C. Engster

The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events

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

Performance of a scintillating fibre detector for the UA2 upgrade

Abstract A large scintillating fibre detector for the UA2 experiment at the CERN p p 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.

The ALICE TPC front end electronics

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.

A Large area transition radiation detector for the NOMAD experiment

Abstract 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.

Performance of the scintillating fibre detector in the upgraded UA2 detector

Abstract A large scintillating fibre detector consisting of ≈ 60 000 scintillating plastic fibres of 1 mm diameter and 2.4 m length has been used successfully as a tracking and preshower detector in the UA2 experiment at CERN. The detector readout, the pattern recognition algorithm and the results from the p p data taking run are described.

The UA2 scintillating fibre detector

Abstract The UA2 experiment at CERN is currently upgrading its apparatus to take advantage of the higher accelerator luminosity to be provided from November 1987. The first large particle tracking detector using scintillating optical fibres will form a major part of this upgrade. The detector is built by the Cambridge, CERN and Saclay groups. The Scintillating Fibre Detector is a cylinder of radius 38 to 44 cm, composed of 60000 plastic optical fibres of length over 2 m. The 1 mm diameter fibres are optically clad and aluminised, and are arranged in 24 layers. The detector will be used to track charged particles produced in pp interactions, and also contains a lead converter to cause neutral and charged electromagnetic particles to shower. The signals from the fibres are amplified, multiplexed and digitised by 32 readout chains. These consist of: • —A large aperture, de-magnifying image intensifier, providing a gain of ∼ 40000. Extremely fast phosphors are employed for the three stages, to match the short time (4 ps) between particle interactions; • —Charge-coupled devices (CCDs) converting the optical image into a single train of electrical pulses for 2000 fibres. A novel use of the anti-blooming electrode of the CCD enables unwanted images to be cleared in • —A Fastbus digitiser, which processes the video signal, providing a large degree of data reduction. A full-scale prototype of 960 fibres with readout has been tested in a particle beam. It has demonstrated a good spatial resolution of the tracks (

Performance of the UA2 scintillating-fibre detector

Abstract A large scintillating-fibre detector consisting of ≈ 60 000 scintillating plastic fibres of 1 mm diameter and 2.4 m length has been used successfully as a tracking and preshower detector in the UA2 experiment at CERN. The detector readout and the results from the p p data-taking run are described.