Alessandro Giassi

The Virgo gravitational wave detector is an interferometer with 3 km long arms in construction near Pisa in Italy. The accessible sources at the design sensitivity and main noises are reviewed. Virgo has devoted a significant effort to extend sensitivity to low frequency reaching the strain level h̃ = 10−21 Hz−1/2 at 10 Hz while at 200 Hz h̃ = 3 · 10−23 Hz−1/2. Design choices and status of construction are presented.

The Virgo gravitational wave detector is an interferometer with 3 km long arms in construction near Pisa to be commissioned in the year 2000. Virgo has been designed to achieve a strain sensitivity of a few times at 200 Hz. A large effort has gone into the conception of the mirror suspension system, which is expected to reduce noise to the level of at 10 Hz. The expected signals and main sources of noise are briefly discussed; the choices made are illustrated together with the present status of the experiment.

VIRGO is a detector of gravitational waves based on a laser interferometer with 3 km long arms, now under construction. In order to detect gravitational waves down to 10 Hz, the seismic noise has to be reduced by several orders of magnitude. New mechanical filters using cantilever springs as elastic elements have been developed for the VIRGO seismic isolation system. The spring total stiffness is reduced by more than one order of magnitude using magnetic antispring. A control system allows one to keep the spring length constant. The new filters provide an attenuation ≥40 dB each for frequencies above 10 Hz and, compared to the previously adopted solution (gas springs), are much less sensitive to temperature changes.

The energy response and the resolution of a hadron calorimeter test module prepared by the ALEPH collaboration at LEP have been studied between 5 and 50 GeV. The energy resolution for pions follows a 0.78√E law for orthogonally incident particles. Effects of different incident polar angles (θ = 90°, 60°, 50°) are studied. The wire readout and the trigger capability are also discussed.

Interstrip and backplane capacitances on silicon microstrip detectors with p+ strip on n substrate of 320μm thickness were measured for pitches between 60 and 240μm and width over pitch ratios between 0.13 and 0.5. Parametrisations of capacitance w.r.t. pitch and width were compared with data. The detectors were measured before and after being irradiated to a fluence of 4×1014protons/cm2 of 24GeV/c momentum. The effect of the crystal orientation of the silicon has been found to have a relevant influence on the surface radiation damage, favouring the choice of a 〈100〉 substrate. Working at high bias (up to 500 V in CMS) might be critical for the stability of detector, for a small width over pitch ratio. The influence of having a metal strip larger than the p+ implant has been studied and found to enhance the stability.

A wideband (dc to 500 Hz) low noise accelerometer has been developed. It makes use of a suspended mass whose displacement relative to the supporting structure is sensed by a linear variable differential transformer. It works both in horizontal and in vertical direction. The electronics is connected to the mechanical structure through 12 m long cables. The spectral sensitivity is 7×10−10 (m/s2)/√Hz below 6 Hz. The accelerometer will be used to perform an inertial damping of the resonances of the suspension of the mirrors in VIRGO, an interferometric antenna for gravitational waves detection.

The VIRGO experiment was approved in September 1993. The goal of the French-Italian collaboration is to detect gravitational waves using a 3 km arm-length Michelson interferometer. The construction of this detector, which will be installed in Pisa, is under way. The experiment is planned to take data, in a large bandwidth (10 Hz-10 kHz), at the beginning of the year 2000 with nominal sensitivity close to h = 3 X 10-‘3/&. The motivations, detection principle, main sources of noise and status of the experiment are presented.

We report the results of two beam tests performed in July and September 1995 at CERN using silicon microstrip detectors of various types: single sided, double sided with small angle stereo strips, double sided with orthogonal strips, double sided with pads. For the read-out electronics use was made of Preshape32, Premux128 and VA1 chips. The signal to noise ratio and the resolution of the detectors was studied for different incident angles of the incoming particles and for different values of the detector bias voltage. The goal of these tests was to check and improve the performances of the prototypes for the CMS Central Detector.

The CMS silicon strip tracker, providing a sensitive area of approximately 200 m2 and comprising 10 million readout channels, has recently been completed at the tracker integration facility at CERN. The strip tracker community is currently working to develop and integrate the online and offline software frameworks, known as XDAQ and CMSSW respectively, for the purposes of data acquisition and detector commissioning and monitoring. Recent developments have seen the integration of many new services and tools within the online data acquisition system, such as event building, online distributed analysis, an online monitoring framework, and data storage management. We review the various software components that comprise the strip tracker data acquisition system, the software architectures used for stand-alone and global data-taking modes. Our experiences in commissioning and operating one of the largest ever silicon micro-strip tracking systems are also reviewed.

The active detectors of the ALEPH hadron calorimeter at LEP consist of plastic streamer tubes developed in Frascati. The standard gas mixture for the operation of such devices is argon-isobutane (3070). However, in underground experiments, for safety reasons, one has to reduce the hydrocarbon content. Therefore a study of the behaviour of streamer tubes operated with a Ar/CO2/n-pentane mixture has been performed. The influence of gas composition on efficiency, charge distribution and stability of operation has been investigated, and the results of these tests are presented.

The measurement of the finesse and the longitudinal locking of a 100 μm long plane mirrors Fabry-Perot cavity is described. a finesse of up to 5400 has been found. If attached to the Virgo antenna suspension (SA), a similar device is sensitive enough to detect the thermal displacement noise of the SA test mass, which is expected to limit the Virgo antenna sensitivity between 10 and 600 Hz. Reducing the Virgo noise floor is a challenge for future antenna development, as this region is the most promising one for coalescing binary stars and pulsar signals.

We present results obtained with full-size wedge silicon microstrip detectors bonded to APV6 (Raymond et al., Proceedings of the 3rd Workshop on Electronics for LHC Experiments, CERN/LHCC/97-60) readout chips. We used two identical modules, each consisting of two crystals bonded together. One module was irradiated with 1.7×1014neutrons/cm2. The detectors have been characterized both in the laboratory and by exposing them to a beam of minimum ionizing particles. The results obtained are a good starting point for the evaluation of the performance of the “ensemble” detector plus readout chip in a version very similar to the final production one. We detected the signal from minimum ionizing particles with a signal-to-noise ratio ranging from 9.3 for the irradiated detector up to 20.5 for the non-irradiated detector, provided the parameters of the readout chips are carefully tuned.

This paper illustrates a method for the discrimination between πs and μs through the energy measurement and tracking capability of a hadron calorimeter followed by a system of chambers. Data taken in a test run with π and μ beams have been analyzed and compared with a sample indicated as π + μ. These π + μ events are obtained off line by taking one muon and one pion, superimposing their digital patterns and summing up their energy releases. The discriminant analysis employed provides a level of identification of about 99.5%. Such a result is very close to the physical limit corresponding to events with sail-through pions.

A proposal for a pixel-based Level 1 trigger for the Super-LHC is presented. The trigger is based on fast track reconstruction using the full pixel granularity exploiting a readout which connects different layers in specific trigger towers. The trigger will implement the current CMS high level trigger functionality in a novel concept of intelligent detector. A possible layout is discussed and implications on data links are evaluated.

This paper describes the main achievements in the development of radiation resistant silicon detectors to be used in the CMS tracker. After a general description of the basic requirements for the operation of large semiconductor systems in the LHC environment, the issue of radiation resistance is discussed in detail. Advantages and disadvantages of the different technological options are presented for comparison. Laboratory measurements and test beam data are used to check the performance of several series of prototypes fabricated by different companies. The expected performance of the final detector modules are presented together with preliminary test beam results on system prototypes.

A set of CMS MicroStrip Gas Chambers (MSGC) was exposed to a high-intensity 3GeV/c pion beam at a CERN PS facility for a period of two weeks. The performance of the detectors is reported in terms of stability of efficiency and response to minimum ionising particles as well as to more heavily ionising fragments generated by nuclear interactions.

The Virgo detector will be a 3 km long interferometer antenna with a design sensitivity aiming at the direct observation of gravitational waves.The construction of this detector which will be installed near Pisa is under way. The data taking should start in year 2000 with a design sensitivity close to h¯≃10−23Hz−1/2. The motivations, detector principle, main sources of noise and status of the experiment are presented.

The response to pions of an ALEPH electromagnetic calorimeter petal combined with the ALEPH hadron calorimeter prototype has been studied in the energy range between 2 and 30 GeV. The resolution of the combined calorimeters was found to be lower than that for the hadron calorimeter alone at low energies and approached this value at higher energies.

We present the beam test results of single-sided silicon microstrip detectors, with different substrate resistivities. The effects of radiation damage are studied for a detector irradiated to a fluence of 2.4×1014n/cm2. The detectors are read out with the APV6 chip, which is compatible with the 40MHz LHC clock. The performance of different detectors and readout modes are studied in terms of signal-to-noise ratio and efficiency.

In this article we describe a new method for the aerodynamic optimisation and inverse design problem resolution. This method is based on the coupling of a classical optimiser with a neural-network. A Navier–Stokes flow solver is used for an accurate computation of the objective function. At first the neural-network, which has been trained by an initial small database, is used to obtain, by the interpolation of the design sensitivities, a new design point, which is then computed by the Navier–Stokes solver in order to update the neural-network training database for further iterative step. Since the neural-network provides the optimiser with the derivatives, the objective function has to be evaluated only once at every step. By this method, the computational effort is significantly reduced with respect to the classical optimisation methods based on the design sensitivities, that are computed directly by the flow solver. The method proposed has been positively tested on the inverse design of a three-dimensio...

In the context of concurrent engineering, this paper presents a quite innovative approach to the collaborative optimization process, which couples a multi-objective genetic algorithm with an asynchronous communication tool. This optimization method allows the collaborative and multi-sites design to be performed without requiring significant investments or changes in the company organization. To illustrate this methodology, the collaboration of three European companies on the optimization of a ship hull is described. The hull shape is automatically optimised distributing the elements of the optimization loop among three distant sites. Our study demonstrates that when multi-objective optimization is carried out in a distributed manner it can provide a powerful tool for concurrent product design.

The Virgo project is a Italian-French collaboration aiming at the construction of a long baseline interferometric antenna for the detection of gravitational radiation signals of cosmic origin. We describe the principles of the system, and high-light the technical challenges we need to overcome for reaching a sensitiity as low as 10−23Hz−1/2.

The CMS experiment at the LHC will comprise a large silicon strip tracker. This article highlights some of the results obtained in the R&D studies for the optimization of its silicon sensors. Measurements of the capacitances and of the high voltage stability of the devices are presented before and after irradiation to the dose expected after the full lifetime of the tracker.

A complete prototype of the CMS tracker read-out and control system has been built using components as close as possible to the final design. It is based on an amplifier and analogue pipeline memory chip (APV), analogue optical links transmitting at 40Ms/s and a VME mounted digitisation and data handling board (FED-PMC), supplemented by a control architecture based on FECs which set and monitor the components of the entire system. This system has been successfully operated for the first time under LHC like beam conditions in a 25ns structured beam provided by the SPS at CERN. The objective was primarily to test the synchronisation and pile-up effects in a high trigger rate environment and to examine the many issues involved in operating a complete readout and control system.

A set of microstrip gas chamber (MSGC) prototypes, developed for the barrel Tracking Detector of the CMS experiment at LHC, has been tested in a beam. The chambers were 10 cm long, with Pestov or diamond coated glass substrate. The results on the performance of the chambers are reported. The spatial uniformity of the chambers is also illustrated.

The data acquisition system for the CMS Silicon Strip Tracker (SST) is based around a custom analogue front-end ASIC, an analogue optical link system and an off-detector VME board that performs digitization, zero-suppression and data formatting. A complex procedure is required to optimally configure, calibrate and synchronize the 10 channels of the SST readout system. We present an overview of this procedure, which will be used to commission and calibrate the SST during the integration, Start-Up and operational phases of the experiment. Recent experiences from the CMS Magnet Test Cosmic Challenge and system tests at the Tracker Integration Facility are also reported. I. THE DATA ACQUISITION SYSTEM The CMS Silicon Strip Tracker (SST) is unprecedented in terms of its size and complexity, providing a sensitive area of >200 m and comprising 10 readout channels. Fig. 1 shows a schematic of the control and readout systems for the SST. The control system [1] comprises 300 “control rings” that start and end at the off-detector Front-End Controller (FEC) boards and is responsible for distributing slow control commands, clock and Level-1 triggers to the front-end electronics. The signals are transmitted optically from the FECs to front-end digital optohybrids via digital links, and then electrically via ‘token rings” of Communication and Control Units (CCUs) to the front-end electronics. The readout system is based around a custom front-end ASIC known as the APV25 chip [2], an analogue optical link system [3] and an off-detector Front-End Driver (FED) processing board [4]. The system comprises 76k APV25 chips, 38k optical fibres (each transmitting data from a pair of APV25 chips) and 440 FEDs. The APV25 chip samples, amplifies, buffers and processes signals from 128 channels of a silicon strip sensor at the LHC collision frequency of 40MHz. On receipt of a Level-1 trigger, pulse height and bunch-crossing information from pairs of APV25 chips are multiplexed onto a single line and the data are converted to optical signals that are transmitted via analogue fibres to the off-detector FED boards. The FEDs digitize, zerosuppress and format the pulse height data from up to 96 pairs of APV25 chips, before forwarding the resulting event fragments to the CMS event builder (EVB) and online computing farm. Figure 1: The SST control system uses ∼300 control rings (based around the FEC and CCU boards) to propagate clock, trigger and slow control information to the front-end. The SST readout system is based around the APV25 chip, an analogue optical link system and the off-

In this paper the capability of GHEISHA as hadron shower generator is investigated and discussed by comparing the test run data from the ALEPH hadron calorimeter prototype with the Monte Carlo simulation developed in the GEANT3 framework. The results on muon, electron and pion simulation are reported. The longitudinal development of hadron showers is well reproduced and saturation effects are also explained. The resolution of the calorimeter for incident pions as computed by the Monte Carlo method is slightly larger than what observed.

The CMS Silicon tracker consists of 70m2 of microstrip sensors which design will be finalized at the end of 1999 on the basis of systematic studies of device characteristics as function of the most important parameters. A fundamental constraint comes from the fact that the detector has to be operated in a very hostile radiation environment with full efficiency. We present an overview of the current results and prospects for converging on a final set of parameters for the silicon tracker sensors.

Le travail présenté dans cet article a pour objectif la création d'une procédure d'optimisation à distance appliquée à la conception de navires. La démarche doit prendre en compte les contraintes industrielles actuelles liées au déploiement de l'ingénierie concourante. Cette optimisation doit être réalisée dans le cadre d'une conception collaborative et multi-sites, en plus elle doit être opérationnelle sans demander des changements importants dans l'organisation de l'entreprise. Elle doit prendre en compte les coûts importants de calcul et les expertises nécessaires à l'évaluation des critères et des contraintes. La solution proposée dans cet article couple un algorithme génétique d'optimisation multi-objectif avec un outil de communication asynchrone. Les avantages des approches abordées et des solutions apportées sont présentés dans le cadre d'une application industrielle. Il s'agit de l'optimisation multi-objectif de la carène d'un navire rapide. L'expérience a été réalisée en grandeur nature entre trois entreprises européennes spécialisées dans l'étude et la conception de navires. L'approche a mis en évidence la possibilité d'améliorer de façon importante les méthodes de travail industrielles existantes.

L'etude applique les methodes de conception optimale en liaison avec les principes de l'ingenierie simultanee dans la gestion du travail de conception. L'idee centrale de la these est que l'optimisation multi-objectif et multidisciplinaire peut fournir une strategie systematique pour une conception simultanee et systemique. Pour l'application industrielle de ce principe, nous avons developpe les strategies suivantes. Une strategie developpee pour le contexte multi-acteur et multi-site permet aux concepteurs de mener une optimisation repartie sur plusieurs sites distants. L'etude propose ensuite l'optimisation comme lien entre la conception et la fabrication. L'optimisation simultanee des performances et du cout de fabrication ameliore le produit et son processus de conception. Enfin, nous avons developpe une methode originale d'optimisation multidisciplinaire qui combine les algorithmes genetiques et la conception robuste et permet de conserver l'independance des differentes disciplines.

For the construction of the silicon microstrip detectors for the Tracker of the CMS experiment, two different substrate choices were investigated: A high-resistivity (6 k cm) substrate with (111) crystalorientation and a low-resistivity (2k cm) one with (100) crystalorientation. The interstrip and backplane capacitances were measured before and after the exposure to radiation in a range of strip pitches from 60 μm to 240 μm and for values of the width-over-pitch ratio between 0.1 and 0.5.

Abstract A large quantity of silicon microstrip detectors is foreseen to be used as part of the CMS tracker. A specific research and development program has been carried out with the aim of defining layouts and technological solutions suitable for the use of silicon detectors in high radiation environment. Results presented here summarise this work on many research areas such as techniques for device manufacturing, pre- and post-irradiation electrical characterization, silicon bulk defects analysis and simulations, system performance analytical calculations and simulations and test beam analysis. As a result of this work we have chosen to use single-sided, AC-coupled, poly silicon biased, 300 μm thick, p + on n substrate detectors. We feel confident that these devices will match the required performances for the CMS tracker provided they can be operated at bias voltages as high as 500 V. Such high-voltage devices have been succesfully manufactured and we are now concentrating our efforts in enhancing yield and reliability.

Hadronic showers in an iron-streamer tube sampling calorimeter have been studied for energies ranging between 3 and 25 GeV. Longitudinal and transverse energy distributions have been parametrized and compared with those determined for iron-scintillator calorimeters.

The breakdown performance of CMS barrelmodule prototype detectors and test devices with single and multi-guard structures were studied before and after neutron irradiation up to 2·1014 1 MeV equivalent neutrons. Before irradiation avalanche breakdown occurred at the guard ring implant edges. We measured 100–300 V higher breakdown voltage values for the devices with multi-guard than for devices with single-guard ring. After irradiation and type inversion the breakdown was smoother than before irradiation and the breakdown voltage value increased to 500–600 V for most of the devices.

In the context of concurrent engineering, this paper presents a quite innovative approach to the collaborative optimisation process, which couples a multi-objective genetic algorithm with an asynchronous communication tool. To illustrate this methodology, three European companies’ collaboration on the optimisation of a ship hull is described. Our study demonstrates that when multi-objective optimisation is carried out in a distributed manner it can provide a powerful tool for concurrent product design.

The gas gain monitoring system of the Aleph hadron calorimeter is described. The dependence of the charge response to a) the ratio between the pressure to temperature and b) the gas mixture parameters (Ar/CO2 ratio and isobutane percentage) have been determined. The total gain variation is measured with a precision of about 0.4%.

A new approach for the test mass suspensions of the VIRGO interferometric antenna has been proposed to increase the sensitivity at low frequencies by the reduction of the effects of vertical noises on the test mass. The experimental results are presented and discussed.

A high senstivity interferometer has been built to test the suspension of the optical elements for the Virgo gravitational antenna. The interferometer is controlled by means of an internal alignment system, without any actuator directly connected to ground. The spectral noise achieved in the interferometer is of the order of 10-13m/√Hz between 20 and 100 Hz, limited by the electronic noise.

A high sensitivity interferometer has been used to test the suspension of the Virgo interferometric antenna for gravitational wave search. Since Virgo is planning to enlarge the detection window down to 10 Hz, particular care is taken to improve the sensitivity in the low frequency region. Noise spectra are discussed. Between 20 and 100 Hz the limiting noise is of the order of 10−14mHz, and it reaches 10−15mHz above 100 Hz. Above 10 kHz the interferometer sensitivity is shot noise limited.

This paper describes the Silicon microstrip Tracker of the CMS experiment at LHC. It consists of a barrel part with 5 layers and two endcaps with 10 disks each. About 10 000 single-sided equivalent modules have to be built, each one carrying two daisy-chained silicon detectors and their front-end electronics. Back-to-back modules are used to read-out the radial coordinate. The tracker will be operated in an environment kept at a temperature of T=−10°C to minimize the Si sensors radiation damage. Heavily irradiated detectors will be safely operated due to the high-voltage capability of the sensors. Full-size mechanical prototypes have been built to check the system aspects before starting the construction.

The CMS Silicon Strip Tracker at the LHC comprises a sensitive area of approximately 200 m2 and 10 million readout channels. Its data acquisition system is based around a custom analogue front-end chip. Both the control and the readout of the front-end electronics are performed by off-detector VME boards in the counting room, which digitise the raw event data and perform zero-suppression and formatting. The data acquisition system uses the CMS online software framework to configure, control and monitor the hardware components and steer the data acquisition. The first data analysis is performed online within the official CMS reconstruction framework, which provides many services, such as distributed analysis, access to geometry and conditions data, and a Data Quality Monitoring tool based on the online physics reconstruction.

Abstract A large use of silicon microstrip detectors is foreseen for the intermediate part of the CMS tracker. A specific research and development program has been carried out with the aim of finding design layouts and technological solutions for allowing silicon microstrip detectors to be reliably used on a high radiation level environment. As a result of this work single sided, AC-coupled, polysilicon biased, 300 μ m thick, p + on n substrate detectors were chosen. Irradiation tests have been performed on prototypes up to fluence 2×10 14  n/cm 2 . The detector performances do not significantly change if the detectors are biased well above the depletion voltage. S / N is reduced by less than 20%, still enough to insure a good efficiency and space resolution. Multiguard structures has been developed in order to reach high voltage operation (above 500 V).

An important tool for the discovery of new physics at LHC is the design of a low level trigger with an high power of background rejection. The contribution of pixel detector to the lowest level trigger at CMS is studied focusing on low-energy jet identification, matching the information from calorimeters and pixel detector. In addition, primary vertex algorithms are investigated. The performances are evaluated in terms of, respectively, QCD rejection and multihadronic jets final states efficiency.

The CMS Silicon Tracker comprises a complicated set of hardware and software components that have been thoroughly tested at CERN before final integration of the Tracker. A vertical slice of the full readout chain has been operated under near-final conditions. In the absence of the tracker front-end modules, simulated events have been created within the FED (Front End Driver) and used to test the readout reliability and efficiency of the final DAQ (Data Acquisition). The data are sent over the S-Link 64 bit links to the FRL (Fast Readout Link) modules at rates in excess of 200 MBytes/s per FED depending on setup and conditions. The current tracker DAQ is fully based on the CMS communication and acquisition tool XDAQ. This paper discusses setup and results of a vertical slice of the full Tracker final readout system comprising 2 full crates of FEDs, 30 in total, read out through 1 full crate of final FRL modules. This test is to complement previous tests done at Imperial College[3] taking them to the next level in order to prove that a complete crate of FRLs using the final DAQ system, including all subcomponents of the final system both software and hardware with the exception of the detector modules themselves, is capable of sustained readout at the desired rates and occupancy of the CMS Tracker. Simulated data are created with varying hit occupancy (1-10%) and Poisson distributed trigger rates (<200KHz) and the resulting behaviour of the system is recorded. Data illustrating the performance of the system and data readout are presented.

We report selected results of laboratory measurements and beam tests of heavily irradiated microstrip silicon detectors. The detectors were single-sided devices, produced by different manufacturers and irradiated with different sources, for several total ionizing doses and fluences up to 4 /spl times/10/sup 14/ 1-MeV-equivalent neutrons per cm/sup 2/. Strip resistance and capacitance, detector leakage currents and breakdown performance were measured before and after irradiations. Signal-to-noise ratio and detector efficiency were studied in beam tests, for different values of the detector temperature and of the read-out pitch, as a function of the detector bias voltage. The goal of these test is to optimise the design of the final prototypes for the Silicon Strip Tracker of the CMS experiment at the CERN LHC collider.

This paper investigates the performance of silicon microstrip detectors after heavy irradiation. Full-size prototype sensors (53 /spl times/ 64 mm/sup 2/) designed for the CMS Tracker have been irradiated with protons and extensively studied in the laboratory and using a beam of minimum ionising particles operated at low temperature as foreseen for the Large Hadron Collider. We present results of large statistics measurements of collected charge, noise, position resolution, and hit finding efficiency for these irradiated detectors.

The paper reports the results of a joint R&D project between INFN Pisa and STMicroelectronics aiming at the development of silicon micro-strip detectors with very high breakdown voltage. Several series of prototypes have been manufactured on 6-in-diameter n-type silicon wafers. The production technology was tuned for the standard high volume production lines and was optimized to reach a high processing yield while maintaining very good detector performance. We present a complete characterization of the devices in terms of leakage current, depletion voltage, quality and uniformity of coupling capacitors and polysilicon resistors. We discuss the main design rules and the most important technological steps which led to breakdown voltage systematically exceeding 1000 V even for very large area detectors.

Abstract The new silicon tracker layout (V4) is presented. The system aspects of the construction are discussed together with the expected tracking performance. Because of the high radiation environment in which the detectors will operate, particular care has been devoted to the study of the characteristics of heavily irradiated detectors. This includes studies on performance (charge collection, cluster size, resolution, efficiency) as a function of the bias voltage, integrated fluence, incidence angle and temperature.

The CMS silicon strip tracker involves about 70 m2 of instrumented silicon, with approximately 18500 microstrip detectors read out by 5 × 106 electronics channels. It has to satisfy a set of stringent requirements imposed by the environment and by the physics expected at the LHC: low cell occupancy and good resolution, radiation hardness aided by adequate cooling, low mass combined with high stability. These conditions have been incorporated in a highly modular design of the detector modules and their support structures, chosen to facilitate construction and to allow for easy assembly and maintenance.

The paper describes the Silicon Tracking System of the Compact Muon Solenoid (CMS) experiment that is foreseen to collect events from p–p collision at the Ecm=14 TeV at the CERN future Large Hadron Collider (LHC). The proposed system consists of four layers of silicon microstrip detectors placed between the two inner layers of the pixel detector and the outer microstrip gas chamber system. The barrel part covers the η region up to 1.8, instrumenting the central radial region between 20 and 50 cm. The forward–backward disks extend the coverage up to η=2.6. This paper will review the main characteristics and performances of the system, the actual status of the R&D activities that we are carrying on, and the status of the milestones we have to fulfill in view of the Technical Design Report expected at the end of the year.

This paper describes the silicon microstrip tracker of the CMS experiment at the future LHC. The silicon tracker consists of a barrel part with 5 layers and two endcaps with 10 disks each. About 6500 modules will have to be built, each one carrying two daisy-chained silicon sensors and their front-end electronics. The modules have been designed to be as simple and robust as possible. Radiation damage in the silicon sensors is minimized by cooling the whole system down to -10°C. Safe operation after heavy irradiation will be possible due to the high-voltage capability of the sensors. We expect the sensors to have a signal-to-noise ratio of 10 at the end of 10years of LHC running, which still gives an efficiency of almost 100%.

B. Caron, A. Dominjon, C. Drezen, R. Flaminio, X. Grave, F. Marion, L. Massonnet, C. Mehmel, R. Morand, B. Mours, V. Sannibale, M. Yvert LAPP, Annecy-Le-Vieux, France D. Babusci, S. Bellucci, G. Candusso, G. Giordano, G. Matone INFN Frascati, Frascati, Italy L. Dognin, J. M. Mackowski, M. Napolitano, L. Pinard IPN Lyon, Villeurbanne, France F. Barone, E. Calloni, L. Di Fiore, A. Grado, L. Milano, G. Russo, S. Solimeno INFN Napoli, Napoli, Italy M. Barsuglia, V. Brisson, F. Cavalier, M. Davier, P. Hello, F. LeDiberder, P. Marin, M. Taubman LAL, Orsay, France F. Bondu, A. Brillet, F. Cleva, H. Heitmann, L. Latrach, C.N. Man, Pham-Tu Manh, J.-Y. Vinet VIRGO laser group, Orsay, France C. Boccara, Ph. Gleyzes, V. Loriette, J.P. Roger ESPCI, Paris, France G. Cagnoli, L. Gammaitoni, J. Kovalik, F. Marchesoni, M. Punturo INFN Perugia, Perugia, Italy M. Bernardini, S. Braccini, C. Bradaschia, R. Del Fabbro, R. DeSalvo, A. Di Virgilio, I. Ferrante, F. Fidecaro, A. Gennai, A. Giassi, A. Giazotto, L. Holloway, P. La Penna, G. Losurdo, F. Palla, Pan Hui-Bao, A. Pasqualetti, D. Passuello, R. Poggiani, G. Torelli, Zhang Zhou INFN Pisa, Pisa, Italy E. Majorana, P. Puppo, P. Rapagnani, F. Ricci INFN Roma, Roma, Italy

An interferometric sapphire transducer has been used to test the super attenuator of the VIRGO laser interferometer gravitational wave antenna project. A test was carried out to characterise the horizontal displacement of the attenuator. The test showed the performance of the super attenuator to the transducer noise floor of 5 × 10−15 m/√Hz at 60 Hz.