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Beam Dynamics of Proton-Nucleus Collisions in the Large Hadron Collider
No full textThis thesis discusses important questions of the beam dynamics in the proton-lead operation in the Large Hadron Collider (LHC) at CERN in Geneva. In two time blocks of several weeks in the years 2013 and 2016, proton-lead collisions have so far been successfully generated in the LHC and used by the experiments at the LHC. One reason for doubts regarding the successful operation in proton-lead configuration was the fact that the beams have to be accelerated with different revolution frequencies. There is long-range repulsion between the beams, since both beams share the beam chamber around the interaction points. Because of the different revolution frequencies, the positions of the interaction between the beams shift each revolution. This can lead to resonant excitation and to an increase in the transverse beam emittance, as was observed in the Relativistic Heavy-Ion Collider (RHIC). In this thesis, simulations for the LHC, RHIC and the High-Luminosity Large Hadron Collider (HL-LHC) are performed with a new model. The results for RHIC show relative growth rates of the emittances of the gold beam in gold-deuteron operation in RHIC from to . Growth rates of this magnitude were observed experimentally in RHIC. Simulations for the LHC show no significant increase of the emittance of the lead beam for different intensities of the counter-rotating beam. The simulation results confirm the measured stability of the beams in the LHC and the issue of strongly increasing emittances in RHIC is reproduced. Also, no significant increase of the emittance is predicted for the Future Circular Collider (FCC) and the HL-LHC. Using a frequency-map analysis, this work verifies whether the interaction of the lead beam with the much smaller proton beam in the proton-lead operation of the LHC leads to diffusion within the lead beam. Experiences at HERA at DESY in Hamburg and at SppS at CERN have shown that the lifetime of the larger beam can rapidly decrease under certain circumstances. The results of the simulation show no chaotic dynamics near the beam centre of the lead beam. This result is supported by experimental observation. A program code has been developed which calculates the beam evolution in the LHC by means of coupled differential equations. This study shows that the growth rates of the lead beam due to intra-beam scattering is overestimated and that particle bunches of the lead beam lose more intensity than assumed in the model. The analysis also shows that bunches colliding in a detector suffer additional losses that increase with decreasing crossing angle at the interaction point. In this work, 2016 data from beam-loss monitors in combination with the luminosity and the loss rate of the beam intensity are used to determine the cross section of proton-lead collisions at TeV. Beam-loss monitors that mainly detect beam losses that are not caused by the collision process itself are used to determine the total cross section via regression. An analysis of the data recorded in 2016 at TeV resulted in a total cross section of b. This corresponds approximately to a hadronic cross section of b. This value deviates only by from the theoretical value b. The simulation code for determining the beam evolution is also used to estimate the integrated luminosity of a future one-month run with proton-lead collisions. The result of the study shows that in the future the luminosity in the ATLAS and CMS experiments will increase from nb per day in 2016 to nb per day, which is a significant increase in terms of the performance. This operation, however, requires the use of the TCL collimators to protect the dispersion suppressors at ATLAS and CMS from collision fragments. This work also gives an outlook on the expected luminosity production in proton-nucleus operation using ion species lighter than lead ions. For example, a change from proton-lead to proton-argon collisions would increase the integrated luminosity from monthly nb to nb in ATLAS and CMS. This is an increase of one order of magnitude and approximately a doubling of the integrated nucleon-nucleon luminosity. There may be a test operation with proton-oxygen collisions in 2023, which will last only a few days and will be operated with a low luminosity. The LHCf experiment (LHCb experiment) would achieve the desired integrated luminosity of nb (nb) within () beam time
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
Progress of the EEHG upgrade at the DELTA short-pulse source
No full textAt DELTA, a 1.5-GeV synchrotron light source operated by the TU Dortmund University, a short-pulse source based on coherent harmonic generation (CHG) is used to generate sub-picosecond synchrotron radiation pulses in the VUV regime, which result from micro-bunching at the center of an electron bunch due to laser-electron interaction. Shorter wavelengths are achievable with the so-called echo-enabled harmonic generation (EEHG) technique by adding a second laser-electron interaction. The current short-pulse source will be modified to include the EEHG scheme. The status of the upgrade project will be presented
Ideas for a slow extraction via SPS LSS4 or LSS6 to a future PBC-SBN beamline
No full textWithin the scope of the Physics Beyond Colliders (PBC) framework and its Conventional Beams Working Group (CBWG), a study for a future Short-Baseline Neutrino Beamline (SBN) at CERN is ongoing. In this context, a preliminary conceptual feasibility analysis of different options of placing the beamline at the PS or the SPS has been carried out. In case that the SPS is chosen as proton driver for this project, a slowly extracted beam from the the LSS4 or LSS6 locations would be needed. The present report complements the feasibility analysis by analysing on a conceptual level, the two possible solutions of a new slow extraction that in first-order may not require important R\&D, since they employ only existing technologies. The first solution is restricted to the SPS LSS4 and LSS6 straight sections exclusively (``local'' solution) that would allow a GeV/ slow extraction. The second solution necessitates the installation of new ZS wire septa in LSS4 to extract the beam at today's slow extraction momentum ( GeV/) in LSS6. The latter solution appears easier to implement since it does not necessitate a modification of the existing fast extraction to the LHC. In addition, it would potentially allow the flexible extraction to two experimental areas simultaneously like it was performed for several years before the LHC started operation. Both solutions have been studied only in a first-order level of detail
Steady-state solutions of split beams in electron storage rings
Get PDFRecently, a novel operation method for synchrotron light sources with transversely split beams has been explored to fulfill the rising demand for flexible and high-throughput X-ray sources required in such diverse fields as time-resolved X-ray spectroscopy, molecular chemistry in organic cells, high-resolution medical imaging, quantum materials science or sustainable energy research. Within that novel operation mode, additional stable regions are produced in the horizontal phase space by operating an electron storage ring on a resonance that is driven by the nonlinear sextupole or octupole magnets. In the longitudinal phase space, a similar split can be produced by introducing an oscillation of the synchrotron phase via a modulation of the phase of the radiofrequency resonator. Strong radiation damping in electron storage rings, however, has to be overcome before additional regions in phase space can become populated by particles and form stable islands. This damping mechanism changes the dynamics of the system and causes diffusion between the different islands in phase space, raising the question what kind of equilibrium state exists in the asymptotic temporal limit. In this paper, a finite-differences approximation in rotating action-angle coordinates is used to solve the Vlasov–Fokker–Planck equation and to study the obtained equilibrium states for the longitudinal as well as the transverse case. The number of solution vectors and the magnitude of the corresponding singular values of the matrix of the underlying finite-differences equation are used as abstract indicators to define the required parameter set that provides stable additional beamlets. As a consequence, the beamlets have a stability that is close to that of the main beam in terms of diffusion caused by the radiation damping and quantum excitation
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
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