LHC Transverse Feedback System and its Hardware Commissioning

A powerful transverse feedback system ("Damper") has been installed in LHC. It will stabilise coupled bunch instabilities in a frequency range from 3 kHz to 20 MHz and at the same time damp injection oscillations originating from steering errors and injection kicker ripple. The transverse damper can also be used as an exciter for purposes of abort gap cleaning or tune measurement. The power and lowlevel systems layouts are described along with results from the hardware commissioning. The achieved performance is compared with earlier predictions and requirements for injection damping and instability control

LHC Transverse Feedback System: First Results of Commissionning

A powerful transverse feedback system ("Damper") has been installed in LHC. It will stabilise the high intensity beam against coupled bunch transverse instabilities in a frequency range from 3 kHz to 20 MHz and at the same time damp injection oscillations originating from steering errors and injection kicker ripple. The LHC Damper can also be used as means of exciting transverse oscillations for the purposes of abort gap cleaning and tune measurement. The LHC Damper includes 4 feedback systems on 2 circulating beams (in other words one feedback system per beam and plane). Every feedback system consists of 4 electrostatic kickers, 4 push-pull wide band power amplifiers, 8 preamplifiers, two digital processing units and 2 beam position monitors with low-level electronics. The power and low-level subsystem layout is described along with first results from the commissioning of 16 power amplifiers and 16 electrostatic kickers located in the LHC tunnel. The achieved performance is compared with earlier predictions and requirements for injection damping and instability control. Requirements and first measurements of the performance of the power and low-level subsystems are summarized

Fostering support for non-democratic rule? Controlled political liberalization and popular support for non-democratic regimes

When the Cold War ended, many non-democratic regimes across the globe embarked on a course of controlled political liberalization, hoping to stabilize their autocratic rule by mitigating popular demands for democratization and increasing regime legitimacy. But does this strategy actually work? This article uses multi-level analyses to examine how the degree of political liberalization affects regime support in non-democratic political systems and to ascertain which mechanisms underlie this effect. Drawing on aggregate measures of political liberalization and comparative survey data from four regional survey projects and 31 non-democracies, the study's results indicate that the degree of liberalization has no decisively positive effect on regime support, suggesting controlled political liberalization might not be an effective legitimizing strategy after all.Nach Ende des Kalten Krieges haben viele nicht-demokratische Regime weltweit einen Kurs der begrenzten politischen Öffnung eingeschlagen, um öffentliche Forderungen nach Demokratisierung zu entschärfen und auf diese Weise die Legitimität ihrer autokratischen Herrschaft zu erhöhen. Doch ist diese Strategie tatsächlich effektiv? Der Beitrag verwendet Mehrebenenanalysen, um zu untersuchen wie der Grad an politischer Öffnung die Regimerunterstützung in nicht-demokratischen politischen Systemen beeinflusst. Auf Basis von Aggregatmaßen zur politischen Öffnung und Individualdaten aus vier regionalen Umfrageprojekten und 31 Autokratien kann kein klarer positiver Effekt des Grads der politischen Öffnung auf die Regimeunterstützung nachgewiesen werden, was eine begrenzte politische Öffnung als wenig effektive Legitimationsstrategie erscheinen lässt

Perceived corruption and individuals’ life satisfaction: The mediating role of Institutional Trust Marco

Corruption degrades the quality of institutions, increases economic inequality and limits growth. Recent studies indicate that corruption is also associated with lower satisfaction with life. This research examines a potential explanation for this association and investigates the role of institutional trust in mediating the linkage between perceived corruption and satisfaction with life. Specifically, in two studies, we tested the novel hypothesises that perceived corruption affects life satisfaction indirectly by undermining individuals’ confidence in institutions. Study 1 (N = 251) involved an opportunity sample from the US. Study 2 (N = 9508) analysed data from the World Value Survey and involved a larger, representative sample of individuals from the MENA region. Across studies, mediation analyses provided evidence for the hypothesized indirect effect of perceived corruption on life satisfaction through institutional trust. Implications of the findings, limitations of the studies and directions for future research are discussed

Ringing in the Pulse Response of Long and Wideband Coaxial Transmission Lines due to Group Delay Dispersion

In particle accelerators coaxial cables are commonly used to transmit wideband beam signals covering many decades of frequencies over long distances. Those transmission lines often have a corrugated outer and/or inner conductor. This particular construction exhibits a significant amount of frequency dependent group delay variation. A comparison of simulations based on theoretical models and S11 and S21 network analyzer measurements up to 2.5 GHz is presented. It is shown how the non-linear phase response and varying group delay leads to ringing in the pulse response and subsequent distortion of signals transmitted through such coaxial transmission lines

ADT and Obsbox in LHC Run 2, Plans for LS2

The primary function of the LHC transverse feedback (ADT), is to damp the injection oscillations and to actively counteract the coupled-bunch instabilities driven by the machine impedance. While the damping function was there since the LHC start-up in 2008, during Run 2 the ADT also became a very important tool to perform active excitation of all kinds and various beam measurements through the whole cycle. High resolution, bunch by bunch, turn by turn beam position data is available within the ADT signal processing, which is made available for real-time, or offline analysis by means of ADTObsBox system. In line with the topic of this Evian LHC performance workshop, the paper documents how both systems evolved during Run 2 and provide an overview of expected upgrades and developments planned for LS2