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 benchfor 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.