  The dual phase Liquid Argon Time Projection Chamber (LAr TPC) is the
state-of-art technology for neutrino detection thanks to its superb 3D tracking
and calorimetry performance. Its main feature is the charge amplification in
gas argon which provides excellent signal-to-noise ratio. Electrons produced in
the liquid argon are extracted in the gas phase. Here, a readout plane based on
Large Electron Multiplier detectors provides amplification of the charges
before its collection onto an anode with strip readout. The charge
amplification enables constructing fully homoge- nous giant LAr-TPCs with
tuneable gain, excellent charge imaging performance and increased sensitivity
to low energy events. Following a staged approach the WA105 collaboration is
con- structing a dual phase LAr-TPC with an active volume of 3x1x1m3 that will
soon be tested with cosmic rays. Its construction and operation aims to test
scalable solutions for the crucial aspects of this technology: ultra high argon
purity in non-evacuable tank, large area dual phase charge readout system in
several square meter scale, and accessible cold front-end electronics. A mile-
stone was achieved last year in the completion of the 24 m3 cryostat that hosts
the TPC. This is the first cryostat based on membrane technology to be
constructed at CERN and is therefore also an important step towards the
realisation of the upcoming protoDUNE detectors. The 3x1x1m3 dual phase LAr-TPC
will be described in and we will report on the latest construction progress.
