TARGET: A Digitizing And Trigger ASIC For The Cherenkov Telescope Array

TL;DR

This paper introduces the TARGET ASIC, a low-cost, high-speed digitizing and triggering solution designed for the Cherenkov Telescope Array, enabling efficient, scalable camera readout for gamma-ray astronomy.

Contribution

It presents the design and preliminary testing results of the TARGET ASIC, a novel split-ASIC system for fast waveform digitization and triggering in CTA telescopes.

Findings

TARGET C achieves a 1 GSa/s sampling rate with 16k sample buffer.

T5TEA trigger ASIC generates four LVDS outputs based on analog sums.

Preliminary tests show promising performance of the ASICs.

Abstract

The future ground-based gamma-ray observatory Cherenkov Telescope Array (CTA) will feature multiple types of imaging atmospheric Cherenkov telescopes, each with thousands of pixels. To be affordable, camera concepts for these telescopes have to feature low cost per channel and at the same time meet the requirements for CTA in order to achieve the desired scientific goals. We present the concept of the TeV Array Readout Electronics with GSa/s sampling and Event Trigger (TARGET) Application Specific Circuit (ASIC), envisaged to be used in the cameras of various CTA telescopes, e.g. the Gamma-ray Cherenkov Telescope (GCT), a proposed 2-Mirror Small-Sized Telescope, and the Schwarzschild-Couder Telescope (SCT), a proposed Medium-Sized Telescope. In the latest version of this readout concept the sampling and trigger parts are split into dedicated ASICs, TARGET C and T5TEA, both providing 16 parallel input channels. TARGET C features a tunable sampling rate (usually 1 GSa/s), a 16k sample deep buffer for each channel and on-demand digitization and transmission of waveforms with typical spans of ~100 ns. The trigger ASIC, T5TEA, provides 4 low voltage differential signal (LVDS) trigger outputs and can generate a pedestal voltage independently for each channel. Trigger signals are generated by T5TEA based on the analog sum of the input in four independent groups of four adjacent channels and compared to a threshold set by the user. Thus, T5TEA generates four LVDS trigger outputs, as well as 16 pedestal voltages fed to TARGET C independently for each channel. We show preliminary results of the characterization and testing of TARGET C and T5TEA.