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

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 an array of up to a million channels 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 the first-generation version of this chip (TARGET 1) 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 1 chip, we present a camera module prototype as well as a second-generation chip (TARGET 2), both of which have now been produced.

Invited Article: miniTimeCube

“…The IRS has been used in a variety of projects that require fast sampling and deep buffering. [29][30][31] The IRS ASIC architecture is shown schematically in Fig. 17, and a list of operating parameters can be found in Table III.…”

MACHETE: A transit imaging atmospheric Cherenkov telescope to survey half of the very high energy γ -ray sky

“…The cost reduction factor depends on the actual technical solution implemented. It must be noted that the cost of the readout may be much lower than the cost of the photodetector with a digitizing chip such as TARGET5 [20].…”

The small size telescope projects for the Cherenkov Telescope Array

“…They ensure appropriate SiPM signal pre-processing before entering the readout chain. The readout is based on the ASIC TARGET 5(7) for CHEC-M (CHEC-S) [15]. The TARGET chip samples and digitizes the incoming waveforms at a rate of 1 Gs/s.…”