  Direct detection of WIMP dark matter candidates has to face many difficult
challenges. In particular, it requires an extremely high level of background
rejection. The only way out seems to be particle identification which, for
experiments based on nucleus recoil, is most efficiently performed by
simultaneously detecting ionization or light and phonons. When comparing
different approaches, it is necessary to keep in mind the potential requirement
of building large detectors and the difficulties that this condition may raise
for some cryogenic devices. It is claimed that the luminescent bolometer
(simultaneous detection of light and phonons) red by arrays of superconducting
tunnel junctions, as proposed by the author some years ago, ultimately provides
the most appropriate WIMP detector. Solar neutrino detection and other
applications are also briefly discussed.
