  We discuss the possibility of new generation neutrino and astroparticle
physics experiments exploiting the liquid Argon Time Projection Chamber (LAr
TPC) technique, following a graded strategy that envisions applications with
increasing detector masses (from 100 ton to 100 kton). The ICARUS R&D program
has already demonstrated that the technology is mature with the test of the
T600 detector at surface. Since 2003 we have been working with the conceptual
design of a very large LAr TPC with a mass of 50-100 kton to be built by
employing a monolithic technology based on the use of industrial, large volume,
cryogenic tankers developed by the petro-chemical industry. Such a detector, if
realized, would be an ideal match for a Super Beam, Beta Beam or Neutrino
Factory, covering a broad physics program that includes the detection of
atmospheric, solar and supernova neutrinos, and searches for proton decay, in
addition to the rich accelerator neutrino physics program. A "test module" with
a mass of the order of 10 kton operated underground or at shallow depth would
represent a necessary milestone towards the realization of the 100 kton
detector, with an interesting physics program on its own. In parallel, physics
is calling for a shorter scale application of the LAr TPC technique at the
level of 100 ton mass, for low energy neutrino physics and for use as a near
station setup in future long baseline neutrino facilities. We outline here the
main physics objectives and the design of such a detector for operation in the
upcoming T2K neutrino beam. We finally present the result of a series of R&D
studies conducted with the aim of validating the design of the proposed
detectors.
