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

Scientific, institutional and personal rivalries among Soviet geographers in the late Stalin era

Scientific, institutional and personal rivalries between three key centres of geographical research and scholarship (the Academy of Sciences Institute of Geography and the Faculties of Geography at Moscow and Leningrad State Universities) are surveyed for the period from 1945 to the early 1950s. It is argued that the debates and rivalries between members of the three institutions appear to have been motivated by a variety of scientific, ideological, institutional and personal factors, but that genuine scientific disagreements were at least as important as political and ideological factors in influencing the course of the debates and in determining their final outcome

Random-phase approximation and its applications in computational chemistry and materials science

The random-phase approximation (RPA) as an approach for computing the electronic correlation energy is reviewed. After a brief account of its basic concept and historical development, the paper is devoted to the theoretical formulations of RPA, and its applications to realistic systems. With several illustrating applications, we discuss the implications of RPA for computational chemistry and materials science. The computational cost of RPA is also addressed which is critical for its widespread use in future applications. In addition, current correction schemes going beyond RPA and directions of further development will be discussed.Comment: 25 pages, 11 figures, published online in J. Mater. Sci. (2012

A measurement of the transverse polarization of Lambda-hyperons produced in inelastic pN-reactions at 450 GeV proton energy

A study of the polarization of Λ hyperons produced in inelastic pN reactions induced by the 450 GeV proton beam from the CERN SPS has been performed with the NA48 detector. The Λ hyperons were detected at a fixed angle of 4.2 mrad in the momentum range from 50 GeV/c to 200 GeV/c. The polarization changes from −0.053 ± 0.034 to −0.298 ± 0.074 for a transverse momentum range of the Λ between 0.28 GeV/c and 0.86 GeV/c. The antiΛ polarization is consistent with zero

The universal values of science and China’s Nobel Prize pursuit

China does not seem to believe the existence of universally acknowledged values in science and fails to promote the observation of such values that also should be applied to every member of the scientific community and at all times. Or, there is a separation between the practice of science in China and the values represented by modern science. In this context, science, including the pursuit of the Nobel Prize, is more a pragmatic means to achieve the end of the political leadership – the national pride in this case – than an institution laden with values that govern its practices. However, it is the recognition and respect of the latter that could lead to achievement of the former, rather than the other way around

Futur dels teixits intel·ligents

Els teixits intel·ligents del futur es desenvolupen amb nous materials i amb tecnologies innovadores, però també amb clau d'eficiència ambiental. Es revisen tendències de la indústria tèxtil relacionades, entre d'altres, amb: Teixits funcionals i materials amb propietats singulars. e-Textil, wearables i gestió 4.0. Automatització, robòtica i impressió 3D. Ecologia industrial, impacte ambiental i valorització energètic

New Combinatorial Complete One-Way Functions

In 2003, Leonid A. Levin presented the idea of a combinatorial complete one-way function and a sketch of the proof that Tiling represents such a function. In this paper, we present two new one-way functions based on semi-Thue string rewriting systems and a version of the Post Correspondence Problem and prove their completeness. Besides, we present an alternative proof of Levin’s result. We also discuss the properties a combinatorial problem should have in order to hold a complete one-way function.