Juan Collar

Senior Member, KICP
Professor, Department of Physics; Enrico Fermi Institute; and the College

Juan Collar
Eckhardt Research Center
Room 489
5640 South Ellis Avenue
Chicago, IL 60637
(773) 702-4253


Ph.D., University of South Carolina, 1992


My main interest is in the development of innovative methods for the detection for hypothetical astroparticles (WIMPs, axions, magnetic monopoles, any yet-to-be-discovered component of cosmic rays that might constitute a fraction of the 'dark matter'). Needless to say, this is a risky business, but I am equally interested in the journey and the destination: the extreme levels of sensitivity required in some of these experiments force us to devise new detection technologies, in an endless quest for the 'better mouse-trap'. It is a very enjoyable challenge. I am also attracted to other exotica such as double-beta decay and some 'hard' problems in neutrino detection (coherent neutrino scattering, detection of the relic neutrino sea). I enjoy the condensed-matter aspects of detector development and anything having to do with the interactions between radiation and matter. I get easily excited about cross-disciplinary endeavors and real-life applications of detectors that might otherwise be chasing ghost particles.

Together with collaborators at the Groupe de Physique des Solides (Universite Paris VII), University of Lisbon, and Pacific Northwest National Laboratory, I developed large-mass, low-background superheated droplet detectors (SDDs) dedicated to WIMP (Weakly Interacting Massive Particle) searches (The SIMPLE dark matter search). On my arrival to Chicago I started investigating the possibility of making large bubble chambers stable enough for the same goal, using CF3I, a target ideal for WIMP detection. Our collaboration with FNAL and Indiana University (The Chicago Observatory for Underground Particle Physics, COUPP) led to the best sensitivity to spin-dependent WIMP interactions. Following this effort the COUPP and PICASSO experiments joined forces to create the PICO collaboration. PICO 60 recently finished its second run, once again giving the best limits on spin-dependent WIMP interactions. Its first run used CF3I and in its second, using C3F8 to increase the sensitivity to spin-dependent interactions. Work is currently focused on PICO 40L, a "right-side-up" detector which eliminates the need for the buffer liquid responsible for much of the background contamination. The next generation experiment, PICO 500 has been funded and is currently under development with construction anticipated to begin in the near future. At CERN I am involved in CAST, a search for solar axions using a decommissioned LHC test magnet, an interesting astroparticle spin-off from the Large Hadron Collider effort. I also work on the application of P-type Point Contact germanium detectors to coherent neutrino-nucleus scattering, double beta decay and searches for light dark matter candidates. These devices have already produced some very interesting results within the CoGeNT, MAJORANA and COHERENT experiments.  The latter demonstrated the first experimental detection of coherent neutrino-nucleus scattering.

Selected Publications