First test runs of a dark-matter detector with interleaved ionization electrodes and phonon sensors for surface-event rejection

To improve surface event rejection for the SuperCDMS experiment, we have designed, fabricated and tested a new detector concept where ionization electrodes are interleaved with phonon sensors on both sides of the detector. This i-(interleaved)-ZIP concept has electrical fields tangential to all detector surfaces. A surface event will produce an ionization signal in one charge read out channel, whereas an event within the bulk of the crystal will cause a signal in both charge read out channels. In addition, the symmetric phonon channels on both sides of the crystal, two semicircles on one side for x and two on the other for y, allow three-dimensional reconstruction of event locations through time delays and relative energy collection between the four phonon channels. Preliminary results from a 100g Si prototype are presented.