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

Abstract

DUNE is a dual-site experiment for long-baseline neutrino oscillation studies, neutrino astrophysics and nucleon decay searches. ProtoDUNE Dual Phase (DP) is a 6 $$\times $$ × 6 $$\times $$ × 6 m$$^3$$ 3 liquid argon time-projection-chamber (LArTPC) that recorded cosmic-muon data at the CERN Neutrino Platform in 2019–2020 as a prototype of the DUNE Far Detector. Charged particles propagating through the LArTPC produce ionization and scintillation light. The scintillation light signal in these detectors can provide the trigger for non-beam events. In addition, it adds precise timing capabilities and improves the calorimetry measurements. In ProtoDUNE-DP, scintillation and electroluminescence light produced by cosmic muons in the LArTPC is collected by photomultiplier tubes placed up to 7 m away from the ionizing track. In this paper, the ProtoDUNE-DP photon detection system performance is evaluated with a particular focus on the different wavelength shifters, such as PEN and TPB, and the use of Xe-doped LAr, considering its future use in giant LArTPCs. The scintillation light production and propagation processes are analyzed and a comparison of simulation to data is performed, improving understanding of the liquid argon properties.

Analysis of signal waveform from a midsize liquid argon detector

“…Full data fitting results indicate that the 1st time constant of TPB is approximately 1.7 ns, which is significantly shorter than liquid argon's fast time constant. The 2nd time constant of TPB is about 31.8 ns, which is similar to the published literature [15,17]. The 3rd time constant is approximately 329 ns.…”

“…Data analysis demonstrates that the slow decay time constant of liquid argon scintillation light is roughly 1482 ns, which is similar to the value reported in ref. [15,16].…”

“…In ref. [15], the authors suggest that signal reflections at the flange feed-through occur approximately 200 ns and 400 ns after the maximum, but without further explanation. Ref [16] indicates that a mismatch of around 9% between the data and signal model occurs at approximately 100 ns.…”

“…In experiments that use WLSs, the signal waveform analysis becomes more complex due to the re-emission process of the WLS. Some authors introduce an intermediate component into the two exponential time structure to fit the liquid argon signal waveforms [6,14,15]. However, as the authors mentioned, the intermediate component is only confirmed by the fitting of the signal shape.…”

“…Several authors have reported the presence of a hump structure after the peak of the liquid argon signal waveform [15,16,18], based on data acquisition using signal waveform digitization electronics. In ref.…”