Performance study of the effective gain of the double phase liquid Argon LEM Time Projection Chamber

Abstract

The Large Electron Multipliers (LEMs) are key components of double phase liquid argon TPCs. The drifting charges after being extracted from the liquid are amplified in the LEM positioned half a centimeter above the liquid in pure argon vapor at 87 K. The LEM is characterised by the size of its dielectric rim around the holes, the thickness of the LEM insulator, the diameter of the holes as well as their geometrical layout. The impact of those design parameters on the amplification were checked by testing seven different LEMs with an active area of 10$\times$10 cm${}^2$ in a double phase liquid argon TPC of 21 cm drift. We studied their response in terms of maximal reachable gain and impact on the collected charge uniformity as well as the long term stability of the gain. We show that we could reach maximal gains of around 150 which corresponds to a signal-to-noise ratio ($S/N$) of about 800 for a minimal ionising particle (MIP) signal on 3 mm readout strips. We could also conclude that the dielectric surfaces in the vicinity of the LEM holes charge up with different time constants that depend on their design parameters. Our results demonstrate that the LAr LEM TPC is a robust concept that is well-understood and well-suited for operation in ultra-pure cryogenic environments and that can match the goals of future large-scale liquid argon detectors.

17 pages, 9 figures

References in corpus (6)

• A concise review on THGEM detectors
• Underground Neutrino Detectors for Particle and Astroparticle Science: the Giant Liquid Argon Charge Imaging ExpeRiment (GLACIER)
• Experiments For CP-Violation: A Giant Liquid Argon Scintillation, Cerenkov And Charge Imaging Experiment ?
• LBNO-DEMO: Large-scale neutrino detector demonstrators for phased performance assessment in view of a long-baseline oscillation experiment
• Construction and operation of a Double Phase LAr Large Electron Multiplier Time Projection Chamber
• Test of a Liquid Argon TPC in a magnetic field and investigation of high temperature superconductors in liquid argon and nitrogen

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• The Thick Gas Electron Multiplier and its derivatives: physics, technologies and applications
• The science and technology of liquid argon detectors
• First test of a high voltage feedthrough for liquid Argon TPCs connected to a 300 kV power supply
• Space charge in liquid argon time-projection chambers: a review of analytical and numerical models, and mitigation methods
• Novel resistive charge-multipliers for dual-phase LAr-TPCs: towards stable operation at higher gains
• Prototype Analog Front-end for Negative-ion Gas and Dual-phase Liquid-Ar TPCs