The LHC Meets Industry

Building the parts for the Large Hadron Collider has presented many challenges but taught many lessons for both particle physics laboratories and their industry partners

Connected components of compact matrix quantum groups and finiteness conditions

We introduce the notion of identity component of a compact quantum group and that of total disconnectedness. As a drawback of the generalized Burnside problem, we note that totally disconnected compact matrix quantum groups may fail to be profinite. We consider the problem of approximating the identity component as well as the maximal normal (in the sense of Wang) connected subgroup by introducing canonical, but possibly transfinite, sequences of subgroups. These sequences have a trivial behaviour in the classical case. We give examples, arising as free products, where the identity component is not normal and the associated sequence has length 1. We give necessary and sufficient conditions for normality of the identity component and finiteness or profiniteness of the quantum component group. Among them, we introduce an ascending chain condition on the representation ring, called Lie property, which characterizes Lie groups in the commutative case and reduces to group Noetherianity of the dual in the cocommutative case. It is weaker than ring Noetherianity but ensures existence of a generating representation. The Lie property and ring Noetherianity are inherited by quotient quantum groups. We show that A_u(F) is not of Lie type. We discuss an example arising from the compact real form of U_q(sl_2) for q<0.Comment: 43 pages. Changes in the introduction. The relation between our and Wang's notions of central subgroup has been clarifie

A theory of the strain-dependent critical field in Nb3Sn, based on anharmonic phonon generation

We propose a theory to explain the strain dependence of the critical properties in A15 superconductors. Starting from the strong-coupling formula for the critical temperature, and assuming that the strain sensitivity stems mostly from the electron-phonon alpha^2F function, we link the strain dependence of the critical properties to a widening of alpha^2F. This widening is attributed to the nonlinear generation of phonons, which takes place in the anharmonic deformation potential induced by the strain. Based on the theory of sum- and difference-frequency wave generation in nonlinear media, we obtain an explicit connection between the widening of alpha^2F and the anharmonic energy. The resulting model is fit to experimental datasets for Nb3Sn, and the anharmonic energy extracted from the fits is compared with first-principles calculations.Comment: 10 pages, 3 figure

An Estimate of the Maximum Gradients in Superconducting Quadrupoles

In this paper we show that the electromagnetic design of several superconducting quadrupoles, built for particle accelerators, can be rather well approximated by a 36 degree sector coil with a wedge, canceling the first two field harmonics. We therefore carry out a complete analysis of this lay-out, obtaining an approximated equation for the critical gradient as a function of the coil area, magnet aperture, and of the superconducting properties of the cable. Using this model, we estimate through numerical methods the maximum critical gradient that can be obtained in quadrupole of a given aperture for Nb-Ti, Nb-Ti-Ta and Nb$_{3}$Sn

Industrial Learning Curves: Series Production of the LHC Main Superconduting Dipoles

By mid August 2006, 1160 of the 1232 of LHC main dipoles have been delivered to CERN by the three suppliers in charge of the production. The training of the staff, mostly hired just for this manufacture, and the improvement of the procedures with the acquired experience, naturally decrease the time necessary for the assembly of a unit. The aim of this paper is to apply methodologies like the cost-based learning curves and the time-based learning curves to the LHC Main Dipole production comparing the estimated learning percentage to the ones experienced in other industries. This type of analysis, already presented on 500 units is here extended to more than 1000 completed units. The work also tries to identify which type of industry presents the learning percentages that are the most similar to our case and to investigate the impact of the production strategy on the process efficiency

Motion of a superconducting loop in an inhomogeneous magnetic field: a didactic experiment

We present an experiment conductive to an understanding of both Faraday's law and the properties of the superconducting state. It consists in the analysis of the motion of a superconducting loop moving under the influence of gravity in an inhomogeneous horizontal magnetic field. Gravity, conservation of magnetic flux, and friction combine to give damped harmonic oscillations. The measured frequency of oscillation and the damping constant as a function of the magnetic field strength (the only free parameter) are in good agreement with the theoretical model.Comment: 9 pages, 5 figure

Preliminary Study of Using "Pipetron-type" Magnets for a Pre-accelerator for the LHC

One of the luminosity limitations of the LHC is the rather low injection energy (0.45 TeV) with respect to the collision energy (7 TeV). The magnetic multipoles in the main dipoles at low field and their dynamic behaviour are considered to limit the achievable bunch intensity and emittance. We report on a preliminary study to increase the injection energy to 1.5 TeV using a two-beam pre-accelerator (LER) in the LHC tunnel. The LER is based on âﾜPipetronâ magnets as originally proposed for the VLHC. The aim of the study is to assess the feasibility and to identify the critical processes or systems that need to be investigated and developed to render such a machine possible

Superconduttività: dalla Fisica delle Particelle all'Adroterapia

La superconduttività ha accompagnato la crescita esponenziale dell'energia e della luminosità degli acceleratori di particelle negli ultimi 50 anni e da lì è penetrata nella società. In particolare i magneti superconduttori sono l'applicazione con maggior impatto: basti pensare ai circa 5000 grandi magneti superconduttori che ogni anno vengono costruiti per altrettanti sistemi di diagnostica medica basata su immagine per risonanza magnetica. Gli acceleratori di particelle, in particolare i grandi collisori adronici o i LINAC per elettroni, vanno riconosciuti come un volano che ha generato lo sviluppo della tecnologia superconduttiva