The PreAmplifier ShAper for the ALICE TPC-Detector

TL;DR

This paper presents the design, implementation, and testing of a specialized ASIC preamplifier for the ALICE TPC detector, demonstrating it meets all operational requirements after extensive testing and two years of use.

Contribution

The paper introduces a novel ASIC preamplifier design optimized for the ALICE TPC, with detailed characterization and validation in real experimental conditions.

Findings

Achieved a conversion gain of 12.74 mV/fC at 25 pF capacitance.

Demonstrated stable operation with a peaking time of 160 ns and noise charge of 244e + 17e/pF.

Validated performance after two years of operation in the ALICE experiment.

Abstract

In this paper the PreAmplifier ShAper (PASA) for the Time Projection Chamber (TPC) of the ALICE experiment at LHC is presented. The ALICE TPC PASA is an ASIC that integrates 16 identical channels, each consisting of Charge Sensitive Amplifiers (CSA) followed by a Pole-Zero network, self-adaptive bias network, two second-order bridged-T filters, two non-inverting level shifters and a start-up circuit. The circuit is optimized for a detector capacitance of 18-25 pF. For an input capacitance of 25 pF, the PASA features a conversion gain of 12.74 mV/fC, a peaking time of 160 ns, a FWHM of 190 ns, a power consumption of 11.65 mW/ch and an equivalent noise charge of 244e + 17e/pF. The circuit recovers smoothly to the baseline in about 600 ns. An integral non-linearity of 0.19% with an output swing of about 2.1 V is also achieved. The total area of the chip is 18 mm$^2$ and is implemented in AMS's C35B3C1 0.35 micron CMOS technology. Detailed characterization test were performed on about 48000 PASA circuits before mounting them on the ALICE TPC front-end cards. After more than two years of operation of the ALICE TPC with p-p and Pb-Pb collisions, the PASA has demonstrated to fulfill all requirements.