SuperCDMS is currently operating a 10-kg array of cryogenic germanium detectors in the Soudan underground laboratory to search for weakly interacting massive particles , a leading dark matter candidate .
These detectors , known as iZIPs , measure ionization and athermal phonons from particle interactions with sensors on both sides of a Ge crystal .
The ionization signal can be used to efficiently tag events at high radius and near the top and bottoms surfaces , where diminished charge collection can cause events to mimic WIMP-induced nuclear recoils .
Using calibration data taken with a ^ { 206 } Pb source underground at Soudan , we demonstrate rejection of surface events of ( 4.5 \pm 0.9 ) \times 10 ^ { -4 } with 46 % acceptance of nuclear recoils using the phonon signal only .
We also show with ^ { 133 } Ba calibration data underground that the phonon channels can efficiently identify events near the sidewall .
This phonon-based approach can also be extended to lower energies than the ionization-based position reconstruction .