Proportional Chamber System Research Articles

Direct measurements of the lifetime of medium-heavy hypernuclei

The lifetime of a Λ particle embedded in a nucleus (hypernucleus) decreases from that of free Λ decay mainly due to the opening of the ΛN→NN weak decay channel. However, it is generally believed that the lifetime of a hypernucleus attains a constant value (saturation) for medium to heavy hypernuclear masses, yet this hypothesis has been difficult to verify. This paper presents a direct measurement of the lifetime of medium-heavy hypernuclei that were hyper-fragments produced by fission or break-up from heavy hypernuclei initially produced with a 2.34 GeV photon-beam incident on thin Fe, Cu, Ag, and Bi target foils. For each event, fragments were detected in coincident pairs by a low-pressure multi-wire proportional chamber system. The lifetime was extracted from decay time spectrum formed by the difference of the time zeros between the pairs. The measured lifetime from each target is actually a statistical average over a range of mass with mean about 1/2 of the target mass and appears to be a constant of about 200 ps. Although this result cannot exclude unexpected shorter or longer lifetimes for some specific hypernuclei or hypernuclear states, it shows that a systematic decrease in lifetime as hypernuclear mass increases is not a general feature for hypernuclei with mean mass up to A≈130. On the other hand, the success of this experiment and its technique shows that the time delayed fissions observed and used by all the lifetime measurements done so far on heavy hypernuclei could likely have originated from hyper-fragments lighter than the assumed masses.

The forward muon detector of the CMS experiment

We describe the forward muon detector of the CMS experiment at the LHC accelerator. The CMS forward muon detector is composed of 4 independent stations, each station being made of a mosaic of six-layer cathode strip chambers. Cathode strip chambers are multiwire proportional chambers with a cathode segmented in strips to provide a precise measurement of the coordinate across the strip direction. The forward muon detector has to be able to measure hits along muon tracks with a precision of 75–150μm per station as well as providing an accurate time tag to be used by the first level trigger. The forward muon detector will cover an area of more than 1000m2 representing one of the largest system of proportional chambers ever built. We also present some results obtained using muon test beams with some cathode strip chamber prototypes.

Design, fabrication and evaluation of an extremely light, small-size multiwire proportional chamber system

We introduce an extremely light, small-size multiwire proportional chamber (MWPC) system. Including its wire frames, the average thickness of the complete detector system, consisting of eight MWPCs, is 5% of a radiation length or 1.68 g/cm 2. Its total weight is < 1.2 kg. In order to obtain such a light-weight detector system conventional methods of MWPC design and fabrication could not be used. New materials had to be introduced as well. The design, fabrication technique and important properties of this low-mass MWPC system are discussed.

Characteristics of a large system of pad readout wire proportional chambers for the HPC calorimeter

A large system of wire proportional chambers is being constructed for the readout of the High-Density Projection Chamber of the DELPHI experiment at the Large Electron-Positron (LEP) storage ring. The system consists of 144 chambers, each 0.3-m/sup 2/, and read out via cathode pads. located at the end of the HPC drift volume. The authors discuss the design of the readout chamber; the chamber construction, the mechanical tolerances and gain uniformity, and the performance. >

Proportional chambers with delay line readout in the MD-1 detector

A system of proportional chambers is described which was used in the MD-1 detector at the VEPP-4 collider for detection of scattered electrons in two-photon reactions. To obtain the necessary spatial resolution proportional chambers with delay-line readout have been used. The system contained 6 chambers of this type with a size of 500×200 mm 2, during three years it was under operation with a counting rate up to 400 kHz per chamber. The long term spatial resolution was not worse than σ = 0.2 m. The energy resolution achieved was 1.3%.

Proportional chambers for registering charged particles and relativistic nuclei

A description is given of the system of proportional chambers used in the SIGMA experiment at IHEP and in the ANOMALON experiment at JINR.

A charged-pion detection sytem with large electron suppression

The experimental apparatus used in electron induced pion-production studies at NIKHEF-K is discussed. It is shown that very large electron-rejection ratios can be obtained by the use of an aerogel Cherenkov counter incorporated in the trigger of the multiwire proportional chamber system in the focal plane of the QDQ hadron spectrometer.

A highly compact multiwire proportional chamber system with 80 μm resolution

A multiwire proportional chamber system with 80 μm spatial resolution is described. Details of the system and of its performance are presented.

Particle identification by ionization measurements: Description of the CLEO [formula omitted] system

We describe the design, construction and performance of a pressurized proportional chamber system intended to identify particles by means of their energy loss in thin gas samples. The system is part of the CLEO detector at the Cornell Electron-Positron Storage Ring (CESR).

Recent Results from the Cleo dE/dx System

The installation of the CLEO dE/dx particle identification system was completed last summer. DE/dx measurements are made with a pressurized gas proportional wire chamber system capable of making 117 ionization measurements. We report on measurements of relativistic rise and resolution from data taken on the T resonances and the nearby continuum. We describe the proven capabilities of the device in identifying hadrons in both the low and high momentum regions and electrons above 1 GeV/c.

The Application of Resistive Charge Division in Large Proportional Tube Chambers

A proportional tube chamber system has been constructed to instrument a high energy neutrino calorimeter at Fermilab. Each proportional wire chamber consists of a stack of extruded aluminum eight cell 1 × 8 extrusion with a 1/2 cell offset. With these modules 12' × 12', 16' × 16' and 24' × 24' chambers have been constructed. A novel resistive charge division system is used for the position measurement. This system, consists of a number of wires resistively connected in a paralled feeding into two amplifiers, one at each end. From a measurement of the pulse height difference normalized to the pulse height sum, the hit wire is uniquely determined thus giving a lateral position measurement.

A triangular tube proportional wire chamber system

We report on the characteristics of the proportional tube chamber system which has been constructed for muon identification in the PEP-4 experiment at SLAC. The mechanical and electrical properties of the extruded aluminum triangular tubes allow these detectors to be used as crude drift chambers.

The Pressurized dE/dx System in the CLEO Detector at CESR

A unique part of the CLEO Detector at CESR is the pressurized wire proportional chamber system for particle identification using measurements of ionization loss (dE/dx) in gaseous argon. Each particle traverses the ∼ 80 cm thick detector and leaves 117 ionization samples. Data obtained from e+e- collisions at CESR in the 10 GeV center of mass energy region have been analyzed. Initial results showing the most probable ionization loss of hadrons and leptons as a function of their momenta will be presented. Also we describe the geometrical, mechanical and electrical construction of this device.

The Pressurized de/Dx System in the Cleo Detector at Cesr

A unique part of the CLEO detector at CESR is the pressurized wire proportional chamber system for particle identification using measurements of ionization loss (dE/dx) in gaseous Argon. Each particle traversing the ~80 cm thick detector leaves 117 ionization samples. Data obtained from e+e- collisions at CESR in the 10 GeV center-of-mass energy region have been analyzed. Initial results showing the most probable ionization loss of hadrons and leptons as a function of their momenta will be presented. We describe the geometrical, mechanical and electrical construction of this device.

A Spherical Drift Chamber Area Detector for X-Ray Crystallography

A multiwire proportional chamber system has been built as an area detector for use in x-ray crystallography with Cu Kα radiation (1.54Å). The chamber, constructed by Charpak and collaborators at CERN, consists of a 10cm thick spherical interaction region with a radial electric field, a transition from spherical to plane geometry and a 50cm × 50cm multiwire proportional chamber and subtends a 90° opening angle. Two dimensional position information is obtained from orthogonal cathode planes using a high speed analog centroid finding technique. Data on spatial and energy resolution as a function of angle and depth of interaction in the spherical drift region using a collimated, pulsed, x-ray source are presented. Ionization loss as a function of drift distance and field and loss due to field shaping grids has also been measured.

A system of multigap proportional wire chambers

A set of proportional chambers has been constructed for a multiparticle spectrometer at the CERN Intersecting Storage Rings (ISR). The detector consists of 73 000 wires and covers an effective area of 300 m 2. In this paper we will describe the design and performance of this detector.

A proportional wire chamber system for beam definition in precision total cross section measurements

We have developed and extensively used a PWC system in precision measurements of total cross sections at low momenta (0.4–1.1 GeV/ c) and at high momenta (23–370 GeV/ c). This “electronic collimator” operated simultaneously in a fast (250 ns) decision making mode, and a slower (0.5 ms) readout mode. The decision making mode utilized adjustable hardwired logic to define acceptable incident beam trajectories and reject multiple beam tracks. A sample of the events was read into an on-line computer for beam tuning, for chamber diagnostics, and for study of the effect of small angle scattering to verify the total cross section extrapolation procedure.

A system of proportional chambers for use in a photon beam experiment

The design, construction and performance, under test conditions, of a large multiwire proportional chamber system are described. The system consists of seven chambers, six 560 x 1298 mm 2 and one 1026 x 1794 mm 2, each containing three signal planes with a common high voltage plane between each adjacent pair. The plane spacing in all the chambers was 6 mm and the signal wire spacing 2 mm. The chambers have operated successfully, with their associated hybrid electronics, in a low intensity electron beam and all signal planes gave average efficiencies of ≈96% over their whole area using a magic gas mixture with a strobe width of 60 ns.

Multiwire proportional chamber system of the Fermilab single arm spectrometer

We describe a system of two groups of multiwire proportional chambers and its special purpose interface used in the Single Arm Spectrometer (SAS) facility at Fermilab. The first set measures the coordinates of the fast particle going into the spectrometer arm with a space resolution down to +/-0.5 mm. The second set, close to the target, measures the multiplicity and angular distributions of charged particles coming from the interaction. The chambers of this set have three sensitive planes with wires at 120 degrees in the same gas volume to measure three coordinates for each physical point, two readout channels per wire to minimize the inefficiency due to the very high flux and insensitive regions at the center of the chambers where they are crossed by the beam.

A multiwire proportional chamber system with digital read-out for the Munich Q3D-spectrograph

A position-sensitive MWPC system with digital read-out for magnetic spectrographs is described. The spatial resolution, as given by the wire spacing, is 0.5 mm. The counter can be used for coincidence experiments with a time resolution of ≈10 ns. A ΔE-signal from the counter allows gross particle identification. With 4 or 5 adjacent wires firing simultaneously because of inclined particle incidence, coincidence requirements between these wires are used to reduce the neutron and γ-sensitivity of the chamber.