SPS Vertical Aperture Studies

We present the results of a series of measurements carried out in order to study the SPS physical aperture in the vertical plane. A vertical kick was applied to the circulating beam while introducing a closed orbit bump at the location of the SPS high energy beam dump absorber (TIDVG) that was suspected of limiting the aperture asymmetrically. Beam intensity and transverse prole measurements, performed before and after the kick, were combined to estimate the aperture

High Accuracy Field Mappings with a Laser Monitored Travelling Mole

The LEP Spectrometer is an alternative method adopted to predict the LEP beam Energy. A bending magnet is flanked on either side by tgree beam position monitors /BPM) used to determine thedeflection angle of the beam. In order to reach the desired accuracy on the beam energy a relative precision of a few 10-5 on the magnetic field intefral is necessary. The magnet is a full-iron core dipole, 5.75 m long, of the MBI type used in the LEP injection region. It has been specially designed in order to have high field uniformity

LO IUS SUPERVENIENS TRA ESIGENZE DI TUTELA DEL LEGITTIMO AFFIDAMENTO E LEGALITÀ DELL¿AZIONE AMMINISTRATIVA, NELLA DIMENSIONE ITALIANA, FRANCESE ED EUROPEA

The dissertation examines the impact of new legislation that negatively affects the asset of private interests, carried out by administrative action. The comparative analysis focuses on the Italian and French legal systems, as they share a similar legal tradition in the field of administrative law. The work is aimed at verifying, through the study of the most recent case law, the existence of a position of legitimate expectation recognised to the administrated subjects with respect to the modification of laws over time, under two different aspects: within a proceedings, as well as during on-going situation created by provisions of long-lasting bindingness. The work analyses the available means of protection and it verifies the current position on the matter in the aforementioned normative systems. In the last part, the work studies the inputs on the subject matter given by the decisions of the European Court of Justice and the European Court of Human Rights, taking the analysis to a supra-national level; it also highlights the influence exercised by the German law on the issue of legitimate expectation, as the German system represent the principal referring model

High accuracy magnetic field mapping of the LEP spectrometer magnet

The Large Electron Positron accelerator (LEP) is a storage ring which has been operated since 1989 at the European Laboratory for Particle Physics (CERN), located in the Geneva area. It is intended to experimentally verify the Standard Model theory and in particular to detect with high accuracy the mass of the electro-weak force bosons. Electrons and positrons are accelerated inside the LEP ring in opposite directions and forced to collide at four locations, once they reach an energy high enough for the experimental purposes. During head-to-head collisions the leptons loose all their energy and a huge amount of energy is concentrated in a small region. In this condition the energy is quickly converted in other particles which tend to go away from the interaction point. The higher the energy of the leptons before the collisions, the higher the mass of the particles that can escape. At LEP four large experimental detectors are accommodated. All detectors are multi purpose detectors covering a solid angle of almost 4. . The first period of operation of LEP (1989-1995) has been to the scan of the Z boson energy range, and the electrons and positrons beams were accelerated up to about 45 GeVper beam (see section 1.3.1). Since the end of 1995 LEP is devoted to operate at higher energies, up to more than 100 GeVper beam in the 1999-2000 runs. It was thus possible to investigate the W boson properties and the HiggÂs particle existence, in case its mass reveals to be at this energy level. The types of event (i.e. the fundamental particles) which can be detected depends on the lepton energy before colliding (see Fig. 1.2). The particle beams energy calibration is thus a focal point for a successful operation of the collider. During normal operation electrons and positrons are bent inside the ideal circular trajectory by mean of a number of dipole magnets. The energy of the leptons depends on the total dipole field along their trajectory. The bending field around LEP is monitored by Nuclear Magnetic Resonance (NMR) probes which sample the field in twenty locations. Such measurements provide part of the data for the energy calibration model (see chapter 2). In 1999 a spectrometer has been installed in a section of the LEP ring as a new tool for the beam energy determination. The spectrometer layout mainly consist in an iron-core bending magnet and six Beam Position Monitor (BPM) stations. The main subject of this thesis work relates to the design, development and application of a special system which is able to measure with high accuracy the total integral field of the spectrometer bending dipole. The dissertation begins with a short introduction to CERN and its accelerator complex. Further on the LEP collider is described in detail and the basics of the beam energy calibration are included. Chapter 3 describes the LEP spectrometer, starting from the concept and layout, outlining the dipole magnet characteristics. The chapter ends with the presentation of some measurements performed on the LEP injection magnets in order to investigate the possible thermal effects to be foreseen on the spectrometer magnet. Chapter 4 introduces basics concepts about magnetic measurements techniques, mainly concentrating on the NMR theory and application. Chapter 5 provides the detailed description of our measurement setup based on a travelling mole equipped with magnetic field detectors and monitored with a laser interferometer. The design, realization and test of the whole system is considered. The following chapter gives the results of the first field mapping with the mole system, performed on an standard LEP iron-concrete core dipole, located in a laboratory at ground level. Chapter 7 finally describes the mapping campaign on the LEP spectrometer dipole magnet with a full analysis of the achieved results

Design and Validation with Measurements of the LEIR Injection Line

The CERN Low Energy Ion Ring (LEIR) commissioning started in the year 2005. O4+and Pb54+ion beams are transferred at 4.2 MeV/nucleon from Linac 3 to LEIR through a low energy transfer line, for which the constraints and the resulting optics design are presented. First trajectory and dispersion measurements agreed only poorly with the theoretical model. Iterations of a refined optics model and further measurements improved the agreement between experimental observations and expectations. In particular, the effect of quadrupole errors in the line dipole magnets is discussed

Comparison between Laboratory Measurements, Simulations and Analytical Predictions of the Resistive Wall Transverse Beam Impedance at low frequencies

The prediction of the resistive wall transverse beam impedance at the first unstable betatron line (8 kHz) of the CERN Large Hadron Collider (LHC) is of paramount importance for understanding and controlling the related coupled-bunch instability. Until now only novel analytical formulas were available at this frequency. Recently, laboratory measurements and numerical simulations were performed to crosscheck the analytical predictions. The experimental results based on the measurement of the variation of a probe coil inductance in the presence of i) sample graphite plates, ii) stand-alone LHC collimator jaws and iii) a full LHC collimator assembly are presented in detail. The measurement results are compared to both analytical theories and simulations. In addition, the consequences for the understanding of the LHC impedance are discussed

Bench measurements of the Low Frequency Transverse Impedance of the CERN LHC Beam Vacuum Interconnects with RF Contacts

The low frequency longitudinal and transverse impedances of the CERN Large Hadron Collider (LHC) have to be specifically minimized to prevent the onset of coherent instabilities. The LHC beam vacuum interconnects were designed as Plug In Modules (PIMs) with RF contacts to reduce their coupling impedances, but the resulting contact resistance is a concern, as this effect is difficult to estimate. High sensitivity measurements of the transverse impedance of a PIM at low frequency using a coil probe are presented. In particular, the increase of the transverse impedance of the PIM when it is elongated to its operating position is discussed in detail. Finally, the issue of non-conforming contact resistance is also addressed