First operation of a double phase LAr Large Electron Multiplier Time Projection Chamber with a two-dimensional projective readout anode

摘要

We have previously reported on the construction and successful operation ofthe novel double phase Liquid Argon Large Electron Multiplier Time ProjectionChamber (LAr LEM-TPC). This detector concept provides a 3D-tracking andcalorimetric device capable of adjustable charge amplification, a promisingreadout technology for next-generation neutrino detectors and direct DarkMatter searches. In this paper, we report on the first operation of a LArLEM-TPC prototype - with an active area of 10$\times$10 cm$^2$ and 21 cm driftlength - equipped with a single 1 mm thick LEM amplifying stage and a twodimensional projective readout anode. Cosmic muon events were collected, fullyreconstructed and used to characterize the performance of the chamber. Theobtained signals provide images of very high quality and the energy lossdistributions of minimum ionizing tracks give a direct estimate of theamplification. We find that a stable gain of 27 can be achieved with thisdetector configuration corresponding to a signal-over-noise ratio larger than200 for minimum ionizing tracks. The decoupling of the amplification stage andthe use of the 2D readout anode offer several advantages which are described inthe text.