Design and Performance of Next Generation Cryogenic Dark Matter Detectors

To achieve the surface electron rejection required for ton scale dark matter searches with germanium, we have demonstrated an advanced interleaved charge and phonon detector. The design's large surface E-fields and small electrodes suppress leakage of surface electrons from $^{109}$Cd into the nuclear recoil band to less than 1:3000 for 69\% wimp search volume efficiency (after radial fiducial volume cuts), 2 orders of magnitude better than current designs. Assymetries in charge collection between the 4 electrodes allow for charge only z fiducial volume reconstruction, which further suppresses this surface leakage by greater than 1:1000 with 62\% total wimp search efficiency. Finally, high fidelity partition and pulse shape information from 6 phonon sensors (3 on each side) allow for full 3D event reconstruction which discriminate against electronic surface events at greater than 1:3000 independent of charge assymetry discrimination with 80\% efficiency. In summary, this design should meet the discrimination requirements for experiments probing $10^{-47}$cm$^{2}$ wimp nucleon cross section scales.