1,078 research outputs found
High Voltage System for the CMS Electromagnetic Calorimeter
No full textThe CMS electromagnetic calorimeter (ECAL) is made of about 75000 lead tungstate crystals. The 61200 crystals of the barrel part are read by avalanche photodiodes (APD) with internal amplification of the signal. Since the gain strongly depends on the bias voltage, the APDs require a very stable power supply system. To preserve the high energy resolution of the calorimeter, a stability of the bias voltage of the order of 10^-4 is required over several months, a typical interval between absolute calibrations of the full read-out chain with physics events. This paper describes the High Voltage power supply system developed for CMS ECAL and its performances as measured in laboratory tests and during test-beam operations of several modules of the calorimeter
Tools for the Inspection of PWO//APD Gluing
No full textThe light produced in each of the 60 thousand PWO crystals of the CMS barrel electromagnetic calorimeter will be readout by Avalanche Photodiodes ( APD). The ratio detected to emitted photons also depends on the PWO//APD gluing quality that must be checked before the crystal mounting in the calorimeter. In this paper two different tools are proposed: one for the visual inspection of the glue layer and the other for the quantitative evaluation of transmittance improvement when the glue replaces the air at the PWO//APD interface. Both the instruments are rugged and cheap. A sequence of operations and checks on the gluing to be done in the Regional Centres is proposed
Neutron Flux Measurement at TAPIRO Fast Reactor for APD's Irradiation Fluence Evaluation
No full textThe Avalanche Photodiodes ( APD) were chosen as photon sensors for the region of the CMS electromagnetic calorimeter. The LHC will be a hard environment for what concerns the radiation levels in the detectors. The most relevant damage on APDs is caused by neutrons that produce an increase in the dark current of these devices. In the CMS-ECAL collaboration a big effort was indeed done to understand this damage, but the evaluation of the absolute effect was limited by the knowledge of the neutron flux calibration of the various irradiation facilities. This investigation describes the calibration of the neutron flux of the Tapiro reactor in Rome and the calculation of the Non-Ionizing-Energy-Loss on Silicon for this reactor. The damage parameter alpha for the APDs is evaluated to be about 10-11*10^-17 A/cm/neutron at 18C and 2 days after the irradiation. Some cross-checks with other irradiation facilities are also presented
Muon Collider. A Path to the Future?
No full textA muon collider would be both a precision and a powerful discovery machine, because it can offer collisions of point-like particles at very high energies, strongly exceeding the energy reach of other lepton colliders. It can even match the discovery of a proton collider with much higher energy, since the muon collision energy is fully available at constituent level unlike for the protons. However, the need for high luminosity faces technical challenges which arise from the short muon lifetime at rest and the difficulty of producing large numbers of muons in bunches with small emittance. Addressing these challenges requires the development of innovative concepts and demanding technologies. In view of the potential importance of muon colliders for the future of high-energy physics it is timely to start an R&D programme now.LPT
Muon Colliders
No full textInternational audienceMuon colliders have a great potential for high-energy physics. They can offer collisions of point-like particles at very high energies, since muons can be accelerated in a ring without limitation from synchrotron radiation. However, the need for high luminosity faces technical challenges which arise from the short muon lifetime at rest and the difficulty of producing large numbers of muons in bunches with small emittance. Addressing these challenges requires the development of innovative concepts and demanding technologies. The document summarizes the work done, the progress achieved and new recent ideas on muon colliders. A set of further studies and actions is also identified to advance in the field. Finally, a set of recommendations is listed in order to make the muon technology mature enough to be favourably considered as a candidate for high-energy facilities in the future
Detection of Photons Generated in PWO Scintillator Crystals
No full textThis work deals with the optical characterization of the surface of EG&G and Hamamatsu APD's and performance of an antireflection coating made of Y2O3 and deposited on a PWO test piece. The effectiveness of antireflection treatments of PWO and Si surfaces is evaluated in a simplified and a realistic situation by means of the ratio of "detected to emitted photons". The complex refractive index of the Dow Corning 02-3067 optical grease is also reported
Muon Colliders
No full textInternational audienceMuon colliders have a great potential for high-energy physics. They can offer collisions of point-like particles at very high energies, since muons can be accelerated in a ring without limitation from synchrotron radiation. However, the need for high luminosity faces technical challenges which arise from the short muon lifetime at rest and the difficulty of producing large numbers of muons in bunches with small emittance. Addressing these challenges requires the development of innovative concepts and demanding technologies. The document summarizes the work done, the progress achieved and new recent ideas on muon colliders. A set of further studies and actions is also identified to advance in the field. Finally, a set of recommendations is listed in order to make the muon technology mature enough to be favourably considered as a candidate for high-energy facilities in the future
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