Lifetime study of the ColdADC for the Deep Underground Neutrino Experiment

TL;DR

The paper addresses the need for guaranteed long-term reliability of the ColdADC digitizer used in DUNE's cryogenic LArTPC detectors. It adopts a hot-carrier aging framework in a 65 nm CMOS process, applying design-rule mitigations and a monotonic-current-degradation criterion to quantify lifetime. By subjecting multiple ColdADC samples to cryogenic stress and monitoring key ADC figures of merit alongside current draw, it extrapolates the device lifetime to nominal operating conditions, obtaining approximately $3.02×10^5$ years. The results demonstrate that ColdADC remains within acceptable performance bounds and that the projected lifetime vastly exceeds the experiment’s timescale, supporting deployment of tens of thousands of channels with high data quality over decades.

Abstract

ColdADC is a custom ASIC digitizer implemented in 65 nm CMOS technology using specialized techniques for long-term reliability in cryogenic environments. ColdADC was developed for use in the DUNE Far Detector complex, which will consist of four liquid argon time projection chambers. Each contains 17 kilotons liquid argon as the target material in order to measure neutrino oscillations. Approximately 40,000 ColdADC ASICs will be installed for DUNE in the first two large detectors and will be operated at cryogenic temperatures during the experiment without replacement. The lifetime of the ColdADC is a critical parameter affecting the data quality and physics sensitivity of the experiment. A measurement of the lifetime of the ColdADC was carried out, and the results shown in this paper assure orders of magnitude longer lifetime of the ColdADC than the planned operation time of the detectors.

Figures (8)

• Figure 1: Examples of the observation parameters.
• Figure 2: Overhead view of the testing setup.
• Figure 3: Components of the test setup.
• Figure 4: Schematic diagram of the test setup.
• Figure 5: Maximum and minimum DNL (a) and INL (b) values varying in time, per channel. The dashed vertical lines indicate times when the dewar was refilled.