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The OPERA spectrometer is built from two large dipoles instrumented with around 1000 Resistive Plate Chambers (RPCs), covering a surface of about 3350 m 2 , 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.

It is believed that critical current reduction in multistrand superconducting cables at nonsteady state conditions is caused by a nonuniform current distribution among strands. This was experimentally proven for small model cables, but is still not verified for large cables. In the ENEA Frascati Laboratory, an ITER relevant, large superconducting magnet has been tested at different field ramp rates. By means of numerous local miniature field sensors (Hall probes and pickup coils) located in a few positions along the conductor, current redistribution phenomena inside the cable have been studied. Fast and slow local field changes have been studied to quantify the current nonuniformity. It has been shown that severe current nonuniformity does exist in the cable and that induced current loops are generated, which decay with very long time constants (up to 10 4 -10 5 s).

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