The WA105-3x1x1 m3 dual phase LAr-TPC demonstrator

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.