A FAST INTEGRATED READOUT SYSTEM FOR A CATHODE PAD PHOTON DETECTOR

A fast integrated electronic chain is presented to read out the cathode pad array of a multiwire photon detector for a fast RICH counter. Two VLSI circuits have been designed and produced. An analog eight channel, low noise, fast, bipolar, current preamplifier and discriminator chip serves as front-end electronics. It has an rms equivalent noise current of 10 nA (2000 e-), 50 MHz bandwidth with 10 mW of power consumption per channel. Two analogue chips are coupled to a digital 16 channels CMOS readout chip, operating at 20 MHz, that provides a pipelined delay of 1.3 mus and zero suppression with a power consumption of about 6 mW per channel. Readout of a 4000 pad sector requires 3-4 mus depending on the number of hit pads. The full RICH counter is made up of many of such sectors (the prototype has three fully equipped sectors), read out in parallel [1,2]. The minimum time to separate successive hits on the same pad is about 70 ns. The time skew of the full chain is about 15 ns.