Absorbed doses and radiation damage during the 11 years of LEP operation

During the 11 years of operation of the Large Electron Positron Collider (LEP), synchrotron radiation was emitted in the tunnel. This ionizing radiation induced degradation in organic insulators and structural materials, as well as in electronics. Annual dosimetric measurements have shown that the level of radiation increased with the ninth power of the beam energy. During the machine shut-downs and at the end of the operation, samples of rigid and flexible polymeric insulators (magnet-coil resins and cable insulations) were taken out and checked for their integrity. The test results are compared with the results obtained during the qualification of the materials, 12 to 15 years ago. At that time, lifetime predictions were done; they are now compared with the real time aged materials

Synchrotron Radiation Effects at LEP

With the increase of the LEP beam energy, synchrotron radiation effects become ever more important. Around the experiments, masks have been successfully used to absorb the higher rates, and photon bac kgrounds have not been a problem. Elsewhere around the ring, however, the increased radiated power has adversely affected various accelerator components; sections of the vacuum chamber, electronics, c ables and beam instrumentation equipment have all suffered. Furthermore, the use of wiggler magnets to control the bunch size has given rise to local problems on nearby separator equipment. These effe cts will be presented, together with the steps taken to avoid further difficulties at the higher energies and higher beam currents foreseen in future

Alignment of the ALICE Inner Tracking System with cosmic-ray tracks

37 pages, 15 figures, revised version, accepted by JINSTALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 micron in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10^5 charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.Peer reviewe

First proton-proton collisions at the LHC as observed with the ALICE detector: measurement of the charged-particle pseudorapidity density at root s=900 GeV

-On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), two counter-rotating proton bunches were circulated for the first time concurrently in the machine, at the LHC injection energy of 450 GeV per beam. Although the proton intensity was very low, with only one pilot bunch per beam, and no systematic attempt was made to optimize the collision optics, all LHC experiments reported a number of collision candidates. In the ALICE experiment, the collision region was centred very well in both the longitudinal and transverse directions and 284 events were recorded in coincidence with the two passing proton bunches. The events were immediately reconstructed and analyzed both online and offline. We have used these events to measure the pseudorapidity density of charged primary particles in the central region. In the range vertical bar eta vertical bar S collider. They also illustrate the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase

First proton-proton collisions at the LHC as observed with the ALICE detector: measurement of the charged-particle pseudorapidity density at root s=900 GeV

On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), two counter-rotating proton bunches were circulated for the first time concurrently in the machine, at the LHC injection energy of 450 GeV per beam. Although the proton intensity was very low, with only one pilot bunch per beam, and no systematic attempt was made to optimize the collision optics, all LHC experiments reported a number of collision candidates. In the ALICE experiment, the collision region was centred very well in both the longitudinal and transverse directions and 284 events were recorded in coincidence with the two passing proton bunches. The events were immediately reconstructed and analyzed both online and offline. We have used these events to measure the pseudorapidity density of charged primary particles in the central region. In the range vertical bar eta vertical bar S collider. They also illustrate the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase

Effets des radiations sur les matériaux polymériques utilisés dans les accélérateurs de particules du CERN

Pour la recherche fondamentale sur la structure intime de la matière, l’Organisation Européenne pour la Recherche Nucléaire (CERN) exploite des accélérateurs de particules à haute énergie autour desquels les matériaux et les composants sont exposés aux radiations ionisantes. Afin d’assurer une exploitation sûre et fiable, le comportement sous irradiation de la plupart des composants est systématiquement testé avant leur sélection. Le programme de tests aux radiations permet d’évaluer le temps de vie des composants dans l’environnement de nos accélérateurs où les doses absorbées sont continuellement enregistrées. Cet article présente les matériaux organiques utilisés au CERN, et des résultats récents sont donnés sur leur comportement sous irradiation

European organization for nuclear research

The CERN Intersecting Storage Rings (ISR) operated from 1971 to 1984. During that time high-energy physics experiments were carried out with 30 GeV colliding proton beams. At the end of this period the machine was decommissioned and dismantled. This involved the movement of about 1000 machine elements, e.g., magnets, vacuum pumps, rf cavities, etc., 2500 racks, 7000 shielding blocks, 3500 km of cables and 7 km of beam piping. All these items were considered to be radioactive until the contrary was proven. They were then sorted, either for storage and reuse or for radioactive or non-radioactive waste. The paper describes the radiation protection surveillance of this project which lasted for five months. It includes the radiation protection standards, the control of personnel and materials, typical radioactivity levels and isotopes, as well as final cleaning and decommissioning of an originally restricted radiation area to a free accessible area

Behaviour of organic materials in radiation environment

Radiation effects in polymers are reminded together with the ageing factors. Radiation-ageing results are mainly discussed about thermosetting insulators, structural composites and cable-insulating materials. Some hints are given about high-voltage insulations, cooling fluids, organic scintillators and light-guides. Some parameters to be taken into account for the estimate of the lifetime of components in radiation environment are also shown. (23 refs)