J. Lindsay

Properties of a Fine Sampling Uranium - Copper Scintillator Hadron Calorimeter

Abstract We present results obtained with a uranium/copper scintillator fine-sampling calorimeter with wavelength shifter readout. Test beam measurements made with e±, π± and protons in the momentum range 0.3–40 GeV/c are presented. The calorimeter achieves energy resolutions of σ(E) E = 0.36 √E and 0.16 √E for hadrons and electrons, respectively. The measured ratio of response for electrons to that for hadrons is 1.11, for energies of 2 GeV or more. The spatial resolution achieved for single particles at normal incidence is ∼1 cm for electromagnetic showers and ∼3 cm for hadronic showers. Operational experience over three years of running at the CERN ISR, including operation at very high luminosities (∼1.4×1032 cm−2 s−1) is described.

A fast and flexible data acquisition system for multiwire proportional chambers and other detectors

Abstract A system is described which can handle high input rates and provide very short read-out times. The delay element is a twisted-pair cable. ECL 10k circuitry is used throughout, part of which is hybridized. The non-destructive and fast read-out makes the system attractive for experiments with data pre-processing. Typical read-out time is ⋍120 ns per coded 16-bit data word. One crate contains a maximum of 704 channels, and up to 16 crates may be chained on a branch. Further expansion is possible by the use of several branches. Additional modules provide for the following: reading of multiple branches, multiple outputs of processed data, reading of several systems via one CAMAC interface, normalized data for chamber and cluster identification, and burst buffering.

A large liquid-argon shower detector for an ISR experiment

A large liquid-argon shower detector system has been constructed for the detection of photons and electrons at the CERN ISR. The calorimeter system is built in a modular way such that eight modules would cover = 2 π azimuthally with a total solid angle of Ω = 8 sr. Each module consists of 1.5 mm thick lead plates, spaced 2 mm apart. Longitudinal grouping and transversal division into strip-like sections of the charge-collecting electrodes provide the required spatial resolution and hadron discrimination. Measurements on energy and space resolution and electron/hadron discrimination are described. The signal-processing system, designed to minimize electronics noise, can handle event rates up to 0.5 MHz and provides energy information for trigger purposes. The performance of this calorimeter system during two years of ISR operation is reported.

A drift chamber vertex detector for intersecting storage rings

Abstract A cylindrical drift chamber detector for use in a high p T experiment at the CERN ISR is described. The sense wires (total of 3444) are grouped in 42 layers at radii between 20 cm and 80 cm and are used to provide determination of 42 space points along tracks passing through all wire layers. The high redundance of space points provides improved pattern recognition for complex events, good momentum resolution when the detector is placed in a magnetic field, and some particle identification via sampling of d E /d x . Results of tests performed with a smaller chamber are presented. In a direction perpendicular to the sense wires, the accuracy of measurement is given by fwhm = 0.5 mm, while fwhm = 9 mm for the coordinate along the wire direction, obtained by the “charge division” method.

Operation of a drift chamber vertex detector at the ISR

Abstract A cylindrical drift chamber with “bicycle-wheel” geometry has been constructed as the central detector for the Axial Field Spectrometer (AFS) at the ISR. To permit particle separation in jet-like event at high events rates, a considerable degree of azimuthal segmentation was chosen together with up to 42 space points per track. These points are obtained from measurements to drift time and charge division. Some particle identification is achieved with ionization loss sampling (d E /d x ). This contribution presents details on the construction and the operation of the drift chamber at the ISR and preliminary performance results.

The drift time and charge division electronics system for the axial field spectrometer vertex detector

Abstract The electronics system of the AFS vertex detector permits the unambiguous determination of space points by drift time and charge division measurement (more than 10 000 electronic channels). Facilities are included for re-ordering of the raw time and pulse height information for optimized preprocessing and off-line analysis. Programmable processors permit trigger decisions and spatial correlation with calorimeter information.

A fast linear gate

The instrument described was designed to operate as a linear gate for fast scintillation counter pulses thereby allowing events to be selected at a suitable rate. After gating, the fast signal is integrated and shaped on a passive network that gives a pulse shape acceptable for the input of commercially available muitichannel pulse-height analyzers. An internal paralysis is provided to the gate opening so that each slow output signal will be completely over before a second input signal can reach the integrating and shaping network. A circuit diagram, a linearity curve, and a gate shape curve are shown. (A.G.W.)

A highly segmented NaI(Tl) detector with vacuum photodiode readout for measuring electromagnetic showers at the CERN ISR

Abstract In this report we describe construction and performance of two identical units of electromagnetic shower counters which were installed in the axial-field spectrometer at the CERN-ISR in 1982 to provide improved detection of photons and electrons over a 1.3 sr solid angle of the AFS calorimeter. Thallium doped sodium-iodide in the form of small blocks served as an active shower material. Vacuum photodiodes and low-noise charge sensitive electronics were used for the deposited energy measurement and signal amplification. The stable performance of the detectors over a period of more than 18 months until the closure of the ISR has proven that vacuum photodiodes can reliably be utilized in highly modularized large scale detectors operating in a high magnetic field environment.

Test Results of the AFS Hadron Calorimeter at the CERN ISR

This paper gives results from a performance test of a large multicell uranium/scintillator hadron calorimeter used in the AFS experiment at the CERN ISR. Front and back sections of the calorimeter are read-out with separate wavelength shifter bars. Information on the longitudinal and transverse shower development provides separation between electromagnetic and hadronic showers. The results presented concentrate on the angular dependence of linearity, energy resolution, spatial resolution and electron vs hadron separation. The emphasis of the analysis is directed towards the implementation of a pattern recognition program for the calorimeter array.

Programmable track selector for nuclear physics experiments

Abstract A rapid Programmable Track Selector (PTS 1) permits track validity decisions to be made on data in pairs of multiwire proportional chambers (MWPCs) in less than 1 μs (according to the number of wires hit). All possible acceptable tracks are pre-calculated and stored in the form of a correlation pattern in the PTS 1 memory which then acts as a rapid look-up table. Acceptable pairs of coordinates falling in chosen areas are made available in buffers for presentation to further, cascaded units. PTS 2 is similar to PTS 1 but rejects, rather than accepts, tracks in the chosen area and is used in experiment SC 73 1 ). Modified PTS units (called FPC = Fast Programmable Calculator) can be used for rapid calculations by loading the memories as look-up tables of the pre-calculated values, thus allowing linear or non-linear single-valued transformations. A fourth unit called Arithmetic Control Unit (ACU) can indicate a chosen opening angle between two tracks detected by one or several post-target chambers.