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Spin Coherence Time studies for the storage ring EDM search
No full textThis thesis is part of the feasibility studies for a search for an Electric
Dipole Moment (EDM) of charged particles in a storage ring. The evidence
for a non-vanishing EDM at the sensitivity of present or planned experiments
would clearly prove the existence of new CP violating meachanisms
beyond the Standard Model. The proposed solution to measure the EDM
of charged particles is the use of a storage ring where the polarized charged
particle beam can be kept circulating while interacting with a radial electric
field. Starting with a longitudinally polarized beam, the EDM signal
would be detected as a polarization precession starting from the horizontal
plane and rotating toward the vertical direction. A long horizontal polarization
lifetime, called spin coherence time, is required since it represents
the time available to observe the EDM signal. In order to have a sensitivity
about 10−29 e·cm to the deuteron EDM, the spin coherence time should
reach 1000 s while the measurement of a vertical polarization change should
detect angles as small as micro-radians.
The aim of this work is the analysis of the mechanisms which control
the spin coherence time in a storage ring. The measurements presented
here were made at the COSY (COoler SYnchrotron) ring located at the
Forschungszentrum-J¨ulich GmbH (Germany).
There are two set of measurements presented in this thesis: the first is a
study of a spin resonance induced by a radio-frequency (rf) solenoid and the
second shows the results from the first direct measurement of the horizontal
polarization as a function of time.
The first experiment sought to estimate the spin coherence time by measuring
the width of a deuteron spin resonance induced by an rf-solenoid.
Since the width of the resonance depends on the spin tune spread and thus
on particle momentum distribution, each mechanism that can change the
particle velocity in the beam could contribute to the spin tune spread. In
particular, these mechanisms are betatron oscillations related to the beam
emittance and synchrotron oscillations that are present only in a bunched
beam.
The experiment consisted in the measurement of the vertical polarization
measurements with the rf-solenoid running at fixed frequency on and
off resonance, for both uncooled and cooled bunched beam. In order to
interpret the data, a simple “no-lattice” model was developed based on two
rotation matrices for the spin precession about the vertical axis and the
solenoid kick about the longitudinal axis; synchrotron oscillations were included
as simple harmonic motion. The model demonstrated that the effect
of synchrotron oscillations on the induced spin resonance were large enough
to hide any dependence on emittance.
The second experiment was the direct measurement of the horizontal
polarization as a function of time. This task was accomplished through
the development of a dedicated data acquisition system synchronized with
the revolution frequency of the beam. By changing the horizontal beam
emittance with a white noise electric field, the measurements gave the first
experimental evidence of a dependence of the spin coherence time on the
horizontal beam size. The dependence is due to the path lengthening introduced
by betatron oscillations which forces the particles to go faster in order
to respect the isochronous condition in a bunched beam. A possible method
to correct for emittance effects is to use sextupole magnets. In fact the field
varies as the square of the radius from the center and provides an adjustment
to the particle orbit to remove the term driving the spin tune change.
It has been demonstrated that for a particular value of sextupole strength
the contribution from the horizontal emittance was canceled, reaching a
spin coherence time of a hundred seconds
Search for Electric Dipole Moments with Polarized Beams in Storage Rings.
No full textThe search for an electric dipole moment (EDM) using a polarized, charged-particle beam in a storage ring requires ring conditions that can maintain a longitudinal polarization for times up to 1000 s. This situation is unstable against the spread of the particle spins in the horizontal plane, so a method to control this effect must be demonstrated. For this reason, a series of dedicated studies is being performed at the COoler SYnchrotron (COSY) at the Forschungszentrum-Jülich to examine the effects of emittance spread on the spin coherence time. To support these studies, a novel polarimeter system has been developed that can monitor the horizontal polarization of the beam circulating in the ring as it precesses at ~120 kH
Synchrotron Oscillations Effects on Observations of an RF-solenoid Spin resonance for a polarized deuteron beam at COSY
Full text linkThe search for an electric dipole moment (EDM) using a polarized, charged-particle beam in a storage ring requires ring conditions that can maintain a longitudinal, and stable, polarization for times up to 1000 s. The EDM signal is a rotation of this polarization into the vertical direction as a consequence of the radial electric fields present in both electric and magnetic storage rings. A study is beginning at the COoler SYnchrotron (COSY) located at the Forschungszentrum-Jülich to examine the effects of emittance and momentum spread on the spin coherence time. As these effects also appear in the properties of an RF-induced spin resonance, this study began by exciting the 1Gg resonance with fixed and variable frequency RF-solenoid scans and a 0:97 GeV/c polarized deuteron beam. Subsequent model analysis of the data recorded for many different beam and solenoid conditions demonstrated through good agreement with the data that most of
the observed effects originated in the time shift of deuterons passing through the solenoid, as they underwent synchrotron oscillations inside first harmonic beam bunching. A model, which does not include the ring lattice, is described along with a summary of phenomena observed during the
experiment
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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