Fig. 8: Bubble chambers used in the PICO experiment.
From: Progress and prospects in the underground laboratories' search for dark matter
When a nuclear recoil from a potential dark matter particle interaction occurs in the superheated liquid, it deposits localized energy that triggers the formation of a bubble. Acoustic sensors and cameras record the event, allowing discrimination between NR signals and ER backgrounds. Operated deep underground at SNOLAB, the PICO series of detectors has achieved world-leading sensitivity to spin-dependent WIMP-proton interactions. Shown here are PICO-60 (Credit: Eric Vázquez Jáuregui from the PICO Collaboration174) and PICO-40L (Credit: PICO Collaboration175).
