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jul10-offprint-piro.pdf

PICASSO developed a new generation of detectors with the intrinsic radioactive background reduced by at least a factor 10!  Presently, more than half of the 32 detectors have been replaced in the SNOLAB underground laboratory in Sudbury. For the first time, PICASSO discovered a significant difference between the acoustic signal of neutron and alpha-particle induced events. A concentrated effort in detector purification and an acoustic discrimination effect between WIMP induced recoils and alpha-particles now available for analysis promises a further substantial reduction in background.