Multiwire 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.

Development of a windowless multi-wire proportional chamber (MWPC) counting system for measuring extended-area beta source

A windowless MWPC counting system has been developed to measure surface emission rate of extended-area sources. A new anode and guard plane design gives better electric-field uniformity in the (250×200)mm2 sensitive volume relative to a previous-generation MWPC at KRISS, which has been used as a national standard with uncertainty <1%. The conditions of stable operation for the new MWPC system were studied, and the uncertainty was estimated with an extended-area 36Cl source. The relative combined standard uncertainty was evaluated to be 0.23%, a 50% improvement over the previous-generation MWPC counting system.

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.

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.

A system of large multiwire proportional chambers for a high intensity experiment

We describe a system of three multiwire proportional chambers used in the experiment NA24 at CERN. Each chamber consists of four wire places (2×2 m2 sensitive area), packed together in the same mechanical frame with only five cathode foils. All planes are electrically independent and can be operated individually although each of the three inner cathode foils is used for two adjacent wire planes. Another feature of the chamber is that an area around the beam can be desensitized to allow operation in a high intensity beam.

A system of large multiwire proportional chambers for a high intensity experiment

We describe a system of three multiwire proportional chambers used in the experiment NA24 at CERN. Each chamber consists of four wire planes (2 × 2 m 2 sensitive area), packed together in the same mechanical frame with only five cathode foils. All planes are electrically independent and can be operated individually although each of the three inner cathode foils is used for two adjacent wire planes. Another feature of the chamber is that an area around the beam can be desensitized to allow operation in a high intensity beam.

A trigger system using cathode read-out chambers and a coincidence matrix

We describe a system of cathode read-out multiwire proportional chambers which performed the trigger of the CERN NA3 experiment. These large chambers-the biggest measures 4.8 × 5.1 m 2-have been operated successfully since May, 1978. The cathodes are divided into about 1000 graphite cells painted on a mylar foil. The same cells are reproduced in silver paint on the other side of the mylar foil, which allows a capacitive transmission of the signals deposited on graphite cells. The signals are then transmitted to the amplifiers via copper strips which may be up to 2 m long. The amplifiers are currently operated with a sensitivity of 1 μA on 50 ω. A coincidence matrix, using fast ECL circuitry, uses the signals given by these chambers to select particles having large transverse momenta, in about 100 ns. This gives a very powerful trigger for the experiment studying high mass dimuon production by hadrons: about 60% of the triggers are true dimuons. An improved version of the coincidence matrix allows on-line selection of dimuons above a given invariant mass.

A trigger system using cathode read-out chambers and fast computing of kinematical quantities

We describe a system of cathode read-out multiwire proportional chambers which performs the trigger of a spectrometer installed at the CERN S.P.S. to study high mass dimuon pairs. These chambers, associated with fast ECL circuitry, allow to select particles with high tranverse momentum in less than 110 ns. A further development of the electronics will permit to trigger on high dimuon masses with a response time of the order of 170 ns.

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 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.

Polarization measurements in p-p elastic scattering between 398 and 572 MeV

Measurements of the analyzing power for p-p elastic scattering at 398, 455, 497, 530 and 572 MeV are reported. A system of multiwire proportional chambers placed directly in a polarized beam was used to observe the angular region 1.5° < θ lab < 10°. An increase in P( θ) is observed as a function of both scattering angle and incident kinetic energy. Electromagnetic-nuclear interference is used to obtain direct information on the nuclear interaction.

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.

A high resolution multiwire proportional chamber system

We describe a high pressure proportional wire chamber detector, fully efficient for minimum ionizing particles, with a resolution σ = 62 μm, 7 cm 2 sensitive area, and a high rate capability.

A modular system of multigap proportional chambers

We describe a system of small multiwire proportional chambers having electrically separated adjacent gaps. The chambers can be stacked in any number and combination of planes.

Development and operation of a multiwire proportional chamber system

A multiwire proportional chamber system consisting of ten beam chambers and seven 0.5 m 2 chambers, each with 2 mm wire spacing, has been developed and used in an experiment at the CERN proton synchrotron. The constructional details of chambers and electronics are described and the overall performance of the system is discussed.

Measurement of the real part of the forward amplitude in [formula omitted] elastic scattering

The differential cross sections of the elastic pp reaction have been measured at 1.2, 1.4, 1.8 and 2.6 GeV/ c incident p momentum. The measurements have been performed at the CERN PS using a system of multiwire proportional chambers. The angular region covers scattering angles from 0 to ∼200 mrad. Interference effects between the Coulomb and the nuclear amplitudes are used to derive the ratio of the real to imaginary part of the forward nuclear amplitude. These ratios are compared with theoretical predictions.

A system of multiwire proportional chambers for a large aperture spectrometer

Five large multiwire proportional chambers, ranging in size from 1.3 × 0.8 m 2 to 2.6 × 1.3 m 2, were built for magnetic spectrometer in use at the Stanford SPEAR I e + e − storage ring. We discuss the design and construction problems raised by the large size of the chambers, and described the solutions that were adopted. Results of efficiency and uniformity tests are also given.

A multiwire proportional chamber system for use in a storage ring experiment

A multiwire proportional chamber system is described which has been used successfully in an experiment at the 2.6 GeV electron-positron storage ring (SPEAR) at the Stanford Linear Accelerator Center. Detailed descriptions of the chamber construction and test procedures are given, together with a description of the electronic read-out circuitry. The performance of the system during the experiment is reported and on-line displays of typical events are shown.