TARGET: A multi-channel digitizer chip for very-high-energy gamma-ray telescopes

TL;DR

This paper introduces the TARGET ASIC, a multi-channel digitizer chip designed for high-energy gamma-ray telescopes, featuring high sampling rates, low power, and modular design to enable cost-effective, large-scale IACT camera readouts.

Contribution

The paper presents the design, performance, and prototype implementation of the TARGET ASIC, a novel multi-channel digitizer tailored for next-generation gamma-ray observatories.

Findings

TARGET achieves high sampling frequency and low power consumption.

The chip supports 16 channels with 4096-sample buffers each.

Prototypes demonstrate suitability for large-scale gamma-ray telescope arrays.

Abstract

The next-generation very-high-energy (VHE) gamma-ray observatory, the Cherenkov Telescope Array, will feature dozens of imaging atmospheric Cherenkov telescopes (IACTs), each with thousands of pixels of photo-sensors. To be affordable and reliable, reading out such a mega-channel array requires event recording technology that is highly integrated and modular, with a low cost per channel. We present the design and performance of a chip targeted to this application: the TeV Array Readout with GSa/s sampling and Event Trigger (TARGET). This application-specific integrated circuit (ASIC) has 16 parallel input channels, a 4096-sample buffer for each channel, adjustable input termination, self-trigger functionality, and tight window-selected readout. We report the performance of TARGET in terms of sampling frequency, power consumption, dynamic range, current-mode gain, analog bandwidth, and cross talk. The large number of channels per chip allows a low cost per channel ($\10 to $\20 including front-end and back-end electronics but not including photosensors) to be achieved with a TARGET-based IACT readout system. In addition to basic performance parameters of the TARGET chip itself, we present a camera module prototype as well as a second-generation chip (TARGET~2), both of which have been produced.