whole the instruments may be seen as documents which envisage the development of the experimental sciences and testify the history of Ferrara University. The article, after a short introduction, describes some instruments of the Collection pertaining not only to Physics but also to Botanic, Chemistry, Pharmacy and analyses the causes and significance of their presence in the modern Collezione Instrumentaria delle Scienze Fisiche
Incontri di Fisica delle Alte Energie - IFAE 2012 - Il Nuovo Cimento C Year 2013 - Issue 1 - January-February - Year 2013 Vol 036 -
No full textIncontri di Fisica delle Alte Energie 201
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“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
Full text linkWe 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
Full text linkWe 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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