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, bi-polar current preamplifier-amplifier and discriminator chip serves as the front-end detection electronics. It has an rms equivalent noise current of 10 nA, 50 MHz bandwidth with 10 mW of power consumption per channel. Two analog chips are coupled to a digital sixteen-channel CMOS readout chip, operating at 20 MHz with a power consumption of 6 mW per channel. Readout of a 4000 pad sector requires 2-3 mus, depending on the number of hit pads. The full RICH counter is made up of many such sectors, read out in parallel. The minimum time needed to separate successive hits on the same pad is 70 ns. The conception of the digital chip and its properties are fully presented in this report. The analog chip is described in less detail since it will be fully covered in a forthcoming paper.