Construction and operation of a Double Phase LAr Large Electron Multiplier Time Projection Chamber

TL;DR

This paper reports the successful operation of a novel double phase liquid argon time projection chamber with a Large Electron Multiplier readout, demonstrating its potential for large-scale neutrino and dark matter detectors.

Contribution

It introduces a new LAr TPC design using a double stage LEM for charge amplification, showcasing its feasibility and performance.

Findings

Successful detection of cosmic ray tracks in double phase Ar

Demonstrated charge amplification with a thick macroscopic LEM

Proof of principle for large, long drift LAr detectors

Abstract

We successfully operated a novel kind of LAr Time Projection Chamber based on a Large Electron Multiplier (LEM) readout system. The prototype, of about 3 liters active volume, is operated in liquid-vapour (double) phase pure Ar. The ionization electrons, after drifting in the LAr volume, are extracted by a set of grids into the gas phase and driven into the holes of a double stage LEM, where charge amplification occurs. Each LEM is a thick macroscopic hole multiplier of 10x10 cm$^2$ manufactured with standard PCB techniques. The electrons signal is readout via two orthogonal coordinates, one using the induced signal on the segmented upper electrode of the LEM itself and the other by collecting the electrons on a segmented anode. Custom-made preamplifiers have been especially developed for this purpose. Cosmic ray tracks have been successfully observed in pure gas at room temperature and in double phase Ar operation. 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.