Benchmarking electron-cloud simulations and pressure measurements at the LHC

During the beam commissioning of the Large Hadron Collider (LHC) with 150, 75, 50 and 25-ns bunch spacing, important electron-cloud effects, like pressure rise, cryogenic heat load, beam instabilities or emittance growth, were observed. A method has been developed to infer different key beam-pipe surface parameters by benchmarking simulations and pressure rise observed in the machine. This method allows us to monitor the scrubbing process (i.e. the reduction of the secondary emission yield as a function of time) in the regions where the vacuum-pressure gauges are located, in order to decide on the most appropriate strategies for machine operation. In this paper we present the methodology and first results from applying this technique to the LHC.Comment: 5 pages, 7 figures, presented at ECLOUD 12: Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects, La Biodola, Isola d Elba, Italy, 5-9 June 201

Régulation de position à l'aide d'un correcteur PID numérique - Application sur l'expérience GRAAL

En augmentant la réactivité du programme LabVIEW de GRAAL et en le dotant d'un correcteur PID logiciel, on a supprimé de pénibles phases de réglage manuel et amélioré les résultats de l'acquisition. La mise au point de l'algorithme de correction sur un simple ordinateur, le réglage de la chaîne de rétroaction sur site et la bonne calibration du PID ont permis le succès de cette application. Ce document décrit le contexte expérimental, le principe et la mise en place du correcteur PID jusqu'à son test

The story of Wakefield -- a history of Wakefield, Massachusetts for third grade children

Thesis (Ed.M.)--Boston Universit

Hu(l)man Medi(t)ations: Intercultural explorations in Keri Hulme’s The Windeater / Te Kaihau

published_or_final_versio

LabVIEW intègre et accélère les processus de développement en physique expérimentale

La physique expérimentale a massivement recours à la programmation d'instruments. Nous présentons deux réalisations LabVIEW du LPSC, pour les expériences GRAAL et PLANCK. En nous appuyant sur ces exemples nous dégagerons certaines qualités qui permetent à LabVIEW d'intégrer l'environnement et les méthodes de la recherche. Enfin nous examinerons des points de concordance profonds entre la technologie LabVIEW et les contraintes techniques de la programmation des expériences

High-temperature ferroelectric order and magnetic field-cooled effect driven magnetoelectric coupling in R2BaCuO5 (R= Er, Dy, Sm)

The high-temperature ferroelectric order and a remarkable magnetoelectric effect driven by the magnetic field cooling are reported in R2BaCuO5 (R = Er, Dy, Sm) series. The ferroelectric (FE) orders are observed at much higher temperatures than their magnetic orders for all three members. The value of FE Curie temperature (TFE) is considerably high as ~ 235 K with the polarization value (P) of ~ 1410 {\mu}C/m2 for a 4 kV/cm poling field in case of Er2BaCuO5, whereas the values of TFE and P are also promising as ~ 232 K and ~ 992 {\mu}C/m2 for Dy2BaCuO5, and ~ 184 K and ~ 980 {\mu}C/m2 for Sm2BaCuO5. The synchrotron diffraction studies of Dy2BaCuO5 confirm a structural transition at TFE to a polar Pna21 structure, which correlates the FE order. An unusual magnetoelectric coupling is observed below the R order for Er and Dy compounds and below the Cu order for Sm compound, when the pyroelectric current is recorded only with the magnetic field both in heating and cooling cycles i.e. typical magnetic field cooled effect. The magnetic field cooled effect driven emergence of polarization is ferroelectric in nature, as it reverses due to the opposite poling field. The unexplored R2BaCuO5 series attracts the community for large TFE, high P value, and strange magnetoelectric consequences.Comment: 9 figures and 2 supporting figure

Observation of Lasing Mediated by Collective Atomic Recoil

We observe the buildup of a frequency-shifted reverse light field in a unidirectionally pumped high-$Q$ optical ring cavity serving as a dipole trap for cold atoms. This effect is enhanced and a steady state is reached, if via an optical molasses an additional friction force is applied to the atoms. We observe the displacement of the atoms accelerated by momentum transfer in the backscattering process and interpret our observations in terms of the collective atomic recoil laser. Numerical simulations are in good agreement with the experimental results.Comment: 4 pages, 3 figure

Framing the change and changing frames:Tensions in participative strategy development

Participative strategy development serves to integrate the interests and perspectives of multiple stakeholders involved in today's complex environmental challenges, aiming at a better-informed strategy for tackling these challenges, increased stakeholder ownership, and more democratic decision making. Prior research has observed inherent tensions between the need for participative strategy to be open to stakeholders' input and the need for closure and guidance. We extend this reasoning using a framing perspective. Our evidence from the development of the England Peat Action Plan suggests that tensions can emerge between the necessary ambiguous initial framing of intended change and the persistence of stakeholders' different framings of this change as well as perceptions of lacking knowledge, guidance, and control. We argue that strategy openness can thereby impede stakeholders' willingness and ability to change and counteract the strategy's aim for major transformation. Interactive spaces help mitigate the tensions and facilitate stakeholders' willingness and ability for change. </p