High Density Projection Chamber Research Articles

Performance of the HPC calorimeter in DELPHI

The performance of the High-density Projection Chamber (HPC), the barrel electromagnetic calorimeter of the DELPHI experiment, is described. The detector adopts the time projection technique in order to obtain exceptionally fine spatial granularity in the three coordinates (/spl sim/2/spl times/20 mrad/sup 2/ in /spl theta//spl times//spl phi/ with nine samplings along the shower axes), using a limited number of readout channels (18432). Among the various topics concerning the HPC construction and operation, major emphasis is given to the aspects related to the calibration in energy of the calorimeter, based mainly on the analysis of the detector response to /sup 83m/Kr decays, and to the treatment of ageing in the readout proportional counters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Beam test of an imaging high-density projection chamber

A beam test of a high-density projection chamber with optical readout is presented. The device consists of a prototype of the DELPHI HPC calorimeter on which a parallel-plate, light-emitting structure was installed, replacing the original multiwire proportional chamber readout system. It produces detailed images of the energy deposited by electromagnetic showers; hadronic interactions are easily discriminated from these. The computerized readout system gives full quantitative information on the events. showing good energy and position resolutions.

A setup for the calibration of the HPC readout chambers

We describe the setup which will be used to calibrate the individual channels of the readout chambers for the high-density projection chamber (HPC), the large-angle calorimeter of the DELPHI experiment at LEP. Due to the lack of test beam time this will be the only calibration of the about 20 000 readout channels before the installation on the beam at LEP. The aim is to reach percent level accuracy on the equalization of the individual channel response and to measure accurately the coupling of the pulsing system to each channel. Results on the first chambers are shown.

The DELPHI high-density projection chamber

The mechanical design (converter, readout chamber, and trigger counters) and electronics (analog components and digitizers) of the High-Density Projection Chamber are described. Results from tests of production modules both in a test beam. showing observed change as a function of incident energy and observed versus expected track location, are presented. Tests using cosmic rays, showing measured drift-velocity and attenuation length for each pad row, are also presented. >

Calibration of the pad readout wire proportional chambers for the HPC calorimeter

The authors describe the setup used to calibrate the individual channels of the readout chambers for the High-Density Projection Chamber (HPC), the large-angle calorimeter of the DELPHI experiment. Due to the lack of test beam time this will be the only calibration of the 22000 readout channels before the installation on the beam at LEP, Percent level accuracy on the equalization of the individual channel response was achieved. The coupling of the pulsing system to each channel was also measured accurately. Results on more than 90 chambers are reported.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

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. >

Some aspects of the Delphi HPC project

The progress of the High-density Projection Chamber is discussed in several respects: production machines and production process, and calibration of the detector with and without beams.

Charge transmission in a time projection calorimeter in a magnetic field

The charge transmission properties of the High-density Projection Chamber electromagnetic calorimeter filled with ArCH 4(80-20) have been measured recording the current produced by a 60Co source as a function of the drift coordinate. The measurements without magnetic field are in agreement with the expectations from transverse diffusion. By switching on a 1 T magnetic field ( B), parallel to the electric field ( E), it is possible to maximize the charge output and to verify the increase in charge transmission due to the combined E and B effect.

Use of a high density lead glass tubing projection chamber in positron emission tomography and in high energy physics

We describe the principle of operation of a high density projection chamber, in which the converter/radiator and drift field shaping structures are combined in the form of high density (5–6 g/cm 2) lead glass tubing. The main applications of this type of detector to Medical Physics (Positron Emission Tomography) and High Energy Physics (Electromagnetic Calorimetry) are discussed.

The DELPHI Barrel Electromagnetic Calorimeter Flash ADC Based Digitizer

We describe the design and performance of an 8-bit Flash ADC based readout system developed for use on the cathode pads of the DELPHI High Density Projection Chamber (HPC). A dynamic range of 800:1 is obtained at input frequencies of 15 MHz using a bilinear voltage divider reference chain. Performance characteristics of the digitizing circuits for a CAMAC version of this readout system are presented. The design of a FASTBUS version is presented.

High density spiral projection chamber (HDSPC): Design of the end-cap detectors of the obelix experiment at lear

We discuss the design of a cylindrical high density projection chamber [1] that uses the spiral projection chamber [2] geometry and will instrument the end-caps of the proposed OBELIX [3] experiment at LEAR. This detector-high density spiral projection chamber (HDSPC [4])- has axial symmetry, radial drift electric field, a radiator made of converter disks alternating with drift volumes and the amplification and readout region in the outer part of the cylinder. It is equipped with FADC electronics and reconstructs in three dimensions primary ionization produced in the active volume. It features fine granularity and high angular resolution near the beam pipe and appears particularly advantageous for λ and prong detection in the forward and very forward region of storage rings and extracted beam experiments.

Design and construction of a cathode readout proportional chamber for the HPC calorimeter

A cathode readout MWPC for the high-density projection chamber (HPC) of the DELPHI experiment at LEP has been built and tested. In order to decouple both electrically and mechanically the drift volume of the HPC from the readout region, the segmented cathodes are made of brass U profiles, with a 100 μm diameter wire wound around the profile with a 2 mm pitch.

Design and Performance of a CCD Based Readout for the Delphi Barrel Electromagnetic Calorimeter

We describe the design criteria and performance of a CCD based readout system developed for use in the DELPHI experiment at LEP. These circuits are designed for use on the cathode pads of the High Density Projection Chamber (HPC) which will serve as the DELPHI central region electromagnetic calorimeter. Two separate CAMAC versions of this system have been tested on prototype HPC modules exposed to both hadrons and electrons. Stability and performance characteristics of these circuits at CCD input frequencies up to 20 MHz are presented. We also present results on the electron shower energy resolution for the HPC prototypes.

Status of the High density Projection Chamber

The High density Projection Chamber (HPC) for the Delphi detector is a lead gas sampling electromagnetic calorimeter constructed using the lead wire technique which is well adapted for mass production. The HPC offers good energy resolution and superb space resolution and may consequently serve as a tracking device.

The High Density Projection Chamber for the Delphi Experiment at LEP

The status of the HPC project for the DELPHI electromagnetic shower counter at LEP is described, including a new construction method for the lead converter structure. Results from test beam measurement on the transverse and longitudinal shower development are presented, together with performance figures for spatial and angular resolution.

Performance of a high density projection chamber

Abstract The high density projection chamber (HPC) is a large volume gas sampling calorimeter. The highly granulated module allows a complete three-dimensional reconstruction of the shower and offers good energy resolution. We will present preliminary results from test runs and discuss operation in a magnetic field.

A Study of Electromagnetic Showers in the High Density Projection Chamber

A prototype module of a High density Projection Chamber (HPC) has been tested in an electron beam. The HPC, with the shower conversion separated from the charge collection, offers a simple, homogeneous large volume detector with an energy resolution of 12.5%/?E and an exceptionally fine granularity both along and transverse to the shower axis. The results from the test are presented together with a description of the calorimeter system.

A High Density Projection Chamber

A High Density Projection Chamber