Front-end electronics for the CERES TPC-detector

The CERES/NA45-Collaboration upgrades the existing lepton-pair spectrometer at the CERN SPS with a TPC detector which improves the momentum resolution. We present the development of new front-end electronics to read out the nearly 20 000 channels of the chamber. It is comprised of two circuits: (i) A continuously sensitive preamplifier with a semi-Gaussian shaper and tail-cancellation, which offers selectable time constants to cope with various detector gases. The design is based on a charge-sensitive amplifier with PMOS input transistor which gives low-noise ( similar to 540e rms) at 12 pF input capacitance and 580 ns peaking time. (ii) A 16 x 256 cell analog-memory stores the input waveform at 14 MHz during the drift time of the chamber. A 16 channel successive approximation ADC sequentially digitizes the signal at 1 MHz with 8 bit precision. Both circuits are developed in a 0.8 mu m CMOS technology. We will focus on the result of prototype measurements and will discuss the feasibility to use this development for the ALICE TPC as well. (C) 1998 Elsevier Science B.V. All rights reserved.