CryoDE: a Digital Cryogenic Detector Emulator for Microwave SQUID Multiplexed Systems

TL;DR

CryoDE is an FPGA-based digital emulator that generates realistic signals for microwave SQUID multiplexed cryogenic detectors, enabling hardware-in-the-loop testing of data acquisition systems without cryogenic hardware.

Contribution

It introduces CryoDE, a novel digital cryogenic detector emulator tailored for microwave SQUID systems, facilitating efficient testing and optimization of readout electronics.

Findings

CryoDE accurately reproduces detector pulse responses.

It enables full HIL testing without cryogenic hardware.

CryoDE supports experiment-specific parameter adjustments.

Abstract

Simultaneous readout of large-scale cryogenic detector arrays relies on multiplexing schemes such as the FDM (Frequency-Division Multiplexing) with microwave SQUID multiplexers and highly customized readout electronics. In traditional detector systems, where mixed-signal ASICs are used in detector front-ends and typically provide a digital interface, HIL (Hardware-in-the-Loop) testing can be readily implemented by reusing the existing digital logic of the front-end for emulation purposes. Such straightforward emulation is not possible for FDM low-temperature detectors, where the sensor signal is encoded in a high-frequency microwave carrier via a two-stage modulation scheme depending on the cryogenic resonators and the SQUID response. To address this challenge, we present CryoDE, a digital cryogenic-detector emulator for microwave SQUID multiplexed detector systems. CryoDE generates the encoded detector signals, including realistic pulse responses, enabling full HIL testing of the room-temperature DAQ system without requiring the cryogenic hardware. This resource-efficient FPGA-based detector twin integrates seamlessly into existing DAQ systems and allows experiment-specific adjustment of detector-signal parameters. We describe the internal architecture and capabilities of CryoDE within our custom HIL framework and demonstrate its use in evaluating the performance of real-time signal processing firmware optimized for different microwave SQUID multiplexed cryogenic-detector experiments.