366 research outputs found
Evolution of Python Tools for the Simulation of Electron Cloud Effects
No full textPyECLOUD was originally developed as a tool for the simulation of electron cloud build-up in particle accelerators. Over the last five years the code has become part of a wider set of modular and scriptable python tools that can be combined to study different effects of the e-cloud in increasingly complex scenarios. The Particle In Cell solver originally included in PyECLOUD later developed into a stand-alone general purpose library (PyPIC) that now includes advanced features like a refined modeling of curved boundaries and optimized resolution based on the usage of nested grids. The effects of the e-cloud on the beam dynamics can be simulated interfacing PyECLOUD with the PyHEADTAIL code. These simulations can be computationally very demanding due to the multi-scale nature of this kind of problems. Hence, a dedicated parallelization layer (PyPARIS) has been recently developed to profit of parallel computing resources in order to significantly speed-up the computation
A test on analytic continuation of thermal imaginary-time data
No full textBurnier Y, Laine M, Mether L. A test on analytic continuation of thermal imaginary-time data. European Physical Journal C. 2011;71(4): 1619
Electron Cloud Effects at the LHC and LHC Injectors
No full textElectron cloud effects are one of the main limitations of the performance of the LHC and its injectors. Enormous progress has been done in the simulation of the electron cloud build-up and of the effects on beam stability while mitigation measures have been identified and implemented (scrubbing, low secondary electron yield coatings, etc.). The above has allowed reaching nominal beam parameters in the LHC during Run 2. A review of the studies and results obtained and the strategy and expected performance for the High Luminosity operation of the LHC will be presented
Modelling of Fast Beam-Ion Instability in Future Accelerators
No full textFremtidige akseleratorer som den kompakte lineære kollideren (CLIC) forventes å være sårbare for fenomenet fast beam-ion instability (FBII) på grunn av deres høye stråleintensitet og små tverrgående strålestørrelse. I motsetning til klassisk ione-ustabilitet, manifesterer FBII seg langs lengden av strålen, noe som betyr at det kan oppstå i lineære akseleratorer (LINAC) så vel som sirkulære akseleratorer. Ioner genereres gjennom strålens interaksjon med gassene som er tilstede i akselerator kanalen og induserer en sammenhengende bevegelse av strålen som gjør at den blir ustabil. De numeriske makropartikkelmodelleringsverktøyene PyECLOUD og PyHEADTAIL har tidligere blitt brukt til å studere FBII i CLIC-demper-ringen.
I dette prosjektet har de numeriske modelleringsverktøyene blitt brukt for å studere effekten av restgasstrykk i hoved-LINAC til CLIC. Simuleringsoppsett med gasssammensetning av flere arter har blitt testet for CLIC-demper-ringen, og ionegenereringsprosessen har blitt oppdatert for å håndtere elektrisk feltionisering.
Resultatene fra simuleringene av demper-ringen viste god samsvar med teorien. Det er imidlertid nødvendig med ytterligere undersøkelser før vellykkede simuleringsstudier av FBII i hoved-LINAC til CLIC kan oppnås. Opp mot dette har master prosjektet lagt grunnlaget for videre utvikling og fremtidige trykkstudier i hoved-LINAC til CLIC.Future accelerators such as the compact linear collider (CLIC) are expected to be vulnerable to the fast beam-ion instability (FBII) phenomenon due to their high beam intensity and small transverse beam size. Unlike classical ion instability, FBII manifests along the length of the bunch train which means that it can arise in linear accelerators (LINAC) as well as circular accelerators. Ions are generated through the beam's interaction with the gases present in the beam duct and induce a coherent motion of the bunches which causes the beam to become unstable. The numerical macroparticle modelling tools PyECLOUD and PyHEADTAIL have previously been used to study FBII in the CLIC damping ring.
In this project the numerical modelling tools have been applied for studying the effects of residual gas pressure in the CLIC main LINAC. Simulation setups with multiple species gas composition have been tested for the CLIC damping ring and the ion generation process has been updated to handle electric field ionisation.
The results from the damping ring simulations showed good alignment with theory. However, further investigation are needed to before successful simulation studies of FBII in the CLIC main LINAC can be achieved. To that end, the project has laid the foundation for continued development and future pressure studies in the CLIC main LINAC
Python tools for simulating beam dynamics
No full textBrief explanation of requirements for fast beam dynamics simulations, why Python, and the PyHEADTAIL package.</p
Prime osservazioni sul rapporto tra il reato di “Diffusione illecita di immagini o video sessualmente espliciti” e le libertà di corrispondenza e di manifestazione del pensiero
No full textL’articolo concerne il rapporto tra il reato di “Diffusione illecita di immagini o video sessualmente espliciti” (art. 612-ter c.p.) e le libertà costituzionali di corrispondenza (art. 15 Cost.) e di manifestazione del pensiero (art. 21 Cost.). Nello specifico, l’Autore si chiede se il reato di cui all’art. 612-ter incida sulle libertà di cui all’art. 15 e all’art. 21
Cost. Invero, l’unico obiettivo del reo è quello di ledere l’identità morale e l’onorabilità della vittima. Per questo motivo, non deve indurre in errore la circostanza che la condotta descritta dall’art. 612-ter verrà (esclusivamente) posta in essere utilizzando mezzi di comunicazione, deputati alla trasmissione del pensiero. Infatti, l’Autore ritiene che il fondamento costituzionale dell’art. 612-ter c.p. è da rinvenirsi negli artt. 2, 3 e 13 (intesa quale libertà di autodeterminarsi) Cost., mentre la libertà di corrispondenza e la libertà di manifestazione del pensiero non vengono compresse dal reato in esame.The paper concerns the relationship between the crime of “Illicit distribution of sexually explicit images or videos” (Article 612-ter of the Italian Criminal Code) and the constitutional freedoms of correspondence and expression of thought.
Specifically, the Author reflects on whether the offence under art. 612-ter affects the freedoms pursuant to Article 15 and Article 21 of the Constitution. Indeed, the offender’s sole objective is to damage the victim’s moral identity and reputation. For this reason, we should not be misled by the fact that the conduct targeted in Article 612-ter may (exclusively) be implemented using means of communication designed for the transmission of thought. In fact, the Author believes that the constitutional foundation for art. 612-ter of the Italian Criminal Code is to be found in Articles 2, 3 and 13 of the Constitution (regarding the freedom of self-determination), while the freedom of correspondence and freedom of expression of thought are not restricted by the crime in question
Un nuovo diritto al tempo del Covid-19? Accesso a Internet e digital divide
No full textThe article analyses the issue of Internet access and digital divide, also considering Covid-19 health emergency. The Author acknowledges that Internet is now a fundamental prerequisite for exercising civil and political rights and for developing individual's personality. Therefore, retracing doctrinal orientations developed on Internet access, he believes that it should not be configured as a right but a mere functional instrument for exercising fundamental rights. Hence the need to shift the centre of gravity of the issue from the right to the instrument to the effectiveness of the right exercisable through the instrument. Therefore, without the need to include Internet access in the list of (fundamental) rights, it is argued that it must be subsumed in the context of the public service, and in particular in the universal service. This in fact would entail the undoubted advantage - with the Constitution unchanged - of not excluding any segment of the population from the Internet service (it would be better, from broadband connection). All this is also investigated from the visual angle of Covid-19 health emergency, which has sharpened digital divide and that made the intervention of the legislator necessary to better guarantee Internet access, since through the remote connection (and only through it) it was possible to exercise certain fundamental rights during the lockdown
Consequences of Supersymmetry in the Early Universe
No full textCurrently, we live in an era characterized by the completion and first runs of the LHC accelerator at CERN, which is hoped to provide the first experimental hints of what lies beyond the Standard Model of particle physics. In addition, the last decade has witnessed a new dawn of cosmology, where it has truly emerged as a precision science. Largely due to the WMAP measurements of the cosmic microwave background, we now believe to have quantitative control of much of the history of our universe.
These two experimental windows offer us not only an unprecedented view of the smallest and largest structures of the universe, but also a glimpse at the very first moments in its history. At the same time, they require the theorists to focus on the fundamental challenges awaiting at the boundary of high energy particle physics and cosmology. What were the contents and properties of matter in the early universe? How is one to describe its interactions? What kind of implications do the various models of physics beyond the Standard Model have on the subsequent evolution of the universe?
In this thesis, we explore the connection between in particular supersymmetric theories and the evolution of the early universe. First, we provide the reader with a general introduction to modern day particle cosmology from two angles: on one hand by reviewing our current knowledge of the history of the early universe, and on the other hand by introducing the basics of supersymmetry and its derivatives. Subsequently, with the help of the developed tools, we direct the attention to the specific questions addressed in the three original articles that form the main scientific contents of the thesis. Each of these papers concerns a distinct cosmological problem, ranging from the generation of the matter-antimatter asymmetry to inflation, and finally to the origin or very early stage of the universe. They nevertheless share a common factor in their use of the machinery of supersymmetric theories to address open questions in the corresponding cosmological models.Hiukkasfysiikka ja kosmologia ovat havaitun maailmankaikkeuden kaikkein pienimmän ja suurimman skaalan rakenteita tutkivat fysiikan alat: hiukkasfysiikassa pyritään ymmärtämään luonnon perusosasten luonne ja vuorovaikutukset, kun taas kosmologia tutkii maailmankaikkeuden syntyhistoriaa sekä nykyistä rakennetta. Näiden kahden näennäisesti toisistaan hyvin kaukaisen alan yhtymäkohta löytyy varhaisesta maailmankaikkeudesta, jossa Big Bang -teorian mukaan universumin täytti erittäin kuuma ja tiheä hiukkaspuuro. Tämän aineen ominaisuuksien ymmärtäminen on yhtäällä välttämätöntä maailmankaikkeuden myöhemmän kehityksen ennustamiseksi, mutta toisaalta - johtuen valtavasta energiatiheydestä - vaatii myös hiukkasfysiikan syvällistä hallintaa.
Elämme tällä hetkellä ajanjaksoa, joka on niin hiukkasfysiikan kuin kosmologian kannalta ainutlaatuinen. CERN-laboratoriossa Sveitsissä on hiljattain käynnistetty kaikkien aikojen tehokkain hiukkaskiihdytin LHC, jonka toivotaan antavan ensimmäisiä viitteitä tämänhetkisen hiukkasfysiikan yleisesti hyväksytyn teoriarakennelman, ns. Standardimallin, ulkopuolisesta fysiikasta. Toisaalta viimeisten kymmenen vuoden aikana kosmologiasta on vihdoin muodostunut tarkkuustiede, kun kosmisen mikroaaltotaustasäteilyn spektriä tutkivan WMAP-satelliitin tuloksista on pystytty päättelemään maailmankaikkeuden historiaa ja nykyrakennetta kuvaavia parametreja huomattavasti entistä tarkemmin.
Samalla kun kokeellisen hiukkasfysiikan ja kosmologian nopea kehitys on avaamassa aivan uudenlaisia ikkunoita maailmankaikkeuden syntyyn ja kehitykseen, se myös lähettää haasteen teoreettiselle fysiikalle: tänä päivänä on entistäkin tärkeämpää pystyä laskemaan Standardimallin ulkopuolisista teorioista seuraavia ennusteita kosmologisille parametreille. Erityisen polttavia ovat kysymykset siitä, mitä seurauksia ns. supersymmetrisillä teorioilla on varhaisen maailmankaikkeuden kehitykselle. Supersymmetrian on nimittäin otaksuttu tarjoavan vastauksen useisiin nykyfysiikan suurimmista avoimista kysymyksistä aina pimeästä aineesta ns. hierarkiaongelmaan, ja siksi sen kosmologiset implikaatiot ovatkin yksi modernin korkeaenergiafysiikan keskeisimmistä tutkimuskohteista.
Käsillä olevassa väitöskirjatyössä luodaan katsaus erilaisten supersymmetristen teorioiden ominaisuuksiin ja niiden merkitykseen varhaisen maailmankaikkeuden kehitykselle. Työ alkaa johdanto-osalla, joka luo yleiskatsauksen alaan ja johdattelee lukijan väitöskirjan kolmen alkuperäisartikkelin aihepiireihin, jotka kaikki liittyvät kosmologisten ongelmien ratkaisuun supersymmetristen kenttäteorioiden keinoin. Ensimmäisessä artikkeleista tarkastellaan erästä ratkaisua hyvin tunnettuun ns. leptonituoton ongelmaan supersymmetrisissä teorioissa, jonka avulla maailmankaikkeudessa havaittu materian ja antimaterian välinen asymmetria pyritään selittämään. Muut artikkelit puolestaan liittyvät ns. MSSM-inflaatioon sekä säiekaasukosmologiaan, joihin liittyviä käsitteellisiä ja laskennallisia ongelmia niissä ratkaistaan.ei saavutettav
Colour-electric spectral function at next-to-leading order
No full textBurnier Y, Laine M, Langelage J, Mether L. Colour-electric spectral function at next-to-leading order. JHEP. 2010;2010(8): 94.The spectral function related to the correlator of two colour-electric fields along a Polyakov loop determines the momentum diffusion coefficient of a heavy quark near rest with respect to a heat bath. We compute this spectral function at next-to-leading order, O(alpha_s^2), in the weak-coupling expansion. The high-frequency part of our result (omega >> T), which is shown to be temperature-independent, is accurately determined thanks to asymptotic freedom; the low-frequency part of our result (omega 0. We also evaluate the colour-electric Euclidean correlator, which could be directly compared with lattice simulations. As an aside we determine the Euclidean correlator in the lattice strong-coupling expansion, showing that through a limiting procedure it can in principle be defined also in the confined phase of pure Yang-Mills theory, even if a practical measurement could be very noisy there
Update on e-cloud and ion build-up in a storage cell gas target
No full textNo abstract available.Presented at PBC-FT WG meeting 20 February, 2019
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