G. Van Beek

The OPERA experiment Target Tracker

The main task of the Target Tracker detector of the long baseline neutrino oscillation OPERA experiment is to locate in which of the target elementary constituents, the lead/emulsion bricks, the neutrino interactions have occurred and also to give calorimetric information about each event. The technology used consists in walls of two planes of plastic scintillator strips, one per transverse direction. Wavelength shifting fibres collect the light signal emitted by the scintillator strips and guide it to both ends where it is read by multi-anode photomultiplier tubes. All the elements used in the construction of this detector and its main characteristics are described.

The CHORUS scintillating fiber tracker and opto-electronic readout system

Abstract A scintillating fiber tracker system consisting of more than one million fibers has been successfully constructed and made operational for the CERN WA95/CHORUS experiment. The design and construction of the tracker system as well as its opto-electronic readout are described. The performance of the detector with high-energy muons is presented.

High-resolution tracking using large capillary bundles filled with liquid scintillator

Abstract We have developed large high-resolution tracking detectors based on glass capillaries filled with organic liquid scintillator of high refractive index. These liquid-core scintillating optical fibres act simultaneously as detectors of charged particles and as image guides. Track images projected onto the readout end of a capillary bundle are visualized by an optoelectronic chain consisting of a set of image-intensifier tubes followed by a photosensitive CCD or by an EBCCD camera. Two prototype detectors, each composed of ≈10 6 capillaries with 20– 25 μm diameter and 0.9–1.8 m length, have been tested, and a spatial resolution of the order of 20– 40 μm has been attained. A high scintillation efficiency and a large light-attenuation length, in excess of 3 m, was achieved through special purification of the liquid scintillator. Along the tracks of minimum-ionizing particles, the hit densities obtained were ∼8 hits / mm at the readout window, and ∼3 hits / mm at ∼1 m away. The level of radiation resistance of the prototype detectors is at least an order of magnitude higher than that of other tracking devices of comparable performance.

Scintillating fiber trackers with optoelectronic readout for the CHORUS neutrino experiment

Abstract The CERN WA95/CHORUS collaboration has been constructing a hybrid detector to search for ( ν μ - ν τ )-oscillations. An essential component of the detector is a scintillating fiber tracking system for precise track reconstruction of particles. The physics motivation is explained, and the detector layout, the tracker design, its optoelectronic readout and test beam results are presented.

Drift chambers operated in the limited streamer mode

Abstract Successful operation of a drift chamber with 10 cm drift in the limited streamer mode is demonstrated. Good results were obtained with a 50-50 argon-isobutane gas mixture. A preliminary search for alternative gas mixtures avoiding the hydrocarbon quencher component is described.

Drift chambers with delay line readout operated in the limited streamer mode

Abstract This report presents the performance of drift chambers operated in the limited streamer mode with 9.4 cm maximum drift distance and position sensing along the 4.35 m long anode wire through delay line timing. Using only three timing channels a position resolution of 1×3 mm 2 is obtained over a detector surface of 19×435 cm 2 . In this contribution, the emphasis is mainly put on the performance of the delay line and on the drift behaviour in streamer mode using safe gas mixtures.

A scanning and measuring table for holographic bubble chamber or streamer chamber images

Abstract We present a description of the Brussels scanning and measuring system for holographic bubble chamber or streamer chamber images. Conclusions are drawn from six months of operation of the system.

The forward muon detector of the DELPHI experiment at LEP

Abstract The layout and construction of the muon drift chambers equipping the end caps of the DELPHI detector are described. The performance of this forward muon detection system, determined from cosmic ray tests and data collected during the first year of LEP operation, is presented.

Large liquid-scintillator trackers for neutrino experiments

Results are given on tests of large particle trackers for the detection of neutrino interactions in long-baseline experiments. Module prototypes have been assembled using TiO2-doped polycarbonate panels. These were subdivided into cells of 1c m 2 cross section and 6 m length, lled with liquid scintillator. A wavelength-shifting bre inserted in each cell captured a part of the scintillation light emitted when a cell was traversed by an ionizing particle. Two different bre-readout systems have been tested: an optoelectronic chain comprising an image intensier and an Electron Bombarded CCD (EBCCD); and a hybrid photodiode (HPD). New, low-cost liquid scintillators have been investigated for applications in large underground detectors. Testbeam studies have been performed using a commercially available liquid scintillator. The number of detected photoelectrons for minimum-ionizing particles crossing a module at dierent distances from the bre readout end was 6 to 12 with the EBCCD chain and a mirror at the non-readout end; 4 to 10 with the HPD and no mirror. The light-attenuation lengths in the bres were 9:4 m with the EBCCD and 6:4 m with the HPD. The detector response to electron showers has also been measured. After 10 radiation lengths of lead, the transverse position of the incoming electron was determined with a precision of a few millimeters for electrons of 4 GeV, and with a precision of 1.5 2.0 cm for electrons of 1 GeV.

Construction of a cylindrical MWPC for the central tracking detector of H1

Abstract A set of two cylindrical multiwire proportional chambers, 2.2 meter long and 1 meter in diameter, are being built as part of the central tracking detector of the H1 experiment, at HERA. The chamber bodies are of sandwich type; the cathodes are segmented in pads. The transmission line, which is part of the sandwich, has an impedance matched to the preamplifiers. The electronic readout has been tested on a flat prototype chamber; the time resolution is well below the 96 ns bunch crossing time at HERA.