EDELWEISS and CRESST will search for WIMP dark matter with an interaction cross section down to 10-8 pb. But as the range of values predicted by supersymmetry models extends down to below 10-10 pb, it is quite possible that neither experiment will detect a neutralino, and this will require a larger experiment. If, however, we detect a positive signal, it will be necessary to collect further data in order to confirm it is due to dark matter (and not radioactive background) and to elucidate its nature.
With these aims in mind, the EURECA collaboration was formed in March 2005 at a meeting of the two experiments. Additional groups have since joined the project. The aim is to build a dark matter search using cryogenic detectors, with a total absorber mass of up to 1 tonne.
EURECA introduces many challenges. The technology must be scaled up in a cost effective manner which will not deteriorate performance. We will need to improve the radiopurity of the materials used, as a cross-section of 10-10 pb corresponds to only a few events per year in a 1 tonne detector. We will need to cool 1000+ detectors to millikelvin temperature, without creating any significant electrical interference. Various research programmes addressing these challenges are under way.