Wire Plane Research Articles

Performance of the hexagonal calorimeter at PEP-4

A Geiger-mode electromagnetic shower calorimeter has been constructed for PEP-4. Six trapezoidal modules cover 75% of 4 π solid angle in a hexagonal array. Each module contains 40 sense wire planes between 0.25 radiation-length thick lead-laminates, and is divided electrically into submodules of 27 and 13 layers. Half-degree wide hodoscopic channels in projective geometry provide excellent spatial resolution. In each gap three stereo views using the sense wires as well as strips on both cathodes at ±60° to the wires provide good shower reconstruction capabilities in multi-track jet events. Calibration and data analysis procedures are outlined. The performance of the calorimeter in the measurement of Bhabha events and the reconstruction of π 0's in jet events is in excellent agreement with Monte Carlo simulations. The π 0 mass resolution is MeV (rms).

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 wire spark chamber capacitive readout system with low leakage current and small systematic error

A wire spark chamber capacitive readout system with analog FET switch multiplexing and CAMAC interface is described. Two wire planes per chamber are read out. The information of each plane is sequentially digitized in one ADC. This and the low leakage current of the FET switches guarantee a small systematic error of the measurement of the spark position.

Some Properties of the Streamer Tube System of the CHARM Neutrino Detector

The spatial resolution of the fine-grain neutrino calorimeter of the CHARM Collaboration has been upgraded by adding 20,000 aluminium tubes, working in the limited streamer mode. Each subunit is now equipped with crossed wire planes. Results of the energy calibration of the system in a test beam, containing pions and electrons from 5 GeV to 140 GeV, are presented. The use of the streamer tube system to discriminate between electromagnetic and hadronic showers is discussed.

Space resolution of a drift chamber with multiware sampling

A drift chamber with a 10 cm drift space and 96 amode wires was built to study spac independent measurements N along a particle track. It is found that this resolution improves with 1 N . For a single wire precision of 150 μm one obtains 25 μ if 36 measurements are combined to reconstruct an average point along the trajectory of a particle. This scaling behaviour is independent of the distance between the track and the wire plane.

A two-dimensional, single-photoelectron drift detector for Cherenkov ring imaging

A detector capable of imaging single photoelectrons has been constructed and tested. UV photons (⩾5.4 eV) are converted to electrons with high quantum efficiency by photoionization of a small admixture (∼1 Torr) of an organic vapour TMAE in a predominantly methane drift and amplifying gas at atmospheric pressure. The produced photoelectrons drift in a uniform applied electric field to a picket fence of proportional wires where each electron is amplified, counted and timed. The two-dimensional source point of each photoelectron is uniquely determined by the hit wire address and the arrival time. The detector has been tested by measuring ionization electrons produced in the drift gas be relativistic charged particles. The limiting precision to which the electron source point can be determined has been measured to be 300 μm (r.m.s.) in the drift direction and 370 μ m in the wire plane direction. Additional independent error sources due to electron diffusion in the drift gas have been measured to be proportional to the square root of the drift distance with a proportionality constant of 235 μ m/ cm 1 2 in both directions. Drift velocities of electrons in various predominantly methane gas mixtures have been measured as a function of the applied electric field. The utilization of such a two-dimensional single electron drift detector for Cherenkov ring imaging is presented with a discussion of the advantages and limitations of the drift method for imaging.

Sensitivity of echolocation in the megachiropteran fruit bat, Rousettus

The ability of Rousettus aegyptiacus to detect targets was measured in both quiet and white noise, using an obstacle avoidance protocol. Bats were trained to fly through a vertical plane of wires in total darkness; the ability of the bat was assessed by comparing the frequency of misses with the frequency expected by chance. The wires were moved frequently to prevent place learning. Wire sizes ranged from 5.0 to 0.14 mm in diameter. Four bandwidths of white noise were used: 2–12, 16–24, 12–24, and 12–32 kHz. The smallest wire size that the bats could detect in quiet was 0.46 mm in diameter. These results extend earlier findings by Griffin, Novick, and Kernfield (1958). When using noise, bandwidths with higher frequencies interfared with wire detection. Jamming frequencies below 12 kHz had no adverse effect and thus seem unimportant for echolocation. These results will be discussed in light of the auditory sensitivity measurements for Rousettus and the frequency spectra of the orientation clicks. [Supported by NSF grant BNS 79-05606.]

Resistive cathode detectors with bidimensional strip readout: Tubes and drift chambers

Resistive tubes in the limited streamer mode with 1 cm granularity are described. Owing to resistive cathode transparency, both coordinates of a tube layer are readout by two sets of pickup strips. A graded cathode drift chamber with about 100 μm accuracy on both coordinates of the wire plane has been developed. It is again based on resistive cathode transparency, with external orthogonal strip readout, to which the charge centroid method is applied.

An electromagnetic shower detector using proportional wire chambers with cathode plane delay-line readout

The construction and performance of a fine-grained electromagnetic shower detector is described. The detector consisted of 49 1 m × 1 m proportional wire chambers interlaced with one radiation length thick aluminum plates. The delay-line readout on the cathode planes measured the centroid positions of the shower. The anode wire planes measured the shower energy and can be used to form an experimental trigger. The detector was used successfully in an elastic neutrino-electron scattering experiment at Fermilab.

A capacitive read-out system for wire spark chambers

We report on the details and performance of a large capacitive read-out system for wire spark chambers used in an experiment at the Rutherford Laboratory. The system used a novel push-pull firing system for the spark chambers. The data was read from all the wire planes directly into the Unibus of a PDP 11/45 minicomputer via a specially constructed interface which included on-line checking facilities.

A sequential/parallel track selector

A medium speed (∼1 μs) hardware pre-analyzer for the selection of events detected in four planes of drift chambers in the magnetic field of the Omicron Spectrometer at the CERN SC is described. Specific geometrical criteria determine patterns of hits in the four planes of vertical wires that have to be recognized and that are stored as patterns of “1”s in random access memories. Pairs of good hits are found sequentially, then the RAMs are used as look-up tables.

A square meter position sensitive parallel plate detector for heavy ions

A parallel plate avalanche counter has been developed for the detection of time, x− y position and energy loss of heavy ions. Construction and performance of prototypes with an active area of 26 × 26 cm 2 and of a final 1 × 1 m 2 version are described in detail. The position determination uses a new principle based on a sense wire plane within the two parallel plate electrodes with a fast interpolating delay line read-out. A time resolution of Δt = 240 ps (fwhm) and a position resolution of Δx = Δy ⩽ 0.5 mm (fwhm) are routinely obtained during actual experiments.

High Intensity Beam Profile Monitors for the LAMPF Primary Beam Lines

Two types of beam profile monitors are in use at LAMPF to measure the properties of the 800 MeV, 500 ?A proton beam external to the linac. Both types use secondary electron emission from a wire to produce a current signal proportional to the amount of proton beam that intercepts the wire. The wire scanner system uses a pair of orthogonal wires which are passed through the beam and the harp system uses two fixed planes of parallel wires. Most of the harps are not retractable and are exposed continuously to the primary beam. The high beam intensities available lead to a number of technical problems for instruments that intercept the beam or are close to primary beam targets. The thermal, electrical, radiation-damage, and material selection problems encountered, and some solutions which have been implemented are discussed.

Drift time relations in rotated multiwire proportional chambers and their advantages in practice

A MWPC is used at various angles to a charged particle beam and is read out with drift time measurement electronics. In this way one obtains a cluster of signals which contains information about the drift times from the path of the ionising track to the individual sense wires. These drift times bear a specific relation to one another which depends on the angle and position of the track. This means that one obtains a better understanding of the MWPC 1,2) as well as valuable advantages in practical use. The point of passage of the particle through the wire plane is obtained with great precision and without the left-right ambiguity of a standard drift chamber. For a larger cluster of signals (the cluster size depends on the ratio of the high voltage plane gap width to the wire distance) it is also possible to obtain a good estimate of the angle. Noise can easily be discriminated against and small distances between two particles can be resolved. Advantages and limitations of the method are discussed.

The construction of ISIS 1, A 4 m×2 m× 1.6 m drift chamber for particle identification

The construction of a large drift chamber for multitrack particle identification is reported. The design of the electrostatic structure, the wire plane and the gas system are described. The result of the first attempt to run the chamber is presented.

Energy loss measurement in a MWPC

Experimental results on the influence of angle and cell geometry on pulse height measurements in a multiwire proportional chamber (MWPC) are presented. Two track orientations are mainly considered: (a) tracks parallel to the wire plane and (b) tracks traversing the gap with one wire touched. In case (a), the positive induced pulse effect is analyzed: pulse heights have to be corrected by factors of 1.3–1.7 and wire inefficiency can be found up to 20%, depending on the cell geometry. The saturation effect starts earlier in case (a), but the influence of the angle between track and wire when approaching 90° is moderate. On the contrary, this influence is very effective in case (b). A detailed study of this phenomenon is then presented with a description of possible mechanisms involved.

Tests of Proportional Wire Shower Counter and Hadron Calorimeter Modules

We present results from test beam measurements at SLAC with prototype modules for the MAC detector at PEP. The modules consist of planes of proportional wires interleaved with lead sheets (shower counter) or iron plates (hadron calorimeter).

Delay Line Proportional Chambers for the Fermilab External Muon Identifier

Thirty nine, one meter square proportional chambers with delay line readout have been constructed for the external muon identifier of the Fermilab 15 foot bubble chamber. 1 They provide X, Y, U(45°) and T (avalanche time) information using a single wire plane, etched strip cathodes and nine amplifiers. They have a time resolution of ±27ns, single particle spatial resolution of ±2 to ±3mm and double particle resolution of ~2 1/2 to 4cm. The energy accessable to each wire is limited so none of the wires in the first 25 chambers has broken since their installation in 1973-4.

The External Muon Identifiers (EMI) at CERN

For the two big bubble chambers BEBC and Gargamelle (GGM), detectors for external muon identification had been requested. Choice was given to multiwire proportional chambers behind additional iron absorbers. 71 chamber modules (each 1 x 3 m2) with two independent anode wire planes and one cathode strip plane have been built. To record the particle hits without deadtime during the spill length of 3 ms the development of a readout system quite different from standard systems was necessary. The chambers, the electronics and the performance of both systems will be described.

Low mass cylindrical multiwire proportional chamber with unambiguous dual coordinate readout

We have built and tested a cylindrical multiwire proportional chamber with dual coordinate readout from the anode wires. The azimuthal coordinate is obtained in the conventional way, the axial one by charge division with a resolution of Δl/ l = 0.4% fwhm. The prototype chamber is 75 cm in diameter and 100 cm high and consists of two thin foil cathodes, two Mylar gas windows and a central anode wire plane with a total mass of 21 mg/cm 2.