The OPERA RPCs front end electronics; a novel application of LVDS line receiver as low cost discriminator

The OPERA spectrometer is built from two large dipoles instrumented with around 1000 Resistive Plate Chambers (RPCs), covering a surface of about 3350 m2, and digitally read out by means of almost 27000 strips. The huge number of channels, the inaccessibility of many parts of the detector and the wide uncertainty about the signal amplitude pushed to study a low cost, high sensitivity discriminator, and a very carefully designed layout for the read out system. Here we will present a novel application of LVDS line receiver as discriminator, showing that it exceeds the requirements of a large RPC based detector and offers the intrinsic advantages of a mature technology in terms of costs, reliability and integration scale. We will also present the layout of the read out system showing as the sensitivity and the noise immunity were preserved in a system where the front end electronics is far away from the detector.