ULTIMA: A bolometric detector for dark matter search using superfluid 3He

ULTIMA (Ultra Low Temperature Instrumentation for Measurements in Astrophysics) is a project of a large detector using superfluid 3He at ultra-low temperatures ( 100 μ K ) for the search for non-baryonic Dark Matter. We review recent advances of the application of superfluid 3He for bolometric particle detection, using a multicell prototype of three adjacent bolometers to allow for background event discrimination by simultaneous detection in different cells. One of the cells contained a low activity 57Co source producing electrons mainly at about 7 and 14 keV, in order to demonstrate the possibility to detect low energy events. We review different tests of the current detector prototype, using thermal neutrons, cosmic muons and low energy electrons. Our current understanding of the detector is described and future directions of the detector project are discussed.