PICO is an experiment searching for direct evidence of dark matter using a bubble chamber of chlorofluorocarbon (Freon) as the active mass.
A bubble detector is a radiation sensitive device that uses small droplets of superheated liquid that are suspended in a gel matrix.
The bubble development in the detector is accompanied by an acoustic shock wave that is picked up by piezo-electric sensors.
The COUPP collaboration operated a bubble chamber with 3.5 kg CF3I in the MINOS underground area at Fermilab.
The COUPP collaboration also operated the same bubble chamber with 4 kg CF3I in SNOLAB from September 2010 to August 2011.
This result has been converted into a cross section limit for WIMP interactions on protons of 0.16 pb (90% CL).
The obtained limits restrict recent interpretations of the DAMA/LIBRA annual modulation effect in terms of spin dependent interactions.
[5] New results were published in May 2012, using 10 detectors with total exposure 14 kg·d, to constrain low-mass WIMP interaction on 19F.
For the Spin-independent near 7 GeV low mass region cross section: 1.41×10−4 pb upper limit (90% C.L.)
After this initial run, the detector was refurbished, the target material was switched to C3F8 and the active volume was increased to full capacity (53 litres).
The PICO-40L is a new type of bubble chamber whose technical structure eliminates the need for a buffer liquid that is a source of measurement noise.
SNOLAB has approved the conceptual design of the experiment and allocated space in the underground facility for PICO-500 in the cube hall area of the lab.