Towards One Tonne Direct WIMP Detectors: Have we got what it takes?

Experimentally have we got what it takes to pursue the direct observation of WIMP interactions down to sensitivities of a few events /100 kg/year? For a Ge target with a low energy threshold (<20 keVr) this corresponds to a WIMP-nucleon sigma~10^-46 cm^2. A number of recent theoretical papers, making calculations in SUSY-based frameworks, show many (>5) orders of magnitude spread in the possible interaction rates for models consistent with existing Cosmology and Accelerator bounds. Some theorists, but certainly not all, are able to generate models, that lead to interaction rates at the few /kg/day that would be implied by the current DAMA annual modulation signal. All theorists demonstrate models that generate much lower interaction rates. This paper takes an unashamed experimentalist`s view of the issues that arise when looking forward to constructing 1 tonne WIMP detectors.