Comparative test results of various beam loss monitors in preparation for LHC

Beam loss detectors will play an important role in the protection of the superconducting LHC magnets. Different types of detectors have been tested in the SPS ring and secondary beam lines with a view to their possible use for this application. This paper describes the measurements made with: microcalorimeters at cryogenic temperatures, PIN diodes, ionisation chambers, scintillators, and ACEMs. Measurements made using proton beams showing their relative sensitivities, linearities in counting or analog mode and minimum detection level will be presented

Protection and Diagnostic Systems for High Intensity Beams

This paper presents a summary of the facilities for beam interlocks and diagnostics to protect the CERN SPS machine. An overview of the existing systems is given, which are based on beam loss and beam current monitors and large beam position excursion in the horizontal plane. The later system mainly protects the system against a failure of the transverse damping system. The design for a new large excursion interlock for both transverse planes is also presented in some detail. For this system a digital approach is being taken to allow post-mortem analysis of the behaviour of the beam prior to the activation of the interlock

Characterization of a nondestructive beam profile monitor using luminescent emission

The LHC (large hadron collider) [LHC study group: LHC. The large hadron collider conceptual design; CERN/AC/95-05] is the future p-p collider under construction at CERN, Geneva. Over a circumference of 26.7 km a set of cryogenic dipoles and rf cavities will store and accelerate proton and ion beams up to energies of the order of 7 TeV. Injection in LHC will be performed by the CERN complex of accelerators, starting from the source and passing through the linac, the four booster rings, the proton synchrotron (PS), and super proton synchrotron (SPS) accelerators. One of the main constraints on LHC performance is emittance preservation along the whole chain of CERN accelerators. The accepted relative normalized emittance blowup after filamentation is ±7%. To monitor the beam and the emittance blowup process, a study of different prototypes of nonintercepting beam profile monitors has been performed. In this context a monitor using the luminescent emission of gases excited by ultrarelativistic protons (450 GeV) was developed and tested in the SPS ring. The results of beam size measurements and their evolution as a function of the machine parameters are presented. The image quality and resolution attainable in the LHC case have been assessed. A first full characterization of the luminescence cross section, spectrum, decay time, and afterglow effect for an ultrarelativistic proton beam is provided. Some significant results are also provided for lead ion beams

Controllo e sindacati azionari nelle società quotate italiane

Lo studio propone un indagine empirica sugli assetti proprietari delle società quotate italiane, per individuare situazioni di controllo individuale o congiunto, messi in relazione alla dimensione a-ziendale delle società, onde verificare l’interazione tra la struttura del controllo societario e le potenzialità economiche dell’impresa. L’indagine si soffermerà sui sindacati azionari, per valutarne la ri-levanza nel contesto delle società quotate: analizzando il contenuto del-le pattuizioni, si cercherà di mettere a fuoco l’incidenza di tali patti su-gli assetti di controllo delle società stesse. L’analisi delle situazioni di controllo congiunto da sindacato azionario potrà fornire ulteriori indica-zioni sulla correlazione tra controllo e dimensione economica. La ricerca intende sperimentare un nuovo approccio nello studio dei problemi applicativi del diritto societario, e avviare la necessaria rifles-sione sulla relativa impostazione metodologica

Control and monitoring of the SPS proton and ion extractions

For the fixed target program of the SPS, protons and ions are accelerated and extracted towards seven target stations in the NORTH and WEST experimental areas. These extractions range from 106 Lead ions to 1013 protons with durations of 5 or 2.5 s and are controlled by a closed loop system. The intensity monitoring for this system is done with fast screens observed with Photo Multipliers and Secondary Emission Monitors sampled every 100 µs. Along the beam lines, the intensities of the extracted beams are monitored with fast screens at 100 ns intervals. Time and frequency domain information are extracted for diagnosis from the acquired data. A slower observation system, with a 1 ms sampling interval, is also available for assessing the evolution of the centre of charge, the intensity and the losses along the beam lines during an extraction

A Collimation Experiment with Protons at 120 GeV

We present the preliminary results of a two-stage collimation experiment made with a 120 GeV coasting proton beam in the SPS at CERN

Sensitivity Studies with the SPS Rest Gas Profile Monitor

During the SPS run in the year 2000 further test measurements were performed with the rest gas monitor. First, profiles of single circulating proton bunches were measured and the bunch charge progressively reduced, in order to determine the smallest bunch intensity which can be scanned under the present operating conditions. The image detector in this case was a CMOS camera. Using a multi-anode strip photo-multiplier with fast read-out electronics, the possibility to record profiles on a single beam passage and on consecutive turns was also investigated. This paper presents the results of these tests and discusses the expected improvements for the operation in 2001. Moreover, the issue of micro channel plate ageing effects was tackled and a calibration system based on electron emission from a heating wire is proposed. The gained experience will be used for the specification of a new monitor with optimised design, to be operated both in the SPS and in the LHC

Crossing Over from Attractive to Repulsive Interactions in a Tunneling Bosonic Josephson Junction

We explore the interplay between tunneling and interatomic interactions in the dynamics of a bosonic Josephson junction. We tune the scattering length of an atomic $^{39}$K Bose-Einstein condensate confined in a double-well trap to investigate regimes inaccessible to other superconducting or superfluid systems. In the limit of small-amplitude oscillations, we study the transition from Rabi to plasma oscillations by crossing over from attractive to repulsive interatomic interactions. We observe a critical slowing down in the oscillation frequency by increasing the strength of an attractive interaction up to the point of a quantum phase transition. With sufficiently large initial oscillation amplitude and repulsive interactions the system enters the macroscopic quantum self-trapping regime, where we observe coherent undamped oscillations with a self-sustained average imbalance of the relative well population. The exquisite agreement between theory and experiments enables the observation of a broad range of many body coherent dynamical regimes driven by tunable tunneling energy, interactions and external forces, with applications spanning from atomtronics to quantum metrology.Comment: 10 pages, 8 figures, supplemental materials are include

Secondary Electron Emission Beam Loss Monitor for LHC

Beam Loss Monitoring (BLM) system is a vital part of the active protection of the LHC accelerators' elements. It should provide the number of particles lost from the primary hadron beam by measuring the radiation field induced by their interaction with matter surrounding the beam pipe. The LHC BLM system will use ionization chambers as standard detectors but in the areas where very high dose rates are expected, the Secondary Emission Monitor (SEM) chambers will be employed because of their high linearity, low sensitivity and fast response. The SEM needs a high vacuum for proper operation and has to be functional for up to 20 years, therefore all the components were designed according to the UHV requirements and a getter pump was included. The SEM electrodes are made of Ti because of its Secondary Emission Yield (SEY) stability. The sensitivity of the SEM was modeled in Geant4 via the Photo-Absorption Ionization module together with custom parameterization of the very low energy secondary electron production. The prototypes were calibrated by proton beams in CERN PS Booster dump line, SPS transfer line and in PSI Optis line. The results were compared to the simulations