Giles Barr

Abstract:

We describe a general purpose 40MHz pipelined trigger processing board containing six look-up tables and the logic needed to programmably route the signals between them. A series of identical boards are connected in cascade in the NA48 CP-violation experiment at CERN, accept digital inputs generated from calorimeter signals and are used to perform the different computations necessary for the trigger reconstruction. The board architecture is designed to be flexible so that a single basic hardware design can perform all the different algorithms we require and so that the trigger algorithms can be adapted if needed. The computation latency of the combined network of eight boards is approximately 3 mu s. We present examples of some of the functions which have been implemented. We discuss the automatic reprogramming software which has been developed so that a new design can be implemented easily.

Abstract:

This paper describes the issues encountered in the design of a large dynamic range digitizer for calorimetry. A gain switching technology developed for the liquid krypton calorimeter of the NA48 CP-violation experiment at CERN is described in detail. 14 bit dynamic range and better than 300 ps time resolution were achieved in beam tests with an 8 channel prototype. A mixed analog/digital ASIC has been developed. A 13'500 channel system is being produced which will be put into operation in 1996.

Abstract:

The NA48 collaboration is preparing a new experiment at CERN aiming to study CP violation in the K0-K0 system with an accuracy of 2 × 10-4 in the parameter ℛe(∈′/∈). Decays in two π0's will be recorded by a quasi-homogeneous liquid krypton calorimeter. A liquid krypton calorimeter has been chosen to combine good energy, position and time resolution with precise charge calibration and long-term stability. The prototype calorimeter incorporating the final design of the electrode read-out structure is presented in this paper. An energy resolution of ≃3.5%/√E with a constant term smaller than 0.5% has been obtained. The time resolution was found to be better than 300 ps above 15 GeV.