ALICE (A Large Ion Collider Experiment) is an experiment at the Large Hadron Collider (LHC) optimized for the study of heavy-ion collisions, at a centre of mass energy ∼ 5.5 TeV. The prime aim of the experiment is to study in detail the behaviour of matter at high densities and temperatures, in view of probing deconfinement and chiral symmetry restoration. The detector consists essentially of two main components: the central part, composed of detectors mainly devoted to the study of hadronic signals and dielectrons in the pseudorapidity range −1 <η< 1, and the forward muon spectrometer, devoted to the study of quarkonia behaviour in dense matter. The layout of the ALICE set-up is shown in colour Fig. 1.i. The first technical challenge is imposed by the large number of particles created in the collisions of lead ions. There is a considerable spread in the presently available predictions for the multiplicity of charged particles produced in a central Pb–Pb collision. The design of the experiment has been based on the highest value, 8000 charged particles per unit of rapidity, at mid rapidity. This multiplicity dictates the granularity of the detectors and their optimal distance from the colliding beams. The detailed characterization of ion–ion collisions requires particles to be measured and identified over a large range of momenta and masses. This second challenge has determined the rather complex particle identification scheme of ALICE.

The design, construction, and commissioning of the ALICE Time-Projection Chamber (TPC) is described. It is the main device for pattern recognition, tracking, and identification of charged particles in the ALICE experiment at the CERN LHC. The TPC is cylindrical in shape with a volume close to 90 m(3) and is operated in a 0.5T solenoidal magnetic field parallel to its axis.In this paper we describe in detail the design considerations for this detector for operation in the extreme multiplicity environment of central Pb-Pb collisions at LHC energy. The implementation of the resulting requirements into hardware (field cage, read-out chambers, electronics), infrastructure (gas and cooling system, laser-calibration system), and software led to many technical innovations which are described along with a presentation of all the major components of the detector, as currently realized. We also report on the performance achieved after completion of the first round of stand-alone calibration runs and demonstrate results close to those specified in the TPC Technical Design Report. (C) 2010 CERN for the benefit of the ALICE collaboration. Published by Elsevier B.V. All rights reserved.

The ALICE detector is a dedicated heavy-ion detector currently built at the large hadron collider (LHC) at CERN. The detector consists of several sub-detectors each of them forming a highly complex device. The detector control system (DCS) covers the task of controlling, configuring and monitoring of the detector system. Since the experiment was running in a radiation environment, fault tolerance, error correction and system stability in general are major concerns. A system consisting of independently running layers has been designed, the functionality layers are running on a large number of nodes and sub-nodes. An autonomous single-board computer, the DCS board, has been developed which allows one to run the operating system Linux in an embedded environment and to perform tasks related to the hardware devices. Further custom hardware devices have been developed covering specific tasks and serving as sub-nodes. These devices together with standard computers in higher control layers form a distributed control system. This article focused on the concept and architecture of the DCS for the front-end electronics of the time-projection chamber (TPC) and present results and experiences from system integration tests.

In this paper we present the front end electronics for the time projection chamber (TPC) of the ALICE experiment. The system, which consists of about 570000 channels, is based on two basic units: (a) an analogue ASIC (PASA) that incorporates the shaping-amplifier circuits for 16 channels; (b) a mixed-signal ASIC (ALTRO) that integrates 16 channels, each consisting of a 10-bit 25-MSPS ADC, the baseline subtraction, tail cancellation filter, zero suppression and multi-event buffer. The complete readout chain is contained in front end cards (FEC), with 128 channels each, connected to the detector by means of capton cables. A number of FECs (up to 25) are controlled by a readout control unit (RCU), which interfaces the FECs to the data acquisition (DAQ), the trigger, and the detector control system (DCS). A function of the final electronics (1024 channels) has been characterized in a test that incorporates a prototype of the ALICE TPC as well as many other components of the final set-up. The tests show that the system meets all design requirements. Originally conceived and optimized for the time projection chamber (TPC) of the ALICE experiment, its architecture and programmability make this system suitable for the readout of a wider class of detectors.

The possibility of colliding heavy nuclei with high luminosity at the Large Hadron Collider, expected to start operating in 2007 at CERN, offers a unique opportunity to investigate the behaviour of strongly interacting matter under extreme conditions of compression and heating. This will allow unprecedented tests of our understanding of equilibration processes and equilibrium states in Quantum Chromo-Dynamics (QCD), the fundamental theory of strong interactions. In particular, equilibrium QCD predicts that a phase transition to a plasma of deconfined partons, (the Quark–Gluon Plasma, or QGP), occurs at a critical energy density which is within experimental reach. Measurements at the LHC will probe extensively the properties of the bulk partonic matter produced in nucleus–nucleus collisions. The ALICE experiment—presently under construction—is the only LHC experiment designed specifically for the study of nucleus–nucleus collisions.

The front-end electronics for the Time Projection Chamber (TPC) for the ALICE experiment consists of 5x10 5 channels. A single readout channel is comprised of three basic units: a charge sensitive amplifier/shaper with a fast tail cancellation; a 10 bit 10 MSPS low power ADC; a digital ASIC which contains the zero suppression circuit and a multiple-event buffer. Data from a number of channels (4096) are multiplexed into an optical link (DDL) by means of a local custom bus which can support a data throughput of 2 MByte/event at a trigger rate of 50Hz. The construction of a prototype of this electronics is presented in this paper.

The NOMAD experiment is a short base-line search for νμ − ντ oscillations in the CERN neutrino beam. The ντ's are searched for through their charged current interactions followed by the observation of the resulting τ− through its electronic, muonic or hadronic decays. These decays are recognized using kinematical criteria necessitating the use of a light target which enables the reconstruction of individual particles produced in the neutrino interactions. This paper describes the various components of the NOMAD detector: the target and muon drift chambers, the electromagnetic and hadronic calorimeters, the preshower and transition radiation detectors and the veto and trigger scintillation counters. The beam and data acquisition system are also described. The quality of the reconstruction and individual particles is demonstrated through the ability of NOMAD to observe Ks0's, Λ0's and π0's. Finally, the observation of τ− through its electronic decay being one of the most promising channels in the search, the identification of electrons in NOMAD is discussed.

A transition radiation detector to identify electrons at 90% efficiency with a rejection factor against pions of 103 on an area of 2.85 × 2.85 m2 has been constructed for the NOMAD experiment. Each of its 9 modules includes a 315 plastic foil radiator and a detector plane of 176 vertical straw tubes filled with a xenon-methane gas mixture. Details of the design, construction and operation of the detector are given.

The NOMAD experiment is a short base-line search for νμ → ντ oscillations in the CERN neutrino beam. The ντ ’s are searched for through their charged-current interactions followed by the observation of the resulting τ− through its electronic, muonic or hadronic decays. These decays are recognized using kinematical criteria necessitating the use of a light target which enables the reconstruction of individual particles produced in the neutrino interactions. This paper describes the various components of the NOMAD detector: the target and muon drift chambers, the electromagnetic and hadronic calorimeters, the preshower and transition radiation detectors, and the veto and trigger scintillation counters. The beam and data acquisition system are also described. The quality of the reconstruction of individual particles is demonstrated through the ability of NOMAD to observe Ks ’s, Λ 0’s and π0’s. Finally, the observation of τ− through its electronic decay being one of the most promising channels in the search, the identification of electrons in NOMAD is discussed.

The CPLEAR collaboration has constructed a detector at CERN for an extensive programme of CP-, T- and CPT-symmetry studies using K0 and K0 produced by the annihilation of p's in a hydrogen gas target. The K0 and K0 are identified by their companion products of the annihilation K±π∓ which are tracked with multiwire proportional chambers, drift chambers and streamer tubes. Particle identification is carried out with a liquid Cherenkov detector for fast separation of pions and kaons and with scintillators which allow the measurement of time of flight and energy loss. Photons are measured with a lead/gas sampling electromagnetic calorimeter. The required antiproton annihilation modes are selected by fast online processors using the tracking chamber and particle identification information. All the detectors are mounted in a 0.44 T uniform field of an axial solenoid of diameter 2 m and length 3.6 m to form a magnetic spectrometer capable of full on-line reconstruction and selection of events. The design, operating parameters and performance of the subdetectors are described.

A large scintillating fibre detector for the UA2 experiment at the CERN pp Collider is under construction. It will be used for tracking and electron identification. The performance of a full scale test module containing 960 fibres of 2.1 m length and 1 mm diameter is described.

A second level trigger system using conventional wire chamber readout and NIM modules is described. The events to be processed by the on-line computer are selected in a time interval of one microsecond on the basis of number of hits in the wire chambers. Some applications and performances of the system are described in detail.

Reliable operation of RAMs as shift registers can be obtained up to frequencies exceeding 125 MHz using standard binary coded addressing.

The electronics systems for the readout of a large drift chamber (25 m3, 6110 sense wires) with image readout, to be used at the CERN p-p collider, is described. The system uses a flash analog-to-digital converter and is able to measure directly the drift time, the charge division, and the energy losses for many tracks on each wire. The results obtained with chamber and electronics prototypes are reported.

This paper addresses the performance of the Front End Card (FEC) for the ALICE Time Projection Chamber (TPC) on measured data. The ALICE TPC Front End Electronics consists of 557568 channels. A single readout channel is made of two basic units: (a) an analogue ASIC (PASA) that incorporates the shaping/amplifier circuits for 16 channels; (b) a mixed-signal ASIC (ALTRO) that integrates 16 channels, each consisting of a 10-bit 25-MSPS ADC, the baseline subtraction, tail cancellation filter, zero suppression and multi-event buffer. The complete readout chain is contained in FECs, with 128 channels each, connected to the detector by means of kapton cables. A fraction of the final electronics (1024 channels) has been characterized in a test that incorporates a prototype of the ALICE TPC as well as many other components of the final set-up. The tests show that the system meets all design requirements.