Abstract
The 3×1×1 m3 demonstrator is a dual phase liquid argon time projection chamber that has recorded cosmic rays events in 2017 at CERN. The light signal in these detectors is crucial to provide precise timing capabilities. The performance of the photon detection system, composed of five PMTs, are discussed. The collected scintillation and electroluminescence light created by passing particles has been studied in various detector conditions. In particular, the scintillation light production and propagation processes have been analyzed and compared to simulations, improving the understanding of some liquid argon properties.
Highlights
While the first one consists of argon in liquid state only (ProtoDUNE Single-Phase [6]), the second adds a layer of gaseous argon to enable charge amplification before collection (ProtoDUNE Dual-Phase [7, 8])
Starting April 2017, using the trigger given by the Cosmic Ray Tagger (CRT) system, scintillation light data were recorded during the purging, cooling down and LAr filling stages prior to the commissioning of the whole detector
Using the same muon-like selection in PMT- and CRT-trigger runs, we studied the evolution of the S2 maximal amplitude and total charge as a function of the amplification field
Summary
The detection of scintillation light in LArTPC detectors is a key feature of this technology. These excimers can be either generated directly through argon excitation, or through the recombination of ionized argon with an electron [10, 11]: Excitation: In both processes, the photons are emitted isotropically with a wavelength peaked at 128 nm in the VUV region [12], and together constitute the primary scintillation light (S1) signal. While primary scintillation occurs in all LAr detectors, secondary scintillation (S2) or electroluminescence light is produced in detectors based on the dual phase concept In this case, electrons produced in LAr are drifted to the top and extracted to an ultra pure gas layer by means of a strong local electric field. Electrons are accelerated with high electric fields in order to generate Townsend avalanches During this process, argon excimers are produced and emit photons in the same VUV region as the primary scintillation light during their decay. The extraction of electrons from liquid to gas over a large area has been proven for the first time
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