  Large liquid argon (LAr) detectors, up to 100 kton scale, are presently being
considered for proton decay searches and neutrino astrophysics as well as far
detectors for the next generation of long baseline neutrino oscillation
experiments, aiming at neutrino mass hierarchy determination and CP violation
searches in the leptonic sector. These detectors rely on the possibility of
maintaining large LAr masses stably at cryogenic conditions with low thermal
losses and of achieving long drifts of the ionization charge, so to minimize
the number of readout channels per unit volume. Many R&D initiatives are being
undertaken throughout the world, following somewhat different concepts for the
final detector design, but with many common basic R&D issues.
