Operation of a double-phase pure argon large electron multiplier Time Projection Chamber (TPC)

Full text: We constructed and operated a double phase (liquid-vapour) pure argon Large Electron Multiplier Time Projection Chamber (LAr LEM-TPC) of 3 l of active volume, with a sensitive area of 10 x 10 cm2 and up to 30 cm of drift length. The LEM is a macroscopic hole electron multiplier built with standard PCB techniques: drifting electrons are extracted from the liquid to the vapour phase and driven into the holes of the LEM where the multiplication occurs and the moving charges induce a signal on the anode and the LEM electrodes. Two multiplication stages in argon vapour provide a gain up to 1000 and the segmented upper face of the upper LEM and anode permit the reconstruction of X-Y spatial coordinates of ionizing events. The TPC is equipped with a photo multiplier tube for triggering the ionizing events and an argon purification circuit to ensure long drift paths. Cosmic muon tracks and source events have been recorded and further characterization of the detector is ongoing. We believe that this proof of principle represents an important milestone in the realization of very large, long drift (cost-effective) LAr detectors for next generation neutrino physics and proton decay experiments, as well as for direct search of dark matter with imaging devices. (author)