Pulse shape discrimination for GRIT: beam test of a new integrated charge and current preamplifier coupled with high granularity Silicon detectors

TL;DR

This paper presents the development and testing of an integrated charge and current preamplifier, iPACI, for the GRIT silicon array, enabling effective pulse shape discrimination for particle identification in nuclear physics experiments.

Contribution

The paper introduces a novel integrated preamplifier, iPACI, optimized for high granularity silicon detectors, with detailed design specifications and successful beam test results.

Findings

iPACI achieves 12 keV energy resolution at 50 MeV.

Pulse shape analysis discriminates particles down to 2-3 MeV.

The preamplifier operates with 40 mW power per channel.

Abstract

The GRIT (Granularity, Resolution, Identification, Transparency) Silicon array is intended to measure direct reactions. Its design is based on several layers (three layers in the forward direction, two backward) of custom-made trapezoidal and square detectors. The first stage is 500 {\mu}m thick and features 128x128 orthogonal strips. Pulse shape analysis for particle identification is implemented for this first layer. Given the compacity of this array and the large number of channels involved (>7,500), an integrated preamplifier, iPACI, that gives charge and current information has been developed in the AMS 0.35 {\mu}m BiCMOS technology. The design specifications and results of the test bench are presented. Considering an energy range of 50 MeV and an energy resolution (FWHM) of 12 keV (FWHM) for the preamplifier, the energy resolution for one strip obtained from alpha source measurement in real conditions is 35 keV. The current output bandwidth is measured at 130 MHz for small signals and the power consumption reaches 40 mW per detector channel. A first beam test was performed coupling a nTD trapezoidal double-sided stripped Silicon detector of GRIT with the iPACI preamplifier and a 64-channel digitizer. Z=1 particles are discriminated with pulse shape analysis technique down to 2 MeV for protons, 2.5 MeV for deuterons and 3 MeV for tritons. The effect of the strip length due to the trapezoidal shape of the detector is investigated on both the N- and the P-side, showing no significant impact.