Study of scintillation light collection, production and propagation in a 4 tonne dual-phase LArTPC

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.

Performance study of a 3×1×1 m3 dual phase liquid Argon Time Projection Chamber exposed to cosmic rays

“…Scintillation photons with wavelengths peaked at 128 nm are also produced and detected by five PMTs placed in line at the bottom of the cryostat. They can provide the trigger and the reference time for the event with an accuracy of a few nanoseconds [11]. The produced charge is free to drift in the ultra pure liquid argon up to the surface where it is extracted to the gas phase.…”

“…All the data are acquired with a trigger requiring a coincidence of all 5 PMTs. Their thresholds are set to maintain a data acquisition rate at the level of 3 Hz [10,11]. At those settings, our event sample predominantly consists of electromagnetically or hadronically induced cascades (showers), emitting large amounts of scintillation light, or MIPs, which cross most of the fiducial volume at a relatively shallow angle.…”

“…From the centre of each volume, a light map was built simulating 100 million photons to compute the probability of and the arrival time for a photon produced at the centre of that volume to reach each photomultiplier. The probability and arrival time for each position in the detector was obtained by a linear extrapolation from the simulated values at the centre of each volume, as described [11]. A simplified trigger simulation was applied, which required all five PMTs to measure at least 1750 photons in a time window of 80 ns.…”

“…[10] clearly demonstrates the excellent imaging capabilities of the detector and provides a proof of principle of the DP technology at the tonne scale. Follow up studies performed with the scintillation light in the detector have been published in [11].…”

Scintillation light detection in the 6-m drift-length ProtoDUNE Dual Phase liquid argon TPC

“…Since the values of TPB efficiency at 127 nm reported in the literature show a large dispersion [32][33][34], a 100% TPB efficiency is assumed as in a previous work [35] ( TPB =1). Then, assuming the PEN efficiency obtained by the relative performance of both systems in Table 4 ( PEN = 0.35 ± 0.09), the corresponding effective efficiency for TPB-coated and PEN-foil PMTs are E TPB = 0.09 and E PEN = 0.016, making the TPB coated-PMT six times more efficient.…”