D. Strom

The OPAL silicon-tungsten calorimeter front end electronics

A pair of small angle silicon-tungsten (Si-W) calorimeters has been built to measure the luminosity to a precision better than 0.1% in the OPAL experiment at the Large Electron Positron (LEP) collider at CERN near Geneva. Each calorimeter contains 19 layers of tungsten (W) plates and silicon (Si) detectors, corresponding to a total of 22 radiation lengths, sampled by about 1 m/sup 2/ of detectors divided into 304/spl times/64 independently read out channels. A complete electronics system has been developed, from the preamplifier up to the VME read out and control interface. It includes a fast trigger based on analogue sums. This paper describes how a large number of channels have been implemented in a dense environment, thanks to the use of ASICs directly bonded on the detector. >

The data acquisition system of the OPAL detector at LEP

Abstract This report describes the 1991 implementation of the data acquisition system of the OPAL detector at LEP including the additional services and infrastructure necessary for its correct and reliable operation. The various tasks in this “on-line” environment are distributed amongst many VME subsystems, workstations and minicomputers which communicate over general purpose local area networks and special purpose buses. The tasks include data acquisition, control, monitoring, calibration and event reconstruction. The modularity of both hardware and software facilitates the upgrading of the system to meet new requirements.

A modular electronic readout system for the OPAL electromagnetic presampler

Abstract The readout system used to sample and digitize the 21 504 channels of the OPAL electromagnetic barrel presampler is described. The system consists of semi-custom analog electronics mounted directly on the detector to provide integrate-and-hold capability and custom VME boards to implement the digitization functions. The data from one event is digitized completely in under 7 ms. This meets the OPAL requirement of a sustained 10 Hz trigger rate with less than 10% dead time. A minimum ionizing particle deposits 2.7 pC in a single layer of the presampler, and the largest signal commonly seen in 200 pC. The dynamic range of the readout system is 0.032 to 1000 pC. The noise on a single channel is typically 0.2 pC. A linear analog calibration is automatically applied on a channel-by-channel basis. Programmable logic is used extensively.