Central Drift Chamber Research Articles

Fast on-line pattern recognition in a microprocessor farm

For the central drift chamber of the OPAL experiment at LEP a pattern recognition program was developed which is suitable for on-line usage in a microprocessor farm. It determines all track parameters which will be used in the third-level trigger in the data acquisition.

The MAC detector

The MAC detector at PEP recorded data for an integrated luminosity of 335 pb −1 between 1980 and 1986. The design of this low-cost MA gnetic C alorimeter was optimized for electron and muon identification, as well as for the measurement of hadronic energy flow. Muon identification is available over 96% of the solid angle, and MAC was the first detector to make large-scale use of gas-sampling calorimetry. Electromagnetic calorimetry in the central section employs alternating layers of lead and proportional wire chambers (PWCs), and hadron and the remaining electromagnetic calorimetry is accomplished with iron plate and PWC layers. A relatively small central drift chamber in an axial magnetic field provides pattern recognition and modest momentum determination. An outer blanket of drift tubes completes the muon identification system. During the latter two years of operation an innovative “soda straw” vertex chamber made more precise lifetime measurements possible. With an evolving trigger system and highly automated data acquisition system, this modest detector has exceeded most of its designers' expectations and has produced a gratifying spectrum of physics results.

The Mark II detector for the SLC

The Mark II detector has been upgraded in preparation for its role as the first detector to take data at the Stanford Linear Collider. The new detector components include the central drift chamber, the time-of-flight system, the coil, the endcap electromagnetic calorimeters and the beam energy and luminosity measuring devices. There have also been improvements in detector hermeticity. All of the major components were installed for a test run at the PEP storage ring (√ s = 29 GeV) in 1985. This paper describes the upgraded detector, including its trigger and data acquisition systems, and gives performance figures for its components. Future improvements are also discussed.

A fast track trigger processor for the OPAL experiment at LEP, CERN

The authors present the operational features and an engineering overview of criteria used in designing and building the fast track trigger processor for the OPAL experiment. The function of the processor is to examine, between successive LEP beam crossings (22 mu m), the multihit data generated by two central drift chambers and to provide the OPAL first-level trigger with information about the topology and the multiplicity of good tracks. The classes of events looked for are in the form of straight tracks in the R-Z plane which originate in the interaction region. The tracks are found in the R-Z and the R- phi planes by 24 fast track-finder circuits operating in parallel using a novel histogramming technique. A semicustom coincidence array circuit is used to match tracks. >

A two level fastbus based trigger system for CDF

We describe a two level FASTBUS based trigger processor designed and built for the CDF detector at the Fermilab p p collider. The Level 1 decision is based on the global energy deposition in the calorimeters as well as on the presence of muon candidates and stiff tracks in the central drift chamber. The Level 1 decision is made in the 3.5 μs between beam crossings, incurring no deadtime while reducing a raw event rate of 50–75 kHz to a few kHz. The remaining events are passed on to Level 2. The Level 2 decision is driven by the topology of the event, operating on calorimeter clusters, central stiff tracks and muon candidates. Level 2 is designed to reduce the rate to 1–100 Hz, incurring less than 10% deadtime, before initiating readout of all the detector elements. A large fraction of the trigger hardware is used for both the Level 1 and Level 2 decisions.

CDF central muon level-1 trigger electronics

We present the level-1 trigger module used for the CDF central muon drift chambers. Addressable registers select trigger mode for calibration, debugging, or data acquisition. A transverse momentum cut on muons exiting the solenoidal magnetic field region is made by using drift time differences between aligned pairs of anode sense wires. Cosmic ray results are presented and track angle selection is shown to be better than 5 mrad.

Test stands for the central drift chamber front end hybrid in the Stanford Linear Collider Detector

The central drift chamber (CDC) of the SLAC Linear Collider Detector (SLD) uses 1280 front-end electronic hybrid modules. Each of these modules contains over 450 components and performs numerous functions. The four test stands for production and detailed circuit characterizations of these hybrids are described, as well as the performance of some of the important functions of the test systems. >

A laser calibration scheme for the UA1 central detector at high luminosity (ACOL)

For the large central drift chambers of the UA1 detector significant geometrical distortions are to be expected, when the new SPS p-p collider program (ACOL) provides a 5 to 10-fold increase in luminosity over present beam intensities. The use of straight tracks from a laser calibration system can help in understanding and mapping these distortions. Such a system is briefly described in this paper. Special emphasis is put upon the selection of suitable doping seeds needed to increase the laser ionization yield in the drift chamber gas.

The hybridized front end electronics of the central drift chamber in the Stanford Linear Collider Detector

A description is given of the front-end electronics, which has been hybridized in order to accommodate high-packaging-density requirements. The hybrid package contains eight channels of amplifiers together with all the associated circuits for calibration, event recognition, and power-economy switching functions. A total of 1280 such hybrids are used. The amplifiers and associated circuits are described, and their performance is discussed. >

Front-end data processing in the SLD data acquisition system

The data acquisition system for the SLD detector will make extensive use of parallel processing at the front-end level. Fastbus acquisition modules are being built with powerful processing capabilities for calibration, data reduction and further preprocessing of the large amount of analog data handled by each module. This paper describes the readout electronics chain and data preprocessing system adapted for most of the detector channels, exemplified by the central drift chamber waveform digitization and processing system.

The UA1 central detector at present and future luminosity (ACOL)

The UA1 central drift chambers have run successfully since the beginning of the p -p collider program at the CERN SPS. So far the sense wires closest to the colliding beams have accumulated a total charge of 1 C/m without showing any degradation of resolution. Due to the future antiproton accumulator ACOL the instantaneous luminosity will be multiplied by a factor of approximately 10. The integrated luminosity over the years to come will also increase correspondingly. Space charge effects due to positive ion screening and limited lifetime of the detector are among the difficulties to be resolved. This paper deals with some proposed solutions.

Test operations of the VENUS superconducting magnet at KEK

The superconducting magnet of the VENUS detector was successfully operated with a central field of 0.75 T. A cryogenic system kept the coil temperature to below 4.5 K. When a coil quench was induced by built-in heaters, the stored energy of 11.7 MJ was safely extracted from the magnet to the outside dump resistor. The iron structure of the magnet yoke supported the magnetic force of about 230 t with a maximum elastic deformation of 0.4 mm. The maximum leakage field at the location of the barrel electromagnetic calorimeter was 33 G. The magnetic field was mapped in the solenoid bore by an NMR probe and by three-dimensional Hall probes with an accuracy of order 10 −4. The field was confirmed to be uniform within 0.3% deviation in the spatial region of a central drift chamber.

The new drift chamber for the Mark II detector at the SLAC linear collider

A new central drift chamber has been constructed for the Mark II detector for use the new SLAC Linear Collider. The design of the new chamber is based on a multi-sense-wire cell of the jet-chamber type. In addition to driftime measurements, pulse-height measurements from the sense wires provide electron-hadron separation by d E/d x. The chamber has been installed in the detector and is being at PEP before being moved to the SLC. The design and construction of the chamber, as well as initial performance results from the PEP data, are presented.

Performance of the SLD central drift chamber prototype

A two-cell prototype of the SLD central drift chamber has been tested using CO 2-isobutane (92%-8%) at 1 atm. Average single wire resolution of 55 μm was achieved. Charge division tests indicate a resolution of the final design of ⪅0.5% of wire length. d E/d x separation of π/e should be useful up to least 7 GeV/ c. 100 MHz waveform digitizers were used in parallel with conventional timing and integration techniques. The results show equivalent performance for single tracks and a two pulse resolution better than 1 mm.

A fast track trigger processor for the opal detector at LEP

A fast hardware track trigger processor being built for the OPAL experiment is described. The processor will analyse data from the central drift chambers of OPAL to determine whether any tracks come from the interaction region, and thereby eliminate background events. The processor will find tracks over a large angular range, |cos θ| ≲ 0.95. The design of the processor is described, together with a brief account of its hardware implementation for OPAL. The results of feasibility studies are also presented.

Pattern Recognition of Charged Particles for the VENUS Central Drift Chamber

We have been developing a pattern-recognition program based on a road method for the VENUS central drift chamber. A unique feature of our algorithm is that it makes use of a particular cell structure of the central drift chamber. We could, thus, construct an efficient pattern-recognition program by solving left-right ambiguities in an early stage of the track-finding processes. Using Monte-Carlo simulation for the detector response, we can now achieve for hadronic jet events at √s = 60 GeV a track-finding efficiency of 96%, which is quite stable against the noise and resolution of the drift chamber. A three-dimensional reconstruction efficiency of almost 100% has been obtained for e+e-→µ+µ- events and 92% for hadronic jet events.

Central Drift Chamber for Rare Kaon Decay Spectrometer

Design of the central drift chamber for BNL experiment 787 and measurement of the decay K+??+??? are discussed. A jet chamber type cell with 6 sense wires and no interspersed field wires has been designed to achieve good spatial resolution and efficiency in a 1 T magnetic field. Results of the testing of a prototype chamber are presented.

Performance of the SLD Central Drift Chamber Prototype

A two-cell prototype of the SLD Central Drift Chamber has been tested using CO2-isobutane (92%-8%) at one atmosphere. Average single wire resolution of 55 μm was achieved. Charge division tests indicate a resolution for the final design of π 0.5% of wire length. dE/dx separation of π - e should be useful up to at least 7 GeV/c.

SLAC Scanner Processor Applications in the Data Acquisition System for the Upgraded Mark II Detector

The SLAC Scanner Processor is a general purpose, programmable FASTBUS crate/cable master/slave module. This device plays a central role in the readout, buffering and preprocessing of data from the upgraded Mark II detector's new central drift chamber. In addition to data readout, the SSPs assist in a variety of other services, such as detector calibration, FASTBUS system management, FASTBUS system initialization and verification, and FASTBUS module testing.

Analysis of Digitized Waveforms in a Prototype of the SLD Central Drift Chamber

100 MHz waveform digitizers have been used to measure drift times and charge division positions of charged particles in a prototype of the SLD central drift chamber at SLAC. Test beam results show performance to be equivalent to conventional timing and charge integration techniques.