FemtoDAQ: A Low-Cost Digitizer for SiPM-Based Detector Studies and Its Application to the HAWC Detector Upgrade

The FemtoDAQ is a low-cost two-channel data acquisition system that we have used to investigate the signal characteristics of silicon photomultipliers (SiPMs) coupled to fast scintillators. The FemtoDAQ system can also be used to instrument low-cost moderate-performance passive detectors, and is suitable for use in harsh environments (e.g., high altitude). The FemtoDAQ is being used as a SiPM test bench for the High Altitude Water Cherenkov (HAWC) Observatory, a TeV gamma ray detector located 4100 m above sea level. Planned upgrades to the HAWC array can benefit greatly from SiPMs, a robust low-voltage low-cost alternative to traditional vacuum photomultipliers. The FemtoDAQ is used to power the SiPM detector front end, bias the SiPM, and digitize the photosensor output in a single compact unit.